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Mars' dayside ionosphere is maintained primarily by ionization from solar ultraviolet photons and subsequent chemical reactions, with small contributions from other mechanisms such as impact ionization and charge exchange. In December 2023, the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission observed the impact of an interplanetary coronal mass ejection (ICME) on Mars' ionosphere, including strongly enhanced fluxes of suprathermal electrons. We show that this enhancement in suprathermal electron fluxes increased ion production from electron impact, so that dayside electron impact ionization rates exceeded photoionization rates during the ICME. This change in ion production mechanisms led to unusually high densities of the minor ions C+ ${\mathrm{C}}^{+}$ and O++ ${\mathrm{O}}^{++}$. Space weather events are known to increase ion escape rates, so changes in ion composition during space weather events have important implications for atmospheric evolution. We show that scaling nominal loss rates to account for space weather may underestimate carbon loss from Mars' atmosphere. Plain Language Summary: Dayside planetary ionospheres are primarily produced through interactions between atmospheric neutral gases and sunlight. Impact by energetic particles, especially electrons, typically only contributes a small amount of plasma. We observed unusually high densities of the minor ions C+ ${\mathrm{C}}^{+}$ and O++ ${\mathrm{O}}^{++}$ in Mars' ionosphere during a space weather event in December 2023, when a large bubble of magnetized plasma launched from the Sun impacted the planet. This plasma bubble compressed the Mars magnetosheath, pushing suprathermal electrons to lower altitudes, where they impacted the atmosphere and significantly increased plasma production through impact ionization. Changes in the production mechanisms of the ionosphere during space weather events lead to changes in its density and composition. This is important because space weather events are known to increase the amount of atmospheric gas escaping from a planet, which can have important implications for how the atmosphere evolves over millions of years. Key Points: Unexpected increases in C+ and rarely detected O++ densities were observed during the December 2023 space weather event at MarsThese ions were produced by electron impact ionization from the intense electron fluxes associated with the space weather eventElectron impact ionization exceeded photoionization during the event, which temporarily altered the composition of ions escaping Mars [ABSTRACT FROM AUTHOR]

With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform (www.spedas.org), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have "crib-sheets," user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer's Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its "modes of use" with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans.Electronic supplementary materialThe online version of this article (10.1007/s11214-018-0576-4) contains supplementary material, which is available to authorized users.

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]

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]

Craters on Mars are a window into Mars' past and the time they were emplaced. Because the crust is heated and shocked during impact, craters can demagnetize or magnetize the crust depending on the presence or absence of a dynamo field at the time of impact. This concept has been used to constrain dynamo timing. Here, we investigate magnetic anomalies associated with craters larger than 150 km. We find that most of those craters, independent of age, exhibit demagnetization signatures in the form of a central magnetic low. We demonstrate a statistically significant association between such signatures and craters, and hypothesize that the excavation of strongly magnetic crustal material may be an important contribution to the dominance of demagnetized craters. This finding implies that the simple presence or absence of crater demagnetization signatures is not a reliable indicator for the activity of the Martian dynamo during or after crater formation. Plain Language Summary: Craters on Mars allow studying the time at which they were emplaced and as such they are a window into Mars' past. Because the crust is heated and shocked during impact and thus recrystallization occurs, craters can demagnetize or magnetize the crust depending on the presence or absence of a dynamo field at the time of impact. A classic magnetization signature is expressed by a magnetic high in the crater interior and the youngest of those craters have been used to constrain dynamo timing. Here, we investigate magnetic anomalies associated with all craters larger than 150 km. We find that most of those craters and independent of age exhibit a demagnetization signature, and fewer a magnetization signature. In general, the largest craters show a demagnetization signature. To explain the dominance of demagnetization signatures we hypothesize that the excavation of strongly magnetic crustal material may be an important process. This finding implies that the simple presence or absence of crater magnetization signatures is not a reliable indicator for dynamo activity and magnetic signatures of craters are dependent on multiple parameters such as crustal thickness. Key Points: Craters on Mars dominantly show demagnetization signaturesLarge craters and thin crust promote magnetic lows in the crater interior irrespective of dynamo activityCrustal excavation is likely an important process that promotes demagnetization signatures [ABSTRACT FROM AUTHOR]

Mars discrete aurorae are caused by accelerated electrons precipitating into the atmosphere and interacting with species such as atomic oxygen. However, the energy of the electrons causing these aurorae remains currently unclear: no simultaneous and concurrent measurements of electron analyzers and spectrometers have been performed so far, preventing from assessing the exact energy of the downgoing auroral electrons. Several auroral emissions have been observed so far on Mars, among which are two oxygen emissions in the far ultraviolet at 130.4 and 135.6 nm. In this study, we simulate the vertical distribution of these auroral oxygen emissions with an electron transport calculation coupled with a radiative transfer model to account for the optical thickness of the atmosphere for the 130.4‐nm triplet. We show that the brightness ratio of these oxygen emissions is independent of the downward electron energy flux and only slightly depends on the atomic oxygen atmospheric composition. In contrast, the brightness ratio is strongly related to the initial energy of the auroral electrons. Measuring the brightness ratio is therefore a unique tool to remotely estimate the energy of the electrons causing the Mars discrete aurorae. We compare our model results with observations from the Emirates Mars Ultraviolet Spectrometer on board the Emirates Mars Mission and find that electrons with typical energies of 250–300 eV are compatible with the observed ratio of 5. Plain Language Summary: Aurorae have been observed on the nightside of Mars. They are caused by energetic electrons that interact with the constituents of the Mars atmosphere. However, since no direct measurement has been performed during auroral events, the energy of these auroral electrons remains currently unclear. In this study, we simulate the brightnesses of two auroral emissions of atomic oxygen in the far ultraviolet as if they were seen from an orbiter. We use a photochemical model as well as an electron transport model and a radiative transfer model. We demonstrate that the brightness of these emissions strongly depends on the initial energy of the auroral electrons and their flux. In contrast, the ratio of the brightness of the emissions is independent on the flux and therefore represents a unique tool to remotely estimate the energy of the electrons causing the Mars discrete aurorae. We compare our model results with observations from the Emirates Mars Ultraviolet Spectrometer on board the Emirates Mars Mission and find that electrons with energies of 250–300 eV are responsible for the observed ratio of 5. Key Points: The 130.4 optically thick and the 135.6 nm optically thin oxygen emissions can be observed during a Mars auroral eventRadiative transfer effects increase the observed nadir brightness of the 130.4‐nm emissionBrightnesses of both emissions depends on O density, initial electron energy and flux, while their ratio depends on the electron energy [ABSTRACT FROM AUTHOR]