Some of these impacts started landslides that left dark trails marking the steep slopes of giant craters. NASA's Mars Global Surveyor has taken new temperature measurements that indicate the surface to be composed largely of finely ground powder at least three feet thick, according to scientists studying infrared data from the Thermal Emission Spectrometer on the spacecraft. Harsh Temperatures on the Dark Side Measurements of the day and night sides of Phobos compare the sunlit side of the moon to a crisp winter day in Chicago, while only a few kilometers away, on the dark side of the moon, the climate is harsher than a night in Antarctica. This has to be an incredibly fine powder formed from impacts over millions of years, and it looks like the whole surface is made up of fine dust. Phobos Landscape Etched by Gravity New images from the spacecraft's Mars Orbiter Camera showing many never-before seen features on Phobos are among the highest resolution pictures ever obtained of the rocky Martian satellites.
Large boulders appear to be partly buried in the surface material.
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