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120 results on '"Holsclaw, G."'

1. Venus upper clouds and the UV-absorber from MESSENGER/MASCS observations

Author

Perez-Hoyos, S., Sanchez-Lavega, A., Garcıa-Munoz, A., Irwin, P. G. J., Peralta, J., Holsclaw, G., McClintock, W. M., and Sanz-Requena, J. F.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

One of the most intriguing, long-standing questions regarding Venus' atmosphere is the origin and distribution of the unknown UV-absorber, responsible for the absorption band detected at the near-UV and blue range of Venus' spectrum. In this work, we use data collected by MASCS spectrograph on board the MESSENGER mission during its second Venus flyby in June 2007 to address this issue. Spectra range from 0.3 {\mu}m to 1.5 {\mu}m including some gaseous H2O and CO2 bands, as well as part of the SO2 absorption band and the core of the UV absorption. We used the NEMESIS radiative transfer code and retrieval suite to investigate the vertical distribution of particles in the Equatorial atmosphere and to retrieve the imaginary refractive indices of the UV-absorber, assumed to be well mixed with Venus' small mode-1 particles. The results show an homogeneous Equatorial atmosphere, with cloud tops (height for unity optical depth) at 75+/-2 km above surface. The UV absorption is found to be centered at 0.34+/-0.03 {\mu}m with a full width half maximum of 0.14+/-0.01 {\mu}m. Our values are compared with previous candidates for the UV aerosol absorber, among which disulfur oxide (S2O) and dioxide disulfur (S2O2) provide the best agreement with our results., Comment: 43 pages, 16 figures

Published
2018
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2. Martian water loss to space enhanced by regional dust storms

Author

Chaffin, M. S., Kass, D. M., Aoki, S., Fedorova, A. A., Deighan, J., Connour, K., Heavens, N. G., Kleinböhl, A., Jain, S. K., Chaufray, J.-Y., Mayyasi, M., Clarke, J. T., Stewart, A. I. F., Evans, J. S., Stevens, M. H., McClintock, W. E., Crismani, M. M. J., Holsclaw, G. M., Lefevre, F., Lo, D. Y., Montmessin, F., Schneider, N. M., Jakosky, B., Villanueva, G., Liuzzi, G., Daerden, F., Thomas, I. R., Lopez-Moreno, J.-J., Patel, M. R., Bellucci, G., Ristic, B., Erwin, J. T., Vandaele, A. C., Trokhimovskiy, A., and Korablev, O. I.

Published
2021
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3. The Emirates Mars Mission

Author

Amiri, H. E. S., Brain, D., Sharaf, O., Withnell, P., McGrath, M., Alloghani, M., Al Awadhi, M., Al Dhafri, S., Al Hamadi, O., Al Matroushi, H., Al Shamsi, Z., Al Shehhi, O., Chaffin, M., Deighan, J., Edwards, C., Ferrington, N., Harter, B., Holsclaw, G., Kelly, M., Kubitschek, D., Landin, B., Lillis, R., Packard, M., Parker, J., Pilinski, E., Pramman, B., Reed, H., Ryan, S., Sanders, C., Smith, M., Tomso, C., Wrigley, R., Al Mazmi, H., Al Mheiri, N., Al Shamsi, M., Al Tunaiji, E., Badri, K., Christensen, P., England, S., Fillingim, M., Forget, F., Jain, S., Jakosky, B. M., Jones, A., Lootah, F., Luhmann, J. G., Osterloo, M., Wolff, M., and Yousuf, M.

Published
2022
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4. Variability of Atomic Hydrogen Brightness in the Martian Exosphere: Insights From the Emirates Ultraviolet Spectrometer on Board Emirates Mars Mission.

Author

Susarla, R., Deighan, J., Chaffin, M. S., Jain, S., Lillis, R. J., Chirakkil, K., Brain, D., Thiemann, E., Eparvier, F., Lootah, F., Holsclaw, G., Gacesa, M., Fillingim, M. O., El‐Kork, N., England, S., Evans, J. S., AlMazmi, H., and AlMatroushi, H.

Subjects
MARTIAN atmosphere, ATOMIC hydrogen, ULTRAVIOLET spectrometers, PHOTON emission, MARS (Planet), SOLAR atmosphere, SOLAR corona, SOLAR radiation
Abstract

The Emirates Mars Ultraviolet Spectrometer (EMUS), aboard the Emirates Mars Mission (EMM), has been conducting observations of ultraviolet emissions within the Martian exosphere. Taking advantage of the distinctive orbit of the EMM around Mars, EMUS utilizes a dedicated strafe observation strategy to scan the illuminated Martian exosphere at tangential altitudes ranging from 130 to over 20,000 km. To distinguish between emissions of Martian origin and those from the interplanetary background, EMUS conducts specialized background observations by looking away from the planet. This approach has allowed us to investigate the radial and seasonal variations in Martian coronal emission features at H Lyman‐α, β and γ wavelengths. Our analysis supports the previous studies indicating that Martian exospheric hydrogen Lyman emission brightness attains its highest levels around the southern summer solstice and reaches its lowest levels when Mars is near aphelion. Additionally, a secondary peak emission at all altitudes is observed after perihelion during Martian Year (MY) 36, which can be attributed to a Class C dust storm. Our study establishes a strong correlation between solar flux and coronal brightness for these emissions, highlighting the impact of solar activity on the visibility of Martian corona. In addition, we have examined interannual variability and found that emission intensities in MY 37 surpassed those in MY 36, primarily due to increased solar activity. These observations help to understand potential seasonal patterns of exospheric hydrogen, which is driven by underlying mechanisms in the lower atmosphere and solar activity, eventually suggesting an impact on water loss in the Martian atmosphere. Plain Language Summary: Atomic hydrogen primarily forms as a product when Martian water undergoes various photochemical reactions. These hydrogen atoms encircle Mars and become illuminated by solar radiation, leading to the creation of Martian hydrogen corona. The Emirates Mars Ultraviolet Spectrometer (EMUS), on the Emirates Mars Mission spacecraft, is currently studying the Martian atmosphere using the ultraviolet light emissions of different atoms and molecules on Mars. In this study, we have analyzed EMUS observations and determined that atomic hydrogen emission intensities increase during the Martian southern summer and decrease as Mars moves farther away from the Sun. Furthermore, we have compared the hydrogen brightness between two consecutive Martian years and have found that the hydrogen brightness is higher in the most recent year primarily due to increased solar radiation. These observations help us understand possible patterns that occur during different seasons on Mars and the mechanisms underlying water loss in the Martian atmosphere. Key Points: We present the variability in Martian atomic hydrogen brightness from early Martian year (MY) 36 to the first quarter of MY 37Martian exospheric H Ly‐β and γ emissions reach their peak brightness during the southern summer of MY 36Martian corona is much brighter at H Ly‐β wavelength in MY 37 compared to the previous year due to increased solar irradiance [ABSTRACT FROM AUTHOR]

Published
2024
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5. Retrieval of Ar, N2, O, and CO in the Martian Thermosphere Using Dayglow Limb Observations by EMM EMUS.

Author

Evans, J. S., Deighan, J., Jain, S., Veibell, V., Correira, J., Al Matroushi, H., Al Mazmi, H., Chaffin, M., Curry, S., El‐Kork, N., England, S., Eparvier, F., Fillingim, M., Holsclaw, G., Khalil, M., Lillis, R., Lootah, F., Mahmoud, S., Plummer, T., and Soto, E.

Subjects
MARTIAN atmosphere, THERMOSPHERE, AIRGLOW, GENERAL circulation model, UPPER atmosphere, ATMOSPHERIC carbon dioxide
Abstract

The Emirates Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM) Hope probe images Mars at wavelengths extending from approximately 100 to 170 nm. EMUS observations began in February 2021 and cover over a full Mars year. We report the first limb scan observations at Mars of ultraviolet emissions Ar I 106.6 nm, N I 120 nm, and carbon monoxide (CO) Fourth Positive Group (A − X) band system excited by electron impact on CO. We use EMUS limb scan observations to retrieve number density profiles of argon, molecular nitrogen, atomic oxygen, and CO in the upper atmosphere of Mars from 130 to 160 km. CO is a sensitive tracer of the thermal profile and winds in Mars' middle atmosphere and the chemistry that balances CO2 in the atmosphere of Mars. EMUS insertion orbit special observations demonstrate that far ultraviolet limb measurements of the Martian thermosphere can be spectroscopically analyzed with a robust retrieval algorithm to further quantify variations of CO composition in the Martian upper atmosphere. Plain Language Summary: This study focuses on satellite observations of ultraviolet light by the Emirates Mars Ultraviolet Spectrometer onboard the Emirates Mars Mission. The observed ultraviolet light is generated by argon, oxygen, nitrogen, and carbon monoxide and is used to determine the abundance of these gases in the upper atmosphere of Mars (130–160 km). We present the first remotely sensed measurements of argon and carbon monoxide abundances in the upper atmosphere of Mars. Mean retrieved argon, nitrogen, and oxygen densities, respectively, are lower than general circulation model predictions and other direct measurements by 10%–15%, ∼75%, and 35%–55%. Carbon monoxide densities measured for the first time agree qualitatively with measurements by other instruments and model predictions for similar conditions. We demonstrate that ultraviolet observations can be analyzed with a robust technique to further quantify variations of carbon monoxide abundance in the Martian upper atmosphere. Key Points: Remotely sensed CO densities retrieved from 130 to 160 km for the first time are ∼45% lower than MCD 6.1 predictions for similar conditionsMean retrieved Ar, N2, and O densities from 130 to 160 km are lower than MCD 6.1 and NGIMS by 10%–15%, ∼75%, and 35%–45%, respectivelyHigh spectral resolution observations by EMM EMUS show the first detection of C I 119.3 nm emission blended with N I 120 nm emission [ABSTRACT FROM AUTHOR]

Published
2024
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6. Discovery of a proton aurora at Mars

Author

Deighan, J., Jain, S. K., Chaffin, M. S., Fang, X., Halekas, J. S., Clarke, J. T., Schneider, N. M., Stewart, A. I. F., Chaufray, J.-Y., Evans, J. S., Stevens, M. H., Mayyasi, M., Stiepen, A., Crismani, M., McClintock, W. E., Holsclaw, G. M., Lo, D. Y., Montmessin, F., Lefèvre, F., and Jakosky, B. M.

Published
2018
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7. Discovery of diffuse aurora on Mars

Author

Schneider, N. M., Deighan, J. I., Jain, S. K., Stiepen, A., Stewart, A. I. F., Larson, D., Mitchell, D. L., Mazelle, C., Lee, C. O., Lillis, R. J., Evans, J. S., Brain, D., Stevens, M. H., McClintock, W. E., Chaffin, M. S., Crismani, M., Holsclaw, G. M., Lefevre, F., Lo, D. Y., Clarke, J. T., Montmessin, F., and Jakosky, B. M.

Published
2015

8. Early MAVEN Deep Dip campaign reveals thermosphere and ionosphere variability

Author

Bougher, S., Jakosky, B., Halekas, J., Grebowsky, J., Luhmann, J., Mahaffy, P., Connerney, J., Eparvier, F., Ergun, R., Larson, D., McFadden, J., Mitchell, D., Schneider, N., Zurek, R., Mazelle, C., Andersson, L., Andrews, D., Baird, D., Baker, D. N., Bell, J. M., Benna, M., Brain, D., Chaffin, M., Chamberlin, P., Chaufray, J.-Y., Clarke, J., Collinson, G., Combi, M., Crary, F., Cravens, T., Crismani, M., Curry, S., Curtis, D., Deighan, J., Delory, G., Dewey, R., DiBraccio, G., Dong, C., Dong, Y., Dunn, P., Elrod, M., England, S., Eriksson, A., Espley, J., Evans, S., Fang, X., Fillingim, M., Fortier, K., Fowler, C. M., Fox, J., Gröller, H., Guzewich, S., Hara, T., Harada, Y., Holsclaw, G., Jain, S. K., Jolitz, R., Leblanc, F., Lee, C. O., Lee, Y., Lefevre, F., Lillis, R., Livi, R., Lo, D., Ma, Y., Mayyasi, M., McClintock, W., McEnulty, T., Modolo, R., Montmessin, F., Morooka, M., Nagy, A., Olsen, K., Peterson, W., Rahmati, A., Ruhunusiri, S., Russell, C. T., Sakai, S., Sauvaud, J.-A., Seki, K., Steckiewicz, M., Stevens, M., Stewart, A. I. F., Stiepen, A., Stone, S., Tenishev, V., Thiemann, E., Tolson, R., Toublanc, D., Vogt, M., Weber, T., Withers, P., Woods, T., and Yelle, R.

Published
2015

9. MAVEN observations of the response of Mars to an interplanetary coronal mass ejection

Author

Jakosky, B. M., Grebowsky, J. M., Luhmann, J. G., Connerney, J., Eparvier, F., Ergun, R., Halekas, J., Larson, D., Mahaffy, P., McFadden, J., Mitchell, D. F., Schneider, N., Zurek, R., Bougher, S., Brain, D., Ma, Y. J., Mazelle, C., Andersson, L., Andrews, D., Baird, D., Baker, D., Bell, J. M., Benna, M., Chaffin, M., Chamberlin, P., Chaufray, Y.-Y., Clarke, J., Collinson, G., Combi, M., Crary, F., Cravens, T., Crismani, M., Curry, S., Curtis, D., Deighan, J., Delory, G., Dewey, R., DiBraccio, G., Dong, C., Dong, Y., Dunn, P., Elrod, M., England, S., Eriksson, A., Espley, J., Evans, S., Fang, X., Fillingim, M., Fortier, K., Fowler, C. M., Fox, J., Gröller, H., Guzewich, S., Hara, T., Harada, Y., Holsclaw, G., Jain, S. K., Jolitz, R., Leblanc, F., Lee, C. O., Lee, Y., Lefevre, F., Lillis, R., Livi, R., Lo, D., Mayyasi, M., McClintock, W., McEnulty, T., Modolo, R., Montmessin, F., Morooka, M., Nagy, A., Olsen, K., Peterson, W., Rahmati, A., Ruhunusiri, S., Russell, C. T., Sakai, S., Sauvaud, J.-A., Seki, K., Steckiewicz, M., Stevens, M., Stewart, A. I. F., Stiepen, A., Stone, S., Tenishev, V., Thiemann, E., Tolson, R., Toublanc, D., Vogt, M., Weber, T., Withers, P., Woods, T., and Yelle, R.

Published
2015

11. Retrieval of CO Relative Column Abundance in the Martian Thermosphere From FUV Disk Observations by EMM EMUS

Author

Evans, J. S., primary, Correira, J., additional, Deighan, J., additional, Jain, S., additional, Al Matroushi, H., additional, Al Mazmi, H., additional, Chaffin, M., additional, Curry, S., additional, England, S., additional, Eparvier, F., additional, Fillingim, M., additional, Forget, F., additional, Holsclaw, G., additional, Lillis, R., additional, Lootah, F., additional, and Thiemann, E., additional

Published
2022
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12. The Mars Atmosphere and Volatile Evolution (MAVEN) Mission

Author

Jakosky, B. M., Lin, R. P., Grebowsky, J. M., Luhmann, J. G., Mitchell, D. F., Beutelschies, G., Priser, T., Acuna, M., Andersson, L., Baird, D., Baker, D., Bartlett, R., Benna, M., Bougher, S., Brain, D., Carson, D., Cauffman, S., Chamberlin, P., Chaufray, J.-Y., Cheatom, O., Clarke, J., Connerney, J., Cravens, T., Curtis, D., Delory, G., Demcak, S., DeWolfe, A., Eparvier, F., Ergun, R., Eriksson, A., Espley, J., Fang, X., Folta, D., Fox, J., Gomez-Rosa, C., Habenicht, S., Halekas, J., Holsclaw, G., Houghton, M., Howard, R., Jarosz, M., Jedrich, N., Johnson, M., Kasprzak, W., Kelley, M., King, T., Lankton, M., Larson, D., Leblanc, F., Lefevre, F., Lillis, R., Mahaffy, P., Mazelle, C., McClintock, W., McFadden, J., Mitchell, D. L., Montmessin, F., Morrissey, J., Peterson, W., Possel, W., Sauvaud, J.-A., Schneider, N., Sidney, W., Sparacino, S., Stewart, A. I. F., Tolson, R., Toublanc, D., Waters, C., Woods, T., Yelle, R., and Zurek, R.

Published
2015
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13. Characteristics of Saturn's polar atmosphere and auroral electrons derived from HST/STIS, FUSE and Cassini/UVIS spectra

Author

Gustin, J., Gerard, J.-C., Pryor, W., Feldman, P.D., Grodent, D., and Holsclaw, G.

Subjects
Astronomy, Methane, Hydrocarbons, Sexually transmitted diseases, Astronomy, Earth sciences
Abstract

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.11.013 Byline: J. Gustin (a), J.-C. Gerard (a), W. Pryor (b), P.D. Feldman (c), D. Grodent (a), G. Holsclaw (d) Keywords: Aurorae; Saturn; Spectroscopy; Ultraviolet observations Abstract: Ultraviolet (UV) spectra of Saturn's aurora obtained with the Hubble Space Telescope Imaging Spectrograph (STIS), the Cassini Ultraviolet Imaging Spectrograph (UVIS) and the Far Ultraviolet Spectroscopic Explorer (FUSE) have been analyzed. Comparisons between the observed spectra and synthetic models of electron-excited H.sub.2 have been used to determine various auroral characteristics. Far ultraviolet (FUV: 1200-1700 A) STIS and UVIS spectra exhibit, below 1400 A, weak absorption due to methane, with a vertical column ranging between 1.4x10.sup.15 and 1.2x10.sup.16cm.sup.-2. Using the low-latitude Moses et al. [Moses, J.I., Bezard, B., Lellouch, E., Feuchtgruber, H., Gladstone, G.R., Allen, M., 2000. Icarus, 143, 244-298] atmospheric model of Saturn and an electron energy-H.sub.2 column relationship, these methane columns are converted into the mean energy of the primary precipitating electrons, estimated to lie in the range 10-18 keV. This result is confirmed by the study of self-absorption with UVIS and FUSE extreme ultraviolet (EUV: 900-1200 A) spectra. Below 1200 A, it is seen that transitions connecting to the v.sup.a[sup.3] Author Affiliation: (a) Laboratoire de Physique Atmospherique et Planetaire, Universite de Liege, Allee du 6 AoA't, 17, 4000 Liege, Belgium (b) Central Arizona College, Coolidge, AZ 85228, USA (c) Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA (d) Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA Article History: Received 24 July 2008; Revised 21 October 2008; Accepted 10 November 2008

Published
2009

14. The science enabled by a dedicated solar system space telescope

Author

Young, Cindy, primary, Wong, M. H., additional, Sayanagi, K. M., additional, Curry, S., additional, Jessup, K. L., additional, Becker, T., additional, Hendrix, A., additional, Chanover, N., additional, Milam, S., additional, Holler, B. J., additional, Holsclaw, G., additional, Peralta, J., additional, Clarke, J., additional, Spencer, J., additional, Kelley, M. S. P., additional, Luhmann, J., additional, MacDonnell, D., additional, Jr., R. J. Vervack,, additional, Rutherford, K., additional, Fletcher, L. N., additional, Pater, I. de, additional, Vilas, F., additional, Feaga, L., additional, Siegmund, O., additional, Bell, J., additional, Delory, G., additional, Pitman, J., additional, Greathouse, T., additional, Wishnow, E., additional, Schneider, N., additional, Lillis, R., additional, Colwell, J., additional, Bowman, L., additional, Lopes, R. M. C., additional, McGrath, M., additional, Marchis, F., additional, Cartwright, R., additional, and Poston, M. J., additional

Published
2021
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16. Comparison of Newly Acquired Lunar Spectra with the Titanium Abundance Maps Derived from Clementine

Author

Holsclaw, G. M, McClintock, W. E, and Robinson, M. S

Subjects
Lunar And Planetary Science And Exploration
Abstract

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) is one of seven science instruments onboard NASA's MESSENGER mission, currently en-route to the planet Mercury. One of MASCS s components, referred to as the Visible and Near Infrared Spectrograph (VIRS), will record reflectance spectra of the surface in order to characterize the mineralogy of the planet [1]. The lunar highlands and the average mercurian crust are proposed to be compositionally similar [i.e. 2]. In preparation to interpret VIRS reflectance spectra of Mercury to be first obtained in 2008, the Moon has been observed with an engineering model of the VIRS from a ground-based telescope. In this study, the ultraviolet and visible region of the spectrum is compared with titanium content in the lunar regolith.

Published
2005

18. Retrieval of Ar, N2, O, and CO in the Martian Thermosphere Using Dayglow Limb Observations by EMM EMUS

Author

Evans, J. S., Deighan, J., Jain, S., Veibell, V., Correira, J., Al Matroushi, H., Al Mazmi, H., Chaffin, M., Curry, S., El‐Kork, N., England, S., Eparvier, F., Fillingim, M., Holsclaw, G., Khalil, M., Lillis, R., Lootah, F., Mahmoud, S., Plummer, T., Soto, E., Tennyson, J., Thiemann, E., and Yurchenko, S. N.

Abstract

The Emirates Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM) Hope probe images Mars at wavelengths extending from approximately 100 to 170 nm. EMUS observations began in February 2021 and cover over a full Mars year. We report the first limb scan observations at Mars of ultraviolet emissions Ar I 106.6 nm, N I 120 nm, and carbon monoxide (CO) Fourth Positive Group (A− X) band system excited by electron impact on CO. We use EMUS limb scan observations to retrieve number density profiles of argon, molecular nitrogen, atomic oxygen, and CO in the upper atmosphere of Mars from 130 to 160 km. CO is a sensitive tracer of the thermal profile and winds in Mars' middle atmosphere and the chemistry that balances CO2in the atmosphere of Mars. EMUS insertion orbit special observations demonstrate that far ultraviolet limb measurements of the Martian thermosphere can be spectroscopically analyzed with a robust retrieval algorithm to further quantify variations of CO composition in the Martian upper atmosphere. This study focuses on satellite observations of ultraviolet light by the Emirates Mars Ultraviolet Spectrometer onboard the Emirates Mars Mission. The observed ultraviolet light is generated by argon, oxygen, nitrogen, and carbon monoxide and is used to determine the abundance of these gases in the upper atmosphere of Mars (130–160 km). We present the first remotely sensed measurements of argon and carbon monoxide abundances in the upper atmosphere of Mars. Mean retrieved argon, nitrogen, and oxygen densities, respectively, are lower than general circulation model predictions and other direct measurements by 10%–15%, ∼75%, and 35%–55%. Carbon monoxide densities measured for the first time agree qualitatively with measurements by other instruments and model predictions for similar conditions. We demonstrate that ultraviolet observations can be analyzed with a robust technique to further quantify variations of carbon monoxide abundance in the Martian upper atmosphere. Remotely sensed CO densities retrieved from 130 to 160 km for the first time are ∼45% lower than MCD 6.1 predictions for similar conditionsMean retrieved Ar, N2, and O densities from 130 to 160 km are lower than MCD 6.1 and NGIMS by 10%–15%, ∼75%, and 35%–45%, respectivelyHigh spectral resolution observations by EMM EMUS show the first detection of C I 119.3 nm emission blended with N I 120 nm emission Remotely sensed CO densities retrieved from 130 to 160 km for the first time are ∼45% lower than MCD 6.1 predictions for similar conditions Mean retrieved Ar, N2, and O densities from 130 to 160 km are lower than MCD 6.1 and NGIMS by 10%–15%, ∼75%, and 35%–45%, respectively High spectral resolution observations by EMM EMUS show the first detection of C I 119.3 nm emission blended with N I 120 nm emission

Published
2024
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19. Loss of the Martian atmosphere to space: Present-day loss rates determined from MAVEN observations and integrated loss through time

Author

Jakosky, B.M., primary, Brain, D., additional, Chaffin, M., additional, Curry, S., additional, Deighan, J., additional, Grebowsky, J., additional, Halekas, J., additional, Leblanc, F., additional, Lillis, R., additional, Luhmann, J.G., additional, Andersson, L., additional, Andre, N., additional, Andrews, D., additional, Baird, D., additional, Baker, D., additional, Bell, J., additional, Benna, M., additional, Bhattacharyya, D., additional, Bougher, S., additional, Bowers, C., additional, Chamberlin, P., additional, Chaufray, J.-Y., additional, Clarke, J., additional, Collinson, G., additional, Combi, M., additional, Connerney, J., additional, Connour, K., additional, Correira, J., additional, Crabb, K., additional, Crary, F., additional, Cravens, T., additional, Crismani, M., additional, Delory, G., additional, Dewey, R., additional, DiBraccio, G., additional, Dong, C., additional, Dong, Y., additional, Dunn, P., additional, Egan, H., additional, Elrod, M., additional, England, S., additional, Eparvier, F., additional, Ergun, R., additional, Eriksson, A., additional, Esman, T., additional, Espley, J., additional, Evans, S., additional, Fallows, K., additional, Fang, X., additional, Fillingim, M., additional, Flynn, C., additional, Fogle, A., additional, Fowler, C., additional, Fox, J., additional, Fujimoto, M., additional, Garnier, P., additional, Girazian, Z., additional, Groeller, H., additional, Gruesbeck, J., additional, Hamil, O., additional, Hanley, K.G., additional, Hara, T., additional, Harada, Y., additional, Hermann, J., additional, Holmberg, M., additional, Holsclaw, G., additional, Houston, S., additional, Inui, S., additional, Jain, S., additional, Jolitz, R., additional, Kotova, A., additional, Kuroda, T., additional, Larson, D., additional, Lee, Y., additional, Lee, C., additional, Lefevre, F., additional, Lentz, C., additional, Lo, D., additional, Lugo, R., additional, Ma, Y.-J., additional, Mahaffy, P., additional, Marquette, M.L., additional, Matsumoto, Y., additional, Mayyasi, M., additional, Mazelle, C., additional, McClintock, W., additional, McFadden, J., additional, Medvedev, A., additional, Mendillo, M., additional, Meziane, K., additional, Milby, Z., additional, Mitchell, D., additional, Modolo, R., additional, Montmessin, F., additional, Nagy, A., additional, Nakagawa, H., additional, Narvaez, C., additional, Olsen, K., additional, Pawlowski, D., additional, Peterson, W., additional, Rahmati, A., additional, Roeten, K., additional, Romanelli, N., additional, Ruhunusiri, S., additional, Russell, C., additional, Sakai, S., additional, Schneider, N., additional, Seki, K., additional, Sharrar, R., additional, Shaver, S., additional, Siskind, D.E., additional, Slipski, M., additional, Soobiah, Y., additional, Steckiewicz, M., additional, Stevens, M.H., additional, Stewart, I., additional, Stiepen, A., additional, Stone, S., additional, Tenishev, V., additional, Terada, N., additional, Terada, K., additional, Thiemann, E., additional, Tolson, R., additional, Toth, G., additional, Trovato, J., additional, Vogt, M., additional, Weber, T., additional, Withers, P., additional, Xu, S., additional, Yelle, R., additional, Yiğit, E., additional, and Zurek, R., additional

Published
2018
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20. Martian Thermospheric Response to an X8.2 Solar Flare on 10 September 2017 as Seen by MAVEN/IUVS

Author

Jain, S. K., primary, Deighan, J., additional, Schneider, N. M., additional, Stewart, A. I. F., additional, Evans, J. S., additional, Thiemann, E. M. B., additional, Chaffin, M. S., additional, Crismani, M., additional, Stevens, M. H., additional, Elrod, M. K., additional, Stiepen, A., additional, McClintock, W. E., additional, Lo, D. Y., additional, Clarke, J. T., additional, Eparvier, F. G., additional, Lefévre, F., additional, Montmessin, F., additional, Holsclaw, G. M., additional, Chamberlin, P. C., additional, and Jakosky, B. M., additional

Published
2018
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21. Global Aurora on Mars During the September 2017 Space Weather Event

Author

Schneider, N. M., primary, Jain, S. K., additional, Deighan, J., additional, Nasr, C. R., additional, Brain, D. A., additional, Larson, D., additional, Lillis, R., additional, Rahmati, Ali, additional, Halekas, J. S., additional, Lee, C. O., additional, Chaffin, M. S., additional, Stiepen, A., additional, Crismani, M., additional, Evans, J. S., additional, Stevens, M. H., additional, Lo, D. Y., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Yelle, R. V., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Lefevre, F., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2018
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22. Mars H Escape Rates Derived From MAVEN/IUVS Lyman Alpha Brightness Measurements and Their Dependence on Model Assumptions

Author

Chaffin, M. S., primary, Chaufray, J. Y., additional, Deighan, J., additional, Schneider, N. M., additional, Mayyasi, M., additional, Clarke, J. T., additional, Thiemann, E., additional, Jain, S. K., additional, Crismani, M. M. J., additional, Stiepen, A., additional, Eparvier, F. G., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Holsclaw, G. M., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2018
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26. Martian mesospheric cloud observations by IUVS on MAVEN: Thermal tides coupled to the upper atmosphere

Author

Stevens, M. H., primary, Siskind, D. E., additional, Evans, J. S., additional, Jain, S. K., additional, Schneider, N. M., additional, Deighan, J., additional, Stewart, A. I. F., additional, Crismani, M., additional, Stiepen, A., additional, Chaffin, M. S., additional, McClintock, W. E., additional, Holsclaw, G. M., additional, Lefèvre, F., additional, Lo, D. Y., additional, Clarke, J. T., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2017
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27. Detection of a persistent meteoric metal layer in the Martian atmosphere

Author

Crismani, M. M. J., primary, Schneider, N. M., additional, Plane, J. M. C., additional, Evans, J. S., additional, Jain, S. K., additional, Chaffin, M. S., additional, Carrillo-Sanchez, J. D., additional, Deighan, J. I., additional, Yelle, R. V., additional, Stewart, A. I. F., additional, McClintock, W., additional, Clarke, J., additional, Holsclaw, G. M., additional, Stiepen, A., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2017
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28. Nitric oxide nightglow and Martian mesospheric circulation from MAVEN/IUVS observations and LMD‐MGCM predictions

Author

Stiepen, A., primary, Jain, S. K., additional, Schneider, N. M., additional, Deighan, J. I., additional, González‐Galindo, F., additional, Gérard, J.‐C., additional, Milby, Z., additional, Stevens, M. H., additional, Bougher, S., additional, Evans, J. S., additional, Stewart, A. I. F., additional, Chaffin, M. S., additional, Crismani, M., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Montmessin, F., additional, Lefèvre, F., additional, Forget, F., additional, Lo, D. Y., additional, Hubert, B., additional, and Jakosky, B. M., additional

Published
2017
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29. Variability of D and H in the Martian upper atmosphere observed with the MAVEN IUVS echelle channel

Author

Clarke, J. T., primary, Mayyasi, M., additional, Bhattacharyya, D., additional, Schneider, N. M., additional, McClintock, W. E., additional, Deighan, J. I., additional, Stewart, A. I. F., additional, Chaufray, J.‐Y., additional, Chaffin, M. S., additional, Jain, S. K., additional, Stiepen, A., additional, Crismani, M., additional, Holsclaw, G. M., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2017
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31. Study of the cold oxygen corona with IUVS/MAVEN

Author

Chaufray, Jean-Yves, Deighan, Justin, Chaffin, M., Schneider, N., McClintock, B., Stewart, I., Holsclaw, G., Clarke, J., Jakosky, B., 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), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Boston University [Boston] (BU), and Cardon, Catherine

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Physics::Space Physics, [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], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.PHYS.PHYS-AO-PH] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Physics::Atmospheric and Oceanic Physics
Abstract

International audience; The Mars Atmosphere and Volatile Evolution Mission (MAVEN) has observed the Martian upper atmosphere for several months. The Imaging Ultraviolet Spectrograph (IUVS) is able to measure the resonance line of the atomic oxygen at 130.4 nm. From this emission we are able to derive information of the oxygen content in the Martian upper atmosphere and its variability. Atomic oxygen is a key species to better understand the chemistry, heating, dynamics and escape of the Martian upper atmosphere.

Published
2015

32. UV Study of the Fourth Positive Band System of CO and O i 135.6 nm From Electron Impact on CO and CO2.

Author

Ajello, J. M., Malone, C. P., Evans, J. S., Holsclaw, G. M., Hoskins, A. C., Jain, S. K., McClintock, W. E., Liu, X., Veibell, V., Deighan, J., Gérard, J.‐C., Lo, D. Y., and Schneider, N.

Subjects
ELECTRONIC excitation, NANOPARTICLES, CARBON dioxide, CARBON compounds, PHOTOLUMINESCENCE, LUMINESCENCE
Abstract

We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A1Π → X1Σ+) of CO and the optically forbidden O (5So → 3P) 135.6 nm atomic transition by electron‐impact‐induced‐fluorescence of CO and CO2. We present a model excitation cross section from threshold to high energy for the A1Π state, including cascade by electron impact on CO. The A1Π state is perturbed by triplet states leading to an extended FUV glow from electron excitation of CO. We derive a model FUV spectrum of the 4PG band system from dissociative excitation of CO2, an important process observed on Mars and Venus. Our unique experimental setup consists of a large vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging Ultraviolet Spectrograph optical engineering unit, operating in the FUV (110–170 nm). The determination of the total O i (5So) at 135.6 nm emission cross section is accomplished by measuring the cylindrical glow pattern of the metastable emission from electron impact by imaging the glow intensity about the electron beam from nominally zero to ~400 mm distance from the electron beam. The study of the glow pattern of O i (135.6 nm) from dissociative excitation of CO and CO2 indicates that the O i (5So) state has a kinetic energy of ~1 eV by modeling the radial glow pattern with the published lifetime of 180 μs for the O i (5So) state. Plain Language Summary: Both Mars and Venus have upper atmospheres that are similar in composition: mostly CO2, CO, and N2 are dominant molecular gases, with nearly identical UV spectra. The modeling studies of atmospheric UV emissions cannot presently be accurately conducted to the same accuracy as the planetary UV measurements, which avail themselves with state‐of‐the‐art calibrated spectrographs. This dichotomy in accuracy between planetary observation and model occurs because the atomic and molecular emission cross sections with uncertainties of certain transitions are greater than 100%. Furthermore, the analysis is complicated by the spectral blending of the various emissions of the low‐resolution spectral spaceborne instruments. We present in this paper a UV laboratory instrument unique in the world at the University of Colorado that can measure for the first time the excitation mechanisms with accurate emission cross sections of both allowed and optically forbidden transitions that are occurring in a planetary atmosphere. Key Points: We measured 30 and 100 eV emission cross sections of Fourth Positive band system of CO and O i (135.6 nm) from electron impact on CO and CO2We conducted a laboratory experiment measuring single‐scattering electron‐impact‐induced‐fluorescence FUV spectra from excitation of CO and CO2Fragment kinetic energy measurement for O i (5So) atoms found to be around ~1 eV from both CO and CO2 molecular dissociation [ABSTRACT FROM AUTHOR]

Published
2019
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34. UV Study of the Fourth Positive Band System of CO and O i135.6 nm From Electron Impact on CO and CO2

Author

Ajello, J. M., Malone, C. P., Evans, J. S., Holsclaw, G. M., Hoskins, A. C., Jain, S. K., McClintock, W. E., Liu, X., Veibell, V., Deighan, J., Gérard, J.‐C., Lo, D. Y., and Schneider, N.

Abstract

We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A1Π → X1Σ+) of CO and the optically forbidden O (5So→ 3P) 135.6 nm atomic transition by electron‐impact‐induced‐fluorescence of CO and CO2. We present a model excitation cross section from threshold to high energy for the A1Π state, including cascade by electron impact on CO. The A1Π state is perturbed by triplet states leading to an extended FUV glow from electron excitation of CO. We derive a model FUV spectrum of the 4PG band system from dissociative excitation of CO2, an important process observed on Mars and Venus. Our unique experimental setup consists of a large vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging Ultraviolet Spectrograph optical engineering unit, operating in the FUV (110–170 nm). The determination of the total O i(5So) at 135.6 nm emission cross section is accomplished by measuring the cylindrical glow pattern of the metastable emission from electron impact by imaging the glow intensity about the electron beam from nominally zero to ~400 mm distance from the electron beam. The study of the glow pattern of O i(135.6 nm) from dissociative excitation of CO and CO2indicates that the O i(5So) state has a kinetic energy of ~1 eV by modeling the radial glow pattern with the published lifetime of 180 μs for the O i(5So) state. Both Mars and Venus have upper atmospheres that are similar in composition: mostly CO2, CO, and N2are dominant molecular gases, with nearly identical UV spectra. The modeling studies of atmospheric UV emissions cannot presently be accurately conducted to the same accuracy as the planetary UV measurements, which avail themselves with state‐of‐the‐art calibrated spectrographs. This dichotomy in accuracy between planetary observation and model occurs because the atomic and molecular emission cross sections with uncertainties of certain transitions are greater than 100%. Furthermore, the analysis is complicated by the spectral blending of the various emissions of the low‐resolution spectral spaceborne instruments. We present in this paper a UV laboratory instrument unique in the world at the University of Colorado that can measure for the first time the excitation mechanisms with accurate emission cross sections of both allowed and optically forbidden transitions that are occurring in a planetary atmosphere. We measured 30 and 100 eV emission cross sections of Fourth Positive band system of CO and O i(135.6 nm) from electron impact on CO and CO2We conducted a laboratory experiment measuring single‐scattering electron‐impact‐induced‐fluorescence FUV spectra from excitation of CO and CO2Fragment kinetic energy measurement for O i(5So) atoms found to be around ~1 eV from both CO and CO2molecular dissociation

Published
2019
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36. Global classification of MESSENGER spectral reflectance data and lab spectra comparison

Author

D'Amore, Mario, Helbert, Jörn, Maturilli, Alessandro, Head, J.W., Sprague, A. L., Izenberg, N. R., Holsclaw, G. M., McClintock, W. E., Vilas, F., and Solomon, S.C.

Subjects
MESSENGER Mercury, Experimentelle Planetenphysik
Abstract

The MESSENGER spacecraft continues to provide new data that change our views on the nature of Mercury’s surface. Assuming that surface composition can be derived from spectral reflectance measurements with the use of statistical techniques, we have employed unsupervised hierarchical clustering analyses to identify spectral units from MESSENGER’s Mercury Atmospheric and Surface Composition Spectrometer (MASCS) observations. To retrieve the number and spectral shapes of the different components present in the dataset, we collected all MASCS observations to date (> 1.5 milion spectra). Because there are no photometric corrections for MASCS available yet, the data were normalized to the reflectance level at 700 nm, yielding a ratio nearly independent of incidence and emission angles. Independent tests on laboratory data show that this approach is effective in reducing phase angle variations. The data were then interpolated to a fixed spatial grid, averaging the sub-pixel spectra. The product is a map of reflectance ratio, along with error and frequency maps to address potential error in the process and to assess reliability. This is the first global geographically registered cube-image of averaged MASCS spectra. We produced a spatial grid resolution between 4 pixels per degree (ppd) for global analyses and 0.5 ppd for regional studies. The unsupervised hierarchical clustering of the global MASCS cube-image produces a tree of data partition, starting from two mega-regions. The first mega-region (MR1) comprises equatorial to mid-latitudes and the second (MR2) the two poles. The boundaries of MR2 at high northern latitudes approximate those of the volcanic northern plains. MR2 areas show redder MASCS spectra than do MR1 areas. The spectral units show some correlation with surface units mapped by visible image acquired by MESSENGER and documented the presence of distinct spectral units on Mercury, as characterized by MASCS observations.Moreover, it seems to closely match some Gamma Ray Spectrometer elemental abudances results and global distribution of pyroclastic geological features. Following iteration produces finer separation of the surface in smaller regions. Each region average spectra is compared with reflectance spectra collected at the Berlin PEL laboratory. Here the angular dependency is treated as in the MASCS data, via normalization at 700nm. This allow us to start a geological and geochemical interpretations of MASCS observations. The materials selected aim to explore the analogs for Hollow-Forming Material on Mercury theory in : a komatiitic substrate with superimposed sulfides layer, due flotation in melted lava during volcanic eruption. We used komatiite spectra from PEL sample collection and various Mg-, Ca- and Mn- bearing sulfides. both at low and high temperature to explore the thermal schok effect on sulfide volatilization and on komatiitic substrate.

Published
2012

37. Probing the Martian atmosphere with MAVEN/IUVS stellar occultations

Author

Gröller, H., primary, Yelle, R. V., additional, Koskinen, T. T., additional, Montmessin, F., additional, Lacombe, G., additional, Schneider, N. M., additional, Deighan, J., additional, Stewart, A. I. F., additional, Jain, S. K., additional, Chaffin, M. S., additional, Crismani, M. M. J., additional, Stiepen, A., additional, Lefèvre, F., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Mahaffy, P. R., additional, Bougher, S. W., additional, and Jakosky, B. M., additional

Published
2015
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38. The structure and variability of Mars upper atmosphere as seen in MAVEN/IUVS dayglow observations

Author

Jain, S. K., primary, Stewart, A. I. F., additional, Schneider, N. M., additional, Deighan, J., additional, Stiepen, A., additional, Evans, J. S., additional, Stevens, M. H., additional, Chaffin, M. S., additional, Crismani, M., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Lo, D. Y., additional, Lefèvre, F., additional, Montmessin, F., additional, Thiemann, E. M. B., additional, Eparvier, F., additional, and Jakosky, B. M., additional

Published
2015
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39. Retrieval of CO2 and N2 in the Martian thermosphere using dayglow observations by IUVS on MAVEN

Author

Evans, J. S., primary, Stevens, M. H., additional, Lumpe, J. D., additional, Schneider, N. M., additional, Stewart, A. I. F., additional, Deighan, J., additional, Jain, S. K., additional, Chaffin, M. S., additional, Crismani, M., additional, Stiepen, A., additional, McClintock, W. E., additional, Holsclaw, G. M., additional, Lefèvre, F., additional, Lo, D. Y., additional, Clarke, J. T., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, Chamberlin, P. C., additional, Bougher, S. W., additional, Bell, J. M., additional, and Jakosky, B. M., additional

Published
2015
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40. Three‐dimensional structure in the Mars H corona revealed by IUVS on MAVEN

Author

Chaffin, M. S., primary, Chaufray, J. Y., additional, Deighan, J., additional, Schneider, N. M., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Thiemann, E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Jain, S. K., additional, Crismani, M. M. J., additional, Stiepen, A., additional, Montmessin, F., additional, Eparvier, F. G., additional, Chamberlain, P. C., additional, and Jakosky, B. M., additional

Published
2015
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41. Study of the Martian cold oxygen corona from the O I 130.4 nm by IUVS/MAVEN

Author

Chaufray, J. Y., primary, Deighan, J., additional, Chaffin, M. S., additional, Schneider, N. M., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Jain, S. K., additional, Crismani, M., additional, Stiepen, A., additional, Holsclaw, G. M., additional, Clarke, J. T., additional, Montmessin, F., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, Chamberlin, P. C., additional, and Jakosky, B. M., additional

Published
2015
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42. New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

Author

Stevens, M. H., primary, Evans, J. S., additional, Schneider, N. M., additional, Stewart, A. I. F., additional, Deighan, J., additional, Jain, S. K., additional, Crismani, M., additional, Stiepen, A., additional, Chaffin, M. S., additional, McClintock, W. E., additional, Holsclaw, G. M., additional, Lefèvre, F., additional, Lo, D. Y., additional, Clarke, J. T., additional, Montmessin, F., additional, Bougher, S. W., additional, and Jakosky, B. M., additional

Published
2015
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43. MAVEN IUVS observation of the hot oxygen corona at Mars

Author

Deighan, J., primary, Chaffin, M. S., additional, Chaufray, J.‐Y., additional, Stewart, A. I. F., additional, Schneider, N. M., additional, Jain, S. K., additional, Stiepen, A., additional, Crismani, M., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Montmessin, F., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, Chamberlin, P. C., additional, and Jakosky, B. M., additional

Published
2015
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44. MAVEN IUVS observations of the aftermath of the Comet Siding Spring meteor shower on Mars

Author

Schneider, N. M., primary, Deighan, J. I., additional, Stewart, A. I. F., additional, McClintock, W. E., additional, Jain, S. K., additional, Chaffin, M. S., additional, Stiepen, A., additional, Crismani, M., additional, Plane, J. M. C., additional, Carrillo‐Sánchez, J. D., additional, Evans, J. S., additional, Stevens, M. H., additional, Yelle, R. V., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2015
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47. Electron impact study of the 100 eV emission cross section and lifetime of the Lyman‐Birge‐Hopfield band system of N2: Direct excitation and cascade

Author

Ajello, J. M., Malone, C. P., Holsclaw, G. M., Hoskins, A. C., Eastes, R. W., McClintock, W. E., and Johnson, P. V.

Abstract

We have measured the 100 eV emission cross section of the optically forbidden Lyman‐Birge‐Hopfield (LBH) band system (a1Πg→ X1Σ+g) of N2by electron‐impact‐induced fluorescence. Using a large (1.5 m diameter) vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN mission Imaging Ultraviolet Spectrograph optical engineering model, we have obtained calibrated spectral measurements of the LBH band system from 115 to 175 nm over a range of lines of sight to capture all of the optical emissions. These measurements represent the first experiment to directly isolate in the laboratory single‐scattering electron‐impact‐induced fluorescence from both direct excitation of the a1Πgstate and cascading contributions to the a1Πgstate (a′1Σ−uand w1Δu→ a1Πg→ X1Σ+g). The determination of the total LBH emission cross section is accomplished by measuring the entire cylindrical glow pattern of the metastable emission from electron impact by imaging lines of sight that measure the glow intensity from zero to ~400 mm radial distance and calculating the ratio of the integrated intensity from the LBH glow pattern to that of a simultaneously observed optically allowed transition with a well‐established cross section: Ni120.0 nm. The “direct” emission cross section of the a1Πgstate at 100 eV was determined to be σemdir= (6.41 ± 1.3) × 10−18cm2. An important observation from the glow pattern behavior is that the total (direct + cascading) emission cross section is pressure dependent due to collision‐induced cascade transitions between close‐lying electronic states. Measured 100 eV total emission cross section of the optically forbidden Lyman‐Birge‐Hopfield (LBH) band system of N2by electron‐impact‐induced fluorescenceLaboratory experiment isolating single‐scattering electron‐impact‐induced fluorescence from direct excitation and cascading contributions to the a1Πgstate of N2Lifetime for the optically forbidden a1Πgstate is found to be ~50 ± 15 μs

Published
2017
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50. Retrieval of CO2and N2in the Martian thermosphere using dayglow observations by IUVS on MAVEN

Author

Evans, J. S., Stevens, M. H., Lumpe, J. D., Schneider, N. M., Stewart, A. I. F., Deighan, J., Jain, S. K., Chaffin, M. S., Crismani, M., Stiepen, A., McClintock, W. E., Holsclaw, G. M., Lefèvre, F., Lo, D. Y., Clarke, J. T., Eparvier, F. G., Thiemann, E. M. B., Chamberlin, P. C., Bougher, S. W., Bell, J. M., and Jakosky, B. M.

Abstract

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 CO2densities to derive temperature variability between 170 and 220 km. Analysis of the data shows (1) low‐mid latitude northern hemisphere CO2densities at 170 km vary by a factor of about 2.5, (2) on average, the N2/CO2increases 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. Retrieved CO2densities at 170 km vary by a factor of about 2.5On average, N2/CO2increases from 4% at 130 km to 12% at 200 kmMean Martian upper atmospheric temperature over the sampled time frame is 324 {±} 22 K

Published
2015
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