WHAT DEPOSITIONAL PROCESSES AND PALEOENVIRONMENTS FORMED THE LAYERED SULFATE UNIT IN GALE CRATER, MARS ? :: INSIGHTS FROM MARKER BAND VALLEY

International audienceThe stratigraphy of Aeolis Mons, Gale crater, is considered to provide a record of the possible ‘drying out’ of Mars with a temporal evolu-tion from clay-bearing mudstones, to sulfate-bearing rocks, to anhydrous minerals [1]. The Mars Science Laboratory Curiosity rover is investigating the deposi-tional environments of the layered sulfate-bearing unit considered to be from a ‘drier’ period than the underly-ing clay-bearing strata [1, 2, 3]. On sol 3560, Curiosity commenced exploration of the informally named Marker Band Valley (Figure 1) where the sulfate-bearing strata are exposed in local buttes. One of the overarching questions is what depositional environ-ments do the sulfate-bearing-units record. Here, we characterize the stratigraphic relations visible in these scarps and reconstruct processes of deposition of the sedimentary strata and their paleoenvironments

WHAT DEPOSITIONAL PROCESSES AND PALEOENVIRONMENTS FORMED THE LAYERED SULFATE UNIT IN GALE CRATER, MARS ? :: INSIGHTS FROM MARKER BAND VALLEY

International audienceThe stratigraphy of Aeolis Mons, Gale crater, is considered to provide a record of the possible ‘drying out’ of Mars with a temporal evolu-tion from clay-bearing mudstones, to sulfate-bearing rocks, to anhydrous minerals [1]. The Mars Science Laboratory Curiosity rover is investigating the deposi-tional environments of the layered sulfate-bearing unit considered to be from a ‘drier’ period than the underly-ing clay-bearing strata [1, 2, 3]. On sol 3560, Curiosity commenced exploration of the informally named Marker Band Valley (Figure 1) where the sulfate-bearing strata are exposed in local buttes. One of the overarching questions is what depositional environ-ments do the sulfate-bearing-units record. Here, we characterize the stratigraphic relations visible in these scarps and reconstruct processes of deposition of the sedimentary strata and their paleoenvironments

Multiple evolution modes of Aeolian Megaripples and implications for mars

International audienceMartian aeolian sedimentary rocks can unveil past wind-regimes and climates. Curiosity is exploring the layered sulphate-bearing unit exposed in the lower foothills of Aeolis Mons, Gale crater. Sedimentary structures indicate these strata were predominantly deposited within aeolian dune and sandsheet environments. Here, we report enigmatic erosional surfaces embedded within the sulphate-bearing strata and discuss their processes of formation. The surfaces form a set of concave-up scour-and-fill structures (width ~60 m; amplitude ~6 m). Their cross-sectional profiles show a planar central section with limbs inclined < 20°. The scour fill consists of: (1) low-angle inclined bedsets at the base which conformably drape the scour surface, overlain by (2) light-toned, relatively-planar strata lacking distinct bounding surfaces. Nearfield observations indicate that the scour-enclosing facies are composed of fine, even-in-thickness, laterally-extensive, planar laminations which are resemble the upper scour-fill strata. We interpret these laminations as wind-ripple strata. The geometry of the scours with broad cross-sectional concave profiles, flat central portions, and similar facies outside of and within the scour-and-fill structures suggest that the scours likely formed by aeolian processes. The scour-fill do not show evidence of fluvial facies. One plausible interpretation of the scours is that they represent saucer-shaped aeolian ‘blowout’ structures. Such structures, observed in both modern and ancient aeolian settings on Earth, commonly form through wind deflation from intense winds. The absence of such scour-and-fill structures in the lower part of the aeolian sulphate-bearing succession suggests that the presence of scours may indicate transition to enhanced wind deflation

Aridification sequence and formation of sulfates in Aeolis Mons, Gale crater

International audienceIn Gale crater, the Curiosity rover is exploring the sulfate-bearing unit, a regional package hundreds of meters thick of yet mostly undefined origin. The terrains orbitally defined as part of the clay-sulfate transition and leading upward to the sulfate-bearing unit show multiple signs consistent with marked changes towards drier paleoenvironments both in the sedimentary and geochemical record. Bedrock in the basal section is marked by diverse diagenetic overprints where sedimentary structures are less visible. Further up, the rover imaged butte-forming outcrops and revealed a >100-m-thick interval with a transition into large-scale trough cross-bedded structures. Within the large-scale cross-bedded strata of most likely eolian origin, ChemCam revealed that sulfates occur in the form of diverse lithologies mostly related to nodular bedrock. The abundance of nodules and related sulfates is highly variable. Indicators of locally and intermittently wet environments, such as mudcracks in the basal section or lenses with wave ripple laminae have been identified in specific intervals. The surrounding dry eolian strata adjacent to these features are also marked by the enhanced occurrence of nodular lithologies. This association and the general stratigraphic control on the distribution of sulfate-enriched nodules is consistent with their formation within the sediments due to evaporation where a sulfate-rich water table reached or came close to the surface in a variably dry climate

Aridification sequence and formation of sulfates in Aeolis Mons, Gale crater

International audienceIn Gale crater, the Curiosity rover is exploring the sulfate-bearing unit, a regional package hundreds of meters thick of yet mostly undefined origin. The terrains orbitally defined as part of the clay-sulfate transition and leading upward to the sulfate-bearing unit show multiple signs consistent with marked changes towards drier paleoenvironments both in the sedimentary and geochemical record. Bedrock in the basal section is marked by diverse diagenetic overprints where sedimentary structures are less visible. Further up, the rover imaged butte-forming outcrops and revealed a >100-m-thick interval with a transition into large-scale trough cross-bedded structures. Within the large-scale cross-bedded strata of most likely eolian origin, ChemCam revealed that sulfates occur in the form of diverse lithologies mostly related to nodular bedrock. The abundance of nodules and related sulfates is highly variable. Indicators of locally and intermittently wet environments, such as mudcracks in the basal section or lenses with wave ripple laminae have been identified in specific intervals. The surrounding dry eolian strata adjacent to these features are also marked by the enhanced occurrence of nodular lithologies. This association and the general stratigraphic control on the distribution of sulfate-enriched nodules is consistent with their formation within the sediments due to evaporation where a sulfate-rich water table reached or came close to the surface in a variably dry climate

Aridification sequence and formation of sulfates in Aeolis Mons, Gale crater

International audienceIn Gale crater, the Curiosity rover is exploring the sulfate-bearing unit, a regional package hundreds of meters thick of yet mostly undefined origin. The terrains orbitally defined as part of the clay-sulfate transition and leading upward to the sulfate-bearing unit show multiple signs consistent with marked changes towards drier paleoenvironments both in the sedimentary and geochemical record. Bedrock in the basal section is marked by diverse diagenetic overprints where sedimentary structures are less visible. Further up, the rover imaged butte-forming outcrops and revealed a >100-m-thick interval with a transition into large-scale trough cross-bedded structures. Within the large-scale cross-bedded strata of most likely eolian origin, ChemCam revealed that sulfates occur in the form of diverse lithologies mostly related to nodular bedrock. The abundance of nodules and related sulfates is highly variable. Indicators of locally and intermittently wet environments, such as mudcracks in the basal section or lenses with wave ripple laminae have been identified in specific intervals. The surrounding dry eolian strata adjacent to these features are also marked by the enhanced occurrence of nodular lithologies. This association and the general stratigraphic control on the distribution of sulfate-enriched nodules is consistent with their formation within the sediments due to evaporation where a sulfate-rich water table reached or came close to the surface in a variably dry climate

'HIGH' BUT NOT SO DRY ON AEOLIS MONS:: TRANSIENT LAKE SYSTEMS IN HESPERIAN DESERTS IN GALE CRATER

International audienceThe stratigraphy preserved within Aeolis Mons in Gale crater (Mars) shows a major transition from a phyllosilicate-bearing unit, which in situ data show is composed of mudstone-rich strata (with subordinate sandstones) recording deposition in lacustrine to fluvial settings into a major sulfatebearingunit that is hundreds of meters thick (the Layered Sulfate-bearing unit (LSu)) [1,2,3,4]. The origin of the LSu unit is not yet constrained.Comparison to other terrains on Mars has led to the hypothesis that the transition from clay minerals to sulfates records a planet-wide change in climate from relatively warm and wet to cold and arid [1]. A leading question is whether this transition is so unidirectional. The lower section of the LSu (claysulphate transition stratigraphy) contains strongy diagenetically altered strata or stacked, cross-bedded facies (Dunnideer and Port Logan mbs of the Mirador fm) that likely records a purely dry aeolian dune environment [5]. However, higher up in the studied section within the Contigo member, we observe sandstone lenses interstratified within aeolian strata that show distinctive sedimentary structures indicative of deposition by lacustrine and fluvial processes in shallow interdune depressions [6]. In late 2022, Curiosity investigated a distinctive dark-toned, resistant unit even higher within the sulfate-bearing stratigraphy of Aeolis Mons – the “Marker Band” [1,4,7,8]. Stratigraphically it has been informally designated the Amapari member of the Mirador formation (Mt. Sharp gp). This unit can be traced for tens of kilometers around Aeolis Mons [7], and from early in the mission was considered an important geologic target for investigation [1]. The key question concerning the “Marker Band” is what geological process led to its formation and how does it relate to the Layered Sulfate-bearing unit. Orbital-scale observations led to favored interpretations of the “Marker Band” as a volcanic ash deposit or a more indurated sulfate unit [7]. The first edge-on view in the distance favored an eolian deflation surface [3]. Here we describe the sedimentology of unit and go on to discuss initial implications for paleoenvironmental and paleoclimatic interpretations

'HIGH' BUT NOT SO DRY ON AEOLIS MONS:: TRANSIENT LAKE SYSTEMS IN HESPERIAN DESERTS IN GALE CRATER

International audienceThe stratigraphy preserved within Aeolis Mons in Gale crater (Mars) shows a major transition from a phyllosilicate-bearing unit, which in situ data show is composed of mudstone-rich strata (with subordinate sandstones) recording deposition in lacustrine to fluvial settings into a major sulfatebearingunit that is hundreds of meters thick (the Layered Sulfate-bearing unit (LSu)) [1,2,3,4]. The origin of the LSu unit is not yet constrained.Comparison to other terrains on Mars has led to the hypothesis that the transition from clay minerals to sulfates records a planet-wide change in climate from relatively warm and wet to cold and arid [1]. A leading question is whether this transition is so unidirectional. The lower section of the LSu (claysulphate transition stratigraphy) contains strongy diagenetically altered strata or stacked, cross-bedded facies (Dunnideer and Port Logan mbs of the Mirador fm) that likely records a purely dry aeolian dune environment [5]. However, higher up in the studied section within the Contigo member, we observe sandstone lenses interstratified within aeolian strata that show distinctive sedimentary structures indicative of deposition by lacustrine and fluvial processes in shallow interdune depressions [6]. In late 2022, Curiosity investigated a distinctive dark-toned, resistant unit even higher within the sulfate-bearing stratigraphy of Aeolis Mons – the “Marker Band” [1,4,7,8]. Stratigraphically it has been informally designated the Amapari member of the Mirador formation (Mt. Sharp gp). This unit can be traced for tens of kilometers around Aeolis Mons [7], and from early in the mission was considered an important geologic target for investigation [1]. The key question concerning the “Marker Band” is what geological process led to its formation and how does it relate to the Layered Sulfate-bearing unit. Orbital-scale observations led to favored interpretations of the “Marker Band” as a volcanic ash deposit or a more indurated sulfate unit [7]. The first edge-on view in the distance favored an eolian deflation surface [3]. Here we describe the sedimentology of unit and go on to discuss initial implications for paleoenvironmental and paleoclimatic interpretations

Wet to Dry Depositional Environments Recorded in the Clay-Sulfate Transition Region in Gale Crater, Mars: Overview and Stratigraphic Context for Curiosity's Exploration Campaign

International audienceOne of the key factors in selecting Gale crater as the landing site for the Mars Science Laboratory (MSL) mission was the ability to observeenvironmental transitions recorded in Aeolis Mons (informally known as Mt. Sharp). Orbital observations had revealed a vertical succession from strata that have abundant clay minerals to strata containing Mg sulfates [1], hypothesized to be tied to a shift from wetter to drier conditions. More recently, the Decadal Survey identified this question as central to Mars exploration: Did habitability persist through dramatic changes in the ancient climate? This work focuses on addressing the environments in which the clay-bearing and sulfatebearing units were deposited, and what that implies about the evolution of the Martian climate. Here we provide an overview of Curiosity’s exploration campaign through the clay-sulfate transition region and into the Mg sulfate-bearing unit (~Sols 3081-3755, elevation from -4072 m to -3850 m, investigated by the MSL science team from April 2021 to February 2023), and provide a summary of the sedimentological and stratigraphic context for the region

Wet to Dry Depositional Environments Recorded in the Clay-Sulfate Transition Region in Gale Crater, Mars: Overview and Stratigraphic Context for Curiosity's Exploration Campaign

International audienceOne of the key factors in selecting Gale crater as the landing site for the Mars Science Laboratory (MSL) mission was the ability to observeenvironmental transitions recorded in Aeolis Mons (informally known as Mt. Sharp). Orbital observations had revealed a vertical succession from strata that have abundant clay minerals to strata containing Mg sulfates [1], hypothesized to be tied to a shift from wetter to drier conditions. More recently, the Decadal Survey identified this question as central to Mars exploration: Did habitability persist through dramatic changes in the ancient climate? This work focuses on addressing the environments in which the clay-bearing and sulfatebearing units were deposited, and what that implies about the evolution of the Martian climate. Here we provide an overview of Curiosity’s exploration campaign through the clay-sulfate transition region and into the Mg sulfate-bearing unit (~Sols 3081-3755, elevation from -4072 m to -3850 m, investigated by the MSL science team from April 2021 to February 2023), and provide a summary of the sedimentological and stratigraphic context for the region