Terrain North of Hellas Planitia (ESP_065379_1620) - Request submitted: March 12, 2020; Request scheduled: June 25, 2020; Request fulfilled: July 7, 2020. This observation targets the confluence of a highlands drainage network located along the northern rim of the Hellas Basin. These drainage channels converge in a small basin that is surfaced by high-thermal inertia materials, consistent with exposed rock at the surface. However, the drainage channels themselves are surfaced by a low-thermal inertia material, suggesting that these materials are unconsolidated. In CTX imagery these materials have a dark tone compared to the surrounding materials, but contain small (3-5 px) bright spots. This dark material may represent surviving remnants of channel fill material, or possible mudflows of more recent origin. High resolution imagery will help determine stratigraphic contacts of the dark material to the surrounding bedrock. In addition, it will help determine whether the small bright spots are boulders or small outcrops of the bedrock poking through the dark material.
Stereo justification: The knob-forming unit targeted here shows hints of internal stratigraphy. Stereo imaging will allow for construction of a DTM which will allow a search for breaks in slope characteristic of changes in lithology. It will allow for construction of a stratigraphic column which could be compared to other light-toned knobby units located within the region.
Layered Bedrock (Stereo Pair: ESP_065747_1740 & ESP_065958_1740) - November 3, 2020 HiRISE Picture of the Day! - Request submitted: December 19, 2019; Request scheduled: July 29, 2020; Request fulfilled: August 5, 2020. This observation targets a highly textured bedrock surface in northeastern Tyrrhena Terra. Due to this location of this material at the junction of incised valley networks, the presence of massive layering at CTX resolution, and the high apparent erosional susceptibility of these materials, this location has a high probability of being a sedimentary deposit. This observation will be used to characterize this deposit. In addition, this material appears to be the source of dark sand dune materials filling deeply incised valleys and in isolated dunes located in the highlands terrain to the south. These dunes appear to originate from light-toned ripples in less degraded bedrock to the north. An observation of these materials with multispectral data may provide an interesting look at the formation and transport processes at work within the dune field.
Stereo justification: Clear layering is present at this location. Anaglyphic/DTM products of this location will aid in interpreting stratigraphic relationships of this material, unit thicknesses. In addition, the anaglyphic/DTM data may enhance the value of the dune processes component of this observation.
Knob Field in Noachis Terra (ESP_065803_1640) - Request submitted: November 27, 2019; Request scheduled: August 5, 2020; Request fulfilled: August 9, 2020. This observation targets a 25 x 15 km knob field located in Noachis Terra. The knobs in the targeted region are morphologically varied, with 3 different types visible. The first type is a ring-shaped hill with rocky exposures. The second type appears to be a rock layer overlying the surrounding intercrater plain materials. The third type are mounds, some of which contain small veins, that appear to be embayed by the surrounding intercrater plains materials. It is unclear if these knobs share a common origin. This observation will help evaluate relationships between the mound types and the surrounding intercrater plains materials. The first type of mound described here bears a resemblance to Veiki-type moraines, and may result from former ground ice in the region. In other places where the third mound type is seen (ESP_060964_1575), the embayment relationship suggests an intrusive origin. It is possible that the targeted knob field may contain evidence of lava-ice interactions.
Rocky Terrain Sample in Terra Cimmeria (ESP_065812_1495) - Request submitted: October 9, 2019; Request scheduled: August 5, 2020; Request fulfilled: August 10, 2020. This observation targets a rugged surface where thermophysical data indicates the presence of exposed bedrock. Several different surface textures are visible within this footprint. This observation will likely see several different surface units, including fill units within a ghost crater and possible units exposed by a wrinkle ridge. In addition, exposures in the wall of a small relatively fresh crater near the top of the observation footprint may provide a near subsurface probe to help assess any possible layering styles.
Lobate features in Southeast Koval'sky Crater (Stereo Images ESP_066600_1485 & ESP_066811_1485) - Request submitted: December 5, 2018; Request scheduled: September 30, 2020; Request fulfilled: October 10, 2020. This observation targets a region of unusual shallow lobate features located on the floor of Koval'sky Crater. These features somewhat resemble veiki moraines and may record a history of ice cover in this region. High-resolution imagery of these features may help determine the regolith that forms these lobate features and allow comparison with the surrounding materials. Note: Stereo imaging was not part of my request.
Resolution justification: Higher resolution imagery of this surface will help determine if the materials within the lobate materials contain large (~0.5 m) clasts consistent with a glacial till.
Knob Field Located Along Dike East of Huygens Crater (ESP_066012_1685) - Request submitted: March 18, 2020; Request scheduled: August 2, 2020; Request fulfilled: August 26, 2020.This observation targets a small (~900 km sq) knob field located NE of Huygens Crater. The knob field appears to be associated with a large dike that is part of the Hellas-Huygens dike system. This dike crosses beneath a section of the knob field. Along the southern edge of the knob field, the dike's generally straight trace curls into a small knob, suggesting that the knob field may be associated with the dike system. This may indicate an origin of the knob field as a sill which has been heavily eroded, or numerous small laccolith structures. HiRISE observations will provide a closer look at the contact between the dike and knob field to help understand the relationship between these materials. In addition, high resolution imagery of the knobs will be used to characterize the morphology of the knobs, helping determine mechanical properties of knob material and internal stratigraphic contacts.
Patchy Outcrop of Light-Toned Materials (ESP_066023_1480) - Request submitted: July 31, 2019; Request scheduled: August 2, 2020; Request fulfilled: August 27, 2020. This observation targets a small region of patchy light-toned materials visible in CTX image B17_016125_1480_XN_32S232W. These outcrops are small (~100 px at CTX resolution) precluding confident geomorphological analysis and assignment of a stratigraphic position relative to the surrounding materials. The morphology of this material closely resembles a sinuous, branching outcrop visible in the same general region (see HiWish request 175428), and loosely resembles sinuous light-toned outcrops seen elsewhere in Terra Cimmeria (HiRISE observation ESP_054748_1735, HiWish requests 175382, 175430). The later group may be fluvial in nature; if so the possible detection of similar materials in a non-fluvial setting may be useful for comparison purposes or aid in understanding aqueous processes related to the light-toned materials.Note: Stereo imaging was not part of my request.
Low Thermal Inertia Mound in Terra Sabaea Bedrock Plain (ESP_066039_1605) - Request submitted: May 19, 2020; Request scheduled: August 5, 2020; Request fulfilled: August 28, 2020. This observation supplements HiWish request 182690 studying an 18km diameter low thermal inertia mound. It targets the eastern contact of the mound with crater fill materials, which will help test the floor fracture and central mound hypotheses outlined in the previous request. This contact is characterized by two high, narrow ridges and several small, rugged mounds, one of which appears to be layered. In addition, this observation targets isolated patches of friable dark-toned material occurring in low spots on the mound. Finally, a small crater impacts along the contact, which provides a possibility to follow the contact into the subsurface. Finally, there is a large tilted block which appears to contain a megabreccia. It is unclear whether this block is related to the mound, and may instead be an isolated exposure of the buried central peak. High-resolution observations will be useful in comparing this exposure to that of nearby mound-forming materials.Note: Stereo imaging was not part of my request.
Putative Chloride Deposit and Ridge Network in Terra Sabaea (ESP_066052_1735) - Request submitted: June 20, 2020; Request scheduled: August 2, 2020; Request fulfilled: August 29, 2020. This observation targets a chloride deposit mapped by Osterloo et al. 2010. This particular deposit is of interest because it is associated with a small network of raised ridges along the northern boundary of the mapped exposure (seen in CTX image J22_053234_1737_XN_06S308W). This chloride deposit also appears to form a thin layer that is underlain by a featureless dark-toned surface. This image will help determine if there is any relationship between the chloride deposit and the raised ridge network and its stratigraphic position in relation to the surrounding surface materials.
Patchy Outcrop of Light-Toned Materials (ESP_066101_1500) - Request submitted: July 31, 2019; Request scheduled: August 26, 2020; Request fulfilled: September 2, 2020. This observation targets patchy exposures of light-toned outcrops. Several outcrops of light-toned materials are hosted in the same intercrater plain; one of these is described in HiWish request 175434. These materials may be chloride bearing, as morphologically-similar outcrops mapped by Osterloo et al. are found ~66 km to the NE. Erosion appears to have cut through the entirety of the light-toned materials in these outcrops, which should allow probing of the stratigraphic context, thickness and any possible internal layering of these materials. Should these materials be related to chloride deposits, it may allow further constraints to be placed on the formation of chloride deposits in this region.
Color and Stereo Justification: This observation targets several exposures of light-toned material. These exposures appear to be a near-subsurface layer (possibly chloride-bearing) that has eroded entirely through in places. Stereo DTMs of these materials can help determine the stratigraphic thickness of these materials. If chloride bearing, the thickness of the unit may help place additional constraints on the formation processes behind the deposition of chlorides in this region.
Light-Toned Materials at Highlands Valley Network Mouth (ESP_066211_1515) - October 10, 2022 HiRISE Picture of the Day! Request submitted: April 10, 2019; Request scheduled: September 3, 2020; Request fulfilled: September 10, 2020. This observation targets a region of light-toned materials visible in CTX image 19_017236_1521_XN_27S324W. These materials are located within a geomorphically complex region at the mouth of a dendritic highlands valley network, and may represent a clastic deposit related to the valley network. This observation targets several particularly interesting landforms including: 1) an outcrop with tabular ledges (suggestive of layering), 2) a cluster of low, sinuous outcrops of darker-toned material (suggestive of topographically inverted channel deposits), and 3) a region of the light-toned material containing unusual ridges of unknown origin. HiRISE imaging resolution will help determine the presence of layering in this material, which may be useful for understanding the channel dynamics of the associated highlands valley network.
Morphologically Diverse Terra Sabaea Intercrater Plain (ESP_067068_1600) - Request submitted: May 31, 2020; Request scheduled: November 9, 2020; Request fulfilled: November 16, 2020. This observation targets an intercrater plain surface with a highly varied morphological expression. At the northern end is an outcrop of a light-toned material with a rugged surface at the 5-50 m scale. This outcrop is bounded by a small escarpment at its southern contact, where it appears to overlie a light-toned surface with low escarpments consistent with possible fine-scale layering. Near the center of the target region is a resistant caprock unit. Some mottled tonal banding occurs along the northern escarpment of this unit, again suggestive of fine-scale layering. Portions of this caprock unit have a washboard-like appearance. The southern edge of this target stamp captures the southern contact of this caprock unit, where it overlies a mottled light-toned unit. This region has a thermal inertia relative to the surrounding materials, consistent with a clastic unit. The goal of this observation is to compare these units with heavily-imaged intercrater plains to the north and south.
Terrain Sample (ESP_067517_1430) - Request submitted: June 19, 2020; Request scheduled: December 14, 2020; Request fulfilled: December 21, 2020. This observation targets a bedrock plain from the Cowart et al. 2019 catalog. CTX imagery of this bedrock plain shows a granular appearance (likely boulder fields) which correlates to the high thermal inertia materials. The surrounding low thermal inertia material also has a granular appearance, but at finer scales. The goal of this observation is to compare the materials on either side of the boundary to search for differences in boulder size, color, and surface mantling to understand the primary factors leading to this sharp thermophysical boundary.
Dome-Like Feature in Deltoton Sinus Basin (ESP_067569_1725) - Request submitted: August 17, 2018; Request scheduled: December 14, 2020; Request fulfilled: December 25, 2020. This observation targets an unusual dome-like feature located within a bedrock plain in Deltoton Sinus. The dome-like feature shows potential layering in this region in CTX image P20_008941_1724_XN_07S304W, and a this observation will help confirm the presence of this layering. This imaging footprint includes a relatively well-preserved 2km crater which has penetrated into the feature and may potentially help understand the subsurface charateristics of this landform. This observation footprint targets basin materials on both sides of the dome in order to investigate potential stratigraphic relationships between the dome and surrounding plains materials. This image will also explore the morphology of this dome and provide insight into its lithological and mechanical properties.
Lithologically Diverse Crater (ESP_068071_1535) - Request submitted: November 13, 2020; Request scheduled: January 26, 2021; Request fulfilled: February 2, 2021. This observation targets a 21-km crater of probable Noachian age. This crater is situated in a region of unusually high variability in TES thermal inertia. Erosional retreat of the crater rim has created an escarpment with an unusually hummocky appearance and subparallel cliff-faces which may be indicative of layering. At the rim's base is a mound with large ridge networks. This mound also has small-scale tonal variation, suggesting that these materials are not heavily mantled by dust or regolith. Finally, the crater floor hosts concentric escarpments, consistent with heavily-eroded, layered crater fill materials. This observation will allow for possible identification of layering below CTX resolution and enable comparisons between crater fill units.
Exposure of Light-Toned Material in Terra Sabaea Intercrater Plain (ESP_068137_1525) - May 19, 2021 HiRISE Picture of the Day! - Request submitted: November 13, 2020; Request scheduled: February 4, 2021; Request fulfilled: February 7, 2021. This observation targets a small (~0.25 sq km) exposure of light-toned materials in a Terra Sabaea intercrater plain. This exposure is located within a shallow depression. In CTX imagery it is difficult to tell whether this material forms a relatively thin layer, or is the uppermost exposed portion of a more substantial subsurface unit. Exposures of a similar material are located ~5 km NW of the target request center, suggesting that this unit is or was relatively extensive. The goal of this observation is to obtain a higher-resolution view of this small exposure, as well as clarify the stratigraphic relationship between this unit and the surrounding intercrater plains materials. To support this goal the target request also includes surrounding terrain, which shows unusually high variation in THEMIS thermal inertia and textural variation in CTX.
Rimless Crater with Gullies (ESP_068186_1445) - Request submitted: August 7, 2018; Request scheduled: February 2, 2021; Request fulfilled: February 11, 2021. This observation targets a ~7.5 km rimless crater located within a large bedrock plain. This crater is unusual because nearby craters in roughly the same degradation state still possess raised rims. This crater may thus represent a volcanic vent such as a maar or large maar-diatreme. A mantling unit on the surrounding plains occurs on the southwest side. The low thermal inertia suggests it is a deposit of relatively fine material. No similar deposits occur around other craters in this plain. HiRISE observations of this feature will be useful for interpreting the origin of this unusual crater.
Banded Massif in Terra Sabaea (ESP_068203_1580) - Request submitted: November 13, 2020; Request scheduled: February 2, 2021; Request fulfilled: February 12, 2021. This observation targets the southern end of a small massif located within a Terra Sabaea intercrater plain. Materials located along the southwestern portion of the central mound contain a polygonal ridge network and faintly alternating tonal variations (~30-50 m wide) which may indicate the presence of compositional banding in these materials. The southern mound contains large (~10 m) subparallel fractures running across its south face, as well as a polygonal fracture network along its northeastern face. The erosional texture of this material is comparable to ejecta blocks exposed in massifs along the NW Hellas Basin rim, suggesting that they have a basement rock lithology, either originating as deep crustal ejecta blocks or as part of an intrusive complex within the intercrater plain. This observation will study these materials to verify the presence of compositional banding with higher-resolution data and determine the structural relationships and controls on fracture networks.
Knob Cluster in Tyrrhena Terra (ESP_068215_1665) - Request submitted: October 1, 2020; Request scheduled: February 2, 2021; Request fulfilled: February 13, 2021. This observation targets an unusual cluster of knobs located in a Tyrrhena Terra basin. These knobs are generally composed of undifferentiated light-toned materials with low crater retention. However, some knobs contain what appear to be small vein-like ridges, while others contain contrasting light-tone and dark-tone units. A small erosional scour within the targeted area will help study deeper exposures of this material. The origin of these materials is unclear. These materials may represent a hydrothermally-altered airfall deposit (based on their superficial resemblance to knob fields in the Eridania paleolake basin), erosional outliers of a former basin-fill sequence, or some other mechanism. This observation will help determine if internal layering is present, study contacts with surrounding materials, and characterize fine-scale morphology of the mounds.
Mesa Cluster within Flat-Floored Crater (ESP_068507_1570) - Request submitted: September 30, 2019; Request scheduled: March 3, 2021; Request fulfilled: March 8, 2021. This observation targets a cluster of mesas located within a degraded crater of probable Noachian age. This mesa cluster somewhat resembles the morphology typical of floor fractured craters, however, summit blocks contain enigmatic moat-like features. This may suggest alternative processes at work during the formation of these features. The mesas are underlain by a ridged and knobby surface that erodes to a mantle-like unit with low crater retention. The goal of this observation is to place the crater floor materials, low crater retention unit, and mesa summits into stratigraphic context. Additionally, this observation will resolve several small scale features (ringed ridges, intersecting ridge sets, knobs) in the low crater retention unit which may expose these materials through the overlying regolith cover. Finally, this observation will provide useful comparisons with similar features elsewhere in the Terra Sabaea region.
Region with Lobate Scarps and Dense Network of Linear Ridges (ESP_069110_1500) - Request submitted: August 7, 2018; Request scheduled: April 14, 2021; Request fulfilled: April 24, 2021. This observation targets a plain hosting unusual regions of bedrock bounded by low, lobate scarps. The bedrock bounded by these scarps also contains a network of narrow (generally < 50 m wide) and relatively long (up to 4 km) linear ridges. These are best seen in CTX image D22_035785_1510_XN_29S216W. Due to their small size, it is difficult to interpret these features at CTX resolution. This observation will allow us to differentiate formation mechanisms for these landforms (e.g. erosional retreat vs. lava flow front for scarps; mineralized fissure vs. dike swarm for the linear ridges) and better interpret similar features seen within this plain and others within the region.
Channel in Intercrater Plains (ESP_069140_1610) - Request submitted: March 11, 2021; Request scheduled: April 20, 2021; Request fulfilled: April 26, 2021. This observation targets a channel feature located in a relatively flat intercrater basin in the Terra Sabaea highlands visible in CTX image G19_025622_1619_XN_18S315W. This channel is irregular, and in several areas appears to be discontinuous, possibly indicating this feature is a collapsed lava tube. Rock appears to be unusually well-exposed around this feature, with the rugged surface here contrasting with the much more subdued intercrater plain landscape. This observation seeks to characterize the morphology of this feature and the surrounding rock at higher resolution in order to evaluate its origin.
Low Thermal Inertia Mound in Terra Sabaea Bedrock Plain (ESP_069219_1605) - Request submitted: May 19, 2020; Request scheduled: April 27, 2021; Request fulfilled: May 21, 2021. This observation targets a 18km diameter mound with a low thermal inertia surface. A deep central valley in the mound exposes faint horizontal tonal banding in CTX image G08_021455_1606_XN_19S311W. The valley also divides mound materials with dramatically different erosional styles. East of the valley behaves as a coherent block of material with high crater retention. To the west the mound is broken into blocks with moderate to poor crater retention with sets of orthogonal linear ridges. The mound's formation mechanism is unclear. Two preliminary hypotheses: 1) an example of a highly-eroded floor fractured crater exposing the underlying intrusive complex, and 2) A highly eroded example of a crater central mound. This observation aims to confirm preliminary CTX ID of layering in the valley walls, infer mechanical behavior of surface materials from exposed rock, and study the northern and southern contacts with its surroundings to differentiate between uplift and sedimentary emplacement .
Crater Fill Unit with Large Pit Chains and Linear Ridges (ESP_069401_1725) - Request submitted: November 26, 2019; Request scheduled: May 13, 2021; Request fulfilled: May 17, 2021. This observation targets an unusual crater fill unit containing numerous pit chains and linear ridges. The pit chains and linear ridges form an orthogonal fabric. The unusual texture of this unit may result from modification of a volatile-rich deposit. At the southern boundary of this unit, large slabs appear to have foundered. Along the southwestern and western edges of this unit, it appears to be partially embayed by the surrounding crater fill unit. High-resolution photographs of this unit will be used to help interpret the fabric of this crater fill unit, as well as detail its relationship to the surrounding crater fill materials. This will be useful in evaluating the formation mechanism of this unusual unit.
Dome with Flow-Like Features (ESP_069505_1475) - Request submitted: November 27, 2019; Request scheduled: May 19, 2021 Request fulfilled: May 25, 2021. This observation targets a 900m tall dome that is 8km in diameter. No objects of comparable positive relief are located in its vicinity. CTX image P07_003584_1469_XN_33S195W indicates several lobate, flow-like structures emerging from craters in its flanks. These observations suggest that this dome is a volcanic ediface. The observation crosses the entire dome to study the feature with high-resolution. This will be useful in assessing possible volcanic features located on the dome. The resolution of HiRISE is particularly important along the southern flank of the dome, where one flow-like structure emerges. The HiRISE imagery will look for possible lava flow textures, as well as evaluate the flow-like structure's relationship with a fissure/crater near its source on the dome's flank.
Crater Floor Mound Located at Junction of Linear Ridges (ESP_069637_1485) - Request submitted: August 23, 2018; Request scheduled: May 26, 2021; Request fufilled: June 4, 2021. This observation targets an unusual mound located within an intracrater bedrock plain in Terra Cimmeria. This mound is located at the junction of two sets of linear ridges. These ridges are part of a system of ridges that occur throughout the bedrock plain. This observation attempts to study the relationship between the mound, these ridges, and the surrounding crater floor bedrock. The linear ridges resemble exposed dike systems, suggesting that the mound may be a small intruded feature. This observation will look for morphological features that could confirm potential origins of this feature.
Potentially Layered Bedrock Deposits in Terra Sabaea (ESP_069655_1510) - May 2, 2022 HiRISE Picture of the Day! - Request submitted: December 5, 2018; Request scheduled: May 26, 2021; Request fulfilled: June 5, 2021. This observation targets a region with suspected layered bedrock materials. The morphological texture of this target at CTX resolution is similar to other HiRISE observations in this region (ESP_044242_1520; ESP_057455_1520) where layered bedrock was found. The targeted area thus has a high probability of detecting layered bedrock. Imaging of this bedrock material will allow study of variations in the thickness and style of layering across this bedrock region.