Geomorphologic and mineralogic characterization of the northern plains of Mars at the Phoenix Mission candidate landing sites

Abstract

[1] A suite of remote sensing data is used to evaluate both geomorphology and mineralogy of the candidate landing sites for the 2007 Phoenix Mission. Three candidate landing site boxes are situated in the northern plains of Mars on the distal flank of Alba Patera in the region from 67°N to 72°N and from $230°E to 260°E. Geomorphology is mapped at subkilometer spatial scales using Thermal Emission Imaging System (THEMIS) visible and Mars Orbiter Laser Altimeter (MOLA) topographic data, supplemented by images from the High-Resolution Imaging Science Experiment (HiRISE) and Context Imager (CTX). Mineralogy and spectral properties are examined using Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) visible and near-infrared multispectral mapping and targeted hyperspectral data at $200 and $20 m/pixel, respectively. Geomorphic mapping supports the idea that terrains along the boundary between the Amazonian Scandia region and Vastitas Borealis marginal geologic units have undergone extensive modification. Intercrater plains are disrupted to form mesas and interlocking blocks, while irregular depressions and knobby terrain are consistent with erosion/subsidence and local deposition. Despite the varied morphology, the present-day surface is nearly homogeneous with spectral signatures dominated by nanophase iron oxides and basaltic sand and rocks, similar to that of the Gusev crater plains at the Mars Exploration Rover (MER) landing site. The compilation of geomorphic and spectral information for the candidate Phoenix landing sites provides a framework for the mission's in situ observations to be extrapolated to the northern plains as a whole.

Periglacial landforms at the Phoenix landing site and the northern plains of Mars

“…Both rubble piles and arcs tend to sit atop slight topographic highs, either mounds or ridges typically 50 cm higher than the intermound terrain [ Kirk et al , 2008]. The boundary between regions dominated by rubble piles and rubble‐pile‐free regions is usually fairly distinct with an abrupt elevation drop of less than a few meters down to the rubble‐free regions over horizontal distances tens to hundreds of meters [see also Seelos et al , 2008]. Small polygons are also ubiquitous throughout the regions dominated by rubble piles (e.g., Figures 4c and 4e).…”

Mars Exploration Program 2007 Phoenix landing site selection and characteristics

“…To focus analysis efforts and concentrate acquisition of new MOC data, four broad regions were selected that met elevation requirements and had a range of soil cover thicknesses over icy soil as inferred from analyses of Odyssey gamma and neutron spectrometer data (Figure 2). Each region (A, B, C, and D) covered the full allowable latitude range and 20° of longitude, and each region was dominated by plains [ Seelos , 2006]. Regions A and D were predicted to have the thinnest soil cover, region C an intermediate value, and region B the thickest cover.…”

“…This paper describes the site requirements, the processes associated with site selection, and the characteristics of the chosen site. Detailed descriptions of the geomorphic and geologic settings for the key candidate sites are presented by Seelos et al [2008], determination of the depth of soil cover over ice as derived from gamma ray, neutron, and emission spectroscopy is covered in detail by Mellon et al [2008], a detailed summary of rock size‐frequency distributions in the northern plains of Mars is presented by Golombek et al [2008], and estimations of slopes are given by Kirk et al [2008]. Finally, a summary of mesoscale atmospheric circulation models for the Phoenix latitude zone and specific candidate landing sites is presented by Tamppari et al [2008].…”

Landing-Site Dispersion Analysis and Statistical Assessment for the Mars Phoenix Lander

“…The team finally settled on an area that became known as Green Valley in region D. Green Valley obtained its name from the map classification Once the search had been narrowed down to the smaller area containing Green Valley, a more targeted imaging campaign was planned with the goal of obtaining high-resolution images in the portion of the Phoenix map where the lander was most likely to touchdown. Figure 3 is a map of the Phoenix landing region where the terrain was classified according to its geomorphology [5]. The white contours outline the portion that was imaged using the HiRISE instrument.…”