Clumps Growing on Phoenix Lander Legs

by Nancy Atkinson on September 9, 2008

Clumps of material have adhered to the legs of the Phoenix Mars Lander, and the clumps continue to change and grow. 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. Below, compare images taken on September 1, 2008, or the 97th Martian Day or sol, since landing with another image taken about three months earlier, on Sol 8.

Sol 97 image under the lander.  Credit:  NASA/JPL/Caltech/U of AZ

Sol 8 image from under the lander.  Credit:  NASA/JPL/Caltech/U of AZ

Phoenix’s Robotic Arm Camera took both images. The top image from Sol 97 was taken at about 4 a.m. local solar time. The view in this Sol 97 image is southward. Illumination is from the early morning sun above the northeastern horizon. This is quite different from the illumination in the Sol 8 image, bottom which was taken in mid-afternoon.

The two images also show a contrast in the flat, smooth patch of exposed ice underneath the lander. Phoenix team members believe the ice was exposed from the spacecraft’s thrusters as it landed. In the latest image, the patches of ice exposed underneath the lander seem to be partly covered by darker material left behind as ice vaporizes away. The flat patch in the center of the image has the informal name “Holy Cow,” based on researchers’ reaction when they saw the initial image of it.

Source: Phoenix Gallery


Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

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