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40 results on '"Chaffin, Michael S."'

1. Nonthermal hydrogen loss at Mars: Contributions of photochemical mechanisms to escape and identification of key processes

Author

Gregory, Bethan S., Chaffin, Michael S., Elliott, Rodney D., Deighan, Justin, Gröller, Hannes, and Cangi, Eryn M.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Hydrogen loss to space is a key control on the evolution of the Martian atmosphere and the desiccation of the red planet. Thermal escape is thought to be the dominant loss process, but both forward modeling studies and remote sensing observations have indicated the presence of a second, higher-temperature "nonthermal" or "hot" hydrogen component, some fraction of which also escapes. Exothermic reactions and charge/momentum exchange processes produce hydrogen atoms with energy above the escape energy, but H loss via many of these mechanisms has never been studied, and the relative importance of thermal and nonthermal escape at Mars remains uncertain. Here we estimate hydrogen escape fluxes via 47 mechanisms, using newly-developed escape probability profiles. We find that HCO$^+$ dissociative recombination is the most important of the mechanisms, accounting for 30-50% of the nonthermal escape. The reaction CO$_2^+$ + H$_2$ is also important, producing roughly as much escaping H as momentum exchange between hot O and H. Total nonthermal escape from the mechanisms considered amounts to 39% (27%) of thermal escape, for low (high) solar activity. Our escape probability profiles are applicable to any thermospheric hot H production mechanism and can be used to explore seasonal and longer-term variations, allowing for a deeper understanding of desiccation drivers over various timescales. We highlight the most important mechanisms and suggest that some may be important at Venus, where nonthermal escape dominates and much of the literature centers on charge exchange reactions, which do not result in significant escape in this study., Comment: 47 pages, 4 figures, 3 tables. Accepted manuscript. An edited version of this paper was published by AGU

Published
2023
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2. Fully coupled photochemistry of the deuterated ionosphere of Mars and its effects on escape of H and D

Author

Cangi, Eryn M., Chaffin, Michael S., Yelle, Roger V., Gregory, Bethan S., and Deighan, Justin

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Although deuterium (D) on Mars has received substantial attention, the deuterated ionosphere remains relatively unstudied. This means that we also know very little about non-thermal D escape from Mars, since it is primarily driven by excess energy imparted to atoms produced in ion-neutral reactions. Most D escape from Mars is expected to be non-thermal, highlighting a gap in our understanding of water loss from Mars. In this work, we set out to fill this knowledge gap. To accomplish our goals, we use an upgraded 1D photochemical model that fully couples ions and neutrals and does not assume photochemical equilibrium. To our knowledge, such a model has not been applied to Mars previously. We model the atmosphere during solar minimum, mean, and maximum, and find that the deuterated ionosphere behaves similarly to the H-bearing ionosphere, but that non-thermal escape on the order of 8000-9000 cm$^{-2}$s$^{-1}$ dominates atomic D loss under all solar conditions. The total fractionation factor, $f$, is $f=0.04$--0.07, and integrated water loss is 147--158 m GEL. This is still less than geomorphological estimates. Deuterated ions at Mars are likely difficult to measure with current techniques due to low densities and mass degeneracies with more abundant H ions. Future missions wishing to measure the deuterated ionosphere in situ will need to develop innovative techniques to do so., Comment: 37 pages, 8 figures, published in Journal of Geophysical Research: Planets

Published
2023
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3. Higher Martian atmospheric temperatures at all altitudes increase the D/H fractionation factor and water loss

Author

Cangi, Eryn M., Chaffin, Michael S., and Deighan, Justin

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Much of the water that once flowed on the surface of Mars was lost to space long ago, and the total amount lost remains unknown. Clues to the amount lost can be found by studying hydrogen (H) and its isotope deuterium (D), which are produced when atmospheric water molecules H$_2$O and HDO dissociate. The difference in escape efficiencies of H and D (which leads to} an enhanced D/H ratio) is referred to as the fractionation factor $f$. Both the D/H ratio and $f$ are necessary to estimate water loss; thus, if we can constrain the range of $f$ and understand what controls it, we will be able to estimate water loss more accurately. In this study, we use a 1D photochemical model of the neutral Martian atmosphere to determine how $f$ depends on assumed temperature and water vapor profiles. We find that the exobase temperature most strongly controls the value of $f$ for thermal escape processes. When we include estimates of non-thermal escape from other studies, we find that the tropopause temperature is also important. Overall, for the standard Martian atmosphere, $f=0.002$ for thermal escape, and $f=0.06$ for thermal + non-thermal escape. We estimate that Mars has lost at minimum 66-122 m GEL of water. Importantly, our results demonstrate that the value of $f$ depends critically on non-thermal escape of D, and that modeling studies that include D/H fractionation must model both neutral and ion processes throughout the atmosphere., Comment: 22 pages, 11 figures, accepted in Journal of Geophysical Research: Planets

Published
2020
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4. EMM EMUS Observations of FUV Aurora on Mars: Dependence on Magnetic Topology, Local Time, and Season.

Author

Chirakkil, Krishnaprasad, Lillis, Robert J., Deighan, Justin, Chaffin, Michael S., Jain, Sonal K., Brain, David A., Fillingim, Matthew O., Susarla, Raghuram, Holsclaw, Greg, Fang, Xiaohua, Schneider, Nick M., AlMazmi, Hoor, AlMatroushi, Hessa, Gacesa, Marko, El‐Kork, Nayla, Thiemann, Ed, and Halekas, Jasper S.

Subjects
THERMOSPHERE, AURORAS, SPACE environment, CORONAL mass ejections, MARS (Planet), SOLAR cycle
Abstract

We present a comprehensive study of the nightside aurora phenomenon on Mars, utilizing observations from EMUS onboard Emirates Mars Mission. The oxygen emission at 130.4 nm is by far the brightest FUV auroral emission line observed at Mars. Our statistical analysis reveals geographic, solar zenith angle, local time, and seasonal dependencies of auroral occurrence. Higher occurrence of aurora is observed in regions of open magnetic topology, where crustal magnetic fields are either very weak or both strong and vertical. Aurora occurs more frequently closer to the terminator and is more likely on the dusk side than on the dawn side of the night hemisphere. A pronounced auroral feature appears close to midnight local times in the southern hemisphere, consistent with the spot of energetic electron fluxes previously identified in the Mars Global Surveyor data. This auroral spot is more frequent after midnight than before. Additionally, some regions on Mars are "aurora voids" where essentially no aurora occurs. Aurora exhibits a seasonal dependence, with a major enhancement near perihelion. Non–crustal field aurora additionally shows a secondary enhancement near Ls 30°. This seasonal variability is a combination of the variability in ionospheric photoelectrons and thermospheric atomic oxygen abundance. Auroral occurrence also shows an increase with the rise of Solar Cycle 25. The brightest auroral pixels are observed during space weather events such as Coronal Mass Ejections and Stream Interaction Regions. These observations not only shed light on where and when Martian aurora occurs, but also add to our understanding of Mars' magnetic environment and its interaction with the heliosphere. Plain Language Summary: In this study, we explore the phenomenon of aurora on the nightside of Mars, using observations from the highly sensitive Emirates Mars Ultraviolet Spectrometer (EMUS) on the Emirates Mars Mission. Our analysis reveals distinct patterns in auroral occurrence on the planet. For instance, there is a higher rate of auroral activity in regions where Mars' magnetic field lines are open (i.e., connected to the collisional atmosphere at one end). We also found that aurora is more common near the terminator (with the occurrence decreasing as the solar zenith angle increases), and particularly during the evening hours, as opposed to early morning. Interestingly, these auroral events also show a seasonal dependence, peaking around perihelion in a Martian year, when Mars is closest to the sun. This seasonal pattern corresponds with the variation of photoelectrons in Mars' dayside ionosphere and the atomic oxygen abundance in the thermosphere. Auroral occurrence increases with increasing solar activity. Also, the auroral brightness increases during space weather events. Our study not only gives us a clearer picture of where and when the aurora occurs on Mars but also hints at the underlying processes influencing them, offering insights into the planet's magnetic and charged particle environment. Key Points: Higher auroral occurrence is observed in regions of open magnetic topology, where crustal fields are either very weak or primarily verticalAurora occurs more frequently near the terminator compared to deep night, with higher occurrence at dusk than at dawnAurora occurs more frequently near perihelion, with the brightest auroral pixels observed during space weather events [ABSTRACT FROM AUTHOR]

Published
2024
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5. EMM EMUS Observations of Hot Oxygen Corona at Mars: Radial Distribution and Temporal Variability.

Author

Chirakkil, Krishnaprasad, Deighan, Justin, Chaffin, Michael S., Jain, Sonal K., Lillis, Robert J., Raghuram, Susarla, Holsclaw, Greg, Brain, David A., Thiemann, Ed, Chamberlin, Phil, Fillingim, Matthew O., Evans, J. Scott, England, Scott, AlMatroushi, Hessa, AlMazmi, Hoor, Eparvier, Frank, Gacesa, Marko, El‐Kork, Nayla, and Curry, Shannon M.

Subjects
ROTATION of the Sun, MARS (Planet), SOLAR cycle, SOLAR oscillations, SOLAR corona, ATMOSPHERIC oxygen, ULTRAVIOLET spectrometers, OXYGEN
Abstract

We present the first observations of the dayside coronal oxygen emission in far ultraviolet (FUV) measured by the Emirates Mars Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM). The high sensitivity of EMUS is providing an opportunity to observe the tenuous oxygen corona in FUV, which is otherwise difficult to observe. Oxygen resonance fluorescence emission at 130.4 nm provides a measurement of the upper atmospheric and exospheric oxygen. More than 500 oxygen corona profiles are constructed using the long–exposure time cross–exospheric mode (OS4) of EMUS observations. These profiles range from ∼200 km altitude up to several Mars radii (>6 RM) across all seasons and for two Mars years. Our analysis shows that OI 130.4 nm is highly correlated with solar irradiance (solar photoionizing and 130.4 nm illuminating irradiances) as well as changes in the Sun–Mars distance. The prominent short term periodicity in oxygen corona brightness is consistent with the solar rotation period (quasi–27–day). A comparison between the perihelion seasons of Mars Year (MY) 36 and MY 37 shows interannual variability with enhanced emission intensities during MY 37, due to the rise of Solar Cycle 25. These observations show a highly variable oxygen corona, which has significant implications on constraining the photochemical escape of atomic oxygen from Mars. Plain Language Summary: The highly sensitive Emirates Mars Ultraviolet Spectrometer (EMUS) onboard Emirates Mars Mission (EMM) is capable of observing ultraviolet emissions emanating from Mars. Oxygen in the Martian exosphere is hard to see because it's tenuous. In this study, the analysis of long exposure time EMUS optical observations show that the hot oxygen corona on Mars has a short term variability due to solar rotation. Hot oxygen corona also shows a long–term variability that depends on the Sun–Mars distance and the solar cycle progression. When comparing data from two Martian years, it is noticed that the oxygen corona became brighter when the Sun is more active. Key Points: Brighter O corona is observed during perihelion and dimmer during aphelion, indicating a strong relationship with the Sun‐Mars distanceThe variation in OI 130.4 nm brightness shows a linear correlation with solar EUV irradiance, with a short‐term solar rotation periodicityInterannual variability is observed from MY 36 to MY 37, showing an enhancement in O corona brightness with the rise of Solar Cycle 25 [ABSTRACT FROM AUTHOR]

Published
2024
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9. Patchy Proton Aurora at Mars: A Global View of Solar Wind Precipitation Across the Martian Dayside From EMM/EMUS

Author

Chaffin, Michael S., primary, Fowler, Christopher M., additional, Deighan, Justin, additional, Jain, Sonal, additional, Holsclaw, Greg, additional, Hughes, Andréa, additional, Ramstad, Robin, additional, Dong, Yaxue, additional, Brain, Dave, additional, AlMazmi, Hoor, additional, Chirakkil, Krishnaprasad, additional, Correira, John, additional, England, Scott, additional, Evans, J. Scott, additional, Fillingim, Matt, additional, Lillis, Rob, additional, Lootah, Fatma, additional, Raghuram, Susarla, additional, McFadden, Jim, additional, Halekas, Jasper, additional, Espley, Jared, additional, Schneider, Nick, additional, Mayyasi, Majd, additional, Lee, Christina O., additional, Curry, Shannon, additional, and AlMatroushi, Hessa, additional

Published
2022
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10. Combined Analysis of Hydrogen and Oxygen 102.6 nm Emission at Mars

Author

Chaffin, Michael S., primary, Deighan, Justin, additional, Jain, Sonal, additional, Holsclaw, Greg, additional, AlMazmi, Hoor, additional, Chirakkil, Krishnaprasad, additional, Correira, John, additional, England, Scott, additional, Evans, J. Scott, additional, Fillingim, Matt, additional, Lillis, Rob, additional, Lootah, Fatma, additional, Raghuram, Susarla, additional, Eparvier, Frank, additional, Thiemann, Ed, additional, Curry, Shannon, additional, and AlMatroushi, Hessa, additional

Published
2022
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11. Investigations of the Mars Upper Atmosphere with ExoMars Trace Gas Orbiter

Author

López-Valverde, Miguel A., Gerard, Jean-Claude, González-Galindo, Francisco, Vandaele, Ann-Carine, Thomas, Ian, Korablev, Oleg, Ignatiev, Nikolai, Fedorova, Anna, Montmessin, Franck, Määttänen, Anni, Guilbon, Sabrina, Lefevre, Franck, Patel, Manish R., Jiménez-Monferrer, Sergio, García-Comas, Maya, Cardesin, Alejandro, Wilson, Colin F., Clancy, R. T., Kleinböhl, Armin, McCleese, Daniel J., Kass, David M., Schneider, Nick M., Chaffin, Michael S., López-Moreno, José Juan, and Rodríguez, Julio

Published
2018
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12. Combined Analysis of Hydrogen and Oxygen 102.6 nm Emission at Mars

Author

Chaffin, Michael S., Deighan, Justin, Jain, Sonal, Holsclaw, Greg, AlMazmi, Hoor, Chirakkil, Krishnaprasad, Correira, John, England, Scott L., Evans, J. Scott, Fillingim, Matt, Lillis, Rob, Lootah, Fatma, Raghuram, Susarla, Eparvier, Frank, Thiemann, Ed, Curry, Shannon, AlMatroushi, Hessa, Chaffin, Michael S., Deighan, Justin, Jain, Sonal, Holsclaw, Greg, AlMazmi, Hoor, Chirakkil, Krishnaprasad, Correira, John, England, Scott L., Evans, J. Scott, Fillingim, Matt, Lillis, Rob, Lootah, Fatma, Raghuram, Susarla, Eparvier, Frank, Thiemann, Ed, Curry, Shannon, and AlMatroushi, Hessa

Abstract

Water is lost from the Mars upper atmosphere to space as hydrogen and oxygen, both of which can be observed in scattered ultraviolet sunlight at 102.6 nm. We present Emirates Mars Mission Emirates Mars Ultraviolet Spectrometer (EMM/EMUS) insertion orbit observations of this airglow, resolving the independent altitude contributions of H and O for the first time. We present the first airglow modeling of the complete H and O 102.6 nm system and the first 3D azimuthally symmetric modeling of the O emission, retrieving temperatures and densities typical of northern spring. Our model reproduces the emission well above 200 km, but does not incorporate partial frequency redistribution needed to reproduce the observed O brightness at lower altitudes and on the disk. These results support future EMM/EMUS science orbit retrievals of H loss and the use of 102.6 nm observations to constrain planetary atmospheres across the solar system.

Published
2022

13. HCO+ Dissociative Recombination: A Significant Driver of Nonthermal Hydrogen Loss at Mars.

Author

Gregory, Bethan S., Elliott, Rodney D., Deighan, Justin, Gröller, Hannes, and Chaffin, Michael S.

Subjects
VENUS (Planet), MARS (Planet), MARTIAN atmosphere, HYDROGEN as fuel, ALBEDO, HYDROGEN atom, HYDROGEN
Abstract

Hydrogen escape to space has shaped Mars' atmospheric evolution, driving significant water loss. An unknown fraction of atmospheric H lost acquires its escape energy from photochemical processes, with multiple observational studies suggesting much higher densities of such "hot" H than models predict. Here, we show that a previously unconsidered mechanism, HCO+ dissociative recombination, produces more escaping hot H than any previously studied process, potentially accounting for more than 50% of escape during solar minimum aphelion conditions and ∼5% of the expected long‐term average loss. This hot H is predicted to impact observed brightness profiles negligibly, posing a significant challenge to the interpretation of spacecraft remote sensing observations. This mechanism's efficiency is largely due to the high (63%–83%) albedo of the planet to H at 1–10 eV energies, indicating the likely importance of dozens of similar photochemical mechanisms for the desiccation of Mars, Venus and planets throughout the universe. Plain Language Summary: The escape of hydrogen atoms from the upper atmosphere of Mars has led to significant loss of water from the planet. Hydrogen needs energy to escape Mars' gravitational pull, which can be sourced from the energy given to H atoms when they are produced by chemical reactions—this results in "hot" hydrogen. However, the importance of hot hydrogen escape is unknown, and there is a disparity between predictions from observations and models. Here, we show that one reaction, HCO+ dissociative recombination (HCO+ + e− → CO + H), which has never been considered before, produces more escaping hot H than any process previously studied. In some seasonal conditions, it accounts for more than half the H loss, while accounting for 5% on longer timescales. Despite its importance, we predict that the hot H produced by this process is very difficult for spacecraft to observe. This mechanism is effective for escape because most H atoms produced by chemical reactions at high altitudes escape, so dozens of similar mechanisms are likely to be important at Mars. HCO+ dissociative recombination is probably significant at Venus, where hot H escape is dominant, and perhaps at other rocky planets outside the solar system. Key Points: We investigate nonthermal hydrogen escape via HCO+ dissociative recombination for the first timeThis is likely the dominant nonthermal mechanism, potentially responsible for >50% of the total escape under certain conditionsThough important for H loss, we predict that this mechanism impacts brightness negligibly, posing a challenge for spacecraft observations [ABSTRACT FROM AUTHOR]

Published
2023
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14. Proton Aurora on Mars: A Dayside Phenomenon Pervasive in Southern Summer

Author

Hughea11, Hughes, Andrea C. G., Mierkiewicz, Edwin J., Chaffin, Michael S., Deighan, Justin, Jain, Sonal, Schneider, Nicholas, Mayyasi, Majd, Jakosky, Bruce, Hughea11, Hughes, Andrea C. G., Mierkiewicz, Edwin J., Chaffin, Michael S., Deighan, Justin, Jain, Sonal, Schneider, Nicholas, Mayyasi, Majd, and Jakosky, Bruce

Abstract

We present observations of proton aurora at Mars made using the Imaging UltraViolet Spectrograph (IUVS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Martian proton aurora display a prominent intensity enhancement in the hydrogen Lyman‐alpha (121.6 nm) emission between ~110 and 150 km altitude. Using altitude‐intensity profiles from periapsis limb scan data spanning nearly two Martian years, we create a comprehensive database of proton aurora and characterize their phenomenology. Due to Mars' lack of a global dipole magnetic field, Martian proton aurora are expected to form on the dayside via electron stripping and charge exchange between solar wind protons and the neutral corona. We observe proton aurora in ~14% of dayside periapsis profiles (with notable seasonal variability), making proton aurora the most commonly observed type of aurora at Mars. We determine that the primary factors influencing proton aurora occurrence rates are solar zenith angle and season. The highest proton aurora occurrence rates are at low solar zenith angles on the Mars dayside, consistent with known formation processes. Proton aurora have highest emission enhancements, peak intensities, peak altitudes, and occurrence rates (nearing 100%) around southern summer solstice. This time period corresponds with the seasonal inflation of the neutral lower atmosphere, the onset of Martian dust storm season, seasonally increased coronal hydrogen column densities, and higher atmospheric temperature and solar wind flux following perihelion. The results of our study provide a new understanding of the primary factors influencing proton aurora, and the long‐term variability of these phenomena as observed over multiple Mars years.

Published
2020

16. 14 years of Mars’ atmosphere monitoring by SPICAM on Mars Express

Author

Lacombe , Gaetan, Montmessin , Franck, Korablev , Oleg, Lefèvre , Franck, Bertaux , Jean-Loup, Fedorova , Anna A., Trokhimovskiy , Alexander, Baggio , Lucio, Reberac , Aurélie, Chapron , Nicolas, Crepel , Mickael, David , L., Rougerie , Bruno, Maltagliati , Luca, Willame , Yannick, Guslyakova , Svetlana, Gérard , Jean-Claude, Stiepen , Arnaud, Fussen , Didier, Mateshvili , Nina, Määttänen , Anni, Forget , François, Witasse , Olivier, Leblanc , François, Vandaele , Ann Carine, Marcq , Emmanuel, Sandel , Bill R., Gondet , Brigitte, Schneider , Nicholas, Chaffin , Michael S., IMPEC - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales ( LATMOS ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Space Research Institute of the Russian Academy of Sciences ( IKI ), Russian Academy of Sciences [Moscow] ( RAS ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), CEA Paris Saclay, Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique ( BIRA-IASB ), Laboratoire de Physique Atmosphérique et Planétaire ( LPAP ), Université de Liège, Laboratoire de Météorologie Dynamique (UMR 8539) ( LMD ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -École polytechnique ( X ) -École des Ponts ParisTech ( ENPC ) -Centre National de la Recherche Scientifique ( CNRS ) -Département des Géosciences - ENS Paris, École normale supérieure - Paris ( ENS Paris ) -École normale supérieure - Paris ( ENS Paris ), European Space Research and Technology Centre ( ESTEC ), European Space Agency ( ESA ), HEPPI - LATMOS, Lunar and Planetary Laboratory [Tucson], University of Arizona, Institut d'astrophysique spatiale ( IAS ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratory for Atmospheric and Space Physics [Boulder] ( LASP ), University of Colorado Boulder [Boulder], PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Space Research Institute of the Russian Academy of Sciences (IKI), Russian Academy of Sciences [Moscow] (RAS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Laboratoire de Physique Atmosphérique et Planétaire (LPAP), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), HELIOS - LATMOS, Lunar and Planetary Laboratory [Tucson] (LPL), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Agence Spatiale Européenne = European Space Agency (ESA), and Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES)

Subjects
[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph]
Abstract

International audience; SPICAM is entering his 8th Martian yeararound Mars and continues to collect measurementswith its infrared channel. This dataset is uniqueinsofar as it comes from the same calibratedinstrument, continuously over the course of 14 years.Hence, it allows to probe different physicalphenomena with multi-annual and seasonal timescale,as well as episodic events (e.g dust storms). SPICAMcontributed to the improvement of the understandingof Mars’s climate in several areas including loweratmosphere composition, chemical processes and thestructure of the atmosphere.

Published
2018

17. First Retrieval of Thermospheric Carbon Monoxide From Mars Dayglow Observations

Author

Evans, J. Scott, Stevens, Michael H., Jain, Sonal, Deighan, Justin, Lumpe, Jerry, Schneider, Nicholas M., Stewart, A. Ian, Crismani, Matteo, Stiepen, Arnaud, Chaffin, Michael S., Mayyasi-Matta, Majd A., Mcclintock, William E., Holsclaw, Greg, Lefèvre, Franck, Lo, Daniel, Clarke, John T., Montmessin, Franck, Bougher, Stephen W., Bell, Jared M., Eparvier, Frank, Thiemann, Ed, Mahaffy, Paul R., Benna, Mehdi, Elrod, Meredith K., Jakosky, Bruce, Computational Physics, Inc., Naval Research Laboratory (NRL), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Space Sciences, Technologies and Astrophysics Research Institute (STAR), Université de Liège, Boston University [Boston] (BU), STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Center for Space Physics [Boston] (CSP), PLANETO - LATMOS, Department of Climate and Space Sciences and Engineering (CLaSP), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, University of Michigan System, and NASA Goddard Space Flight Center (GSFC)

Subjects
[SDU]Sciences of the Universe [physics], Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics
Abstract

International audience; As a minor species in the Martian thermosphere, Carbon Monoxide (CO) is a tracer that can be used to constrain changing circulation patterns between the lower thermosphere and upper mesosphere of Mars. By linking CO density distributions to dynamical wind patterns, the structure and variability of the atmosphere will be better understood. Direct measurements of CO can therefore provide insight into the magnitude and pattern of winds and provide a metric for studying the response of the atmosphere to solar forcing. In addition, CO measurements can help solve outstanding photochemical modeling problems in explaining the abundance of CO at Mars. CO is directly observable by electron impact excitation and solar resonance fluorescence emissions in the far-ultraviolet (FUV). The retrieval of CO from solar fluorescence was first proposed over 40 years ago, but has been elusive at Mars due to significant spectral blending. However, by simulating the spectral shape of each contributing emission feature, electron impact excitation and solar fluorescence brightnesses can be extracted from the composite spectrum using a multiple linear regression approach. We use CO Fourth Positive Group (4PG) molecular band emission observed on the limb (130 - 200 km) by the Imaging Ultraviolet Spectrograph (IUVS) on NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft over both northern and southern hemispheres from October 2014 to December 2016. We present the first direct retrieval of CO densities by FUV remote sensing in the upper atmosphere of Mars. Atmospheric composition is inferred using the terrestrial Atmospheric Ultraviolet Radiance Integrated Code adapted to the Martian atmosphere. We investigate the sensitivity of CO density retrievals to variability in solar irradiance, solar longitude, and local time. We compare our results to predictions from the Mars Global Ionosphere-Thermosphere Model as well as in situ measurements by the Neutral Gas and Ion Mass Spectrometer on MAVEN and quantify any differences.

Published
2017

18. First Detection of the Nitric Oxide Dayglow on Mars

Author

Stevens, Michael H., Siskind, David E., Evans, J. Scott, Fox, Jane L., Jain, Sonal, Deighan, Justin, Schneider, Nicholas M., Stewart, A. Ian F., Crismani, Matteo, Stiepen, Arnaud, Chaffin, Michael S., Mcclintock, William E., Holsclaw, Greg, Lefèvre, Franck, Lo, Daniel, Clarke, John T., Montmessin, Franck, Jakosky, Bruce, Naval Research Laboratory (NRL), Computational Physics, Inc., Wright State University, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire de Physique Atmosphérique et Planétaire (LPAP), Université de Liège, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), and Cardon, Catherine

Subjects
[SDU] Sciences of the Universe [physics], [SDU]Sciences of the Universe [physics]
Abstract

International audience; Nitric oxide (NO) is a well-known indicator of solar and auroral activity in the terrestrial upper atmosphere. Direct measurements of NO on Mars can therefore constrain studies of energetic processes controlling the composition and structure of its upper atmosphere (80-200 km). Identifying and quantifying these processes is one of the science objectives of NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission currently orbiting Mars. NO can be observed directly by solar resonance fluorescence in the mid-ultraviolet (MUV). Indeed, this approach has routinely been used to measure terrestrial NO for 50 years. On Mars, this “dayglow” emission is very weak relative to other bright MUV features and thus has confounded attempts at its detection there for nearly the same amount of time. Here, we report the first detection of the NO dayglow in the Martian atmosphere using limb observations by the Imaging Ultraviolet Spectrograph (IUVS) on the MAVEN spacecraft. The detection is enabled by the spectral modeling and removal of the carbon monoxide Cameron bands, which dominate the MUV limb spectra. We focus on the spectral region between 213.0-225.5 nm, where three NO gamma bands emit. We will infer NO densities from the dayglow spectra and compare our observations with predictions from a photochemical model. We will discuss the implications, particularly in the context of previous in situ measurements.

Published
2017

19. Global UV Imaging by MAVEN/IUVS: Diurnal Cloud Formation, Dust Storms and Atmospheric Scattering

Author

Schneider, Nicholas M., Deighan, Justin I., Jain, Sonal Kumar, Derks, Alysa, Chaffin, Michael S., Crismani, Matteo, Stewart, A. Ian F., Mcclintock, William E., Holsclaw, Gregory M., Jakosky, Bruce M., Lefèvre, Franck, Montmessin, Franck, Wolff, Michael J., Stiepen, Arnaud, Stevens, Michael H., Evans, J. Scott, Yelle, Roger V., Lo, Daniel Y., Clarke, John T., Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Space Science Institute [Boulder] (SSI), Laboratoire de Physique Atmosphérique et Planétaire (LPAP), Université de Liège, Naval Research Laboratory (NRL), Computational Physics, Inc., Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Center for Space Physics [Boston] (CSP), and Boston University [Boston] (BU)

Subjects
[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR]
Abstract

International audience; A new UV spectral imaging dataset of Mars global images is being obtained by the Imaging Ul- traViolet Spectrograph (IUVS) on the Mars Atmos- phere and V olatile Evolution mission (MA VEN). Of particular interest for atmospheric studies are spec- trally-resolved mid-UV datacubes as shown in Fig- ure 1. Clouds, haze, dust and ozone can all be detect- ed and quantified through image analysis and re- trieval. IUVS observations are the only MAVEN data capable of probing below the spacecraft alti- tude, and provide an important link between the denser atmosphere and escape processes which are MAVEN’s primary focus (Jakosky et al. 2015).

Published
2017

20. Mars topographic clouds: MAVEN/IUVS observations and LMD MGCM predictions

Author

Schneider, Nicholas M., Connour, Kyle, Forget, François, Deighan, Justin, Jain, Sonal, Vals, Margaux, Wolff, Michael J., Chaffin, Michael S., Crismani, Matteo, Stewart, A. Ian F., Mcclintock, William E., Holsclaw, Greg, Lefèvre, Franck, Montmessin, Franck, Stiepen, Arnaud, Stevens, Michael H., Evans, J. Scott, Yelle, Roger, Lo, Daniel, Clarke, John T., Jakosky, Bruce, Cardon, Catherine, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Space Science Institute [Boulder] (SSI), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Atmosphérique et Planétaire (LPAP), Université de Liège, Naval Research Laboratory (NRL), Computational Physics, Inc., Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)

Subjects
[SDU] Sciences of the Universe [physics], [SDU]Sciences of the Universe [physics]
Abstract

International audience; The Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian atmosphere. From these apoapse disk images, information about clouds and aerosols can be retrieved and comprise the only MAVEN observations of topographic clouds and cloud morphologies. Measuring local time variability of large-scale recurring cloud features is made possible with MAVEN’s ~4.5-hour elliptical orbit, something not possible with sun-synchronous orbits. We have run the LMD MGCM (Mars global circulation model) at 1° x 1° resolution to simulate water ice cloud formation with inputs consistent with observing parameters and Mars seasons. Topographic clouds are observed to form daily during the late mornings of northern hemisphere spring and this phenomenon recurs until late summer (Ls = 160°), after which topographic clouds wane in thickness. By northern fall, most topographic clouds cease to form except over Arsia Mons and Pavonis Mons, where clouds can still be observed. Our data show moderate cloud formation over these regions as late as Ls = 220°, something difficult for the model to replicate. Previous studies have shown that models have trouble simulating equatorial cloud thickness in combination with a realistic amount of water vapor and not-too-thick polar water ice clouds, implying aspects of the water cycle are not fully understood. We present data/model comparisons as well as further refinements on parameter inputs based on IUVS observations.

Published
2017

21. Variations of the Martian cold oxygen exosphere derived from the O 130.4 nm line by IUVS/MAVEN

Author

Chaufray, Jean-Yves, Deighan, Justin, Schneider, Nicholas M., Jain, Sonal Kumar, Stewart, Ian, Chaffin, Michael S., Clarke, John T., Eparvier, Francis G., Thiemann, Edward M. B., Chamberlin, Phillip C., Jakosky, Bruce Martin, HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), NASA Goddard Space Flight Center (GSFC), and Cardon, Catherine

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; The Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has systematically observed the Martian oxygen exosphere for nearly one Martian year now. The OI 130.4 nm resonance scattering line is observed all the time at the dayside providing unprecedented information on the oxygen content of the Martian upper atmosphere. These variations are important to understand the chemistry, dynamics, energetics and escape processes of the Martian upper atmosphere. Using a radiative transfer model, we have estimated the amount of oxygen in the Martian exosphere needed to reproduce the observations of IUVS during the first Martian year of the mission. In this work, we will present the seasonal variations of the exospheric oxygen density derived from this set of observations and discussed these variations in the frame of global models of the Martian upper atmosphere.

Published
2016

23. Limb Observations of Solar Scattered Light by the Imaging Ultraviolet Spectrograph on MAVEN: New Constraints on Martian Mesospheric Cloud Variability

Author

Stevens, Michael H., Siskind, David E., Evans, Scott, Schneider, Nicholas M., Stewart, A. Ian F., Deighan, Justin, Jain, Sonal Kumar, Crismani, Matteo, Stiepen, Arnaud, Chaffin, Michael S., Mcclintock, William, Holsclaw, Gregory, Lefèvre, Franck, Montmessin, Franck, Lo, Daniel, Clarke, John T., Jakosky, Bruce, Naval Research Laboratory (NRL), Computational Physics, Inc., Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), and Cardon, Catherine

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; The Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission observed the Martian upper atmosphere in late 2015 (Ls ~ 70) and early 2016 (Ls ~ 150). Although designed to measure the dayglow between 90-200 km IUVS also scans the limb down to 60 km, where solar scattered light dominates the mid-ultraviolet (MUV) signal. Occasionally, this MUV light shows enhanced scattering between 60-90 km indicating the presence of aerosols in the mesosphere. We quantify the solar scattering for each daylight scan obtained between October and December, 2015 and between April and June, 2016. We then identify over 100 scans of enhanced scattering between 60-90 km and assemble them both geographically and diurnally. The geographical distribution of the enhancements in 2015 is preferentially located near the equator, consistent with previous observations of mesospheric clouds for this part of the season. A wave three pattern in equatorial cloud occurrence suggests forcing from a non-migrating tide, possibly linked to the longitudinal variation of Mars surface topography. At the same time, there are indications of a diurnal variation such that the clouds seen in 2015 and 2016 are preferentially observed in the early morning, between 0600-0900 local solar time. This suggests an important role for a migrating temperature tide controlling the formation of Martian mesospheric clouds.

Published
2016

24. Mars Ozone Mapping with MAVEN IUVS

Author

Lefèvre, Franck, Montmessin, Franck, Schneider, Nicholas M., Deighan, Justin, Jain, Sonal K., Stewart, Ian, Stiepen, Arnaud, Chaffin, Michael S., Mcclintock, William, Lo, Daniel, Clarke, John, Holsclaw, Greg, Jakosky, Bruce M., STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], University of Arizona, Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), and Cardon, Catherine

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; Ozone (O3) on Mars is a product of the CO2 photolysis by ultraviolet radiation. It is destroyed with a timescale of less than ~1 hour during the day by the H, OH, and HO2 radicals. This tight coupling between O3 and HOx species makes ozone a sensitive tracer of the odd hydrogen chemistry that stabilizes the CO2 atmosphere of Mars, and ozone measurements offer a powerful constraint for photochemical models. Ozone is also expected to be anti-correlated to water vapour, the source of hydrogen radicals HOx. At high latitudes in winter, the absence of H2O prevents the production of HOx and the chemical lifetime of ozone may increase up to several days. In these conditions, the ozone column abundance usually reaches its largest values of the Martian year and ozone turns into a measurable tracer of the polar vortex dynamics.The Imaging Ultraviolet Spectrograph (IUVS) is one of nine science instruments aboard the Mars Atmosphere and Volatile and Evolution (MAVEN) spacecraft. In the apoapse imaging phase, the spacecraft motion carries the IUVS lines-of-sight across the Martian disk while the scan mirror is used to make transverse swaths. This observation mode allows mapping the ozone vertically-integrated column from its signature in the solar ultraviolet flux backscattered by the surface and the atmosphere.This paper will present an overview of the first year of ozone mapping by IUVS. We will describe in particular the last Mars northern winter (2015) when the largest ozone columns have been observed since the beginning of the MAVEN mission. The data will be compared to prior Earth-based observations and to the SPICAM and MARCI ozone datasets. We will also test our quantitative understanding of the Martian ozone by comparing the IUVS observations to our three-dimensional model with photochemistry.

Published
2015

25. Mars Nitric Oxide Nightglow as observed by MAVEN/IUVS

Author

Stiepen, Arnaud, Stewart, Ian, Jain, Sonal K., Deighan, Justin, Schneider, Nicholas M., Stevens, Michael H., Bougher, Stephen, Evans, Joseph, Chaffin, Michael S., Mcclintock, Bill, Clarke, John, Holsclaw, Greg, Montmessin, Franck, Lefèvre, Franck, Lo, Daniel, Jakosky, Bruce, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Naval Research Laboratory (NRL), Department of Climate and Space Sciences and Engineering (CLaSP), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Computational Physics, Inc., Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Arizona, and Cardon, Catherine

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; We report results from a study of nitric oxide nightglow over the northern hemisphere of Mars during winter. We present observations of the nitric oxide δ and γ band emissions between 190 and 270 nm by the Imaging UltraViolet Spectrograph on the MAVEN spacecraft. The emission reveals recombination of N and O atoms dissociated on the dayside of Mars, and is known to trace upper atmosphere hemispheric circulation patterns. We extend previous studies to higher latitudes, finding brighter emissions lower in the atmosphere as predicted from global circulation models. Statistically signicant variability suggests variation of the fluxes of N and O carried from the dayside thermosphere, as well as possible variations of the wind pattern in the nightside thermosphere and mesosphere. We report unexpected variability between the individual components of the nitric oxide band system. We provide statistical characteristics and evaluate possible explanations for this phenomenon.

Published
2015

26. Mars’ ultraviolet dayglow observations by IUVS/MAVEN: Structure and variability of Martian upper atmosphere

Author

Jain, Sonal K., Stewart, Ian, Schneider, Nicholas M., Deighan, Justin, Stiepen, Arnaud, Evans, Joseph, Stevens, Michael H., Chaffin, Michael S., Crismani, Matteo, Mcclintock, Bill, Clarke, John, Holsclaw, Greg, Lo, Daniel, Lefèvre, Franck, Montmessin, Franck, Thiemann, Ed, Epavier, Francis, Jakosky, Bruce M., Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Computational Physics, Inc., Naval Research Laboratory (NRL), Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), University of Arizona, STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Cardon, Catherine

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; Mars has been studied extensively at ultraviolet wavelengths starting from Mariner 6 and 7 (Barth et al. JGR, 1971; Stewart, JGR, 1972), Mariner 9 (Barth et al., Icaurs, 1972; Stewart et al. Icarus, 1972), and more recently by SPICAM aboard Mars Express (Leblanc et al., JGR, 2006). The results from these measurements reveal a large variability in the composition and structure of Martian upper atmosphere. However, due to the lack of simultaneous measurements of energy input in the atmosphere, such as solar electromagnetic and particle flux as well as limitations in the observation geometry and data itself, this variability is still not fully understood.We report a comprehensive study of Mars dayglow observations by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite, focusing on upper atmospheric structure and seasonal variability. The dayglow emission spectra show features similar to previous UV measurements at Mars. The IUVS detected a second, low-altitude peak in the emission profile of OI 297.2 nm, confirmation of the prediction that the absorption of solar Lyman alpha emission is an important energy source there. We find a significant drop in thermospheric scale height and temperature between Ls = 218° and Ls = 337 - 352°, attributed primarily to the decrease in solar activity and increase in heliocentric distance. The CO2+ UVD peak intensity is well correlated with simultaneous observations of solar 17 - 22 nm irradiance at Mars by Extreme Ultraviolet Monitor (EUVM) aboard MAVEN. I will present and discuss the variability in Martian UV dayglow, its dependence on solar EUV irradiance, and the importance of IUVS observations in our current understanding of Mars’ thermosphere.

Published
2015

27. New Observations of Molecular Nitrogen by the Imaging Ultraviolet Spectrograph on MAVEN

Author

Stevens, Michael H., Evans, J. Scott, Schneider, Nicholas M., Stewart, A. Ian F., Deighan, Justin, Jain, Sonal K., Crismani, Matteo M. J., Stiepen, Arnaud, Chaffin, Michael S., Mcclintock, William E., Holsclaw, Greg M., Lefèvre, Franck, Montmessin, Franck, Lo, Daniel Y., Clarke, John T., Bougher, Stephen W., Jakosky, Bruce M., Naval Research Laboratory (NRL), Computational Physics, Inc., Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), Department of Climate and Space Sciences and Engineering (CLaSP), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, and Cardon, Catherine

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; The Martian ultraviolet dayglow provides information on the basic state of the Martian upper atmosphere. The Imaging Ultraviolet Spectrograph (IUVS) on NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission has observed Mars at mid and far-UV wavelengths since its arrival in September 2014. In this work, we describe a linear regression method used to extract components of UV spectra from IUVS limb observations and focus in particular on molecular nitrogen (N2) photoelectron excited emissions. We identify N2 Lyman-Birge-Hopfield (LBH) emissions for the first time at Mars and we also confirm the tentative identification of N2 Vegard-Kaplan (VK) emissions. We compare observed VK and LBH limb radiance profiles to model results between 90 and 210 km. Finally, we compare retrieved N2 density profiles to general circulation (GCM) model results. Contrary to earlier analyses using other satellite data that indicated N2 densities were a factor of three less than predictions, we find that N2 abundances exceed GCM results by about a factor of two at 130 km but are in agreement at 150 km.

Published
2015

29. H Escape in 3D: MAVEN IUVS observations of the Mars corona

Author

Chaffin, Michael S., Chaufray, Jean-Yves, Deighan, Justin, Schneider, Nicholas M., Mcclintock, William, Stewart, Ian, Thiemann, Ed, Clarke, John, Holsclaw, Greg, Jain, Sonal K., Crismani, Matteo, Stiepen, Arnaud, Montmessin, Franck, Eparvier, Francis, Chamberlin, Phillip, Jakosky, Bruce M., Cardon, Catherine, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), PLANETO - LATMOS, and NASA Goddard Space Flight Center (GSFC)

Subjects
[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
Abstract

International audience; Mars has lost a significant fraction of its initial water inventory to space, as evidenced by surface morphology and an enrichment of the heavy isotope deuterium relative to hydrogen. This loss continues today via thermal Jeans escape of neutral hydrogen from the extended H corona. The Mars Atmosphere and Volatile EvolutioN mission's Imaging Ultraviolet Spectrometer IUVS constrains this escape with high cadence, spatially resolved measurements of the corona in scattered sunlight in the Lyman alpha line of neutral H at 121.6 nm. These measurements indicate spatial variability in the corona never before recognized, with potential effects on reconstructing the escape history of water and on retrieved escape rates from previous spatially unresolved observations. I will present our current progress in retrieving escape rates and density distributions from the IUVS observations, including the degree to which observations of the H corona can constrain the thermospheric general circulation at Mars.

Published
2015

30. Retrieval of CO2 and N2 in the Martian thermosphere using dayglow observations by IUVS on MAVEN

Author

Evans, J. Scott, Stevens, Michael H., Lumpe, Jerry D., Schneider, Nick M., Stewart, A. Ian F., Deighan, Justin, Jain, Sonal K., Chaffin, Michael S., Crismani, Matteo, Stiepen, Arnaud, Mcclintock, William E., Holsclaw, Greg M., Lefèvre, Franck, Lo, Daniel Y., Clarke, John T., Eparvier, F. G., Thiemann, E. M. B., Chamberlin, Phillip C., Bougher, S. W., Bell, Jared M., Jakosky, Bruce M., Computational Physics, Inc., Naval Research Laboratory (NRL), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), NASA Goddard Space Flight Center (GSFC), Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] (AOSS), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, and National Institute of Aerospace [Hampton] (NIA)

Subjects
thermosphere, dayglow, composition, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], limb scan, retrieval
Abstract

International audience; We present direct number density retrievals of carbon dioxide (CO2) and molecular nitrogen (N2) for the upper atmosphere of Mars using limb scan observations during October and November 2014 by the Imaging Ultraviolet Spectrograph on board NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We use retrieved CO2 densities to derive temperature variability between 170 and 220 km. Analysis of the data shows (1) low-mid latitude northern hemisphere CO2 densities at 170 km vary by a factor of about 2.5, (2) on average, the N2/CO2 increases from 0.042 ± 0.017 at 130 km to 0.12 ± 0.06 at 200 km, and (3) the mean upper atmospheric temperature is 324 ± 22 K for local times near 14:00.

Published
2015

31. Non-Migrating Tides in the Martian Atmosphere as Observed by MAVEN IUVS

Author

Lo, Daniel Y., Yelle, Roger V., Schneider, Nicholas M., Jain, Sonal K., Stewart, A. Ian F., England, Scott L., Deighan, Justin I., Stiepen, Arnaud, Evans, J. Scott, Stevens, Michael H., Chaffin, Michael S., Crismani, Matteo M. J., Mcclintock, William E., Clarke, John T., Holsclaw, Gregory M., Lefèvre, Franck, Jakosky, Bruce M., Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Space Sciences Laboratory [Berkeley] (SSL), University of California [Berkeley], University of California-University of California, Naval Research Laboratory (NRL), Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), and Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], upper atmosphere, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Mars, MAVEN/IUVS, atmospheric tides, CO2 density
Abstract

International audience; Using the Mars Atmospheric and Volatile EvolutioN mission (MAVEN) Imaging Ultraviolet Spectrograph (IUVS), we found periodic longitudinal variations in CO2 density in the Martian atmosphere. The variations exhibit significant structure with longitudinal wave numbers 1, 2, and 3 in an effectively constant local solar time frame, and we attribute this structure to nonmigrating tides. The wave-2 component is dominated by the diurnal eastward moving DE1 tide at the equator and the semidiurnal stationary S0 tide at the midlatitudes. Wave-3 is dominated by the diurnal eastward moving DE2 tide, with possibly the semidiurnal eastward moving SE1 tide causing an amplitude increase at the midlatitudes. Structure in the wave-1 component can be explained by the semidiurnal westward moving SW1 tide.

Published
2015

32. Study of the Martian cold oxygen corona from the O I 130.4 nm by IUVS/MAVEN

Author

Chaufray, Jean-Yves, Deighan, Justin, Chaffin, Michael S., Schneider, Nicholas M., Mcclintock, Bill, Stewart, Ian, Jain, Sonal K., Crismani, Matteo, Stiepen, Arnaud, Holsclaw, Greg, Clarke, John, Montmessin, Franck, Eparvier, Francis, Thiemann, Ed, Chamberlin, Phillip, Jakosky, Bruce M., Cardon, Catherine, HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), PLANETO - LATMOS, and NASA Goddard Space Flight Center (GSFC)

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Physics::Space Physics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics::Earth and Planetary Astrophysics, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; The observations of the O I 130.4 nm resonant line performed by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile Evolution Mission (MAVEN) are presented. This emission line is observed during the different orbit phases of MAVEN : disk observations at apoapsis, limb scans at periapsis and coronal scans during the outbound orbit leg. The atomic oxygen density which is an important parameter to understand the heating, composition, dynamics of the Martian upper atmosphere and the temperature at 200 km are retrieved from an automatic inversion algorithm. A set of observations performed by IUVS during the first months of the mission are analyzed to study the variabiity of the atomic oxygen in the Martian upper atmosphere. The derived oxygen density and the temperature at the exobase are in the predicted range (107 - 108 cm-3; 200 – 300K) by the current thermospheric models of Mars. The derived parameters are very sensitive to the absolute calibration of the instrument which is the main source of uncertainty on the results presented.

Published
2015

33. Nonmigrating tides in the Martian atmosphere as observed by MAVEN IUVS

Author

Lo, Daniel Y., primary, Yelle, Roger V., additional, Schneider, Nicholas M., additional, Jain, Sonal K., additional, Stewart, A. Ian F., additional, England, Scott L., additional, Deighan, Justin I., additional, Stiepen, Arnaud, additional, Evans, J. Scott, additional, Stevens, Michael H., additional, Chaffin, Michael S., additional, Crismani, Matteo M. J., additional, McClintock, William E., additional, Clarke, John T., additional, Holsclaw, Gregory M., additional, Lefèvre, Franck, additional, and Jakosky, Bruce M., additional

Published
2015
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34. Ultraviolet observations of the hydrogen coma of comet C/2013 A1 (Siding Spring) by MAVEN/IUVS

Author

Crismani, Matteo M. J., primary, Schneider, Nicholas M., additional, Deighan, Justin I., additional, Stewart, A. Ian F., additional, Combi, Michael, additional, Chaffin, Michael S., additional, Fougere, Nicolas, additional, Jain, Sonal K., additional, Stiepen, Arnaud, additional, Yelle, Roger V., additional, McClintock, William E., additional, Clarke, John T., additional, Holsclaw, Gregory M., additional, Montmessin, Frank, additional, and Jakosky, Bruce M., additional

Published
2015
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36. HCO+Dissociative Recombination: A Significant Driver of Nonthermal Hydrogen Loss at Mars

Author

Gregory, Bethan S., Elliott, Rodney D., Deighan, Justin, Gröller, Hannes, and Chaffin, Michael S.

Abstract

Hydrogen escape to space has shaped Mars' atmospheric evolution, driving significant water loss. An unknown fraction of atmospheric H lost acquires its escape energy from photochemical processes, with multiple observational studies suggesting much higher densities of such “hot” H than models predict. Here, we show that a previously unconsidered mechanism, HCO+dissociative recombination, produces more escaping hot H than any previously studied process, potentially accounting for more than 50% of escape during solar minimum aphelion conditions and ∼5% of the expected long‐term average loss. This hot H is predicted to impact observed brightness profiles negligibly, posing a significant challenge to the interpretation of spacecraft remote sensing observations. This mechanism's efficiency is largely due to the high (63%–83%) albedo of the planet to H at 1–10 eV energies, indicating the likely importance of dozens of similar photochemical mechanisms for the desiccation of Mars, Venus and planets throughout the universe. The escape of hydrogen atoms from the upper atmosphere of Mars has led to significant loss of water from the planet. Hydrogen needs energy to escape Mars' gravitational pull, which can be sourced from the energy given to H atoms when they are produced by chemical reactions—this results in “hot” hydrogen. However, the importance of hot hydrogen escape is unknown, and there is a disparity between predictions from observations and models. Here, we show that one reaction, HCO+dissociative recombination (HCO++ e−→ CO + H), which has never been considered before, produces more escaping hot H than any process previously studied. In some seasonal conditions, it accounts for more than half the H loss, while accounting for 5% on longer timescales. Despite its importance, we predict that the hot H produced by this process is very difficult for spacecraft to observe. This mechanism is effective for escape because most H atoms produced by chemical reactions at high altitudes escape, so dozens of similar mechanisms are likely to be important at Mars. HCO+dissociative recombination is probably significant at Venus, where hot H escape is dominant, and perhaps at other rocky planets outside the solar system. We investigate nonthermal hydrogen escape via HCO+dissociative recombination for the first timeThis is likely the dominant nonthermal mechanism, potentially responsible for >50% of the total escape under certain conditionsThough important for H loss, we predict that this mechanism impacts brightness negligibly, posing a challenge for spacecraft observations We investigate nonthermal hydrogen escape via HCO+dissociative recombination for the first time This is likely the dominant nonthermal mechanism, potentially responsible for >50% of the total escape under certain conditions Though important for H loss, we predict that this mechanism impacts brightness negligibly, posing a challenge for spacecraft observations

Published
2023
Full Text
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37. Lower atmosphere water/hydrogen activity during the MY 34 regional dust storm

Author

Holmes, James A., Lewis, Stephen R., Patel, Manish R., Aoki, Shohei, Fedorova, Anna A., Chaffin, Michael S., Schneider, Nicholas M., Kass, David M., Vandaele, Ann C., Holmes, James A., Lewis, Stephen R., Patel, Manish R., Aoki, Shohei, Fedorova, Anna A., Chaffin, Michael S., Schneider, Nicholas M., Kass, David M., and Vandaele, Ann C.

Abstract

Our understanding of the evolution of water on Mars can be advanced through the provision of bounded constraints on the rates of water loss. To understand observed variations in the loss rate, the processes via which hydrogen escapes the martian atmosphere and coupling to the lower atmosphere water cycle also need to be explored. During the Mars Year (MY) 34 regional dust storm that occurred from LS = 320.6-336.5°, an increase in the Lyman alpha brightness (a proxy for hydrogen escape) was observed by the Mars Atmosphere and Volatile EvolutioN Imaging Ultraviolet Spectrograph (MAVEN/IUVS) instrument. Vertical profiles of water vapour can be retrieved from the Nadir and Occultation for MArs Discovery (NOMAD) and Atmospheric Chemistry Suite (ACS) instruments on the ExoMars Trace Gas Orbiter (TGO). Retrievals could not be made, however, at the time of peak activity observed by MAVEN/IUVS, during the MY 34 regional dust storm. We investigate the global distribution of lower atmosphere water using data assimilation covering the time period leading up to and during the MY 34 regional dust storm. The data includes observations of water vapour from NOMAD/ACS (that constrain the initial global distribution of water), temperature profiles from ACS and the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter spacecraft, and dust column from MCS, which are combined with the Open University modelling group Mars Global Circulation model. During the time period of the MY 34 regional dust storm unobserved by ExoMars TGO we can still constrain the simulation using MCS temperature and dust column retrievals, a powerful advantage of multi-spacecraft data assimilation. This method provides the most realistic simulation possible of the chemical and dynamical structure of the lower atmosphere during the observed peak in MAVEN/IUVS observations. We identify peak abundance of water vapour and hydrogen at altitudes above 70 km that are consistent with the peak emission observed by

38. Investigations of the Mars Upper Atmosphere with ExoMars Trace Gas Orbiter

Author

López-Valverde, Miguel A., Gerard, Jean-Claude, González-Galindo, Francisco, Vandaele, Ann-Carine, Thomas, Ian, Korablev, Oleg, Ignatiev, Nikolai, Fedorova, Anna, Montmessin, Franck, Määttänen, Anni, Guilbon, Sabrina, Lefevre, Franck, Patel, Manish R., Jiménez-Monferrer, Sergio, García-Comas, Maya, Cardesin, Alejandro, Wilson, Colin F., Clancy, R. T., Kleinböhl, Armin, McCleese, Daniel J., Kass, David M., Schneider, Nick M., Chaffin, Michael S., López-Moreno, José Juan, Rodríguez, Julio, López-Valverde, Miguel A., Gerard, Jean-Claude, González-Galindo, Francisco, Vandaele, Ann-Carine, Thomas, Ian, Korablev, Oleg, Ignatiev, Nikolai, Fedorova, Anna, Montmessin, Franck, Määttänen, Anni, Guilbon, Sabrina, Lefevre, Franck, Patel, Manish R., Jiménez-Monferrer, Sergio, García-Comas, Maya, Cardesin, Alejandro, Wilson, Colin F., Clancy, R. T., Kleinböhl, Armin, McCleese, Daniel J., Kass, David M., Schneider, Nick M., Chaffin, Michael S., López-Moreno, José Juan, and Rodríguez, Julio

Abstract

The Martian mesosphere and thermosphere, the region above about 60 km, is not the primary target of the ExoMars 2016 mission but its Trace Gas Orbiter (TGO) can explore it and address many interesting issues, either in-situ during the aerobraking period or remotely during the regular mission. In the aerobraking phase TGO peeks into thermospheric densities and temperatures, in a broad range of latitudes and during a long continuous period. TGO carries two instruments designed for the detection of trace species, NOMAD and ACS, which will use the solar occultation technique. Their regular sounding at the terminator up to very high altitudes in many different molecular bands will represent the first time that an extensive and precise dataset of densities and hopefully temperatures are obtained at those altitudes and local times on Mars. But there are additional capabilities in TGO for studying the upper atmosphere of Mars, and we review them briefly. Our simulations suggest that airglow emissions from the UV to the IR might be observed outside the terminator. If eventually confirmed from orbit, they would supply new information about atmospheric dynamics and variability. However, their optimal exploitation requires a special spacecraft pointing, currently not considered in the regular operations but feasible in our opinion. We discuss the synergy between the TGO instruments, specially the wide spectral range achieved by combining them. We also encourage coordinated operations with other Mars-observing missions capable of supplying simultaneous measurements of its upper atmosphere.

39. Investigations of the Mars Upper Atmosphere with ExoMars Trace Gas Orbiter

Author

López-Valverde, Miguel A., Gerard, Jean-Claude, González-Galindo, Francisco, Vandaele, Ann-Carine, Thomas, Ian, Korablev, Oleg, Ignatiev, Nikolai, Fedorova, Anna, Montmessin, Franck, Määttänen, Anni, Guilbon, Sabrina, Lefevre, Franck, Patel, Manish R., Jiménez-Monferrer, Sergio, García-Comas, Maya, Cardesin, Alejandro, Wilson, Colin F., Clancy, R. T., Kleinböhl, Armin, McCleese, Daniel J., Kass, David M., Schneider, Nick M., Chaffin, Michael S., López-Moreno, José Juan, Rodríguez, Julio, López-Valverde, Miguel A., Gerard, Jean-Claude, González-Galindo, Francisco, Vandaele, Ann-Carine, Thomas, Ian, Korablev, Oleg, Ignatiev, Nikolai, Fedorova, Anna, Montmessin, Franck, Määttänen, Anni, Guilbon, Sabrina, Lefevre, Franck, Patel, Manish R., Jiménez-Monferrer, Sergio, García-Comas, Maya, Cardesin, Alejandro, Wilson, Colin F., Clancy, R. T., Kleinböhl, Armin, McCleese, Daniel J., Kass, David M., Schneider, Nick M., Chaffin, Michael S., López-Moreno, José Juan, and Rodríguez, Julio

Abstract

The Martian mesosphere and thermosphere, the region above about 60 km, is not the primary target of the ExoMars 2016 mission but its Trace Gas Orbiter (TGO) can explore it and address many interesting issues, either in-situ during the aerobraking period or remotely during the regular mission. In the aerobraking phase TGO peeks into thermospheric densities and temperatures, in a broad range of latitudes and during a long continuous period. TGO carries two instruments designed for the detection of trace species, NOMAD and ACS, which will use the solar occultation technique. Their regular sounding at the terminator up to very high altitudes in many different molecular bands will represent the first time that an extensive and precise dataset of densities and hopefully temperatures are obtained at those altitudes and local times on Mars. But there are additional capabilities in TGO for studying the upper atmosphere of Mars, and we review them briefly. Our simulations suggest that airglow emissions from the UV to the IR might be observed outside the terminator. If eventually confirmed from orbit, they would supply new information about atmospheric dynamics and variability. However, their optimal exploitation requires a special spacecraft pointing, currently not considered in the regular operations but feasible in our opinion. We discuss the synergy between the TGO instruments, specially the wide spectral range achieved by combining them. We also encourage coordinated operations with other Mars-observing missions capable of supplying simultaneous measurements of its upper atmosphere.

40. Lower atmosphere water/hydrogen activity during the MY 34 regional dust storm

Author

Holmes, James A., Lewis, Stephen R., Patel, Manish R., Aoki, Shohei, Fedorova, Anna A., Chaffin, Michael S., Schneider, Nicholas M., Kass, David M., Vandaele, Ann C., Holmes, James A., Lewis, Stephen R., Patel, Manish R., Aoki, Shohei, Fedorova, Anna A., Chaffin, Michael S., Schneider, Nicholas M., Kass, David M., and Vandaele, Ann C.

Abstract

Our understanding of the evolution of water on Mars can be advanced through the provision of bounded constraints on the rates of water loss. To understand observed variations in the loss rate, the processes via which hydrogen escapes the martian atmosphere and coupling to the lower atmosphere water cycle also need to be explored. During the Mars Year (MY) 34 regional dust storm that occurred from LS = 320.6-336.5°, an increase in the Lyman alpha brightness (a proxy for hydrogen escape) was observed by the Mars Atmosphere and Volatile EvolutioN Imaging Ultraviolet Spectrograph (MAVEN/IUVS) instrument. Vertical profiles of water vapour can be retrieved from the Nadir and Occultation for MArs Discovery (NOMAD) and Atmospheric Chemistry Suite (ACS) instruments on the ExoMars Trace Gas Orbiter (TGO). Retrievals could not be made, however, at the time of peak activity observed by MAVEN/IUVS, during the MY 34 regional dust storm. We investigate the global distribution of lower atmosphere water using data assimilation covering the time period leading up to and during the MY 34 regional dust storm. The data includes observations of water vapour from NOMAD/ACS (that constrain the initial global distribution of water), temperature profiles from ACS and the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter spacecraft, and dust column from MCS, which are combined with the Open University modelling group Mars Global Circulation model. During the time period of the MY 34 regional dust storm unobserved by ExoMars TGO we can still constrain the simulation using MCS temperature and dust column retrievals, a powerful advantage of multi-spacecraft data assimilation. This method provides the most realistic simulation possible of the chemical and dynamical structure of the lower atmosphere during the observed peak in MAVEN/IUVS observations. We identify peak abundance of water vapour and hydrogen at altitudes above 70 km that are consistent with the peak emission observed by

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