Knobby Unit in Intercrater Plain (Stereo images ESP_060819_1575; ESP_060964_1575) - Request submitted: January 18, 2018; Request scheduled: July 10, 2019; Request fulfilled: July 18, 2019. This observation targets an unusual knobby unit located within a Noachian intercrater basin. This unit is strikingly different from the surrounding flat-laying intercrater plains surface unit. It contains rugged veined topography and unusual fractures that are located within individual knobs. This type of unit occurs throughout the intercrater basin and in surrounding degraded craters. This particular observation samples a "representative" outcrop, while also allowing the northern and southern contacts of the outcrop to be sampled within a relatively small image stamp. This observation will characterize the morphology of this unit (e.g. characterize the surface at the meter scale, determine stratigraphic relationships between the intercrater plain unit, knobby unit, veins, and fractured units), allowing additional interpretation of this interesting, regionally prominent unit.
Stereo Justification: This unit has an unclear relationship with the surrounding intercrater basin floor. Stereo imaging of this unit will allow us to determine if this contact is an embayment relationship, or if this unit overlies the surrounding crater floor. In addition, it should allow more accurate determination of the relief of this unit and the relationship of internal features such as veinwork and fractures between individual knobs to be more closely evaluated.
Unusual Dome in Terra Sabea Intercrater Plain (ESP_060962_1630) - Request submitted: August 16, 2018; Request scheduled: July 23, 2019; Request fulfilled: July 29, 2019. This observation targets a dome of material located within a highlands intercrater basin in Terra Sabaea. The formation mechanism of this dome is enigmatic. It is unclear whether this mound pre- or post-dates surrounding intercrater plains materials. Potential coarse layers are observed in this unit in CTX image B18_016497_1641_XN_15S310W, especially around the contacts of this unit with the surrounding plain. This observation will be used to confirm the presence of layering and determine the stratigraphic relationship of the dome to the surrounding plains. This observation targets several adjacent landforms to aid in this task. A 3km exposing intercrater plains layering will help determine if the potential layering exposed in the dome is consistent with that of the surrounding intercrater plains. We also observe a portion of a wrinkle ridge to the south to determine whether motion along this fault has disrupted dome materials.
Possible Exposure of Layered Materials in Noachis Terra (ESP_061662_1580) - Request submitted: April 10, 2019; Request scheduled: September 18, 2019; Request fulfilled: September 22, 2019. This observation targets an erosional window located at the base of a ~500 m scarp associated with a Hellas-circumferential graben feature. This erosional window contains several planar surfaces, which may indicate layering in the basin-fill materials. This observation targets these materials to confirm the presence of layering, and if so, characterize the layering styles and stratigraphy contained within this deposit. This observation will help characterize the upper sequence of basin fill materials.
Crater Floor Mound Located at Junction of Linear Ridges (ESP_061736_1485) - Request submitted: August 23, 2018; Request scheduled: September 18, 2019; Request fulfilled: September 27, 2019 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.
Morphologically Diverse Mound on Antoniadi Crater Floor (ESP_061845_2030) Request submitted: December 26, 2018; Request scheduled: October 1, 2019; Request fulfilled: October 6, 2019. This observation targets a 10 km wide mound located within an otherwise flat region of Antoniadi Crater. Several distinctive morphologies occur within this mound (CTX reference image F20_043555_2032_XN_23N300W), including: a) exposed networked veins; b) a relatively planar surface with knobby erosional characteristics; and c) steep hillslopes with parallel striations indicating layering. This mound demonstrates an embayment relationshi with the surrounding plains, indicating a complex geologic history of this mound. This observation will be used in a survey to characterize a diverse range of knob and mound forming materials found on the floors of many heavily degraded highlands craters.
Arabia Terra Crater Floor Knobs (ESP_061964_1975) - Request submitted: December 26, 2018; Request scheduled: October 9, 2019; Request fulfilled: October 15, 2019. This observation targets mounds located on the floor plains of a 60 km crater in eastern Arabia Terra. These mounds potentially contain fine layering, as evidenced by thin parallel striations along the base of the northernmost mound and potential planar slope breaks in the southern mound (see CTX image K05_055225_1981_XN_18N307W). This observation will be used in a survey to characterize knob-forming materials present in some heavily degraded craters throughout the highlands region. In addition to the mounds, enigmatic linear ridges are found on the surrounding crater floor. These ridges morphologically resemble TARs, but in some regions of the crater floor appear to follow a tectonic fabric of exposed veinwork and wrinkle ridges (see CTX image D21_035564_1955_XI_15N308W). A secondary objective of this image will be to study the origin of these linear features.
Channels and Ridges in Terra Sabaea (ESP_062743_1530) - Request submitted: September 26, 2019; Request scheduled: December 10, 2019; Request fulfilled: December 15, 2019. This observation targets a cluster of enigmatic linear ridges exposed on a highlands surface. These ridges are evenly spaced appx. 1.25 km apart and in some cases extend up to 30 km along a SW-NE strike (for local context, see CTX image G22_026994_1515_XN_28S330W). These features are cross-cut by an incised crater inlet valley, and in most cases they form dam-like features across the valley. The morphology and erosional behavior of these features suggest an intrusive origin with a regional strucutral control. However, dust cover appears to be a major issue in further characterizing these ridges. The steep walls of this inlet valley may aid in creating dust-free exposures of this material for further characterization. The northern half of this image also targets the ridges to better see fine scale erosional morphology in any dust-free exposures that may be present.
Cluster of Craters on Floor of Koval'sky Crater (ESP_062947_1485) - Request submitted: December 5, 2018; Request scheduled: December 18, 2019; Request fulfilled: December 31, 2019. This observation targets a cluster of ring mold craters located on the southeastern floor of Kovalski crater. These ring mold craters occur within a region of lobate landforms resembling both terminal and veiki moraines. The terrain in this area suggests that several very shallow ring mold craters occur at or near the resolution limits of CTX. High resolution imagery of this surface will help characterize the size distribution of ring mold craters, particularly whether there is a minimum size for such craters in this region. Fresh, non-ring mold craters are also present in this region, implying the disappearance of near-surface ice. This observation may thus help investigate the presence of ice and temporal changes in the depth to ice.
Spectrally-Diverse Massif in Terra Sabaea (ESP_063401_1575) - March 24, 2021 HiRISE Picture of the Day! Request submitted: October 10, 2019; Request scheduled: January 24, 2020; Request fulfilled: February 4, 2020. This observation targets a spectrally-diverse massif in Terra Sabaea. In THEMIS 8-7-5 decorrelation stretch imagery (tied strongly to mafic variability) indicates the possible presence of at least four spectral units. These include DCS purple and magenta units, typical of olivine-rich surfaces; a DCS yellow unit, typical of silica-rich surfaces; and a DCS dark green unit, which may indicate the presence of alteration minerals. This massif may represent a crustal block excavated during the Hellas Basin impact. If so, the spectrally-diverse nature of this massif may provide some insight into the petrologic variability of the deep crust under the impact site. High-resolution imagery of this site will help determine if there are visible textural contacts corresponding to the spectral units. Imagery will also be used to search for possible exposures of mega-breccia. Finally, the southern half of this observation examines a contact with plains material to explore the unconformity surface.
Light-Toned Knobby Unit in Degraded Crater (Stereo Images ESP_064772_1715; ESP_065260_1715) - Request submitted: January 28, 2018; Request scheduled: May 13, 2020; Request fulfilled: May 21, 2020 This observation targets light-toned knobby units located within a heavily degraded crater. This unit is superficially similar to light-toned knobby deposits located within the Eridania paleolake basin, which appear to be altered ashfall deposits washed into the lake or hydrothermally altered basin floor deposits. The units here may be the result of a similar process. This observation attempts to characterize the morphology of these units e.g. crater retention within the knob forming unit and potential internal lithostratigraphy (see CTX image B19_016905_1714_XN_08S290W for hints of layering).
Incised Channel with Light-Toned Deposits in Intercrater Plain (ESP_064782_1485) - Request submitted: August 23, 2018; Request scheduled: May 1, 2020; Request fulfilled: May 22, 2020 This observation targets a long incised channel located within a Terra Cimmeria intercrater plain. This channel is floored by light-toned deposits and has an apparent anastamosing structure as seen in several locations in CTX image F05_037802_1473_XN_32S200W. A chloride deposit (Osterloo et al. 2010) located at the northern end of this channel, and appears to be tonally similar to the channel floor deposits. This observation will help determine whether these materials are related. In addition, this observation will help determine if this channel incised into a regional chloride deposit, or if this material was deposited within the channel feature.