Gamma Ray Spectrometer - 2001 Mars Odyssey Lunar and Planetary Lab The University of Arizona


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Epithermal Video

Epithermal Neutron Video

This video records the time variation of the flux of epithermal neutrons recorded by the Neutron Spectrometer component of the Gamma-Ray Spectrometer suite of instruments aboard Mars Odyssey.

Eight maps of the north (left) and south (right) poles of Mars were constructed from data measured between February 19, 2002 and November 26, 2002. Over this time period Mars went from late winter in the north (Areocentric longitude, Ls = 328) through mid summer (Ls = 99). These maps were extrapolated and interpolated to form a set of 32 images of each pole. The season for each image is updated in the diagram near the upper center of each image.

The color code of epithermal neutron counts was chosen such that terrain containing the most water-equivalent hydrogen is the deepest blue and that containing the least hydrogen is deep red. We interpret the deepest blue to be buried deposits of water ice mixed with dessicated Mars Pathfinder soil.

Note that in the north, water ice can be seen only near the fringes of the cap at latitudes less than about 60 degrees. It cannot be seen poleward of these latitudes because the north polar terrain is covered by a thick layer of CO2 frost. As time progresses, this frost sublimes, revealing a water-rich basement that increases in abundance with decreasing distance to the pole. The opposite time sequence is seen at the south pole, which transits seasons spanning late summer to mid winter. Here, the water-rich terrain is fully visible at the beginning, but becomes less visible as time progresses because the CO2 frost cover grows as time proceeds through the southern fall into mid southern winter.

Animated GIF (2.0 Megabytes)

[Mid Resolution version available here (640x354)]

[High Resolution version available here (1280x709!!, 6.5 Megabytes)]

The Mars Odyssey Gamma-Ray suite of instruments is managed by University of Arizona under the direction of W.V. Boynton, the Neutron Spectrometer is provided by Los Alamos National Laboratory under the direction of W.C. Feldman, and this video was produced by Observatoire Midi-Pyrenees under the direction of Sylvestre Maurice.

Additional information about the 2001 Mars Odyssey and the gamma-ray spectrometer is available on the Internet at: http://mars.jpl.nasa.gov/odyssey/ and http://grs.lpl.arizona.edu .

The color code of epithermal neutron counts was chosen such that terrain containing the most water-equivalent hydrogen is the deepest blue and that containing the least hydrogen is deep red. We interpret the deepest blue to be buried deposits of water ice mixed with dessicated Mars Pathfinder soil.


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