Search

The current Martian cratering rate has been determined either from repeated orbital imaging (e.g.[1][2]), or using lunar rates extended to Mars in combination with crater counting [3]. Eight seismic events detected by the NASA InSight seismometer have been confirmed as impacts by orbital imaging [4]. Six of those events are part of the Very High Frequency (VF) group of marsquakes, which consists of 70 events in total. The impact signals are very similar to other VF events, suggesting that more or all VF events could be impact related. The unique characteristics of VF events, such as a long seismic coda interpreted as a result of shallow source in a strongly scattering near-surface layer [5] and their temporal and spatial distributions, are consistent with impact origin.Assuming all high quality VF events are impacts allows us to place a novel constraint on the impact rate on Mars, independent of the formation of easy-to-spot large blast zones, necessary to identify fresh craters in orbital images. We test the compatibility with the existing cratering rate estimates by using two approaches to derive a first seismically constrained impact rate for Mars. First, we use the Gutenberg-Richter law to determine the slope of the VF event magnitude-frequency distribution. The impact rate is derived by applying a relationship between seismic moment and crater diameter [6]. We refine our estimates by extrapolating the detectability of each event using a semi-empirical relationship between crater size and seismic amplitude [6]. We find that both approaches give similar rates, varying slightly depending on the detectability conditions assumed by each method. The cumulative rates N(D≥8m) = 1-4x10-6 /km2/yr are higher than those from previous imaging studies, but consistent with isochron rates [3].The discrepancy with imaging-based rates could indicate that there are impacts which are missed in imagery due to absent blast zones or that are located in unfavourable terrain, unaccounted for in the imaging-based area correction. References:[1] Daubar et al. (2013). doi: 10.1016/j.icarus.2013.04.009[2] Daubar et al. (2022). doi: 10.1029/2021JE007145[3] Hartmann (2005). doi: 10.1016/j.icarus.2004.11.023[4] Daubar et al. (2023). InSight Seismic Events Confirmed as Impacts Thus Far. Lunar and Planetary Science Conference 2023 abstract.[5] van Driel et al. (2021). doi: 10.1029/2020JE006670[6] Wójcicka et al. (2023). Impact Rate on Mars Implied by Seismic Observations. Lunar and Planetary Science Conference 2023 abstract.

The crater density on planetary surfaces is used to determine their ages throughout the solar system, which requires a model for the rate of meteorite impacts of different sizes. For craters smaller than 30 meters, this rate has been observed from the generation of new craters in repeated orbital images. For larger craters, the rate was extrapolated from the lunar surface ages, taking into account the atmospheric removal of small craters. It has been observed that both estimates do not match for crater diameters smaller than 30 meters. The NASA InSight seismometer SEIS provided a new independent constraint, when it recorded seismic signals of several impacts during its mission. These confirmed impacts are part of a larger class of marsquakes (Very High Frequency, VF), all of which have characteristics consistent with an impact origin. We show that these VFs are plausibly caused by meteorite impacts and derive the impact rate required to explain their numbers. An empirical scaling relationship is used to convert between seismic moment and crater diameter. We apply area and time corrections to derive a global impact rate and find that the derived rate is 210--290 craters >8m globally per year, consistent with previously published chronology model rates and above the rates derived from freshly imaged craters.

We report confirmed impact sources for two seismic events on Mars detected by the NASA InSight mission. These events have been positively associated with fresh impact craters identified from orbital images, which match predicted locations and sizes, and have formation time constraints consistent with the seismic event dates. They are both of the Very High Frequency family of seismic events and display impact-acoustic chirps. This brings the total number of confirmed martian impact-related seismic events to eight thus far. All seismic events with chirp signals have now been confirmed as having been caused by impact cratering events. This includes all seismic activity within 100 km of the lander, and two out of the four events with source locations between 100-300 km distance.

Introduction: The habitability of Europa is a property within a system, with many interdependent physical and chemical parameters, among a number of processes, of which no single measurement or investigation can characterize. Therefore, investigating Europa as an integrated system must occur to understand the complete picture. To accomplish this, the Europa Clipper mission has three main mission objectives to assess Europa’s habitability: (1) characterize the Ice Shell and Ocean: including their heterogeneity, properties, and the nature of surface–ice–ocean exchange; (2) characterize the Composition: understanding Europa’s ocean through investigations of the composition and chemistry; (3) and characterize the Geology: including surface features and high-science-interest localities. Europa Clipper will also assess any current or recent activity by searching for evidence of thermal anomalies and plumes and will perform high resolution observations to provide reconnaissance for a future potential landed mission. Synthesizing the mission’s science measurements in such a way as to constrain Europa’s habitability is a complex task and is being guided by the Habitability Assessment Board (HAB).The HAB is charged with providing a high-level, cross-instrument and cross-discipline, habitability-driven science perspective. All members of the Europa Clipper Science Team are considered members of the HAB and so contribute to addressing the overarching goal of the mission. Rotating members of the science team serve as leadership of the HAB and convene regular meetings to discuss and formulate recommendations to the project’s science leadership. Particularly, HAB works to connect activities and measurements across the Europa Clipper Geology, Composition, and Interior Working Groups to investigate habitability and can recommend formation of focus groups of experts on the team to address scientific and technical problems related to habitability.System Science: To achieve mission level 1 requirements and assess Europa’s habitability, investigations will contribute observations towards science themes. Themes that support the Ice Shell and Ocean characterization include Full Depth Subsurface Exchange, Shallow Subsurface Structure, Ice Shell Properties, and Ocean Properties. For Composition characterization, themes that contribute include Global Composition Surface Mapping, Regional Composition, Atmospheric Composition, and Space Environment Composition. The Geology objective has contributions of Global Surface Mapping, Landform Geology, and Local Scale Surface Properties (which also contributes to reconnaissance). Current activity is supported by Remote Plume Search (and Characterization, if applicable), In-Situ Plume Search (and Characterization, if applicable), Surface Thermal Anomaly Search, and Surface Activity Evidence.Current Activity: Searches for and characterization of any recent activity would greatly contribute to assessing Europa’s habitability. Europa Clipper plans observations for potential activity through remote observations including: the Europa-Ultraviolet Spectrograph (Europa-UVS) instrument through occultations, aurora, and UV scans; the Europa Imaging System (EIS) Narrow Angle Camera (NAC) through high resolution imaging; and the Europa Thermal Imaging System (E-THEMIS) through thermal infrared mapping. Additionally, in-situ measurements by the SUrface Dust Analyzer (SUDA) will also make observations of activity through detections of positive and negative ions and characterization of particle compositions and their locations of origin on the surface. Contributions by the other instruments will also inform on current/recent activity through remote and in-situ observations through magnetic, plasma, radar, and compositional measurements.Remote observations to search for (and characterize if present) current activity at Europa by ground based, near-earth orbiting observatories, and other spacecraft could also occur, even while Europa Clipper is in transit to Jupiter. Recent observations by the Hubble Space Telescope (HST) have made putative detections of plume activity at Europa (Roth et al., 2014; Sparks et al., 2016) and future observations by the James Webb Space Telescope (JWST) and ground-based observatories may be able to confirm these findings. JWST can make measurements in the mid-infrared, for which the Galilean moons are relatively poorly characterized, enabling further constraints on composition and mechanisms driving the activity. Other observatories including the Very Large Telescope (VLT), the Atacama Large Millimeter/submillimeter Array (ALMA), and measurements by the Juno spacecraft and future JUICE mission could all contribute further to assessing Europa’s potential activity and habitability. The Europa Clipper science team is currently working to informally coordinate efforts with the JUICE team to enhance our science as possible at Europa on a non-interference basis.Summary: Europa Clipper will assess the habitability of Europa as a system, guided by the HAB, through the synergy of multiple measurements and incorporation of remote observations by JWST and other remote observatories and spacecraft. Potential detections (and subsequent characterization) of any activity would greatly contribute to understanding Europa’s habitability and potential to harbor life. Discovery awaits!References:Roth et al. (2014), Transient water vapor at Europa’s south pole. Science, 343(6167), 171-174.Sparks et al. (2016), Probing for evidence of plumes on Europa with HST/STIS. The Astrophysical Journal, 829(2), 121.Acknowledgments: This work was supported by NASA through the Europa Clipper Project. Portions of this work were performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Motivation Granular avalanches such as slope streaks, have been observed on Mars since the beginning of the high resolution era with MOC on MGS. Such mass wasting processes are active and their dynamics has a few implications in terms of climatic conditions. However, understanding the slope streaks dynamics is still undergoing. Many authors have proposed dry spreading of fine dust or wet processes (e.g., Schorghofer et al., 2002; 2007). For instance, Head et al., (2007) have proposed spring discharge involving salty ground-water. Many of those studies have been performed from interpretations of geomorphic features by comparing knowing processes occurring on Earth and/or a few comparisons with experimental works. Consequently, a key parameter is the triggering conditions, along with the dynamical behavior of these avalanches. We hence propose a combined approach involving numerical simulations, seismology and orbital imagery in order to provide new insights. Orbital image constraints We investigate the orbital images from CTX and HiRISE cameras, both onboard MRO spacecraft. They provide a complete coverage of the two regions of interest being the InSight landing site (135.61ºE 4.49ºN) and the vicinity of the large quake (170.85ºE, 7.05ºS, being at 37º from the SEIS instrument) named 1222 which occurred on 5 May 2020. In both areas, we identified many past avalanche events (Figure 1-A). More specifically, we investigate the complete set of orbital data (imagery, topography, and thermo-physical properties) to estimate in particular the rate of formation of these avalanches in the vicinity of the 1222 event location (Fig. 1-B,C). This has led to request new orbital observations targeted to the most favorable areas for avalanches and hence try to link the ground acceleration resulting from the 1222 event with the triggering of new avalanches by using detection techniques (Fig. 1-D). This work, essentially observational, is combined with the following part on the detectability of this type of source by the SEIS sensor. Figure 1 - (A) Location of identifiable landslides and avalanches (rockfall sign) around the InSight landing site (symbolized with the SEIS/WTS sign). The circles show epicentral distance from the receiver at 5º (red), 10º (orange), 15º (yellow) and 20º (light gray), which correspond to ∼300, ∼600, ∼900 and ∼1200 km respectively. Active avalanches (slope streaks) are detected at 150°E. (B) Location of active avalanches (rockfall sign) around the 1222 event location (green flag). (C) Examples of avalanches in the vicinity of the 1222 event location as seen by the CTX camera. This image was taken in May 2011 and reflects the high occurrence of such processes in the area. (D) Detection of slope streaks (and old craters) from neural networks (i.e., using darknet algorithm). Dynamics and source function of avalanches from numerical simulations In order to generate synthetic seismic sources due to gravity-driven sediment transport we based our simulations on a depth-averaged Saint-Venant equations model, named SHATLOP, which accounts for the curvature of the topography and on various frictional behavior for the source term following (Lucas & Mangeney, 2007; Lucas et al., 2011;2014). Volumes involved are around 8,000-40,000 m3 with a total drop height up to 1 km. The typical duration of the event is of a few minutes up to 20 minutes for a +2 km runout slope streaks, depending on the frictional law considered and small fluctuation on the bottom topography, which generates surges as shown on Fig. 2-A. ​​The source is considered as a point force applied at the surface from the spatial integration of the avalanche resultant force, where the velocity, the resistance force, the density of the flow and the acceleration due to gravity accounting for the bottom topography curvature are all taken into account (Fig. 2-B). The velocity models are obtained after geological considerations after Pan et al., (2019), where active mass wasting processes have been identified (Fig. 2-C). Examples of resulting seismograms are shown in Fig. 2-D. The velocity model, still under investigation for Mars, is also an important open issue that has a strong impact on the resulting seismic signal. Finally, depending on source functions, velocity models, such an event may be detectable, in particular when occurring during the night at local time of the sensors, when the noise level is low and when spectral content is above SEIS sensitivity (Fig. 2-E). Figure 2 - (A) Example numerical simulation of a martian dust avalanche over a DTM generated from HiRISE stereo pair (Color scales with the velocity). (B) Resulting source force history. (C) Example of a velocity and attenuation model for Mars. (D) Synthetic seismograms accounting source distance for various velocity models and epicentral distances. (E) ADS example for a small event at 140 km. References Head, J., Marchant, D., Dickson, J.,Levy, J., Morgan, G. Slope streaks in the Antarctic Dry Valleys: Characteristics, candidate formation mechanisms, and implications for slope streak formation in the Martian environment. 7 th International Conf. (2007) Lucas A., and A. Mangeney. “Mobility and topographic effects for large Valles Marineris landslides on Mars”. In: Geophys. Res. Lett., 34, L10201 (2007) Lucas A., et al. “Influence of the scar geometry on landslide dy-namics and deposits: Application to Martian landslides”. In: J. Geophys. Res. - Planets, 116, E10001 (2011) Lucas, A., A. Mangeney, and J-P. Ampuero. “Frictional velocity-weakening in landslides on Earth and on other planetary bodies”. In: Nature Comm.,5:3417 (2014) Pan L., et al. “Crust stratigraphy and heterogeneities of the first kilometers at the dichotomy boundary in western Elysium Planitia and implications for InSight lander”. In: Icarus (2019) Schorghofer N., Aharonson O., and Khatiwala S. “Slope streaks on Mars: Correlations with surface properties and the potential role of water”. In: Geophys. Res. Lett.,29(23) (2002) Schorghofer, N., Aharonson, O., Gerstell, M. & Tatsumi, L. Three decades of slope streak activity on Mars. Icarus. 191. 132-140 (2007)

Introduction: With a launch readiness date of late 2024, NASA’s Europa Clipper will set out on a journey to explore the habitability of Jupiter’s moon Europa. In the early 2030s, the spacecraft will enter Jupiter orbit then fly by Europa nearly 50 times to collect data on Europa’s ice shell and ocean, study its composition, investigate its geology, and search for and characterize any current activity. The mission’s science objectives will be accomplished using a highly capable suite of remote-sensing and in-situ instruments.Mission Context: Interpretation of Galileo mission data suggests that Europa likely hides a global saltwater ocean beneath the icy surface. Chemistry at the ice surface and ocean-rock interface might provide the building blocks for life. NASA’s Europa Clipper mission is intended to assess Europa’s potential habitability.The Voyager and Galileo missions first revealed a deformed surface at Europa with an average surface age younger than Earth’s, dominated by water ice and renewed through recent or current geologic activity. Galileo data indicates that Europa has an induced magnetic field, implying the presence of a global, electrically conductive fluid layer beneath the surface, most likely a saltwater ocean. Geological data including structural patterns are also consistent with a subsurface ocean. Recent observations also suggest the presence of plumes may release internal water into space, indicating the potential for additional shallow water reservoirs beneath Europa’s icy surface.There are many open questions regarding the viability of Europa to support life. Intense radiation from Jupiter at Europa’s surface forms water and impurities into oxidants, chemical reagents capable of carrying out oxidation. Active geologic cycling of seawater through rocky material on the Europan seafloor is expected to be chemically reducing. If mixing between the surface oxidants and the reduced ocean water occurs, there is an opportunity in Europa’s ocean or ice shell to produce a reduction-oxidation (redox) potential. All known life on Earth relies on such redox potentials to extract chemical energy from the environment in exchange for heat energy and entropy, enabling cellular maintenance, metabolism, and reproduction. Europa may have the ingredients that could support life: liquid water, bioessential elements, chemical energy, and a stable environment through time.Science Goal and Objectives: The overarching goal of the Europa Clipper mission is to explore Europa to investigate its habitability. This will be achieved through the accomplishment of three science objectives:Characterize the ice shell and any subsurface water, including their heterogeneity, ocean properties, and the nature of surface-ice- exchange. Understand the habitability of Europa’s ocean through composition and chemistry. Understand the formation of surface features, including sites of recent or current activity, and characterize high science interest localities. Science Payload: The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments comprise the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and Radio Science (G/RS) will be achieved using the spacecraft's telecommunication system, and valuable scientific data will be acquired by the spacecraft’s Radiation Monitoring system (RADMON).Status and Advancement Toward Launch: Both the spacecraft and the payload are currently under construction, as the mission begins its assembly, testing, and launch operations (ATLO) phase. Recent major milestones include selection of a launch vehicle and launch readiness date by NASA, evaluation of candidate tours by the science team, and preparations for the cruise and operational phases of the mission. The project, flight system, and payload have completed their Critical Design Reviews, and the project has completed its System Integration Review. Europa Clipper is now formerly a Phase D mission. Meanwhile, the science team is preparing a set of manuscripts describing the mission’s science and instruments for publication in the journal Space Science Reviews.One Team Philosophy: Our “One Team” philosophy prioritizes synergistic science by bridging across the individual instrument-based investigations, while promoting collaborations among members of the Europa Clipper science team. Each of the Europa Clipper individual instruments will be used to investigate Europa and its environs, finding critical clues about how Europa works as a planetary body. In combining and assessing the datasets from each instrument's experiments, we can collectively gain clarity into Europa’s mysteries. It is at the overlapping boundaries of our subfields that the greatest insights and discoveries will be made. Integrated science celebrates our individual expertise, challenges our assumptions, breaks through our limitations, and expands our intellectual boundaries. Associated visibility brings trust, promotes partnerships, and enhances personal relationships. These aspirations are the inherent basis for functioning as one Europa Clipper science team.JUICE-Clipper Coordination: The JUICE spacecraft is expected to be in the Jovian system at the same time as Europa Clipper, and there is substantial overlap between these missions’ primary phases. The Europa Clipper and JUICE science teams have begun informal collaboration to suggest synergistic science that could be supported on a non-interference basis. The scientific collaborations currently extend across two ad hoc working groups, one on the Galilean satellites and one on Jupiter’s magnetosphere. Current discussions are to form a joint focus group to advise the two project teams on potential collaborations and propose a plan for synergistic observations, joint publications, and joint archival data products.Acknowledgments: Portions of this work were performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This work was supported by NASA through the Europa Clipper Project.

With a launch readiness date of late 2024, NASA’s Europa Clipper will set out on a journey to explore the habitability of Jupiter’s moon Europa. At the beginning of the next decade, the spacecraft will orbit Jupiter, flying by Europa more than 40 times over a four-year period to observe this moon’s ice shell and ocean, study its composition, investigate its geology, and search for and characterize any current activity. The mission’s science objectives will be accomplished using a highly capable suite of remote-sensing and in-situ instruments. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments comprise the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be achieved using the spacecraft's telecommunication system, and valuable scientific data will be acquired by the spacecraft’s radiation monitoring system. Major milestones from the past year include selection of a launch vehicle and launch readiness date by NASA, evaluation of candidate tours by the science team, and preparations for the cruise and operational phases of the mission. The project, flight system, and payload have completed their Critical Design Reviews, and the mission has recently completed its System Integration Review. Spacecraft subsystems and payload are actively being developed, and assembly, test, and launch operations are expected to begin in March 2022. In the meantime, the science team is preparing a set of manuscripts describing the mission science and the instruments that enable these investigations for publication in the journal Space Science Reviews.

NASA's InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission has operated a sophisticated suite of seismology and geophysics instruments on the surface of Mars since its arrival in 2018. On 18 February 2021, we attempted to detect the seismic and acoustic waves produced by the entry, descent and landing of the Perseverance rover using the sensors onboard the InSight lander. Similar observations have been made on Earth using data from both crewed(1,2) and uncrewed(3,4) spacecraft, and on the Moon during the Apollo eras(5), but never before on Mars or another planet. This was the only seismic event to occur on Mars since InSight began operations that had an a priori known and independently constrained timing and location. It therefore had the potential to be used as a calibration for other marsquakes recorded by InSight. Here we report that no signal from Perseverance's entry, descent and landing is identifiable in the InSight data. Nonetheless, measurements made during the landing window enable us to place constraints on the distance-amplitude relationships used to predict the amplitude of seismic waves produced by planetary impacts and place in situ constraints on Martian impact seismic efficiency (the fraction of the impactor kinetic energy converted into seismic energy)., Nature Astronomy, 6 (1), ISSN:2397-3366

The third stage of the Saturn IV rocket used in the five Apollo missions made craters on the Moon ∼30 m in diameter. Their initial impact conditions were known, so they can be considered controlled impacts. Here, we used the iSALE‐2D shock physics code to numerically simulate the formation of these craters, and to calculate the vertical component of seismic moment (∼4 × 1010 Nm) and seismic efficiency (∼10−6) associated with these impacts. The irregular booster shape likely caused the irregular crater morphology observed. To investigate this, we modeled six projectile geometries, with footprint area between 3 and 105 m2, keeping the mass and velocity of the impactor constant. We showed that the crater depth and diameter decreased as the footprint area increased. The central mound observed in lunar impact sites could be a result of layering of the target and/or low density of the projectile. Understanding seismic signatures from impact events is important for planetary seismology. Calculating seismic parameters and validating them against controlled experiments in a planetary setting will help us understand the seismic data received, not only from the Moon, but also from the InSight Mission on Mars and future seismic missions.

Hundreds of new impact craters have been observed to form on Mars since spacecraft began imaging that planet. New impact craters produced visible ejecta deposits and many of them also have visible rays, similar to lunar and mercurian craters. However, some of the new martian impact craters have a circular feature of relatively low reflectance that we call a “halo.” This feature is distinct from the usual visible ejecta deposits or ray patterns. In this paper we present an observational study of this halo feature and we discuss the results of this study with respect to the nature of the halos: what they are and how they may have formed. To address these questions, we measured diameters of both halos and their central craters. We found a strong correlation between halo diameter and crater diameter, which indicates that the nature of the halos is fundamentally governed by the amount of impact energy available at their formation. Specifically, halo size is controlled by impact energy according to the non-linear relationship DH ∝ E2/3, where DH is the diameter of the halo and E is the impact energy. We also found that certain factors may influence the formation of the halos: a thicker dust layer and lower elevations are both correlated with larger halos. From these correlations we conclude that the local surface characteristics as well as local atmospheric pressure influence the formation of the halos. Our description and analysis of the martian halo features provide a framework upon which specific halo formation mechanisms can be developed and tested in the future.

Compositions of the Amazonian-aged Tharsis and Elysium volcanic provinces of Mars have been largely obscured in Mars-orbital remote sensing data by windblown dust. Fresh impact craters formed within the last few years have disturbed surface dust, providing unique windows to explore these regions' relatively dust-free mineralogic compositions. Such fresh craters, plus other small exposures of less dusty materials, are resolved spatially in high-resolution targeted observations of visible/short-wave infrared spectral reflectance by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Analysis of CRISM observations of small, relatively dust-free locations in the Tharsis and Elysium regions shows that these provinces are dominated by high-Ca pyroxene and olivine, similar to volcanic materials of Hesperian age. Thus, the mafic mineral compositions of Hesperian and Amazonian volcanic materials appear similar to each other, but distinct from the olivine- and low-Ca pyroxene-rich compositions that dominate Noachian rocks. In the core regions of both provinces, where thermal infrared data indicate the thickest dust cover, the dust is sufficiently thick that few fresh craters penetrate to expose the underlying volcanics. These results may be consistent with low Si contents of surface materials in Elysium and western Tharsis measured by gamma-ray spectroscopy resulting from a thick cover of dust depleted in Si-rich phases, possibly due to eolian sorting.

This study maps and measures assorted properties of new dated crater clusters that formed recently when impactors fragmented in the atmosphere of Mars. We report these statistics for 77 clusters: number of craters, size of cluster, dispersion of cluster, direction (azimuth) from which the impactor approached, and an estimate of the angle from vertical of the impact. Clusters range from a few to hundreds of craters, with most containing tens of craters. They are most commonly dispersed over hundreds of meters, with extents ranging from a few meters to a few kilometers. We find that dispersion generally does not correlate with topographic elevation. However, when the highest elevations are disregarded, clusters are more dispersed at lower elevations, as expected. Impact azimuths are randomly distributed and do not express a clear directionality of incoming meteoroids. Results suggest impacts occur closer to horizontal than expected, which could be due to observational effects. The characteristics we report here provide important constraints for future work in understanding atmospheric fragmentation processes; properties of the impactors themselves, such as density and orbital parameters; and the seismic detectability of impacts. These are critical aspects to understand, as approximately half of current impacts are observed to be clusters.

Measurements from the InSight lander radiometer acquired after landing are used to characterize the thermophysical properties of the Martian soil in Homestead hollow. This data set is unique as it stems from a high measurement cadence fixed platform studying a simple well-characterized surface, and it benefits from the environmental characterization provided by other instruments. We focus on observations acquired before the arrival of a regional dust storm (near Sol 50), on the furthest observed patch of soil (i.e., ∼3.5 m away from the edge of the lander deck) where temperatures are least impacted by the presence of the lander and where the soil has been least disrupted during landing. Diurnal temperature cycles are fit using a homogenous soil configuration with a thermal inertia of 183 ± 25 J m

Introduction: A possible source of seismic activity on Mars is meteoroid impacts [5]. Nevertheless, in the first Martian year of the the NASA InSight Mission [2] no signal has been unambiguously associated with an impact event [4]. This calls for further investigation of meteorite strikes and the relationship between impact conditions and the seismic signals they generate. One of the ways to understand the seismic signature of meteoroid impacts is to analyze already existing data from other planetary bodies. During the Apollo era, over one thousand seismic signals were recorded on the Moon [e.g. 12]. Part of the Apollo seismic experiments were artificial impacts of Lunar modules (LM) and Saturn booster drops (S-IVB). Artificial impacts are considered large scale controlled experiments, because the exact position of the crater and the impactor parameters that made it are known. In this work, we model S-IVB artificial impacts on the Moon, using the iSALE-2D shock physics hydrocode [e.g., 1, 3, 21]. We simulated both the crater formation and the pressure wave propagation and attenuation. We examined size of the crater, cratering efficiency, impact momentum transferred to the target and two seismic parameters: seismic efficiency and seismic moment, and compared these measurements to the existing data [e.g., 10, 8, 7]. One challenge with modelling the S-IVB artificial impacts is the realistic presentation of the projectile. The Apollo S-IVB boosters were hollow aluminum cylinders, with a very low bulk density of 23 gcm−3 and mass of 14 t. The booster was 17.8 m long and 6.6 m in radius. The impact speed at the ground level was 2.54-2.66 kms−1. The drop angle was reported to be between 13.2◦ and 35◦ from vertical. [e.g., 14, 19]. There were five such impacts, and they all impacted into mare basalts and made elliptical craters (long and short axis in between 29.71 m and 38.7 m) with a central mound (crater depth was roughly estimated to 2-3 m) [e.g., 14]. Numerical modelling: All simulations in this work used the iSALE-2D shock physics hydrocode [e.g., 1, 3, 21]. To exclude any influence of target properties, all simulations used the same uniform target model of a 44% porous basaltic regolith [20, 15]. The mass and impact velocity of the projectile in our simulations were the same in all simulations and consistent with the experi- ments. Given the axial symmetry of the mesh geometry employed, we investi- gated five simplified representations of the irregularly shaped projectile. Three cases had a geometry of right-cylinder, with 90% porosity and different dimen- sions: 1. 11.7 m radius and height 0.5 m; 2. 5.8 m radius and 2 m height; 3. 0.992 m radius and 16.7 m height. The last two cases were spheroids: one was non-porous aluminum sphere with 1.06 m radius and the other one was 90% porous and had a radius of 2.3 m [13,21]. To calculate momentum transfer, the vertical component of the seismic moment and seismic efficiency we use approaches described extensively in previous studies [9, 7, 20, 15]. Here, we focus only on the vertical component of the seismic moment Mz [11, 7, 20]. To calculate seismic efficiency we used the same approach described in numerous previous work [e.g., 9, 20, 15]. Results: The shape of the projectile has a substantial effect on crater for- mation but little effect on the seismic signature of the impact. The largest crater was formed in Case 3, while the best agreement with observed crater properties was provided by Case 1 (for depth) and Case 5 (diameter). The porosity of the projectile affected the size of the mound at the bottom of the crater, which supports the idea that the observed central mounds at the bottom of the ob- served craters are projectile remenants [14]. The seismic efficiency k 10−6 and seismic moment Mz 4 1010 Nm were of the same order of magnitude for all cases. This seismic efficiency is in agreement with lower estimates of [10], and the seismic moment is consistent with the scaling proposed in [17, 16, 20, 6]. Conclusion: We have successfully replicated the S-IVB artificial impacts on the moon with iSALE2D, producing craters that are consistent with obser- vations in their approximate dimensions and morphology. The simulations also constrain the seismic efficiency and seismic moment of the artificial impacts, which are relatively insensitive to the density and shape of the impactor. The low seismic efficiency determined here for artificial impacts on the Moon may help explain the non-detection of impacts by InSight in the first Martian year of operating. Moreover, the insensitivity of seismic moment to impactor density and shape suggests that results from the Apollo seismic experiment of these artificial impacts are useful analogs for small impacts on Mars that can be used to better inform their detectability by InSight [17, 16, 20, 6]. [1] Amsden A.A. et al. 1980. Technical report. [2] Banerdt B.W. et al. 2020. Nature Geoscience, pages 1–7. [3] Collins G.S. et a. 2004. Meteoritics & Planetary Science, 39(2):217– [4] Daubar I.J. et al. 2020. Journal of Geophysical Research: Planets 125(8). [5] Daubar I.J. et al. 2018. Space Science Reviews, 214(8):1–68. [6] Fernando B. et al. 2020 Journal of Geophysical Research: Planets. [7] Gudkova T. et al. 2015. Earth and Planetary Science Letters, 427:57–65. [8] Gudkova TV et al. 2011. Icarus, 211(2):1049–1065. [9] Guldemeister & Wunnemann K.2017. Icarus, 296:15–27. [10] Latham G. et al. 1970. Science, 170(3958):620–626. [11] Lognonne P. et al. 2009. Journal of Geophysical Research: Planets, 114(E12). [12] Lognonne & Mosser B.1993. Surveys in Geophysics, 14(3):239–302. [13] Lundborg N. 1968. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, volume 5, pages 427–454. [14] Plescia J.B. et al. 2016. Planetary and Space Science, 124:15–35. [15] Rajsic A., et al. 2021. Journal of Geophysical Research: Planets. [16] Teanby N.A. 2015. Icarus, 256:49–62. [17] Teanby N.A. & Wookey J. 2011. Physics of the Earth and Planetary Interiors, 186(1-2):70–80. [18] Tillotson J.H. Technical report. [19] Wagner RV., et al. 2017. Icarus, 283:92–103, [20] Wojcicka N. et al. 2020. Journal of Geophysical Research: Planets. 125(10) [21] Wunnemann K., et al. 2006. Icarus 180(2).

The crust on Mars has been structurally affected by various geologic processes such as impacts, volcanism, mantle flow and erosion. Previous observations and modelling point to a dynamically active interior in early Martian history, that for some reason was followed by a rapid drop in heat transport. Such a change has significantly influenced the geological, geophysical and geochemical evolution of the planet, including the history of water and climate. Impact-induced seismic signature is dependent on the target properties (conditions in the planetary crust and interior) at the time of crater formation; Thus, we can use simulations of impact cratering mechanics as a tool to probe the interior properties of a planet.Contrary to large impacts happening in Mars’ early geologic history, the present-day impact bombardment is limited to small meter-size crater-forming impacts (in the atmosphere and on the ground), which are also natural seismic sources (Daubar et al., 2018, 2020; Neidhart et al., 2020). Impact simulations, in tandem with NASA InSight seismic observations (Benerdt et al., 2020, Giardini et al., 2020), can help understand the crustal properties over the course of Mars’ evolution, including the state of Mars’ crust today. Our most recent numerical investigations include: estimating the seismic efficiency and moment from small meter-size impact events, tracking pressure propagation from the impact point into far field, transfer of impact energy into seismic energy, etc (Rajsic et al., 2020, Wojcicka et al., 2020). Understanding coupling between impact crater formation process with the generation and progression of seismic energy can help identify small impact everts in seismic data on Mars. We also looked at the same process on the Earth (Neidhart et al., 2020) and the Moon (Rajsic, et al., this issue).Since the landing of the NASA InSight mission on Mars, there was a dozen known new impacts (Miljkovic et al., 2021). However, all but one impact occurred much too far away (3000 to 8400 km distance from the InSight lander) to be within the detectability threshold estimates (Teanby et al., 2015; Wojcicka et al., 2020). About 50% of the observed craters were likely single impacts and the other 50% were evidently cluster craters with less than 40 individual craters in the largest cluster. The largest single crater was ~14 m in diameter, and the largest crater in a cluster was ~13 m (Neidhart et al., this issue), consistent with crater cluster observations (Daubar et al., 2013). The one impact that had a possibility of being detected by SEIS was 1.5 m in diameter at 37 km distance (Daubar et al. 2020).Considering that orbital imaging is limited in space and time, these known new impacts represent only a fraction of the total number of impacts that have occurred on Mars in the last ~2 years. According to impact flux calculations (Teanby and Wookey, 2011), there should have been ~3000 detectable craters, larger than 1 m in diameter, formed on Mars since InSight landed. If any of these unobserved impacts have been large enough and close enough to InSight to detect seismically, we have not yet discerned them in the seismic data.References:Banerdt, W.B. et al. (2020) Nature Geosci. 13, 183-189.Giardini, D. et al. (2020) Nature Geosci. 13, 205-212.Daubar, I.J. et al. (2020) J. Geophys. Res. Planets, 125: e2020JE006382.Wójcicka, N. et al. (2020) J. Geophys. Res. Planets, 125, e2020JE006540.Rajšić et al. (2021) J. Geophys. Res. Planets, 126, e2020JE006662.Daubar et al. (2013) Icarus 225, 506-516.Teanby, N.A. & Wookey, J. (2011) PEPI 186, 70-80.Neidhart, T. et al. (2020) PASA, 38, E016.Teanby, N.A. et al. (2015) Icarus 256, 46-62.Miljkovic, K. et al. (2021) LPSC, LPI Contribution No. 1758.

International audience; We report the aeolian changes observed in situ by NASA's InSight lander during the first 400 sols of operations: Granule creep, saltation, dust removal, and the formation of dark surface tracks. Aeolian changes are infrequent and sporadic. However, on sols, when they do occur, they consistently appear between noon to 3 p.m., and are associated with the passage of convective vortices during periods of high vortex activity. Aeolian changes are more frequent at elevated locations, such as the top surfaces of rocks and lander footpads. InSight observed these changes using, for the first time, simultaneous insitu and orbital imaging and high-frequency meteorological, seismological, and magnetic measurements. Seismometer measurements of ground acceleration constrain the timing and trajectory of convective vortex encounters, linking surface changes to source vortices. Magnetometer measurements show perturbations in magnetic field strength during the passage of convective vortices consistent with chargedparticle motion. Detachment of sand-scale particles occurs when high background winds and vortexinduced turbulence provide a peak surface friction wind speed above the classic saltation fluid threshold. However, detachment of dust-and granule-scale particles also occurred when the surface friction wind speed remained below this threshold. This may be explained by local enhancement of the surface roughness and other effects described here and further studied in Part 2 (Baker et al., 2021). The lack of saltation and bright dust-coated surfaces at the InSight landing site implies surface stability and the onset of particle motion may be suppressed by dust "cushioning." This differentiates the InSight landing site from other areas on Mars that exhibit more aeolian activity. Plain Language Summary Aeolian activity, the movement of dust and sand by the wind, is common on Earth and has been observed on other planets, including Mars. A new Mars lander, InSight, has for the first time monitored aeolian changes by combining imaging with weather, seismic and CHARALAMBOUS ET AL.

International audience; The entry, descent, and landing (EDL) sequence of NASA's Mars 2020 Perseverance Rover will act as a seismic source of known temporal and spatial localization. We evaluate whether the signals produced by this event will be detectable by the InSight lander (3,452 km away), comparing expected signal amplitudes to noise levels at the instrument. Modeling is undertaken to predict the propagation of the acoustic signal (purely in the atmosphere), the seismoacoustic signal (atmosphere-to-ground coupled), and the elastodynamic seismic signal (in the ground only). Our results suggest that the acoustic and seismoacoustic signals, produced by the atmospheric shock wave from the EDL, are unlikely to be detectable due to the pattern of winds in the martian atmosphere and the weak air-to-ground coupling, respectively. However, the elastodynamic seismic signal produced by the impact of the spacecraft's cruise balance masses on the surface may be detected by InSight. The upper and lower bounds on predicted ground velocity at InSight are 2.0 × 10 −14 and 1.3 × 10 −10 m s −1. The upper value is above the noise floor at the time of landing 40% of the time on average. The large range of possible values reflects uncertainties in the current understanding of impact-generated seismic waves and their subsequent propagation and attenuation through Mars. Uncertainty in the detectability also stems from the indeterminate instrument noise level at the time of this future event. A positive detection would be of enormous value in constraining the seismic properties of Mars, and in improving our understanding of impact-generated seismic waves.

Mars exhibits diverse surface changes at all latitudes and all seasons. Active processes include impact cratering, aeolian sand and dust transport, a variety of slope processes, changes in polar ices, and diverse effects of seasonal CO

The first seismometer operating on the surface of another planet was deployed by the NASA InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission to Mars. It gives us an opportunity to investigate the seismicity of Mars, including any seismic activity caused by small meteorite bombardment. Detectability of impact generated seismic signals is closely related to the seismic efficiency, defined as the fraction of the impactor's kinetic energy transferred into the seismic energy in a target medium. This work investigated the seismic efficiency of the Martian near surface associated with small meteorite impacts on Mars. We used the iSALE‐2D (Impact‐Simplified Arbitrary Lagrangian Eulerian) shock physics code to simulate the formation of the meter‐size impact craters, and we used a recently formed 1.5 m diameter crater as a case study. The Martian crust was simulated as unfractured nonporous bedrock, fractured bedrock with 25% porosity, and highly porous regolith with 44% and 65% porosity. We used appropriate strength and porosity models defined in previous works, and we identified that the seismic efficiency is very sensitive to the speed of sound and elastic threshold in the target medium. We constrained the value of the impact‐related seismic efficiency to be between the order of ∼10‐7 to 10‐6 for the regolith and ∼10‐4 to 10‐3 for the bedrock. For new impacts occurring on Mars, this work can help understand the near‐surface properties of the Martian crust, and it contributes to the understanding of impact detectability via seismic signals as a function of the target media.

The age of a planetary surface may be inferred from the size-frequency distribution of impact craters covering it. On Mars, the accuracy of this crater chronology technique may be compromised by past or present aeolian, fluvial, and pluvial erosion and sedimentation. Here, we review how these processes influence the crater age of the surface, employing as a case study the floor of Jezero crater, the landing site of the Mars 2020 Perseverance rover mission. We count craters and derive the retention ages of three prominent geologic units on the floor of Jezero, discussing some of the challenges faced during crater counting analysis. Our estimate for the retention age of the dark-toned floor unit is slightly younger compared to previous studies and is sensitive to statistical outliers. These factors should be taken into account when calibrating the crater age of the surface of the unit with its measured radiometric age.

The InSight lander (Banerdt et al. 2020) on Mars is equipped with two cameras capable of sky imaging both of which have been used opportunistically to search for meteors. The rate of occurrence of Martian meteors has not been directly measured and initial reports of an imaged meteor by Selsis et al. 2005 were likely incorrect (Domokos et al. 2007). The meteor search is part of the investigation into the flux of impactors at Mars (Daubar et al. 2018).The InSight cameras have been described by Maki et al. (2018). The Instrument Deployment Camera (IDC) can be aimed by a robotic arm and has a 45-degree square field of view (FOV). However, this camera was typically unavailable, and has only been used twice. The Instrument Context Camera (ICC) has a 120-degree fisheye FOV. It is aimed downward, but sees a broad section of the southern sky to around 20-degrees elevation angle.IDC images are shown in Fig. 1. They were aimed to the southwest at an elevation of about 35 degrees, and on sols 126 and 176 (5 April and 27 May 2019), four 5-minute exposures were acquired. Stars are visible in the images, and will be used to determine the sensitivity. Many cosmic rays were seen (e.g., Fig. 2)—long ones can be mistaken for meteors, but they have a distinctive morphology with a narrow end and a diffuse end due to the charge diffusion process after the charged particles pass through the detector (Fisher-Levine and Nomerotski, 2015). Despite the Sun being 60 degrees down, diffuse sky brightness was visible (Banfield et al. 2020). No meteors were detected.ICC images are shown in Fig. 3—about 75% of the images do not include sky. On 25 sols from 254 to 432 (15 August 2019 to 6 February 2020), the ICC acquired four, 5-minute exposures. No meteors were seen.We will present an analysis of the results and their implication for the meteor rate at Mars. While no meteors were seen, the upper limit is likely to be constraining. Total exposure time is 540 minutes, using cameras more sensitive than the limiting exposures of Domokos et al. (2007) and with wider FOVs. However, the complex geometry and the time variable atmospheric dust extinction will be considered.References. Banerdt et al. 2020. Nature Geoscience, 13, 183-189. Banfield et al. 2020. Nature Geoscience, 13, 190-198. Daubar et al. 2018. Space Science Rev. 214, 132. Domokos et al. 2007. Icarus 191, 141-150. Fisher-Levine and Nomerotski 2015. BNL-108381-2015-JA. Maki et al. 2018. Space Sci. Rev. 214, 105. Selsis et al. 2005. Nature 435, 581.

Introduction: Meteoroid bombardment is one of the sources of seismic activity on planetary bodies. The very first seismometer operating on the surface of another planet was successfully deployed by the NASA InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission to Mars. It gives us an opportunity to investigate the seismicity of Mars, including impact-induced seismic activity. This work investigated the seismic efficiency associated with small meteorite impacts on Mars, using numerical methods in targets analogue to the Martian surface. The Martian crust was simulated as non-porous bedrock (0% porosity) or regolith with different porosities (25%, 44% and 65%) The seismic efficiency, k, is presented as a portion of impact energy that is transferred into seismic energy. It has been suspected that consolidated (bedrock) and non-consolidated (regolith) materials will have different values of seismic efficiency. Estimates of seismic efficiency range from k=10-2 to 10-6 (Schultz and Gault, 1975; Daubar et al., 2018; McGarr et al., 1969; Hoerth et al., 2014; Richardson & Kedar, 2013; Güldemeister & Wünnemann, 2017). High seismic efficiency is typical in bedrock or highly consolidated materials (k>10-3). Low seismic efficiency is typical for sediments or unconsolidated sands and soils (k-5) (e.g., Patton and Walter 1993). In this work, we used a simplified approach (e.g. Güldemeister & Wünnemann, 2017) that defines the seismic efficiency as: ; where x represents distance from the impact point, P is the amplitude of the pressure pulse, t is the duration of the pressure pulse, ρ is the density of the target, Cp is the speed of sound in the target and Ek is the kinetic energy of the impactor. Numerical impact modelling: All simulations were performed with the iSALE-2D shock physics hydrocode (Collins, et al., 2004; Wünnemann et al., 2006). The impact conditions were modelled to replicate recent fresh meter size impact that occurred on Mars since the landing of InSight (Daubar et al., 2020). Impact crater was estimated to be ~1.5 m in diameter. Impactor radius was 4.4 cm and kinetic energy of 1.8x106 J. To simulate bedrock and fractured bedrock (25% porosity) we used the ROCK strength model (Collins et al., 2004). To simulate the regolith (44% and 65% porosity) we used Lundborg strength model (Lundborg, 1968) (Table 1). We used the Tillotsen equation of state for basalt (Tillotson, 1962; Wójcicka et al., 2020). For porous cases, we used the ε-α porosity model (Wünnemann et al., 2006;) (Table 2). Table 1. Strength model parameters for targets with different porosity Parameter 0% 25% 44% 65% Strength model ROCK ROCK LUNDD LUNDD Strength (damaged) (kPa) 10 0 10 0.3 Friction (damaged) 0.6 0.67 0.7 0.7 Limiting strength (damaged) (GPa) 3.5 0.17 0.25 0.25 Strength (intact) (MPa) 10 0.2 Friction (intact) 1.2 1.8 Limiting strength (intact) (GPa) 3.5 0.17 Table 2. ε-α porosity model parameters (Borg et al., 2005; Wünnemann et al., 2006; Wójcicka et al, 2020). Parameter 25% 44% 65% Initial distension, α 1.33 1.8 2.8 Elastic threshold, ε0 -4x10-4 10-4 10-5 Distension at transition αx 1.1 1.15 1.0 The rate change of distension with respect to volumetric strain, k 0.98 0.98 0.98 Ratio of speed of sound in porous over non-porous medium, χ 0.6 0.33 0.21 All variables in the equation for the seismic efficiency were calculated from iSALE outputs. The pressure wave was observed via gauges cells, placed at 45° equidistantly throughout the target. The pressure wave amplitude and pulse duration were calculated at full width half maximum. The sound speed was calculated from assumed bulk modulus of basalt (Wójcicka et al, 2020). Results: Seismic efficiency was calculated for the same impact conditions in all four material models, representing the reference 1.5 m crater recently observed on Mars. There is a clear decrease in seismic efficiency with increasing porosity. It is of the order of 10-5 for porous and highly porous regolith and 10-4 for fractured bedrock. Estimates for the non-porous basalt bedrock are in the order of 10-3 (Figure 1). Porosity of the target affected pressure wave amplitudes, duration of the pressure pulse and speed of sound in the target. These are all parameters used in calculation of seismic efficiency. This implies that if impact occurs on very dusty parts of Mars with thick regolith cover, efficiency would be smaller than efficiency of the impact that occurred on the bedrock, or area with thinner regolith cover. Figure 1. Seismic efficiency calculated in targets with different porosity Conclusions. Impact cratering represents one of the most important geological processes in the Solar System. Defining relationship between target’s properties and seismic efficiency is of interest to the NASA InSight science, since it helps in understanding the properties of the uppermost crust on Mars. Previous approximations of seismic efficiency were of 2x10-5 with an order of magnitude uncertainty for seismic efficiency on Mars (Teanby and Wookey, 2011) and Daubar et al. (2018) adopted the seismic efficiency of 5x10-4 calculated from the seismic moment (Gudkova et al., 2011; 2015; Teanby 2015). In this work, we calculated the seismic efficiency in meter-size impacts on Mars to be different for bedrock (order of 10-3) and porous materials (order of 10-5).

Since landing in late 2018, the InSight lander has been recording seismic signals on the surface of Mars. Despite nominal pre-landing estimates of 1–3 meteorite impacts detected per Earth year, none have yet been identified seismically. To inform revised detectability estimates, we simulated numerically a suite of small impacts onto Martian regolith and characterized their seismic source properties. For the impactor size and velocity range most relevant for InSight, crater diameters are 1-30 m. We found that in this range scalar seismic moment is 106 − 1010 Nm and increases almost linearly with impact momentum. The ratio of horizontal to vertical seismic moment tensor components is ∼1, implying an almost isotropic P-wave source, for vertical impacts. Seismic efficiencies are ∼ 10−6, dependent on the target crushing strength and impact velocity. Our predictions of relatively low seismic efficiency and seismic moment suggest that meteorite impact detectability on Mars is lower than previously assumed. Detection chances are best for impacts forming craters of diameter >10m

Comprehensive analysis of remote sensing data used to select the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) landing site correctly predicted the atmospheric temperature and pressure profile during entry and descent, the safe landing surface, and the geologic setting of the site. The smooth plains upon which the InSight landing site is located were accurately predicted to be generally similar to the Mars Exploration Rover Spirit landing site with relatively low rock abundance, low slopes, and a moderately dusty surface with a 3–10 m impact fragmented regolith over Hesperian to Early Amazonian basaltic lava flows. The deceleration profile and surface pressure encountered by the spacecraft during entry, descent, and landing compared well (within 1σ) of the envelope of modeled temperature profiles and the expected surface pressure. Orbital estimates of thermal inertia are similar to surface radiometer measurements, and materials at the surface are dominated by poorly consolidated sand as expected. Thin coatings of bright atmospheric dust on the surface were as indicated by orbital albedo and dust cover index measurements. Orbital estimates of rock abundance from shadow measurements in high‐resolution images and thermal differencing indicated very low rock abundance and surface counts show 1–4% area covered by rocks. Slopes at 100 to 5 m length scale measured from orbital topographic and radar data correctly indicated a surface comparably smooth and flat as the two smoothest landing sites (Opportunity and Phoenix). Thermal inertia and radar data indicated the surface would be load bearing as found., Key Points The atmosphere, safe surface, and geologic setting of the landing site were correctly predicted by remote sensing data before landingThe modeled atmospheric temperature profiles and surface pressure were within 1 sigma of the measured deceleration profile and surface pressureInSight’s surface is similar to Spirit’s with low rock abundance, low slopes, moderate dust, and is composed of impact regolith over basalt

A new 1.5 m diameter impact crater was discovered on Mars only ~40 km from the InSight lander. Context camera images constrained its formation between 21 February and 6 April 2019; follow‐up High Resolution Imaging Science Experiment images resolved the crater. During this time period, three seismic events were identified in InSight data. We derive expected seismic signal characteristics and use them to evaluate each of the seismic events. However, none of them can definitively be associated with this source. Atmospheric perturbations are generally expected to be generated during impacts; however, in this case, no signal could be identified as related to the known impact. Using scaling relationships based on the terrestrial and lunar analogs and numerical modeling, we predict the amplitude, peak frequency, and duration of the seismic signal that would have emanated from this impact. The predicted amplitude falls near the lowest levels of the measured seismometer noise for the predicted frequency. Hence, it is not surprising this impact event was not positively identified in the seismic data. Finding this crater was a lucky event as its formation this close to InSight has a probability of only ~0.2, and the odds of capturing it in before and after images are extremely low. We revisit impact‐seismic discriminators in light of real experience with a seismometer on the Martian surface. Using measured noise of the instrument, we revise our previous prediction of seismic impact detections downward, from ~a few to tens, to just ~2 per Earth year, still with an order of magnitude uncertainty. ISSN:0148-0227 ISSN:2169-9097 ISSN:2169-9100

Orbital and surface observations demonstrate that aeolian activity is occurring on Mars. Here we report the aeolian changes observed in situ by NASA's InSight lander during the first 400 sols of op...

The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed in western Elysium Planitia on November 26, 2018. Because of its stationary position and a multi-instrument package, InSight offers the unique opportunity of detecting changes induced by aeolian activity and constraining the atmospheric conditions responsible for particle motion.In this work, we present the most significant changes from aeolian activity as detected by the InSight lander during its first 400 Martian days of operations. We will show that particle entrainment by wind activity around InSight is a subtle process and report simultaneous measurements observed across multiple instruments. The changes observed are episodic and are seen correlated with excursions in both seismic and magnetic signals, which will be discussed further. Our observations show that all aeolian movements are consistent with the passage of deep convective vortices between noon to 3 pm local time. These vortices may be the primary initiators for aeolian transportation at InSight, inducing episodic particulate motion of grains up to 3 mm in diameter.

The idea of visualizing shock wave passage along a dusty (sooty) surface was first proposed and tested by Ernst Mach. High resolution HiRISE images of new impact craters on dusty areas of Mars gave in many cases revealed dark “fresh” halos around craters. In ~7% of cases they have low albedo/color contrasting curved strips near craters referred to as “parabolas” and “scimitars”. We analyze these albedo details as the possible surface footprints of atmospheric shock waves generated during atmospheric passage and shocks from impact cratering by small meteoroids and their fragments. In this approach “parabolas” are the trace of two colliding air shocks propagated from a pair of neighboring craters formed after a meteoroid fragmented during the atmosphere passage. The mechanism of the “scimitar’s” formation is more enigmatic and tentatively could be related to the interaction of the ballistic cone wave and a spherical wave from the point of impact. The study of images is accompanied by numerical modeling of impact of small projectiles at the atmosphere/rock boundary. This modeling constrains the minimum efficiency of an impact to generate the air shock wave in the rarified Martian atmosphere below of 0.1% of the kinetic energy for non-volatile targets. Targets with near surface volatiles could amplificated the air blast (if volatiles are presented in the shocked zone). The study is intended to estimate the air-shock wave parameters along the visible surface traces around impact craters. By constraining shock wave parameters opens new possibilities for investigating the mechanical properties of the Martian surface.The work is supported by RAS program 12 “Universe Origin and Evolution from Earth-based Observations and Space Missions” (BAI), and a grant from the NASA Mars Data Analysis Program, number 80NSSC18K1368.

The InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) lander will deploy a seismic monitoring package on Mars in November 2018. In prepara- tion for the data return, we prepared a blind test in which we invite participants to detect and characterize seismicity included in a synthetic dataset of continuous waveforms from a single station that mimics both the streams of data that will be available from InSight, as well as expected tectonic and impact seismicity and noise conditions on Mars. We expect that the test will ultimately improve and extend the current set of methods that the InSight team plan to use in routine analysis of the Martian dataset.