Data from HEND/Odyssey Show That Northern and Southern Permafrost Regions of Mars Have Different Subsurface Structure

Details Data from HEND/Odyssey Show That Northern and Southern Permafrost Regions of Mars Have Different Subsurface Structure Data from HEND/Odyssey Show That Northern and Southern Permafrost Regions of Mars Have Different Subsurface Structure

May 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agusm.p53a..06m&link_type=abstract

American Geophysical Union, Spring Meeting 2004, abstract #P53A-06

Physics

5400 Planetology: Solid Surface Planets, 5462 Polar Regions, 5464 Remote Sensing, 5470 Surface Materials And Properties, 5494 Instruments And Techniques

Scientific paper

After the first Martian year of mapping neutron emission by Mars Odyssey the existence of large regions with very strong depression of neutron albedo has been discovered around both poles. The depression is about a factor of 10 for both regions relative to the maximum emission at Solis Planum. The origin of these depressions is explained by the presence of a large amount of ground water ice in the shallow subsurface, about 1-2m. Accordingly, these regions of depressed neutron flux were identified with Northern and Southern permafrost regions on Mars with a very high content of subsurface water ice. Neutrons observed from the Odyssey orbit depend on the thickness of the atmosphere, the current flux of cosmic rays and the composition of subsurface. Additionally, the leakage flux of neutrons is contributed by the entire visible surface of the planet, and neutron mapping data do not provide direct measurements of ground water distribution and stratification of the subsurface. To get this knowledge, one must model the subsurface, consistent with the observations, and perform model-dependent deconvolution of measured neutron counts to estimate water content. It was found that the Northern permafrost region is well described by a simple model of the subsurface with homogeneous distribution of water ice throughout. This model uses soil of fixed composition consistent with APXS observations and a variable content of water over the subsurface. The average content of water ice in the subsurface was estimated as 44, 25 and 13wt% for the northern latitude belts >80° , 70-80° and 60-70° , respectively. For the Southern permafrost region the simple model with homogeneous subsurface distribution of water ice is not supported by observations. The model with double-layered subsurface was proposed for this region, with only 2wt% of water in the top dry layer of variable thickness and with variable content of water in the bottom layer. The double-layered model was found to be consistent with observations for the Southern region. The average content of water ice in the bottom layer was estimated as 55, 54 and 25wt% for the southern latitude belts >80° , 70-80° and 60-70° , respectively. Correspondingly, the average thickness of the top layer is about 16, 19 and 22 g/cm2 for the same latitude belts >80° , 70-80° and 60-70° , respectively. So, the northern and southern permafrost regions have different subsurface structure. One may suppose that the southern shield of water ice was produced a long time ago, and subsequently the top dry layer was formed by losing water by sublimation into the atmosphere. In contrast, the absence of a dry blanket above the ice bearing material at the northern region suggests that at the present time condensation of water dominates over sublimation into the atmosphere. Thus, in the current climate epoch the surface of the northern permafrost region is being built up by ice and dust deposition from the atmosphere.

Affiliated with

Also associated with

No associations

Rating

Data from HEND/Odyssey Show That Northern and Southern Permafrost Regions of Mars Have Different Subsurface Structure does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Data from HEND/Odyssey Show That Northern and Southern Permafrost Regions of Mars Have Different Subsurface Structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data from HEND/Odyssey Show That Northern and Southern Permafrost Regions of Mars Have Different Subsurface Structure will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1177985