Lineaments in Northern Martian Polar Layered Deposits: Recent Faulting?

Details Lineaments in Northern Martian Polar Layered Deposits: Recent Faulting? Lineaments in Northern Martian Polar Layered Deposits: Recent Faulting?

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p31b0143n&link_type=abstract

American Geophysical Union, Fall Meeting 2006, abstract #P31B-0143

Other

5460 Physical Properties Of Materials, 5462 Polar Regions, 5475 Tectonics (8149), 6225 Mars

Scientific paper

For the past several years, starting with Mars Global Surveyor, spacecraft have returned abundant data from the Martian polar layered deposits, PLD (e.g., surface composition, high-resolution topography). These, coupled with laboratory results on the solid-state behavior of ice and numerical mechanical models, have hinted on the possibility of viscous flow over the PLD history [1,2]. On Earth, glacial viscous flow at depth is accompanied by brittle deformation of near-surface ice (crevasses). This results from an increase in temperature with depth in polar ice. Such a temperature trend is likely in the Martian PLD, and surface expressions of brittle deformation should be expected if the ice is to be flowing at depth. Here we report a series of lineaments on the Northern PLD surface and interpret them to be recent faults. These lineaments are detectable in the 512 pix/deg MOLA grid, albeit near resolution limit, as troughs ~10 m deep, 100's m wide, and 10's km long. Interestingly, they follow the crest of one of the polar undulations. These lineaments are also present in a number of THEMIS-Vis images under different Ls and incidence angles, appearing to be troughs bound by sharp edges. MOC coverage is sparse, but one frame shows several parallel segments along the crest of the undulation. Furthermore, MOC reveals tens of other smaller lineaments (~1 km long) on the ice south from the undulation, all with the same orientation (~E-W). In all cases, lineaments appear to intersect the mottled texture of the surface. We interpret these lineaments to be extensional faults based on their dimension, negative topography, sharp boundaries, and coincidence with undulation crest (where tensile stresses should be greatest). The relatively large number of smaller lineaments away from the undulation but with parallel orientation reinforces this interpretation. They are likely to be the youngest regional features as they superimpose the undulation and intersect surface texture. If faults indeed, they strongly suggest that at least a portion of the cap is mechanically deforming or has deformed until very recently, <100 ka as this is the cratering age estimate of the NPLD [3]. We hypothesize two scenarios for their formation: i) the faults are genetically linked to the undulation (implying a mechanical component to the process forming undulations), or ii) differential stresses created by regional deformation are concentrated at the undulation. [1] Durham & Stern, AREPS. 29, 295, 2001 [2] Pathare & Paige, Icarus 174, 419, 2005 [3] Herkenhoff & Plaut, Icaurs 114, 243, 2000.

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