The Curiosity rover's discovery of rocks preserving evidence of past habitable conditions in Gale crater highlights the importance of constraining the timing of responsible depositional settings to ...understand the astrobiological implications for Mars. Crater statistics and mapping reveal the bulk of the alluvial deposits in Gale, including those interrogated by Curiosity, were likely emplaced during the Hesperian, thereby implying that habitable conditions persisted after the Noachian. Crater counting data sets and upper Peace Vallis fan morphology also suggest a possible younger period of fluvial activation that deposited ~10–20 m of sediments on the upper fan after emplacement of the main body of the fan. If validated, water associated with later alluvial activity may have contributed to secondary diagenetic features in Yellowknife Bay.
Key Points
The bulk of alluvial deposits in Gale were likely emplaced during the HesperianHabitable conditions persisted in Gale crater after the NoachianLimited evidence for possible younger fluvial activation on Peace Vallis fan
Several Open Source planetary orbital mapping and utility image processing software packages, including, VICAR, AFIDS, ISIS, GDAL, and GeoTIFF, have been integrated into a single software environment ...(POMM), where package programs can be run independently from a Linux command line, or combined in synergistic scripts that facilitate advanced trans-package applications. Several integrated scripts have been prepared to simplify some of the more difficult database building tasks such as (1) image co-registration (for stacking and time series analysis), (2) mosaicking (for regional analysis), and (3) map-projection of raw Planetary Data System (PDS) images for selected Mars and Luna sensor systems. A user interface/GUI is provided for the three planetary applications, but the underlying scripts can also be modified by an advanced user and run at the command-line. POMM is Open Source software available in “docker” container and “Yum-Install” versions that support cross-platform installation on Windows, Apple, and Linux products using available desktop applications and/or virtual containers. However, installation on systems requiring emulation can be slow, and the installation process can be challenging.
This investigation documents that the Rugged Terrain Unit, the Stimson formation, and the Greenheugh sandstone were deposited in a 1200 m-deep lake that formed after the emergence of Mt. Sharp in ...Gale crater, Mars, nearly 4 billion years ago. In fact, the Curiosity rover traversed on a surface that once was the bottom of this lake and systematically examined the strata that were deposited in its deepest waters on the crater floor to layers that formed along its shoreline on Mt. Sharp. This provided a rare opportunity to document the evolution of one aqueous episode from its inception to its desiccation and to determine the warming mechanism that caused it. Deep water lacustrine siltstones directly overlie conglomerates that were deposited by mega floods on the crater floor. This indicates that the inception phase of the lake was sudden and took place when flood waters poured into the crater. The lake expanded quickly and its shoreline moved up the slope of Mt. Sharp during the lake-level rise phase and deposited a layer of sandstone with large cross beds under the influence of powerful storm waves. The lake-level highstand phase was dominated by strong bottom currents that transported sediments downhill and deposited one of the most distinctive sedimentological features in Gale crater: a layer of sandstone with a 3 km-long field of meter-high subaqueous antidunes (the Washboard) on Mt. Sharp. Bottom current continued downhill and deposited sandstone and siltstone on the foothills of Mt. Sharp and on the crater floor, respectively. The lake-level fall phase caused major erosion of lacustrine strata that resulted in their patchy distribution on Mt. Sharp. Eroded sediments were then transported to deep waters by gravity flows and were re-deposited as conglomerate and sandstone in subaqueous channels and in debris flow fans. The desiccation phase took place in calm waters of the lake. The aqueous episode we investigated was vigorous but short-lived. Its characteristics as determined by our sedimentological study matches those predicted by an asteroid impact. This suggests that the heat generated by an impact transformed Mars into a warm, wet, and turbulent planet. It resulted in planet-wide torrential rain, giant floods on land, powerful storms in the atmosphere, and strong waves in lakes. The absence of age dates prevents the determination of how long the lake existed. Speculative rates of lake-level change suggest that the lake could have lasted for a period ranging from 16 to 240 Ky.
•Resurfacing on Mars influences small area crater counts globally.•Spatial variability in the cratering pattern influences small area crater counts.•Spatial variability and resurfacing create large ...age uncertainties at 100km2.•Uncertainties from crater counting markedly improve from 1000km2 to 10,000km2.
The acquisition of high-resolution imagery for the surface of Mars has enabled mapping of spatially limited (order of <103km2) landforms such as alluvial fans, deltas, and lacustrine deposits that are targets for exploration due to their association with liquid water. It is essential for our understanding of the planet’s geologic and climate history therefore to place these landforms within the global chronostratigraphic context. Here, we analyze both the statistical variability in the cratering pattern as well as the influence of small crater resurfacing on crater counting small landforms. We identified and counted craters (diameter (D)>200m) on four type terrains using Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) imagery that span the Noachian, Hesperian, and Amazonian epochs. The counts from each location include a region covering 10,000km2, ten 1000km2 subsets of that larger area, and approximately one hundred 100km2 samples. The data demonstrate significant variation in the crater size frequency and derived model ages across a single terrain type for the 100km2 samples. The crater size frequency at this area scale varies across a single, uniform geologic unit by up to a factor of 2–3 on the four different terrains. At 1000km2, the local pattern variations that are relevant at the 100km2 scale become less important and the age variations are tighter. In all four terrain cases, the 10,000km2 and 1000km2 samples capture distinct crater populations (km-sized craters) that formed before and after resurfacing event(s). However, due to the relatively high mean distance between km-sized craters, the 100km2 size area samples more commonly than not exclude a statistically significant sample at the kilometer size range, masking important information about the pre-resurfacing history of the terrain. We therefore suggest that due to the effect of pattern variability in cratering over 100km2 and the susceptibility of smaller craters to resurfacing, crater counts derived from small area samples are suspect to major uncertainties.
•Impact crater processes observed during MSL’s first 360 Sols were studied.•Possible impactites are scarce, but include shatter cones and disrupted bedrock.•Loose igneous and sedimentary blocks ...identified near the rover may be distal ejecta.•The smallest observed crater is 0.6m in diam., consistent with atmospheric filtering.•Crater counts constrain the aeolian erosion rate to ~10mm per million years.•The erosion rate is consistent with the observed erosion of the Peace Vallis fan.
Impact processes at all scales have been involved in the formation and subsequent evolution of Gale crater. Small impact craters in the vicinity of the Curiosity MSL landing site and rover traverse during the 364 Sols after landing have been studied both from orbit and the surface. Evidence for the effect of impacts on basement outcrops may include loose blocks of sandstone and conglomerate, and disrupted (fractured) sedimentary layers, which are not obviously displaced by erosion. Impact ejecta blankets are likely to be present, but in the absence of distinct glass or impact melt phases are difficult to distinguish from sedimentary/volcaniclastic breccia and conglomerate deposits. The occurrence of individual blocks with diverse petrological characteristics, including igneous textures, have been identified across the surface of Bradbury Rise, and some of these blocks may represent distal ejecta from larger craters in the vicinity of Gale. Distal ejecta may also occur in the form of impact spherules identified in the sediments and drift material. Possible examples of impactites in the form of shatter cones, shocked rocks, and ropy textured fragments of materials that may have been molten have been observed, but cannot be uniquely confirmed. Modification by aeolian processes of craters smaller than 40m in diameter observed in this study, are indicated by erosion of crater rims, and infill of craters with aeolian and airfall dust deposits. Estimates for resurfacing suggest that craters less than 15m in diameter may represent steady state between production and destruction. The smallest candidate impact crater observed is ∼0.6m in diameter. The observed crater record and other data are consistent with a resurfacing rate of the order of 10mm/Myr; considerably greater than the rate from impact cratering alone, but remarkably lower than terrestrial erosion rates.
The Mars 2020 Perseverance rover landing site is located within Jezero crater, a
∼
50
km
diameter impact crater interpreted to be a Noachian-aged lake basin inside the western edge of the Isidis ...impact structure. Jezero hosts remnants of a fluvial delta, inlet and outlet valleys, and infill deposits containing diverse carbonate, mafic, and hydrated minerals. Prior to the launch of the Mars 2020 mission, members of the Science Team collaborated to produce a photogeologic map of the Perseverance landing site in Jezero crater. Mapping was performed at a 1:5000 digital map scale using a 25 cm/pixel High Resolution Imaging Science Experiment (HiRISE) orthoimage mosaic base map and a 1 m/pixel HiRISE stereo digital terrain model. Mapped bedrock and surficial units were distinguished by differences in relative brightness, tone, topography, surface texture, and apparent roughness. Mapped bedrock units are generally consistent with those identified in previously published mapping efforts, but this study’s map includes the distribution of surficial deposits and sub-units of the Jezero delta at a higher level of detail than previous studies. This study considers four possible unit correlations to explain the relative age relationships of major units within the map area. Unit correlations include previously published interpretations as well as those that consider more complex interfingering relationships and alternative relative age relationships. The photogeologic map presented here is the foundation for scientific hypothesis development and strategic planning for Perseverance’s exploration of Jezero crater.
The landing site for the Curiosity rover is located at the distal end of the Peace Vallis fan in Gale Crater. Peace Vallis fan covers 80 km2 and is fed by a 730 km2 catchment, which drains an upland ...plains area through a 15 km wide gap in the crater rim. Valley incision into accumulated debris delivered sediment through a relatively low density valley network to a main stem channel to the fan. An estimated total fan volume of 0.9 km3 matches the calculated volume of removal due to valley incision (0.8 km3) and indicates a mean thickness of 9 m. The fan profile is weakly concave up with a mean slope of 1.5% for the lower portion. Numerous inverted channels outcrop on the western surface of the fan, but on the eastern portion such channels are rare suggesting a change in process from distributary channel domination on the west to sheet flow on the eastern portion of the fan. Runoff (discharge/watershed area) to produce the fan is estimated to be more than 600 m, perhaps as much as 6000 m, indicating a hydrologic cycle that likely lasted at least thousands of years. Atmospheric precipitation (possibly snow) not seepage produced the runoff. Based on topographic data, Peace Vallis fan likely onlapped Bradbury Rise and spilled into a topographic low to the east of the rise. This argues that the light‐toned fractured terrain within this topographic low corresponds to the distal deposits of Peace Vallis fan, and in such a setting, lacustrine deposits are expected.
Key Points
Distal end of Peace Vallis fan was near MSL landing
Sediment in the fan was derived from valley incision into colluvium
Fan morphology consistent with fluvial processes
•Calculations indicate the air within Gale Crater is less dusty than expected.•Low dust within the crater reconciles column optical depths at MER-B and MSL.•REMS and Navcam comparison indicate ...vortices are unable to raise dust at Gale.•One optically thick dust devil is observed at 3-sigma level and described.•Dustless vortices, low in-crater dust consistent with modeled suppressed PBL modeled suppressed PBL.
The Navigation Cameras (Navcam) of the Mars Science Laboratory rover, Curiosity, have been used to examine two aspects of the planetary boundary layer: vertical dust distribution and dust devil frequency. The vertical distribution of dust may be obtained by using observations of the distant crater rim to derive a line-of-sight optical depth within Gale Crater and comparing this optical depth to column optical depths obtained using Mastcam observations of the solar disc. The line of sight method consistently produces lower extinctions within the crater compared to the bulk atmosphere. This suggests a relatively stable atmosphere in which dust may settle out leaving the air within the crater clearer than air above and explains the correlation in observed column opacity between the floor of Gale Crater and the higher elevation Meridiani Planum. In the case of dust devils, despite an extensive campaign only one optically thick vortex (τ=1.5±0.5×10−3) was observed compared to 149 pressure events >0.5Pa observed in REMS pressure data. Correcting for temporal coverage by REMS and geographic coverage by Navcam still suggests 104 vortices should have been viewable, suggesting that most vortices are dustless. Additionally, the most intense pressure excursions observed on other landing sites (pressure drop >2.5Pa) are lacking from the observations by the REMS instrument. Taken together, these observations are consistent with pre-landing circulation modeling of the crater showing a suppressed, shallow boundary layer. They are further consistent with geological observations of dust that suggests the northern portion of the crater is a sink for dust in the current era.
The Mars 2020 Mastcam‐Z stereo camera investigation enables the generation of three dimension (3D) data products needed to visualize and analyze rocks, outcrops, and other geological and aeolian ...features. The Planetary Robotics Vision Processing framework “PRoViP” as well as the Instrument Data System on a tactical—sol‐by‐sol—timeframe generate 3D vision products, such as panoramas, distance maps, and textured meshes. Structure‐from‐motion used by the Advanced Science Targeting Toolkit for Robotic Operations (ASTTRO) “Landform” tool and long baseline stereo pipelines add to the 3D vision products' suite on various scales. Data fusion with textured meshes from satellite imagery and 3D data analysis and interpretation of the resulting large 3D data sets is realized by visualization assets like the Planetary Robotics Vision 3D Viewer PRo3D, the 3D Geographical Information System GIS CAMP (Campaign Analysis Mapping and Planning tool), the ASTTRO 3D data presentation and targeting tool, and the Mastcam‐Z planning tool Viewpoint. The pipelines' workflows and the user‐oriented features of the visualization assets, shared across the Mars 2020 mission, are reported. The individual role and interplay, complements and synergies of the individual frameworks are explained. Emphasis is laid on publicly available 3D vision data products and tools. A representative set of scientific use cases from planetary geology, aeolian activity, soil analysis and impact science illustrates the scientific workflow, and public data deployment modes are briefly outlined, demonstrating that 3D vision processing and visualization is an essential mission‐wide asset to solve important planetary science questions such as prevailing wind direction, soil composition, or geologic origin.
Plain Language Summary
Image processing enables to describe the surface of Mars in three dimension (3D) using the Mastcam‐Z stereo cameras' images. The 3D reconstruction of the rocks, geological outcrops, as well as aeolian and mineralogical features, are crucial for understanding the planet's past. Image processing tools to reconstruct the surface of Mars from the images are available to the Mars 2020 Team, generating 3D data products with various information about the surface on Mars like elevation maps or distance maps that record the 3D coordinates of each point. To interpret these products, tools needed for their visualization and analysis are presented here. In a combination with data from other sensors or sources—including 3D models obtained from satellite, and at different scales the interpretation of the processed products is enhanced. The reader learns about the synergies and interplay between these tools, including publicly available tools. Demonstrative planetary science examples, processed by the Mastcam‐Z science team with the above mentioned tools, are presented. Geological features, such as wind activity, soil analysis, and impact science, are analyzed, illustrating the scientific work carried out and in particular the benefit of 3D vision processing and visualization for such analysis work.
Key Points
The Mars 2020 Mastcam‐Z investigation's stereoscopic zoom camera pair enables the assembly of 3D models of the rover environment
Processing and visualization for scientific 3D data exploitation establishes mission science in full knowledge about spatial relationships
Important scientific use cases for Mastcam‐Z 3D vision processing and visualization illustrate the importance of 3D for Mars science
Twenty confirmed impacts over a 7‐year time period on Mars were qualitatively and statistically compared to 287 secondary craters believed to originate from Zunil, an ∼500 ka, 10‐km diameter, primary ...crater. Our goal was to establish criteria to distinguish secondaries from primaries in the general crater population on the basis of their horizontal planforms. Recent primary impacts have extensive “air blast” zones, distal ray systems (>100 crater radii, R), and ephemeral ejecta. Recent primaries formed clusters of craters from atmospheric fragmentation of the meteoroid body. Secondary craters have ejecta blankets with shorter rays that are consistent with emplacement by low‐impact velocities (near 1 km/s). The mean extent of the continuous ejecta blankets was less distal for secondaries (5.38 ± 1.57R) versus primaries (18.07 ± 7.01R), though primary ejecta were less fractal (Fractal Dimension Index (FDI) < 1.30) and more circular on average (Circularity Ratio (CR) = 0.55 ± 0.25 versus 0.27 ± 0.13 for secondaries). Crater rims were remarkably circular (primaries CR = 0.97 ± 0.02, secondaries at 0.94 ± 0.05), though secondaries have the lowest values (CR < 0.9). Secondary crater rims were elongated toward or orthogonal to their primary of origin. Uprange source directions for most secondaries, determined by ejecta planform and crater rim ellipticity, point toward Zunil, although contamination from other primaries is considered in some areas. Ejecta blanket discrepancies between recent primaries and Zunil secondaries are attributable to differences in impact velocity and retention age. After removal of the ejecta blanket, crater rims are generally not diagnostic for determining crater origin. Fragmentation of primaries may play some role in steepening the size‐frequency distribution of crater diameters in the 5 m < D < 30 m range.
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