Early observations from the Perseverance rover suggested a deltaic origin for the western fan of Jezero crater only from images of the Kodiak butte. Here, we use images from the SuperCam Remote Micro-Imager and the Mastcam-Z camera to analyze the western fan front along the rover traverse, and further assess its depositional origin. Outcrops in the middle to lower half of hillslopes are composed of planar, inclined beds of sandstone that are interpreted as foresets of deltaic deposits. Foresets are locally structured in ~20-25 m thick, ~80-100 m long, antiformal structures interpreted as deltaic mouth bars. Above these foresets are observed interbedded sandstones and boulder conglomerates, interpreted as fluvial topset beds. One well-preserved lens of boulder conglomerate displays rounded clasts within well-sorted sediment deposited in fining upward beds. We interpret these deposits as resulting from lateral accretion within fluvial channels. Estimations of peak discharge rates give a range between ~100 and ~500 m3.s-1 consistent with moderate to high floods. By contrast, boulder conglomerates exposed in the uppermost part of hillslopes are poorly sorted and truncate underlying beds. The presence of these boulder deposits suggests that intense, sediment-laden flood episodes occurred after the deltaic foreset and topset beds were deposited, although the origin, timing, and relationship of these boulder deposits to the ancient lake that once filled Jezero crater remains undetermined. Overall, these observations confirm the deltaic nature of the fan front, and suggest a highly variable fluvial input.

High-resolution 2D and 3D data remotely acquired by SuperCam's Remote Micro-Imager and Mastcam-Z aboard the Perseverance rover enabled us to characterize the stratigraphic architecture and sedimentary record of the Kodiak butte, an isolated remnant of the western delta fan of Jezero crater. Using these data, we build up on previous interpretations of the butte interpreted as a prograding Gilbert-type deltaic series. We characterize three individual stratigraphic Units 0 to 2 on the eastern and northern faces of the butte. Each Unit displays the same vertical succession of prodeltaic/lacustrine bottomsets, delta slope toesets and foresets, and fluvially influenced topsets of a deltaic plain with a braided river pattern, shown by 11 individual sedimentary facies. We infer that these individual Units record the formation of three distinct deltaic mouth bars successively across time and space. For the first time on another planet than Earth, we are able to construct a precise sequence stratigraphic framework to highlight lake-level fluctuations at the time the Kodiak butte was emplaced, during the latest stages of deltaic activity. We identify four hydrogeological cycles indicated by alternating rises and falls of the lake-level on the order of 5-10 m. These were most probably linked to climatic events and variations controlling lake water inputs in probable relation to an astronomical control. Kodiak butte is an isolated remnant of the main western sedimentary fan of Jezero crater. It displays the characteristic structures of a Gilbert-type delta, a structure that shows deposition of fluvial material into a standing body of water, here interpreted to be a lake within Jezero crater. 11 individual sedimentary facies (textures, grain-sizes, and structures) of the rocks exposed at Kodiak suggest that the depositional environments ranged from the fluvial plain to a steep subaqueous slope and into the bottom of the shallow Jezero lake. Our observations further show that Kodiak butte is organized into three distinct stratigraphic Units (0-2), each displaying the same vertical succession of bottomsets, toesets, foresets and topsets. This architecture is interpreted as reflecting three distinct deltaic packages, formed consecutively and not at the same time. Using these facies and stratigraphic architecture data, we are able for the first time on another planet than Earth, to precisely construct a sequence stratigraphic framework for the formation of Kodiak. This framework illustrates with unprecedented precision successive episodes of rises and falls of the paleo-lake-level (in the order of 5-10 m) involved in the construction and evolution of the western Jezero delta. New observations on the Kodiak delta remnant were carried out to characterize its detailed facies and stratigraphic architecture Three deltaic mouth bars are identified showing 4D succession of depositional settings ranging from deltaic plain to slope to shallow lake The first ever sequence stratigraphic framework on Mars shows four cycles of alternating rises and falls of the lake-level within 5-10 m

The recent discoveries of telluric exoplanets in the habitable zone of different stars have led to questioning the nature of their atmosphere, which is required to determine their habitability. Atmospheric escape is one of the challenging problems to be solved: simply adapting what is currently observed in the solar system is doomed to fail due to the large variations in the conditions encountered around other stars. A better strategy is to review the different processes that shaped planetary atmospheres and to evaluate their importance depending upon the stellar conditions. This approach allowed us to show that processes like ion-pickup were a more important way to lose atmosphere at Mars in the past. We reviewed the different escape mechanisms and their magnitude in function of the different conditions. This led us to discover discrepancies in the current literature concerning problems such as the Xenon paradox or the importance of a magnetic field in protecting an atmosphere. This shows that one should be very careful before claiming the presence of an atmosphere on planets in the habitable zone of their M-dwarfs: new criteria such as the Alfven surface location with respect to the planet should be taken into account a-priori. Overall, the habitability of a planet should not be claimed only on by its location in the habitable zone but also after careful analysis of the interaction between its atmosphere and its parent star [Gronoff et al. 2020]. Gronoff, G., Arras, P., Baraka, S., Bell, J. M., Cessateur, G., Cohen, O., et al. ( 2020). Atmospheric Escape Processes and Planetary Atmospheric Evolution. Journal of Geophysical Research: Space Physics, 125, e2019JA027639. https://doi.org/10.1029/2019JA027639

The Geospace Dynamics Constellation (GDC) is NASA's next strategic Living With a Star mission. GDC's goals are: 1) Understand how the high-latitude ionosphere-thermosphere system responds to variable solar wind/magnetosphere forcing; and 2) Understand how internal processes in the global ionosphere-thermosphere system redistribute mass, momentum, and energy.Planned for launch by the end of the decade, GDC will use six identical observatories, each identically instrumented to fully characterize the magnetospheric drivers of the I-T system as well as the global response of the ionized and neutral gases. GDC will do this with a series of orbital conegurations that will enable it to study the widest range of spatial and temporal scales to date, ranging from hundreds of kilometers and several seconds to tens of minutes, and extending through the regional to the global scale.This poster presents GDC's current status, measurement capabilities, sampling scheme, and model development efforts and show how GDC will et into the larger Heliophysics ecosystem, by 1) obtaining critically needed scientiec observations; 2) providing a source for real-time space weather and situational awareness, as well as retrospective studies to further the science of space weather; 3) serving as a "strategic hub" for other space-based and ground- based efforts that want to leverage GDC to perform complementary science.

Here we present observations and simulations of oxygen particle bombardment into Titan’s thermosphere that represents a new class of upper atmospheric stimulus. We find that these large bursts of energetic oxygen ions contain sufficient energy to perturb Titan’s thermosphere, if the energy is applied at the right altitude. In this study we present Cassini observations during the T20 flyby of Titan in 2006 specifically from the Cassini Magnetospheric Imaging Instrument (MIMI; Krimigis et al. [2004]) and the Cassini Plasma Spectrometer (CAPS; Young et al. [2004]). We utilize simulations using the Titan-Global Ionosphere Thermosphere Model to assess the impact of energetic oxygen bursts similar to the one observed during T20 on the thermospheric structure. We find that energy deposited higher in Titan’s thermosphere has a much greater effect on the temperatures that Cassini would observe from the INMS instrument. These higher altitude energy deposition events are similar to those that occur from corotational oxygen and water group ions in Saturn’s magnetosphere. We find that the more energetic heavy ions tend to penetrate deeper into the thermosphere resulting in a much more benign heating rate and minimal temperature change, however when these events carry along lower energy thermal oxygen ions that will deposit energy at higher altitudes the temperature change can be much more substantial.

This is the first part of a two‐part paper. NASA's Mars 2020 Perseverance rover measured winds on the Jezero crater floor close to the delta of an ancient river. A mostly repeatable diurnal cycle was observed and presented two regimes: (a) a convective regime, from dawn to sunset, with average easterly to southeasterly winds, during which maximum wind speeds were measured, and (b) a nighttime regime with westerly‐northwesterly winds followed by a relatively calm period with highly variable wind directions as a function of sol and time of night. The timing and magnitude of the observed regimes are consistent with primary control by regional and local slope flows. Data suggest that the surface circulation at Jezero region in northern spring and summer is highly unaffected by large‐scale circulation except during particular periods in the diurnal cycle or generally during dust storms, which is supported by MarsWRF model simulations. Consequently, the observed seasonal variability was weak. However, sol‐to‐sol and seasonal variability were measured, most of it during certain nighttime periods. Traveling waves consistent with baroclinic instability were clearly observed in surface winds at L s ∼ 75°. The early MY36/2022A regional dust storm at L s ∼ 153° disturbed the wind patterns with changes suggesting enhanced tidal flows. After sunset, the dust storm also produced detectable gravity wave activity, increasing the mixing in the nighttime planetary boundary layer during storm conditions. Inferred wind directions from dust devil movies strongly suggest that prevailing winds continued to be slope‐driven during the late summer, fall and early winter seasons.

Wind speeds measured by the Mars 2020 Perseverance rover in Jezero crater were fitted as a Weibull distribution. InSight wind data acquired in Elysium Planitia were also used to contextualize observations. Jezero winds were found to be much calmer on average than in previous landing sites, despite the intense aeolian activity observed. However, a great influence of turbulence and wave activity was observed in the wind speed variations, thus driving the probability of reaching the highest wind speeds at Jezero, instead of sustained winds driven by local, regional, or large‐scale circulation. The power spectral density of wind speed fluctuations follows a power‐law, whose slope deviates depending on the time of day from that predicted considering homogeneous and isotropic turbulence. Daytime wave activity is related to convection cells and smaller eddies in the boundary layer, advected over the crater. The signature of convection cells was also found during dust storm conditions, when prevailing winds were consistent with a tidal drive. Nighttime fluctuations were also intense, suggesting strong mechanical turbulence. Convective vortices were usually involved in rapid wind fluctuations and extreme winds, with variations peaking at 9.2 times the background winds. Transient high wind events by vortex‐passages, turbulence, and wave activity could be driving aeolian activity at Jezero. We report the detection of a strong dust cloud of 0.75–1.5 km in length passing over the rover. The observed aeolian activity had major implications for instrumentation, with the wind sensor suffering damage throughout the mission, probably due to flying debris advected by winds.

The habitability of the surface of any planet is determined by a complex evolution of its interior, surface, and atmosphere. The electromagnetic and particle radiation of stars drive thermal, chemical and physical alteration of planetary atmospheres, including escape. Many known extrasolar planets experience vastly different stellar environments than those in our Solar system: it is crucial to understand the broad range of processes that lead to atmospheric escape and evolution under a wide range of conditions if we are to assess the habitability of worlds around other stars. One problem encountered between the planetary and the astrophysics communities is a lack of common language for describing escape processes. Each community has customary approximations that may be questioned by the other, such as the hypothesis of H-dominated thermosphere for astrophysicists, or the Sun-like nature of the stars for planetary scientists. Since exoplanets are becoming one of the main targets for the detection of life, a common set of definitions and hypotheses are required. We review the different escape mechanisms proposed for the evolution of planetary and exoplanetary atmospheres. We propose a common definition for the different escape mechanisms, and we show the important parameters to take into account when evaluating the escape at a planet in time. We show that the paradigm of the magnetic field as an atmospheric shield should be changed and that recent work on the history of Xenon in Earth's atmosphere gives an elegant explanation to its enrichment in heavier isotopes: the so-called Xenon paradox.

We present a method to quantify the upper-limit of the energy transmitted from the intense stellar wind to the upper atmospheres of three of the Trappist-1 planets (e, f, and g). We use a formalism that treats the system as two electromagnetic regions, where the efficiency of the energy transmission between one region (the stellar wind at the planetary orbits) to the other (the planetary ionospheres) depends on the relation between the conductances and impedances of the two regions. Since the energy flux of the stellar wind is very high at these planetary orbits, we find that for the case of high transmission efficiency (when the conductances and impedances are close in magnitude), the energy dissipation in the upper planetary atmospheres is also very large. On average, the Ohmic energy can reach 0.5 - 1 W/m 2, about 1% of the stellar irradiance and 5-15 times the EUV irradiance. Here, using constant values for the ionospheric conductance, we demonstrate that the stellar wind energy could potentially drive large atmospheric heating in terrestrial planets, as well as in hot jupiters. More detailed calculations are needed to assess the ionospheric conductance and to determine more accurately the amount of heating the stellar wind can drive in close-orbit planets.

The Pioneer and Voyager spacecraft made close-up measurements of Saturn's ionosphere and upper atmosphere in the 1970s and 1980s that suggested a chemical interaction between the rings and atmosphere. Exploring this interaction provides information on ring composition and the influence on Saturn's atmosphere from infalling material. The Cassini Ion Neutral Mass Spectrometer sampled in situ the region between the D ring and Saturn during the spacecraft's Grand Finale phase. We used these measurements to characterize the atmospheric structure and material influx from the rings. The atmospheric He/H2 ratio is 10 to 16%. Volatile compounds from the rings (methane; carbon monoxide and/or molecular nitrogen), as well as larger organic-bearing grains, are flowing inward at a rate of 4800 to 45,000 kilograms per second.

While Jupiter’s gravity strongly binds the neutral atmosphere to the planet, energization in the auroral region can lead to field-aligned upward transport and escape of electrons and ions. This field-aligned transport mechanism provides a way for heavier ions like H2+ and H3+ to enter Jupiter’s magnetosphere. Formation of H3+ from H2+ occurs quickly in the collisional ionosphere, so rapid field-aligned transport of H2+ is the most likely mechanism for H2+ ions present in Jupiter’s high-latitude ionosphere and magnetosphere. We model these processes using the PWOM model for ionospheric field-aligned transport and J-GITM providing the neutral atmosphere and lower ionospheric boundary. The ionosphere is formed and heated by a combination of solar EUV flux and electorn precipitaiton. The effects of energization from electron precipitation and resonant wave heating are also accounted for. We show the energy input that is needed to produce ion escape in both the fluid and kinetic regimes, and we show the formation of ion conics in the kinetic PWOM model. We discuss what observations from JUNO are needed to allow us to constrain and test our model results.

Observations of the Mars upper atmosphere made from the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft have been used to determine the loss rates of gas from the upper atmosphere to space for a complete Mars year (16 Nov 2014 - 3 Oct 2016). Loss rates for H and O are sufficient to remove similar to 2-3 kg/s to space. By itself, this loss would be significant over the history of the planet. In addition, loss rates would have been greater early in history due to the enhanced solar EUV and more-active Sun. Integrated loss, based on current processes whose escape rates in the past are adjusted according to expected solar evolution, would have been as much as 0.8 bar CO2 or 23 m global equivalent layer of H2O; these losses are likely to be lower limits due to the nature of the extrapolation of loss rates to the earliest times. Combined with the lack of surface or subsurface reservoirs for CO2 that could hold remnants of an early, thick atmosphere, these results suggest that loss of gas to space has been the dominant process responsible for changing the climate of Mars from an early, warmer environment to the cold, dry one that we see today.

In order to assess the effects of ionospheric feedback on different modes of energy transport in the magnetosphere, we investigate an isolated substorm and a steady magnetospheric convection (SMC) event with very similar solar wind drivers. The primary focus is on a comparison between the isolated substorm and the substorm that initiates the SMC. Auroral data from Polar UVI LBHl and LBHs, along with assimilative mapping of the ionosphere electrojet potential patterns are used as inputs to the global ionosphere‐thermosphere model to calculate conductances and Joule heating rates. Results from this study show that the conductances both before and during the events play a large role the ability of the magnetosphere to remain in steady driven state. The substorm that initiates the SMC event shows very different signatures in the ionosphere than isolated substorm; these signatures indicate that there is very weak substorm current wedge, or possibly a pseudo‐breakup.

The Mars thermosphere (above approximately 120km) has been probed in situ for one Mars year using accelerometers on board the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. This region is affected by radiation and energy deposition from the Sun and by energy and momentum from the lower atmosphere. Densities derived from measurements made during the nominal science orbits (periapsis > 140 km) show consistent trends with solar zenith angle and Sun-Mars distance, reflecting direct and indirect heating of the thermosphere, although orbit-to-orbit variability is still significant. The six Deep Dip campaigns that MAVEN has conducted (with periapsis dropping below similar to 135 km) significantly extend the vertical profiles of the densities derived from accelerometer data. These show complex structure and high variability, both dependent on season, local time, location, and lower atmosphere activity, including dust storms and wave propagation from a dynamic lower atmosphere. In particular, the terminators are a region of convoluted structure and high variability, which may be greatest in the postmidnight, predawn hours of the sol. This space-time regime was not sampled by previous orbiters at Mars. While initial comparisons with thermospheric general circulation modes show broad areas of agreement, these terminator transition regions are not simulated well by current models. Judicious choice of the timing of these Deep Dip campaigns during the remaining MAVEN mission, as periapsis continues to precess through local time, latitude, and longitude in both hemispheres and in different seasons, should help clarify the processes at work in this complicated region.

We investigate auroral energy deposition by using a nonhydrostatic global atmospheric model coupled to a two-stream electron transport model. We present several electron beam study cases, discussing energy flux and electron energy effects on the ion and neutral densities, the atmospheric thermal profile, H-3(+) and hydrocarbon infrared (IR) emissions, H-2 far ultraviolet (FUV) emissions and color ratios, and vibrationally excited molecular hydrogen. Using the nonhydrostatic Jupiter Global Ionosphere-Thermosphere Model, we find that FUV spectral characteristics consistent with previous Hubble Space Telescope results derive primarily from electrons with energies above 10 keV, over energy fluxes of 10-100 erg/cm(2) s, while IR emissions are predominantly due to electrons with energies below 10 keV, over energy fluxes of 10-100 erg/cm(2) s. Electrons with energies below about 10 keV produce enough H-2(nu) to deplete the H+ population, modifying the ionospheric composition, and consequently the H-3(+) emissions, which can be used to directly relate H-2 vibrational excitation to auroral observations. New observations by Juno will provide better electron energy distributions to constrain the electron energy spectrum and magnitude at the upper boundary of the model and simultaneously provide a determination of the FUV and IR spectra that can be cross-correlated with the observations.

Analysis of the Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere Volatiles and EvolutioN (MAVEN) spacecraft closed source data from all orbits with good pointing revealed an enhanced Helium [He] density on the nightside orbits and a depressed He density on the dayside by about a factor of 10-20. He was also found to be larger in the polar regions than in the equatorial regions. The northern polar winter nightside He bulge was approximately twice that of the northern polar summer nightside bulge. The first 6 weeks of the MAVEN prime mission had periapsis at high latitudes on the nightside during northern winter, followed by the midlatitudes on the dayside moving to low latitudes on the nightside returning to the high latitudes during northern summer. In this study we examined the NGIMS data not only in the different latitudes but sorted by solar longitude (Ls) in order to separate the diurnal or local solar time (LST) effects from the seasonal effects. The Mars Global Ionosphere-Thermosphere Model (M-GITM) has predicted the formation of a He bulge in the upper atmosphere of Mars on the nightside early morning hours (Ls =2-5h) with more He collecting around the poles. Taking a slice at constant altitude across all orbits indicates corresponding variations in He and CO2 with respect to LST and Ls and a diurnal and seasonal dependence.

We use our fully coupled 3-D Jupiter Thermosphere General Circulation Model (JTGCM) to quantify processes which are responsible for generating neutral winds in Jupiter's oval thermosphere from 20 mu bar to 10(-4)nbar self-consistently with the thermal structure and composition. The heat sources in the JTGCM that drive the global circulation of neutral flow are substantial Joule heating produced in the Jovian ovals by imposing high-speed anticorotational ion drifts (similar to 3.5kms(-1)) and charged particle heating from auroral processes responsible for bright oval emissions. We find that the zonal flow of neutral winds in the auroral ovals of both hemispheres is primarily driven by competition between accelerations resulting from Coriolis forcing and ion drag processes near the ionospheric peak. However, above the ionospheric peak (<0.01 mu bar), the acceleration of neutral flow due to pressure gradients is found to be the most effective parameter impacting zonal winds, competing mainly with acceleration due to advection with minor contributions from curvature and Coriolis forces in the southern oval, while in the northern oval it competes alone with considerable Coriolis forcing. The meridional flow of neutral winds in both ovals in the JTGCM is determined by competition between meridional accelerations due to Coriolis forcing and pressure gradients. We find that meridional flow in the lower thermosphere, near the peak of the auroral ionosphere, is poleward, with peak wind speeds of similar to 0.6kms(-1) and similar to 0.1kms(-1) in the southern and northern oval, respectively. The corresponding subsiding flow of neutral motion is similar to 5ms(-1) in the southern oval, while this flow is rising in the northern oval with reduced speed of similar to 2ms(-1). We also find that the strength of meridional flow in both auroral ovals is gradually weakened and turned equatorward near 0.08 mu bar with wind speeds up to similar to 250ms(-1) (southern oval) and similar to 75ms(-1) (northern oval). The corresponding neutral motion in this region is upward, with wind speeds up to 4ms(-1) in both ovals.