DOOMED MARTIAN MOON, PHOBOS AS SEEN FROM MARS EXPRESS.
Photo By: European Space Agency (ESA) – Mars Express Orbiter and stitched together by Peter Masek (Links below).
This photo of the larger of the two Martian Moons, Phobos (The other being Deimos) was taken way back in the stone ages, 2010 to be exact by ESA’s Orbiter Mars Express during orbit 7982 and what an amazing shot it is. Below the surface of Mars stretches off into the distance, couple that with the cratering on the surface and the HD detail on Phobos itself you get a wonderful sense of depth. Not only depth but it gives you a clear idea of just how small Mars’s moons are to the small planet itself.
This photo also illustrates how dark Phobos is, which leads to the question to weather it’s a captured asteroid or a piece of Mars itself that was blown into orbit by a previous impact. It’s comprised of C-type rock similar to carbonaceous chondrite asteroids and its surface is covered by a few meters of fine powder from the massive bombardments that it has endured. One crater, Stickney (Not in the photo), is 6 miles in diameter. Phobos, at 16.7 miles in diameter at its greatest length demonstrates just how large Stickney crater is. The layer of fine powder resists heat absorption which keeps Phobos very cold. High temperature in sunlight is only 25 degrees F while its coldest point with no sunlight is -170 degrees F. Its orbit is so close that it orbits Mars three times a day at an altitude of 5826 miles (9380km). Its orbit is in continuous decay, nearing the surface at a rate of 1.8m per century and in about 50 million years it will end its life by impacting the planet’s surface. Astronomers are unsure if it will break up or impact intact but as of now the breakup hypothesis is winning. Phobos was discovered on August 17, 1877 by Asaph Hall and its name means fear or panic and in Greek mythology is the Son of Ares, the Greek counterpart to the Roman Mars.
ESA Mars Express page: http://www.esa.int/Our_Activities/Space_Science/Mars_Express
ESA Mars Express Phobos fly-by images: http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Phobos_flyby_images
NASA APOD page for this image: http://apod.nasa.gov/apod/ap101201.html
NASA Solar System Phobos facts: http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos