Computer Science – Sound
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p13b1278s&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P13B-1278
Computer Science
Sound
[5462] Planetary Sciences: Solid Surface Planets / Polar Regions, [5464] Planetary Sciences: Solid Surface Planets / Remote Sensing, [6225] Planetary Sciences: Solar System Objects / Mars, [6969] Radio Science / Remote Sensing
Scientific paper
The SHAllow RADar (SHARAD) instrument on Mars Reconnaissance Orbiter greatly expands our ability to study the Polar Layered Deposits (PLDs) by resolving internal layers and structure with a theoretical vertical resolution in ice of ~ 8 m and horizontal resolution of 0.3-1 km (along track) x 3-6 km (cross track). This complements high-resolution optical imagery, which has been used for decades as the basis for studying surface features and developing hypotheses linking them to known processes. Spiral trough and scarp migration in the northern PLD (NPLD) has been a topic of debate since the idea was first proposed (Howard, Icarus 34/3, pp. 581-599, 1978). Layers observed on the equator-facing slopes of the troughs are generally truncated at the surface, while no layers are generally seen on the pole-facing slopes. Scenarios involving wind erosion, solar ablation, and atmospheric deposition in relative amounts have been hypothesized to explain this stratigraphy. Other studies indicate that the troughs have not migrated, instead being recently eroded into the NPLD. The advent of high-resolution radar sounding provides the first opportunity to address this debate through the analysis of subsurface stratigraphy. SHARAD data reveal stratigraphic discontinuities indicating that most troughs initiated ~ 500 m below the present surface, persisted throughout subsequent deposition, and have indeed migrated (Smith et al., LPSC 40, Abstract 1423, 2009). We have conducted additional analyses at various NPLD localities showing that the migration takes multiple stratigraphic forms, some of which do not include discontinuities. The longest troughs of the NPLD, in the 0-90°E quadrant north of Gemini Lingula, have stratigraphy with layer thickness variations that correlate well to those predicted by wind-driven migration. Troughs nearer the NPLD margin at ~90°E show a different structure corresponding more to insolation-dominated ablation. Between these locations and at other places in the NPLD, a mixture of the two can be seen in SHARAD data. The potential now exists to link trough stratigraphy as revealed by radar to climate-driven processes through time and across regions, helping to elucidate recent polar climate history on Mars and possibly leading to a determination of how the spiral troughs initiated.
Holt Jeremy William
Phillips James R.
Smith Ian
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