•Putative hydrothermal deposits are found in Auki crater.•Formation and post impact hydrous environments in Thyrrena Terra, Mars.•Impact-generated hydrothermal alteration formed phyllosilicates, ...carbonates, zeolites, chlorites, serpentines and opals.•New evidence for impact-generated hydrothermal systems on Mars is presented using CRISM and HiRISE data.
A variety of hydrothermal environments have been documented in terrestrial impact structures. Due to both past water interactions and meteoritic bombardment on the surface of Mars, several authors have predicted various scenarios that include the formation of hydrothermal systems. Geological and mineralogical evidence of past hydrothermal activity have only recently been found on Mars. Here, we present a geological and mineralogical study of the Auki Crater using the spectral and visible imagery data acquired by the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars), CTX (Context Camera) and HiRISE (High Resolution Imaging Science Experiment) instruments on board the NASA MRO mission.
The Auki Crater is a complex crater that is ∼38km in diameter located in Tyrrhena Terra (96.8°E and 15.7°S) and shows a correlation between its mineralogy and morphology. The presence of minerals, such as smectite, silica, zeolite, serpentine, carbonate and chlorite, associated with morphological structures, such as mounds, polygonal terrains, fractures and veins, suggests that the Auki Crater may have hosted a post impact-induced hydrothermal system. Although the distribution of hydrated minerals in and around the central uplift and the stratigraphic relationships of some morphological units could also be explained by the excavation and exhumation of carbonate-rich bedrock units as a consequence of crater formation, we favor the hypothesis of impact-induced hydrothermal circulation within fractures and subsequent mineral deposition. The hydrothermal system could have been active for a relatively long period of time after the impact, thus producing a potential transient habitable environment.
Wind‐formed features are abundant in Oxia Planum (Mars), the landing site of the 2022 ExoMars mission, which shows geological evidence for a past wet environment. Studies of aeolian bedforms at the ...landing site were focused on assessing the risk for rover trafficability, however their potential in recording climatic fluctuations has not been explored. Here we show that the landing site experienced multiple climatic changes in the Amazonian, which are recorded by an intriguing set of ridges that we interpret as Periodic Bedrock Ridges (PBRs). Clues for a PBR origin result from ridge regularity, defect terminations, and the presence of preserved megaripples detaching from the PBRs. PBR orientation differs from superimposed transverse aeolian ridges pointing toward a major change in wind regime. Our results provide constrains on PBR formation mechanisms and offer indications on paleo winds that will be crucial for understanding the landing site geology.
Plain Language Summary
Oxia Planum on Mars is the landing site for the ExoMars 2022 mission. The region likely hosted a standing body of water, but the effect of the wind was also important in shaping the landscape. In this study, we first describe a set of linear ridges that, in our interpretation, were sculpted by the wind in a more recent past. We also show that the wind that formed the ridges (Periodic Bedrock Ridges) was blowing from a different direction than the ones that formed younger ripples on top, suggesting a complex geological history of wind erosion and deposition that will be further investigated during the ExoMars mission.
Key Points
We present the first evidence for a periodic bedrock ridge (PBRs) pattern from the ExoMars 2022 landing site
Formative paleowind directions are extrapolated from PBRs and transverse aeolian ridges
Evidence for an Amazonian change in the wind regime are provided
A multidisciplinary study of an ancient area of Mars (Early to Late Noachian) located in Arabia Terra is presented, centred at 6°1′N, 354°54′ E and including the 55 km size Vernal crater. By means ...of different spatial scale imagery datasets and digital terrain models (MOLA, THEMIS, HRSC, CTX, CaSSIS and HiRISE), we prepare a high-resolution geological map of the study site. We highlight the different bedrock stratigraphy inside the Vernal crater which is of particular exobiological interest given the presence of putative ancient hot springs, as well as identifying multiple transverse aeolian ridges, inverted fracture networks and paleochannels, mounds, and a 58 m fresh crater located just outside Vernal crater rim. Within all low-latitude regions of Mars, the studied site presents the highest values (up to 16.0 wt%) of water equivalent hydrogen, hence suggesting that there is a widespread presence of in situ subsurface (at maximum depths of 1–2 m) natural resources, such as water ice and/or hydrated minerals. The equatorial location of the area results in the maximum surface temperature and the highest mean solar flux gatherable on the surface of the planet throughout the year. The interesting scientific case, coupled with the presence of in situ exploitable resources and the thorough accomplishment of all landing/roving engineering safety requirements, make the Vernal crater area a strong landing site candidate for future human exploration of Mars.
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•ISRU and Human landing site candidate close to Mars equator.•First high-resolution geological map of Vernal crater and its surroundings.•Ancient hot springs exobiological potential.•In situ subsurface resource identification.•Engineering safety fulfilment and exploration zones characterization.
An extensive distribution of water‐altered equatorial layered deposits (ELDs) characterizes the densely cratered terrain of Arabia Terra (AT), Mars. The majority of these deposits reside within ...craters and are easily identified by laterally continuous layering. The processes that led to their formation have been widely investigated, but remain unresolved. Furthermore, their precise spatial distribution as a whole, as well as their relationship to one another individually, has yet to be fully appreciated. This work examines 1,013 craters and emphasizes 45 that were observed to contain ELDs within the eastern half of AT. We present the statistical relationships between crater characteristics (e.g., location, diameter, depth), as well as evidence supporting a southeast‐northwest facies change. The 30–2,000‐m range of measured deposit thicknesses, accompanied with individual layer thicknesses, correlate with crater elevation either due to water level differences within craters, or a proximal‐distal relationship to the source. Air fall or fluid expulsion appear to stand out among all the prevailing depositional hypotheses, however the volume required to fill these craters in an ash fall scenario is in opposition with the locations of known volcanic provinces and the volume of ash that volcanic eruptions produce. This new evidence of a regional facies change provides a unique opportunity to better understand past climate and sedimentary processes on Mars, as well as the putative groundwater level in ancient AT. Ultimately, our results do not agree well with a unified depositional method for these deposits and the possibility of mixed origins should be taken seriously.
Plain Language Summary
Layer thicknesses of equatorial layered deposits (ELDs) within craters in western Arabia Terra (AT) show a regional NW‐SE thickening, correlating with both elevation and latitude. The trend does not correlate with locations of established volcanic provinces or proposed locations of nearby calderas. Additionally, the volume necessary to completely fill craters may be problematic in an ash fall scenario. The discrepancy of ELD size between craters is problematic and requires specialized erosional intensities unique to each crater. Fluctuating water level might create a proximal‐distal effect either from the putative ocean to the northwest which hinders thicker ELD formation, or fluid expulsion focused at Meridiani Planum which aids thicker ELD formation. Thinning and thickening sequences in individual craters suggests repeated changes from low to high energy environments. Low to moderate layer attitudes are indicative of compaction or draping during deposition over pre‐existing topography, whereas steeply dipping layers suggests post‐depositional deformation in specific craters. This implies post‐depositional histories are often unique to individual craters. Observations demonstrate that determining the depositional method requires a regional overview to establish the controls that create these unique characteristics. Thus, a unifying depositional theory does not fit all characteristics of ELDs in AT and multiple or mixed origins should be considered.
Key Points
Geological evidence supporting a SE‐NW facies change within intracrater layered deposits in western Arabia Terra
Measurements of deposit thickness and individual layer thickness decrease with elevation and latitude
The volume required to fill these craters in an air fall scenario is in opposition with the locations of known volcanic provinces and the volume of ash volcanic eruptions produce
Equatorial Layered Deposits (ELDs) reveal aspects of past depositional environments useful for timing climatic and geological events on Mars. However, their formation has several contending ...hypotheses which reflect a diverse range of possible environments. To better constrain their formation mechanism, we analyzed the stratigraphic and mineralogical characteristics and mapped the distribution of ELDs within three close craters, Sera, Jiji, and an unnamed crater in central Arabia Terra. Analyses of craters' geology allowed us to reconstruct the paleo‐environments where ELDs have been deposited. Thinning and thickening sequence trends show shared and repeated variations in the depositional environment, reflecting sediment accumulation strongly controlled by a regional groundwater reservoir. Layered deposits are characterized by monohydrated and polyhydrated sulfate signatures implying an interaction between water and rock in acidic conditions. Our study contributes to the understanding of regional geological processes in Arabia Terra revealing long‐term aqueous activity.
Plain Language Summary
Despite years of orbital observations of the surface of Mars, mid‐to low‐latitude layered deposits (LD) in Arabia Terra are not yet fully understood. These deposits record an important geological sequence of the early Martian history, but their exact formation, specifically the putative role of the water in their formation and preservation, remains an unanswered question. This study helps in further understanding these processes by comparing and contrasting LD present in craters in very close proximity to each other. In this way, proposed hypotheses benefit from having a control that is not limited to a singular crater or location. Our study contributes to the understanding of regional geological processes in Arabia Terra revealing long‐term aqueous activity. Results combine various analyses, including measurements of layer thickness and attitudes, orbital spectroscopy, basin geometry, and morphologies aimed at reconstructing the geological evolution of the area. In particular, we interpreted that LD were emplaced in a depositional environment reflecting sediment accumulation strongly controlled by a regional groundwater reservoir in acidic conditions.
Key Points
Regional groundwater fluctuations influenced the deposition, mineralogy, and preservation of Equatorial Layered Deposits (ELDs) in Arabia Terra
Four different stratigraphic sequences of layered deposits have been identified on the basis of strata thickness and attitude
Mineralogical analyses of ELDs suggest the presence of different levels of hydration of sulfates
Understanding the origin of the Hesperian‐aged sulfate‐bearing Equatorial Layered Deposits (ELDs) is crucial to infer Mars' climatic conditions during their formation and to assess their habitability ...potential. We investigated well‐exposed ELDs in Kotido crater (Arabia Terra) and produced a detailed geological map of the crater infill, distinguishing different units within the ELDs based upon their morphological and sedimentological characteristics.
The ELDs consist of interbedded light‐toned, darker‐toned deposits and mounds, associated with possible fissure ridges. Although heavily eroded by younger eolian processes, we interpret these deposits and their associated morphologies as remnants of depositional features and propose that they are the result of fluid, gas, and sediment expulsion processes sourced from the groundwater. The textural characteristics, their depositional geometry, the associated morphologies, and the inferred composition of the light‐toned deposits suggest an evaporitic origin, whereas the darker‐toned deposits might reflect clastic sedimentary processes, related or not to fluid expulsion and/or residual deposition following dissolution of the evaporites. The relative ratio of fluids, salts, and clasts controlled the depositional process, analogous to what happens in terrestrial playas. The controls on fluid expulsion is interpreted to depend on groundwater emplacement and fluctuations, possibly related to climatic changes, and to the interactions with the fractures related to the crater formation, which allowed the actual upwelling from a pressurized aquifer.
Plain Language Summary
Light‐toned layered deposits rich in sulfates are widespread on Mars in several locations. Understanding how these deposits formed is crucial to infer the climatic conditions during Martian history and, in light of the fact that potentially similar deposits on Earth have been shown to be conducive to bacterial life, is critical in the search for habitable environments on Mars. We focused on Kotido crater because it shows a remarkable infill and excellent data coverage. We drew a detailed geological map, recognizing subunits interbedded within the layered deposits: light‐toned and darker‐toned layers, subconical mounds, and associated fractures. We interpret these materials to result from episodes of water upwelling sourced from the subsurface: a mixture of fluids, gases, and sediments emerged in Kotido leading to the deposition of the different subunits depending on the relative ratio of the upwelling materials in the different phases. The mounds and fractures would represent the morphological expression of the upwelling process, while the light‐ and darker‐toned material would represent the resulting deposits. The proposed mechanism is identical to that of terrestrial environments such as playa and spring deposition typical of arid settings where bacterial life is well adapted.
Key Points
We mapped the Equatorial Layered Deposits of Kotido crater, recognizing their geological variability and stratigraphic relations
Fluid expulsion processes controlled by groundwater fluctuations appear to be the driving mechanism on the deposition/preservation
The importance of groundwater control raises issues on the possible lateral relations with other deposits/morphologies in Arabia Terra
Understanding the initial and flow conditions of contemporary flows in Martian gullies, generally believed to be triggered and fluidized by CO2 sublimation, is crucial for deciphering climate ...conditions needed to trigger and sustain them. We employ the RAMMS (RApid Mass Movement Simulation) debris flow and avalanche model to back calculate initial and flow conditions of recent flows in three gullies in Hale crater. We infer minimum release depths of 1.0–1.5 m and initial release volumes of 100–200 m3. Entrainment leads to final flow volumes that are ∼2.5–5.5 times larger than initially released, and entrainment is found necessary to match the observed flow deposits. Simulated mean cross‐channel flow velocities decrease from 3–4 m/s to ∼1 m/s from release area to flow terminus, while flow depths generally decrease from 0.5–1 to 0.1–0.2 m. The mean cross‐channel erosion depth and deposition thicknesses are ∼0.1–0.3 m. Back‐calculated dry‐Coulomb friction ranges from 0.1 to 0.25 and viscous‐turbulent friction between 100 and 200 m/s2, which are values similar to those of granular debris flows on Earth. These results suggest that recent flows in gullies are fluidized to a similar degree as are granular debris flows on Earth. Using a novel model for mass flow fluidization by CO2 sublimation we are able to show that under Martian atmospheric conditions very small volumetric fractions of CO2 of ≪1% within mass flows may indeed yield sufficiently large gas fluxes to cause fluidization and enhance flow mobility.
Key Points
We use RAMMS to back calculate initial and flow conditions of recent flows in three gullies in Hale crater
Recent flows in gullies are fluidized to a similar degree as are wet granular debris flows on Earth
Very small volumetric fractions of CO2 of ≪1% may yield sufficiently large gas fluxes to fluidize contemporary flow in Martian gullies
A widely hypothesized but complex transition from widespread fluvial activity to predominantly aeolian processes is inferred on Mars based on remote sensing data observations of ancient landforms. ...However, the lack of analysis of in situ martian fluvial deposits hinders our understanding of the flow regime nature and sustainability of the martian fluvial activity and the hunt for ancient life. Studying analogs from arid zones on Earth is fundamental to quantitatively understanding geomorphic processes and climate drivers that might have dominated during early Mars. Here we investigate the formation and preservation of fluvial depositional systems in the eastern Sahara, where the largest arid region on Earth hosts important repositories of past climatic changes. The fluvial systems are composed of well‐preserved single‐thread sinuous to branching ridges and fan‐shaped deposits interpreted as deltas. The systems' configuration and sedimentary content suggest that ephemeral rivers carved these landforms by sequential intermittent episodes of erosion and deposition active for 10–100s years over ∼10,000 years during the late Quaternary. Subsequently, these landforms were sculpted by a marginal role of rainfall and aeolian processes with minimum erosion rates of 1.1 ± 0.2 mm/yr, supplying ∼96 ± 24 × 1010 m3 of disaggregated sediment to adjacent aeolian dunes. Our results imply that similar martian fluvial systems preserving single‐thread, short distance source‐to‐sink courses may have formed due to transient drainage networks active over short durations. Altogether, this study adds to the growing recognition of the complexity of interpreting climate history from orbital images of landforms.
Plain Language Summary
Mars is currently a dry and cold desert, but rivers preserved in inverted topography suggest that water once flowed during its early history. However, how sustained and how frequently these rivers flowed remains uncertain. Here we study ancient fluvial systems (rivers and deltas) from the eastern Sahara that formed during the late Quaternary, in much wetter conditions than those prevailing today in this desert and which bear striking analogies to martian systems. We find that rivers and deltas, now preserved as ridges, record short distance source‐to‐sink high‐energy systems formed due to heavy rainfall events. Our observations and measurements of the meandering systems within the deltaic features suggest that such wet conditions might have spanned tens to a few hundred years over a total duration of ∼10,000 years. Since the wet conditions ceased, arid conditions prevailed, and the aeolian processes resumed, sculpting ridges out of ancient channels. Our results imply that martian fluvial systems may have been associated with similar local and heavy runoff conditions that lasted 10–100s years over thousands of years, possibly sufficient to support habitability. A shift toward arid environments led to the sculpting of fluvial ridges and the widespread formation of dunes across the modern martian landscape.
Key Points
Ancient depositional rivers in southern Egypt record ephemeral fluvial systems formed due to intense rainfall over ∼10 ka
These fluvial systems suggest tens to hundreds of years of river activity
Similar martian systems imply that early Mars's surface was punctuated by local and transient drainage systems fed over short durations
The research project ‘Moon Mapping’ has been established in 2014 between the Italian and Chinese Governments to promote cooperation and exchange between undergraduate students from both countries. ...The operational phase of the project started in early 2015, and will end in 2017, for a total length of three years. The main aim is to train new scholars to be able to work on different kinds of remotely-sensed data collected over the Moon surface by the Chinese space missions Chang’E-1/2. The project coordination has been assigned to the Italian Space Agency for the Italian side and to the Center of Space Exploration, China Ministry of Education, for the Chinese side. Several Chinese universities and Italian national research institutes and universities have been officially involved in this project. Six main research topics have been identified: (1) map of the solar wind ion; (2) geomorphological map of the Moon; (3) data preprocessing of Chang’E-1 mission; (4) map of element distribution; (5) establishment of 3D digital visualization system; and (6) compilation and publication of a tutorial on joint lunar mapping.
The research project ‘Moon Mapping’ has been established in 2014 between the Italian and Chinese Governments to promote cooperation and exchange between undergraduate students from both countries. ...The operational phase of the project started in early 2015, and will end in 2017, for a total length of three years. The main aim is to train new scholars to be able to work on different kinds of remotely-sensed data collected over the Moon surface by the Chinese space missions Chang’E-1/2. The project coordination has been assigned to the Italian Space Agency for the Italian side and to the Center of Space Exploration, China Ministry of Education, for the Chinese side. Several Chinese universities and Italian national research institutes and universities have been officially involved in this project. Six main research topics have been identified: (1) map of the solar wind ion; (2) geomorphological map of the Moon; (3) data preprocessing of Chang’E-1 mission; (4) map of element distribution; (5) establishment of 3D digital visualization system; and (6) compilation and publication of a tutorial on joint lunar mapping.
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