Last updated on April 17, 2014 at 21:23 EDT
Centauri Montes Region Figure A
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Centauri Montes Region Figure A

October 19, 2009
The new gully deposit in an unnamed crater in the Centauri Montes region is located near 38.7 degrees south latitude, 263.3 degrees west longitude. Like the new gully deposit in Terra Sirenum, this one has a light tone relative to its surroundings. It is on an equator-facing slope on which numerous narrow gully channels occur. As this slope is always in sunlight during the afternoons when Mars Global Surveyor passes overhead, the gullies always appear somewhat "washed out," just as craters on a full Moon do when viewed from Earth with a telescope.

The new, light-toned flow was first noticed by the Mars Orbiter Camera science operations team in an image acquired on Sept. 10, 2005. Re-examination of other images of this crater showed that the new deposit had actually been present on Feb. 21, 2004, when the distal (down-slope) end of the deposit was captured in other images. In February 2004, the deposit had gone unnoticed because only a small portion of it was imaged. This location was first imaged by the Mars Orbiter Camera on Aug. 30, 1999. The deposit was not present at that time. Thus, it formed between Aug. 30, 1999 and Feb. 21, 2004.3

Roughly 20 percent brighter than the surface as it appeared before the flow occurred, the new deposit exhibits characteristics consistent with transport and deposition of a fluid that behaved like liquid water and likely transported some fine-grained sediment along with it. The distal end of the flow broke into several branches, or digits, and the material diverted and flowed around low obstacles. As with the example in Terra Sirenum, the depth of the flow is too thin to be measured in 1.5-meter-per-pixel (1.7-yard-per-pixel) images, so a very small volume of liquid and sediment was involved. While the material flowed and easily budded into several branches, it also must have moved slow enough to not topple over some of the low obstacles in its path.

Figure A: This figure shows the southeast wall of the unnamed crater in the Centauri Montes region, as it appeared in August 1999, and later in September 2005. No light-toned deposit was present in August 1999, but appeared by February 2004. The 300-meter scale bar represents 328 yards.