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"Holy Cow" and other patches beneath the lander are darker.

By University Communications
September 9, 2008

Clumps adhering to a leg strut on NASA's Phoenix Mars Lander are larger than they were three months ago, according to a recent photograph from the lander on the northern polar region of Mars.

The Robotic Arm Camera took the image on Sept. 1, 2008, at about 4 a.m. local solar time during the 97th Martian day, or sol, since landing. The view underneath the lander shows growth of the clumps adhering to leg strut seen at the upper left in the picture, compared with a view of the same strut in a similar image taken about three months earlier.

The view in the Sol 97 image is southward. Illumination is from the early morning sun above the northeastern horizon. This illumination is quite different from the illumination in the Sol 8 image, which was taken in mid-afternoon.

The science team has discussed various possible explanations for these clumps. One suggestion is that they may have started from a splash of mud if Phoenix's descent engines melted icy soil during the landing. Another is that specks of salt may have landed on the strut and began attracting atmospheric moisture that freezes and accumulates. The clumps are concentrated on the north side of the strut, usually in the shade, so their accumulation could be a consequence of the fact that condensation favors colder surfaces.

The flat, smooth patches of ice exposed underneath the lander seem to be partly covered by darker material left behind as ice vaporizes away in the recent image, compared with the one taken thee months earlier. The flat patch in the center of the image has the informal name "Holy Cow," based on researchers' reaction when they initially saw the feature.

The Phoenix Mission is led by Peter Smith of The University of Arizona, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif.