Martian Paleolake Outlet Canyons - Evidence for Controls on Valley Network Formation

Martian valley networks (VNs) have been viewed as one of the most compelling pieces of evidence for ancient fluvial activity during the Late Noachian and Early Hesperian periods (3.7–3.5 Ga), likely as a result of precipitation (snowfall/rainfall). During this period, paleolakes also formed, predominantly due to water accumulation within impact crater interiors. Some of these paleolakes breached the rim of their basins (e.g., crater rim) which caused outburst flooding and incision of a paleolake outlet canyon over a short period of time (weeks to years). After the Late Hesperian, valley formation vastly decreased indicating a waning water cycle. There have been inferences that paleolake outlet canyons may have controlled the trajectories of adjacent valley networks that formed after them, yet no direct evidence has been observed. In this study, we map and apply paleohydraulic, morphometric, and morphological calculations to two hydrological systems located west of the Tharsis Rise, where hydrological systems are defined as a combination of a paleolake outlet canyon and adjoining VNs. We aim to determine whether the paleolake outlet canyons show evidence of control on the trajectory of adjacent VNs and the impact this has on their development. We find that the paleolake outlet canyons do place control on the trajectories of adjacent VNs, causing them to detour from the regional slope direction and causing the basin to deviate from the natural fractal geometry formed by precipitation-fed fluvial incision. Additionally, the paleolake outlet canyons display a decrease in the cross-sectional area down their profile, indicating they experienced water loss as they were active. The examined paleolake outlet canyons have altered the evolution and interconnectivity of the adjoining VNs, leading to water loss, likely to the subsurface. Finally, given the proximity of these hydrological systems to the Tharsis Rise, we note that they display a complex history of fluvial and tectonic activity, indicating that fluvial activity both preceded and post-dates Tharsis-induced tectonic activity

The Hypanis Valles delta: The last highstand of a sea on early Mars?

One of the most contentious hypotheses in the geological history of Mars is whether the northern lowlands ever contained an oceanic water body. Arguably, the best evidence for an ocean comes from the presence of sedimentary fans around Mars' dichotomy boundary, which separates the northern lowlands from the southern highlands. Here we describe the palaeogeomorphology of the Hypanis Valles sediment fan, the largest sediment fan complex reported on Mars (area >970 km2). This has an extensive catchment (4.6 x 105 km2) incorporating Hypanis and Nanedi Valles, that we show was active during the late-Noachian/early-Hesperian period (∼3.7 Ga). The fan comprises a series of lobe-shaped sediment bodies, connected by multiple bifurcating flat-topped ridges. We interpret the latter as former fluvial channel belts now preserved in inverted relief. Meter-scale-thick, sub-horizontal layers that are continuous over tens of kilometres are visible in scarps and the inverted channel margins. The inverted channel branches and lobes are observed to occur up to at least 140 km from the outlet of Hypanis Valles and descend ∼500 m in elevation. The progressive basinward advance of the channellobe transition records deposition and avulsion at the margin of a retreating standing body of water, assuming the elevation of the northern plains basin floor is stable. We interpret the Hypanis sediment fan to represent an ancient delta as opposed to a fluvial fan system. At its location at the dichotomy boundary, the Hypanis Valles fan system is topographically open to Chryse Planitia – an extensive plain that opens in turn into the larger northern lowlands basin. We conclude that the observed progradation of fan bodies was due to basinward shoreline retreat of an ancient body of water which extended across at least Chryse Planitia. Given the open topography, it is plausible that the Hypanis fan system records the existence, last highstand, and retreat of a large sea in Chryse Planitia and perhaps even an ocean that filled the northern plains of Mars

Aram Dorsum: an extensive mid-Noachian age fluvial depositional system in Arabia Terra, Mars

A major debate in Mars science is the nature of the early Mars climate, and the availability of precipitation and runoff. Observations of relict erosional valley networks have been proposed as evidence for extensive surface run‐off around the Noachian‐Hesperian boundary. However, these valley networks only provide a time‐integrated record of landscape evolution and thus the timing, relative timescales and intensity of aqueous activity required to erode the valleys remain unknown. Here, we investigate an ancient fluvial sedimentary system in western Arabia Terra, now preserved in positive relief. This ridge, ‘Aram Dorsum’, is flat‐topped, branching, ~ 85 km long, and particularly well‐preserved. We show that Aram Dorsum was an aggradational alluvial system and that the existing ridge was once a large river channel‐belt set in extensive flood plains, many of which are still preserved. Smaller, palaeochannel‐belts feed the main system; their setting and network pattern suggest a distributed source of water. The alluvial succession is up to 60 m thick, suggesting a formation time of 105 to 107 years by analogy to Earth. Our observations are consistent with Aram Dorsum having formed by long‐lived flows of water, sourced both locally, and regionally as part of a wider alluvial system in Arabia Terra. This suggests frequent or seasonal precipitation as the source of water. Correlating our observations with previous regional‐scale mapping shows that Aram Dorsum formed in the mid‐Noachian, making it one of the oldest fluvial systems described on Mars and indicating climatic conditions that sustained surface river flows on early Mars

NOAH-H, a deep-learning, terrain classification system for Mars: Results for the ExoMars Rover candidate landing sites

In this investigation a deep learning terrain classification system, the “Novelty or Anomaly Hunter – HiRISE” (NOAH-H), was used to classify High Resolution Imaging Science Experiment (HiRISE) images of Oxia Planum and Mawrth Vallis. A set of ontological classes was developed that covered the variety of surface textures and aeolian bedforms present at both sites. Labelled type-examples of these classes were used to train a Deep Neural Network (DNN) to perform semantic segmentation in order to identify these classes in further HiRISE images. This contribution discusses the methods and results of the study from a geomorphologists perspective, providing a case study applying machine learning to a landscape classification task. Our aim is to highlight considerations about how to compile training datasets, select ontological classes, and understand what such systems can and cannot do. We highlight issues that arise when adapting a traditional planetary mapping workflow to the production of training data. We discuss both the pixel scale accuracy of the model, and how qualitative factors can influence the reliability and usability of the output. We conclude that “landscape level” reliability is critical for the use of the output raster by humans. The output can often be more useful than pixel scale accuracy statistics would suggest, however the product must be treated with caution, and not considered a final arbiter of geological origin. A good understanding of how and why the model classifies different landscape features is vital to interpreting it reliably. When used appropriately the classified raster provides a good indication of the prevalence and distribution of different terrain types, and informs our understanding of the study areas. We thus conclude that it is fit for purpose, and suitable for use in further work

Active Upper-atmosphere Chemistry and Dynamics from Polar Circulation Reversal on Titan

Saturn's moon Titan has a nitrogen atmosphere comparable to Earth's, with a surface pressure of 1.4 bar. Numerical models reproduce the tropospheric conditions very well but have trouble explaining the observed middle-atmosphere temperatures, composition and winds. The top of the middle-atmosphere circulation has been thought to lie at an altitude of 450 to 500 kilometres, where there is a layer of haze that appears to be separated from the main haze deck. This 'detached' haze was previously explained as being due to the colocation of peak haze production and the limit of dynamical transport by the circulation's upper branch. Herewe report a build-up of trace gases over the south pole approximately two years after observing the 2009 post-equinox circulation reversal, from which we conclude that middle-atmosphere circulation must extend to an altitude of at least 600 kilometres. The primary drivers of this circulation are summer-hemisphere heating of haze by absorption of solar radiation and winter-hemisphere cooling due to infrared emission by haze and trace gases; our results therefore imply that these effects are important well into the thermosphere (altitudes higher than 500 kilometres). This requires both active upper-atmosphere chemistry, consistent with the detection of high-complexity molecules and ions at altitudes greater than 950 kilometres, and an alternative explanation for the detached haze, such as a transition in haze particle growth from monomers to fractal structures

Hypotheses for the Origin of the Hypanis Fan-Shaped Deposit at the Edge of the Chryse Escarpment, Mars: Is it a Delta?

We investigated the origin of the fan-shaped deposit at the end of Hypanis Valles that has previously been proposed as an ExoMars, Mars 2020, and human mission candidate landing site, and found evidence that the landform is an ancient delta. Previous work suggests that the deposit originated from a time of fluvial activity both distinct from and prior to catastrophic outflow, and crater counting placed the deposit’s age at  ≥ 3.6 Ga. We found over 30 thin sedimentary strata in the proposed delta wall, and from our slope analysis conclude that the fluvial sequence is consistent with a lowering/retreating shoreline. We measured nearly horizontal bedding dip angles ranging from 0° to 2° over long stretches of cliff and bench exposures seen in HiRISE images and HiRISE stereo DTMs. From THEMIS night IR images we determined that the fan-shaped deposit has a low thermal inertia (150-240 Jm-2 K-1 s-1/2) and the surrounding darker-toned units correspond to thermal inertia values as high as 270-390 Jm-2 K-1 s-1/2. We interpret these findings to indicate that the fan-shaped deposit consists mostly of silt-sized and possibly finer grains, and that the extremely low grade and large lateral extent of these beds implies that the depositional environment was calm and relatively long-lived. We interpret the geomorphology and composition as incompatible with an alluvial fan or mudflow hypothesis. From our stratigraphic mapping we interpret the order of events which shaped the region. After the Chryse impact, sediment filled the basin, a confined lake or sea formed allowing a large delta to be deposited near its shoreline, the water level receded to the north, darker sedimentary/volcanic units covered the region and capped the light-toned deposit as hydro-volcanic eruptions shaped the interior of Lederberg crater, freeze/thaw cycles and desiccation induced local fracturing, and finally wrinkle ridges associated with rounded cones warped the landscape following trends in degraded crater rims and existing tectonic features. The ancient deltaic deposit we observe today was largely untouched by subsequent catastrophic outflows, and its surface has been only moderately reshaped by over 3 billion years of aeolian erosion

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context

The geography of Oxia Planum

We present the geography of Oxia Planum, the landing site for the ExoMars 2022 mission. This map provides the planetary science community with a framework to understand this, until recently, unexplored area. The map comprises (1) a mosaic of the panchromatic Context Camera (CTX) Digital Elevation Models (DEM) and Ortho Rectified Images (ORI) controlled to the High Resolution Stereo Camera (HRSC) multiorbit Digital Elevation Models (DEM) and (2) a mosaic of Colour and Stereo Surface Imaging System (CaSSIS) synthetic colour data products, registered to the CTX ORI mosaic. We define a grid of exploration quadrangles (quads) and an informal group of geographic regions to describe Oxia Planum. These regions bridge the scale gap between features observed on large areas (∼100s km2) and the local geography (10s km2) relevant to the Rosalind Franklin rover’s operations in Oxia Planum

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context.The ExoMars Rosalind Franklin Mission is a partnership between ESA and NASA. The Rosalind Franklin Rover has eight instruments in its ‘Pasteur’ Payload, with Principal Investigators from seven countries all of whom we would like to thank for there support of this project. We would like to acknowledge the following funding bodies, people and institutions supporting the lead authors of this work. We thank the UK Space Agency (UK SA) for funding P. Fawdon, on grants; ST/W002736/1, ST/L00643X/1 and ST/R001413/1, MRB on grants; ST/T002913/1, ST/V001965/1, ST/R001383/1, ST/R001413/1, P. Grindrod on grants; ST/L006456/1, ST/R002355/1, ST/V002678/1 and J. Davis on grants ST/K502388/1, ST/R002355/1, ST/V002678/1 through the ongoing Aurora space exploration programme. C. Orgel was supported by the ESA Research Fellowship Program. Alessandro Frigeri: was funded by the Italian Space Agency (ASI) grant ASI-INAF number 2017-412-H.0 (ExoMars/Ma_MISS) and D. Loizeau was funded by the H2020-COMPET-2015 programme (grant 687302), C. Quantin-Nataf was supported by the French space agency CNES, I. Torres was supported by an ESA Young Graduate Traineeship, A. Nass was supported by Helmholtz Metadata Projects (#ZT-I-PF-3-008). We thank NASA and the HiRISE camera team for data collection support throughout the ExoMars landing site selection and charectorisation process. The USGS for the HiRISE DTM data and maintaining the ISIS and SOCET SET DEM workflows. The authors wish to thank the CaSSIS spacecraft and instrument engineering teams. CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA's PRODEX programme. The instrument hardware development was also supported by the Italian Space Agency (ASI) (ASI-INAF agreement no. I/2020-17-HH.0), INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw. Support from SGF (Budapest), the University of Arizona (Lunar and Planetary Lab.) and NASA are also gratefully acknowledged. Operations support from the UK Space Agency under grant ST/R003025/1 is also acknowledged. This research has made use of the USGS Integrated Software for Imagers and Spectrometers (ISIS) Technical support for setup of the Multi-Mission Geographic Information System for concurrent team mapping was provided by F. Calef (III) and T. Soliman at NASA JPL and S. de Witte at ESA-ESTEC.This work was supported by Agencia Estatal de Investigación [grant number ID2019-107442RB-C32, MDM-2017-0737]; Agenzia Spaziale Italiana [grant number 2017-412-H.0]; Bundesministerium für Wirtschaft und Technologie [grant number 50 QX 2002]; Centre National de la Recherche Scientifique; Centre National d’Etudes Spatiales; Euskal Herriko Unibertsitatea [grant number PES21/88]; Istituto Nazionale di Astrofisica [grant number I/ 060/10/0]; Ministerio de Economía y Competitividad [grant number PID2019-104205GB-C21]; Ministry of Science and Higher Education of the Russian Federation [grant number AAAA-A18-118012290370-6]; National Aeronautics and Space Administration [grant number NNX15AH46G]; Norges Forskningsråd [grant number 223272]; European Union's Horizon 2020 (H2020-COMPET-2015) [grant number 687302 (PTAL)]; Sofja Kovalevskaja Award of the Alexander von Humboldt Foundation; MINECO [grant number PID2019-107442RB-C32]; The Open University [grant number Space Strategic Research Area]; European Union's Horizon 2020 research and innovation programme [grant number 776276]; H2020-COMPET-2015 [grant number 687302]; The Research Council of Norway, Centres of Excellence funding scheme [grant number 223272]; Helmholtz Metadata Projects [grant number ZT-I-PF-3-008]; The Research Council of Norway [grant number 223272]; Swiss Space Office via ESA's PRODEX programme; Ines Torres was supported by an ESA Young Graduate Traineeship; Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung [grant number 200021_197293]; Science and Technology Facilities Council [grant number 1967420]; UK Space Agency [grant number ST/K502388/1, ST/R002355/1, ST/V002678/1]. The ExoMars Rosalind Franklin Mission is a partnership between ESA and NASA. The Rosalind Franklin Rover has eight instruments in its ‘Pasteur’ Payload, with Principal Investigators from seven countries all of whom we would like to thank for there support of this project. We would like to acknowledge the following funding bodies, people and institutions supporting the lead authors of this work. We thank the UK Space Agency (UK SA) for funding P. Fawdon, on grants; ST/W002736/1, ST/L00643X/1 and ST/R001413/1, MRB on grants; ST/T002913/1, ST/V001965/1, ST/R001383/1, ST/R001413/1, P. Grindrod on grants; ST/L006456/1, ST/R002355/1, ST/V002678/1 and J. Davis on grants ST/K502388/1, ST/R002355/1, ST/V002678/1 through the ongoing Aurora space exploration programme. C. Orgel was supported by the ESA Research Fellowship Program. Alessandro Frigeri: was funded by the Italian Space Agency (ASI) grant ASI-INAF number 2017-412-H.0 (ExoMars/Ma_MISS) and D. Loizeau was funded by the H2020-COMPET-2015 programme (grant 687302), C. Quantin-Nataf was supported by the French space agency CNES, I. Torres was supported by an ESA Young Graduate Traineeship, A. Nass was supported by Helmholtz Metadata Projects (#ZT-I-PF-3-008). We thank NASA and the HiRISE camera team for data collection support throughout the ExoMars landing site selection and charectorisation process. The USGS for the HiRISE DTM data and maintaining the ISIS and SOCET SET DEM workflows. The authors wish to thank the CaSSIS spacecraft and instrument engineering teams. CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA's PRODEX programme. The instrument hardware development was also supported by the Italian Space Agency (ASI) (ASI-INAF agreement no. I/2020-17-HH.0), INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw. Support from SGF (Budapest), the University of Arizona (Lunar and Planetary Lab.) and NASA are also gratefully acknowledged. Operations support from the UK Space Agency under grant ST/R003025/1 is also acknowledged. This research has made use of the USGS Integrated Software for Imagers and Spectrometers (ISIS) Technical support for setup of the Multi-Mission Geographic Information System for concurrent team mapping was provided by F. Calef (III) and T. Soliman at NASA JPL and S. de Witte at ESA-ESTEC.Peer reviewe

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context