NASA today said the ground where Spirit is stuck last year holds evidence that water, perhaps as snow melt, trickled into the subsurface fairly recently and on a continuing basis.
15 reasons why Mars is one hot, hot, hot planet
"Stratified soil layers with different compositions close to the surface led the rover science team to propose that thin films of water may have entered the ground from frost or snow. The seepage could have happened during cyclical climate changes during periods when Mars tilted farther on its axis. The water may have moved down into the sand, carrying soluble minerals deeper than less-soluble ones. Spin-axis tilt varies over timescales of hundreds of thousands of years. The relatively insoluble minerals near the surface include what is thought to be hematite, silica and gypsum. Ferric sulfates, which are more soluble, appear to have been dissolved and carried down by water. None of these minerals is exposed at the surface, which is covered by wind-blown sand and dust," NASA stated.
NASA said researchers took advantage of Spirit's situation after it got stuck to look the Martian soil the rover spun up. Spirit made 13 inches of progress in its last 10 backward drives before energy levels fell too low for further driving in February. Those drives exposed a new area of soil for possible examination if Spirit does awaken and its robotic arm is still usable, NASA said.
Ray Arvidson of Washington University in St. Louis, deputy principal investigator for the twin rovers Spirit and Opportunity and 36 co-authors filed a paper on the finding with the Journal of Geophysical Research.
Since May, with the Mars Winter solstice officially upon it, Spirit has pretty much disconnected itself with the outside world and is no longer communicating. In fact, no communication has been received from the rover since March 22.
As expected, it is likely that Spirit has experienced a low-power fault will use the available solar array energy to recharge her batteries, NASA said. When the batteries gain enough charge, Spirit will wake up and communicate over X-band. When that does happen, Spirit will also trip an up-loss timer fault. This fault response will let the rover communicate over Ultra-High Frequency (UHF) as well, NASA said.
NASA said Spirit will spend the coming winter month's tilted 9 degrees toward the south, an unfavorable attitude for the solar panels to catch rays from the sun in the northern sky. Spirit's parking positions for its previous three Martian winters tilted northward. Engineers anticipate that, due to the unfavorable tilt for this fourth winter, Spirit could be out of communication with Earth for several months.
In January NASA said it was resigned to leaving the rover in place and making adjustments to help it survive as a remote but stationary science robot. Spirit has been stuck in a place NASA calls "Troy" since April 23, 2009 when the rover's wheels broke through a crust on the surface that was covering brightly-toned, slippery sand underneath. After a few drive attempts to get Spirit out in the subsequent days, it began sinking deeper in the sand trap.
Follow Michael Cooney on Twitter: nwwlayer8
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