Mars From Afar
Frozen Water
Use the slider (in enlarged version) to compare these two color
images from the Phoenix Mars Lander, which touched down on the Red
Planet on May 25, 2008. The lander's Surface Stereo Imager took
these pictures on June 15 and June 19, respectively. The pictures
show sublimation—the passing of a substance, in this case ice,
directly from a solid to a gas—in a lander-dug trench over the
course of four days. In the lower left of the lefthand image, a
group of white lumps is visible within the shadow; in the righthand
image, they're gone. Look closely also at the white patches in full
sun—other loss of ice can be seen there. These images
confirmed the presence of water ice in the subsoil of the martian
arctic.