Context Camera Images Research Articles

A global dataset of pitted cones on Mars

Pitted cones are positive-relief features that display prominent central craters, and are common features on the northern lowland plains of Mars. Pitted cones have been proposed to form from different mechanisms, including those producing volcanic cinder cones or sedimentary mud volcanoes. Here, we apply a deep learning model to globally map 65,620 pitted cones on Mars using Context Camera images from the Mars Reconnaissance Orbiter. Using model recall and a hand-mapped dataset, we conjecture there could be up to ∼81,900–162,000 individual pitted cones on Mars. A majority of pitted cones (>97%) occur in three of the northern plains' basins—Utopia, Isidis, and Acidalia Planitiae—and occur within geologic units from the late Hesperian and the early–middle Amazonian. The global dataset shows cone estimated diameter increases moving poleward, but pitted cones largely disappear north of ∼50 N, perhaps due to polar processes that erase or modify the cones. Approximately 94% of cones overlie a single geologic unit, the Vastitas Borealis Formation (VBF), interpreted as sediment from the highland terrains deposited via outflow channels. This global distribution supports sedimentary volcanism following deposition of sediments by the outflow channels. On Earth, rapidly-deposited sediments make an ideal setting for trapping water in the subsurface that is later erupted as mud flows, and this appears to be feasible on Mars.

Flash flooding on Mars could be linked to large fault slip events

Studies of Martian fault-related landform morphology have noted an interesting phenomenon associated with large thrusts — isolated channels that run from the crests of these landforms down their slopes. One such example is Ogygis Rupes, an east-verging, 180 km long thrust-fault-related landform located near 55°W, 33°S. Geometric modeling efforts have indicated the fault underlying this landform has experienced approximately 2850 m of slip, and a large anticlinal fold has grown above the fault. We mapped 72 channels on back and front slopes of this massive landform at 1:24,000 scale on 10 mosaiced Context Camera images (6 m/pixel) and one High-Resolution Imaging Experiment image (2.5 m/pixel). The morphology of these channels indicates that they formed through flash flood events that originated near the hinge of the fold. We propose that these flooding events were due to the melting of subsurface ice during fault slip. We apply a thermodynamic model for heat generation along the fault surface during slip events of various magnitudes to estimate the volumes of water produced during each hypothetical event. By comparing these estimates to channel discharge values estimated from channel morphologies, we resolve fault slip magnitudes that could produce the channels. We find that slip events of approximately 28 m produce enough heat to melt the ice associated with channel flow (4.867 × 109 m3). This estimate is based on slip within a 1 m basaltic fault zone, with a friction coefficient of 0.6 where all pore space is occupied by water ice. Results indicate that only mature faults with well-developed, fractured hinges are capable of both (1) melting enough subsurface ice and (2) transporting the water to the surface to result in flooding, explaining why this impressive phenomenon remains a rare but important hazard of which to be aware during planning of the exploration and settlement of Mars.

The global distribution and morphologic characteristics of fan-shaped sedimentary landforms on Mars

Fan-shaped sedimentary landforms on Mars are important geomorphic markers of past water flow and characterizing the distribution and morphology of these features can yield insights into the planet's climatic evolution. We present a new database of 1501 martian fan-shaped sedimentary landforms that builds upon previous surveys and uses Context Camera images. This comprehensive global survey includes both alluvial fans and putative deltas, which we term scarp-fronted fan deposits (SFDs), across the entire martian surface. We classified each fan-shaped landforms based on their morphology as alluvial fans, channelized SFDs, smooth SFDs, and terraced SFDs. Martian alluvial fans are highly concentrated in the high southern tropical latitudes while SFDs are more common near the equator. Both alluvial fans and SFDs are found at lower elevations than Late Noachian to Early Hesperian valley networks, suggesting a climatic change in the locations of stable liquid water. Alluvial fans within impact craters are preferentially located on north, south, and east facing slopes, and are concentrated near the location of highest rim topographic relief; together these observations support orographically-influenced precipitation and snowmelt as a runoff source. For every fan in the database we collected morphologic data, which we compare with terrestrial alluvial fans. Relationships between alluvial fan catchment and fan morphology vary little across the martian surface, suggesting relatively similar processes. Although stratigraphic evidence of a deltaic deposition is lacking, previously conducted experiments along with the depositional basins of the channelized and terraced SFDs generally support deltaic formation. Crater counts indicate that many alluvial fans are within Hesperian and Amazonian impact craters, indicating that significant fluvial erosion occurred during Mars' relatively recent history.

The Global Distribution of Craters With Alluvial Fans and Deltas on Mars

AbstractWe present an inventory of alluvial fans and deltas within martian impact craters based on a systematic global survey of Context Camera images. Our database includes 314 fan‐hosting craters, with a total of 890 alluvial fans and 114 deltas. Alluvial fans and deltas are more widespread than previously reported (∼40°N to 54°S) and are strongly banded with respect to latitude. Most craters with alluvial fans occur at higher elevations (10°S–30°S) and along the dichotomy boundary (0°–10°N). Deltas occur at lower elevations (0°–40°N) where access to groundwater may have enabled the formation of lakes, and to a lesser extent in the highlands (0°–30°S). Alluvial fans in southern mid‐latitude craters preferentially formed along the northern and southern walls, which may reflect climatic control through solar insolation. The widespread distribution within the observed latitude bands and the similar Hesperian to Amazonian age of alluvial fan‐hosting craters is consistent with late‐stage synoptic precipitation.

DoMars16k: A Diverse Dataset for Weakly Supervised Geomorphologic Analysis on Mars

Mapping planetary surfaces is an intricate task that forms the basis for many geologic, geomorphologic, and geographic studies of planetary bodies. In this work, we present a method to automate a specific type of planetary mapping, geomorphic mapping, taking machine learning as a basis. Additionally, we introduce a novel dataset, termed DoMars16k, which contains 16,150 samples of fifteen different landforms commonly found on the Martian surface. We use a convolutional neural network to establish a relation between Mars Reconnaissance Orbiter Context Camera images and the landforms of the dataset. Afterwards, we employ a sliding-window approach in conjunction with a Markov Random field smoothing to create maps in a weakly supervised fashion. Finally, we provide encouraging results and carry out automated geomorphological analyses of Jezero crater, the Mars2020 landing site, and Oxia Planum, the prospective ExoMars landing site.

Empirical Brightness Control and Equalization of Mars Context Camera Images

AbstractThe Mars Reconnaissance Orbiter (MRO) spacecraft has been in orbit around Mars since March 2006. The Context Camera (CTX) on MRO has returned over 115,000 images of the planet at approximately 5–6 m per pixel, providing nearly global coverage. During that time, Mars has gone through nearly seven of its own years, changing solar distance from 1.38 to 1.67 AU and the corresponding solar flux by 45% due to its orbital eccentricity. Seasonal effects and transient phenomena affect atmospheric transparency. These changes, along with an aging detector, prevent easily equalizing images to create a visually smoothly illuminated product from CTX images. We have developed a method, based on previous work by other researchers for other data sets, to mitigate almost all brightness variations between images in order to create the appearance of an evenly illuminated, practically seamless mosaic. We describe how the process works, which uses a reference source to tie brightness values, and demonstrate its effects across Mars' surface. While the workflow developed for this product is applicable to other planetary bodies, it requires a reference source, which may not yet exist.

A Multi-Annotator Survey of Sub-km Craters on Mars

We present here a dataset of nearly 5000 small craters across roughly 1700 km2 of the Martian surface, in the MC-11 East quadrangle. The dataset covers twelve 2000-by-2000 pixel Context Camera images, each of which is comprehensively labelled by six annotators, whose results are combined using agglomerative clustering. Crater size-frequency distributions are centrally important to the estimation of planetary surface ages, in lieu of in-situ sampling. Older surfaces are exposed to meteoritic impactors for longer and, thus, are more densely cratered. However, whilst populations of larger craters are well understood, the processes governing the production and erosion of small (sub-km) craters are more poorly constrained. We argue that, by surveying larger numbers of small craters, the planetary science community can reduce some of the current uncertainties regarding their production and erosion rates. To this end, many have sought to use state-of-the-art object detection techniques utilising Deep Learning, which—although powerful—require very large amounts of labelled training data to perform optimally. This survey gives researchers a large dataset to analyse small crater statistics over MC-11 East, and allows them to better train and validate their crater detection algorithms. The collection of these data also demonstrates a multi-annotator method for the labelling of many small objects, which produces an estimated confidence score for each annotation and annotator.

A New Crater Near InSight: Implications for Seismic Impact Detectability on Mars

AbstractA 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.

Quantified Aeolian Dune Changes on Mars Derived From Repeat Context Camera Images

AbstractAeolian systems are active across much of the surface of Mars and quantifying the activity of bedforms is important for understanding the modern and recent Martian environment. Recently, the migration rates and sand fluxes of dunes and ripples have been precisely measured using repeat High Resolution Imaging Science Experiment (HiRISE) images. However, the limited areal extent of HiRISE coverage means that only a small area can be targeted for repeat coverage. Context Camera (CTX) images, although lower in spatial resolution, have wider spatial coverage, meaning that dune migration can potentially be monitored over larger areas. We used time series, coregistered CTX images and digital elevation models to measure dune migration rates and sand fluxes at six sites: Nili Patera, Meroe Patera, two sites at Herschel crater, McLaughlin crater, and Hellespontus Montes. We observed dune displacement in the CTX images over long‐term baselines (7.5–11 Earth years; 4–6 Mars years). Bedform activity has previously been measured at all these sites using HiRISE, which we used to validate our results. Our dune migration rates (0.2–1.1 m/EY) and sand fluxes (2.4–11.6 m3 m−1 EY−1) compare well to measurements made with HiRISE. The use of CTX in monitoring dune migration has advantages (wider spatial coverage, faster processing time) and disadvantages (ripples not resolved, digital elevation model dune heights may be underestimates); the future combined use of HiRISE and CTX is likely to be beneficial.

The geology of the Navua Valles region of Mars

ABSTRACTThe Navua Valles are a system of channels and valleys on the inner rim of Hellas Basin. The aim of this mapping study was to determine the geologic history of the Navua Valles region; and the relationships between the basement, flow, and channel units along the northeastern slope of Hellas Basin. We have produced a 1:1 million scale geologic map of the Navua Valles region, utilizing standard USGS geologic mapping procedures, but not within a regular USGS mapping project. We selected the mapping area boundaries specifically to cover the Navua Valles drainage systems. The primary base of this mapping effort was a mosaic of 161 Mars Reconnaissance Orbiter Context Camera images, at approximately 6 m/pixel. This paper is part of a double publication, one paper describing the geology of this area, and this paper presenting the geologic map produced during the investigation.

Modification history of the Harmakhis Vallis outflow channel, Mars, based on CTX-scale photogeologic mapping and crater count dating

Harmakhis Vallis is one of the four major outflow channel systems (Dao, Niger, Harmakhis, and Reull Valles) that cut the eastern rim region of the Hellas basin, the largest well-preserved impact structure on Mars. The structure of Harmakhis Vallis and the volume of its head depression, as well as earlier dating studies of the region, suggest that the outflow channel formed in the Hesperian period by collapsing when a large amount of subsurface fluid was released. Thus Harmakhis Vallis, as well as the other nearby outflow channels, represents a significant stage of the fluvial activity in the regional history. On the other hand, the outflow channel lies in the Martian mid-latitude zone, where there are several geomorphologic indicators of past and possibly also contemporary ground ice. The floor of Harmakhis also displays evidence of a later-stage ice-related activity, as the outflow channel has been covered by lineated valley fill deposits and debris apron material.The eastern rim region of the Hellas impact basin has been the subject of numerous geologic mapping studies at various scales and based on different imaging data sets. However, Harmakhis Vallis itself has received less attention and the studies on the outflow channel have focused only on limited parts of the outflow channel or on separated different geologic events. In this work, the Harmakhis Vallis floor is mapped and dated from the head depression to the beginning of the terminus based on the Mars Reconnaissance Orbiter’s ConTeXt camera images (CTX; ∼ 6 m/pixel).Our results show that Harmakhis Vallis has been modified by several processes after its formation. Age determinations on the small uncovered parts of the outflow channel, which possibly represent the original floor of Harmakhis, imply that Harmakhis may have experienced fluvial activity only 780–850 ( ± 400–600) Ma ago. The discovered terrace structure instead shows that the on-surface activity of the outflow channel has been periodic. The most significant of the modification processes on Harmakhis Vallis has been the formation of lineated valley fill units. The lineated valley fills now cover the outflow channel almost entirely. They formed not later than ∼ 400 Ma ago based on stratigraphic analyses and crater counts. All the floor units have also been resurfaced several, usually two or three times. The resurfacing ages of the dated units show that the later modification processes have occurred at least on a local scale in the Harmakhis Vallis region, not only inside the outflow channel. This, in turn, may indicate that the processes resulted from a larger-scale change, for example in the local climate or endogenic conditions.

Geomorphology of Ius Chasma, Valles Marineris, Mars

ABSTRACTCartographic products of the Martian trough system, Valles Marineris, are useful to identify the diversity and complexity of geological activity that has occurred there. A huge fraction of the processes that have shaped the surface of Mars are also concentrated there. A geomorphological map of Ius Chasma in western Valles Marineris is presented. The map is published in three sheets at 1:260,000. It was drawn on the basis of 100 Mars Reconnaissance Orbiter’s Context Camera images of 12 m/pixel resolution, mosaiced using the USGS ISIS Planetary Image Processing Software, and subsequently mapped and interpreted for geomorphology in ArcGIS. The map displays 52 main geomorphological units of which some are further subdivided. They include both well-established features (e.g. spur-and-gully morphology on trough walls, landslide scars, and deposits), and newly reported landforms (e.g. alluvial fans with dendritic channels, moraines in western Ius Chasma). The proposed classifications of landslide deposits, glacial landforms, and floor areas are more detailed than on any previous map of Valles Marineris. The Ius Chasma map is the first cartographic product presenting a full inventory of dune fields, impact craters, light-toned outcrops, and mass-wasting features.

Floor-Fractured Craters on Mars – Observations and Origin

Floor-Fractured Craters (FFCs) represent an impact crater type, where the infilling is separated by cracks into knobs of different sizes and shapes. This work focuses on the possible processes which form FFCs to understand the relationship between location and geological environment. We generated a global distribution map using new High Resolution Stereo Camera and Context Camera images. Four hundred and twenty-one potential FFCs have been identified on Mars. A strong link exists among floor fracturing, chaotic terrain, outflow channels and the dichotomy boundary. However, FFCs are also found in the Martian highlands. Additionally, two very diverse craters are used as a case study and we compared them regarding appearance of the surface units, chronology and geological processes. Five potential models of floor fracturing are presented and discussed here. The analyses suggest an origin due to volcanic activity, groundwater migration or tensile stresses. Also subsurface ice reservoirs and tectonic activity are taken into account. Furthermore, the origin of fracturing differs according to the location on Mars.

Outflow channels with deltaic deposits in Ismenius Lacus, Mars

A connected series of outflow channels in the Ismenius Lacus quadrangle are identified for the first time and characterized using High Resolution Stereo Camera images of Mars Express, the Context camera images of Mars Reconnaissance Orbiter and the topography of the Mars Observer Laser Altimeter. These channels (named Okavango Valles), which stretch over >400km south to north and join the northern plains, were identified from braided channels, scour/groove marks, poorly sinuous valleys and depositional landforms. Discharge rates were estimated to 0.1–5×106m3s−1 from analysis of the topography of scour marks. Pathways of channels segments were extracted from topography showing a unique source at a breached crater rim, suggesting overflow from ponded depressions. A series of delta fans are observed inside depressions along the channel pathways. The presence of these deltas formed in former bodies of water is a compelling argument for formation of this outflow channel system by fluvial flows. The similarity of these flows with other outflow channels on Mars proves that volcanically-related outflows cannot explain all such features. In addition, this study also shows that catastrophic floods are able to create fan deltas in transient lakes. This example has to be taken into account in the interpretation of late stage fans associated with poorly branched valleys and single channels.

The origin and timing of fluvial activity at Eberswalde crater, Mars

The fan deposit in Eberswalde crater has been interpreted as strong evidence for sustained liquid water on early Mars with a paleolake formed during the Noachian period (>3.7Gy). This location became a key region for understanding the Mars paleo-environment. Eberswalde crater is located 50km north of the rim of the 150km diameter crater Holden. Stratigraphic relationships and chronology obtained using recent Mars Express High Resolution Stereo Camera and Mars Reconnaissance Orbiter Context Camera images show that Eberswalde fluvial activity crosscuts Holden ejecta and thus postdates Holden crater, whose formation age is estimated from crater counts as Late Hesperian (∼3.5Gy, depending on models). Fluvial modeling shows that short term activity (over several years to hundreds of years) involving dense flows (with sediment:water ratio between 0.01 and 0.3) may be as good an explanation of the fluvial landforms as dilute flow over longer durations. Modeling of the thermal effect of the Holden impact in the Eberswalde watershed is used to evaluate its potential role in aqueous activity. The relative timing of the Holden impact and Eberswalde’s fan is a constraint for future studies about the origin of these landforms. Holden ejecta form a weak and porous substrate, which may be easy to erode by fluvial incision. In a cold climate scenario, impact heating could have produced runoff by melting snow or ground ice. Any attempt to model fluvial activity at Eberswalde should take into account that it may have formed as late as in the Late Hesperian, after the great majority of valley network formation and aqueous mineralization on Mars. This suggests that hypotheses for fan formation at Eberswalde by transient and/or localized processes (i.e. impact, volcanism, unusual orbital forcing) should be considered on a par with globally warmer climate.

Hesperian equatorial thermokarst lakes in Ares Vallis as evidence for transient warm conditions on Mars

On Earth, permafrost thawing is linked to climate warming. Similarly, on Mars, permafrost degradation, described from mid-latitude and equatorial settings, is likely linked to global or regional climate change. Putative thermokarst depressions identified on Mars are widely considered to be the result of sublimation, evaporation, or thawing of an ice-rich substrate. The possibility that the depressions formed by melting of permafrost to create alas-like lakes has been recently proposed, but is controversial, owing to the lack of primary evidence for liquid filling the depressions. Here we use high-resolution Mars Reconnaissance Orbiter Context Camera images and derived topographic data to characterize possible thermokarst terrain in Ares Vallis. The terrain comprises subcircular to irregular, flat-floored rimless topographic depressions that occur at varying elevations. We report the discovery of narrow channels connecting thermokarst-like depressions that provide evidence for the previous presence of ponded liquid water. Crater counts on these surfaces indicate resurfacing that is likely related to flood deposition of water-saturated sediments in Ares Vallis during the Hesperian (ca. 3.6–3.0 Ga). We infer that thermokarst lakes formed after flooding by thawing of ice within the sediments during transient warm periods in the Hesperian, a time previously considered to be too cold to permit ice thaw.