Here’s a quick animation of Mars’ moon Phobos, made from five images – released today – taken by ESA’s Mars Express during its flyby on January 9, 2011. Passing by the 14-mile-wide moon at a distance of about 62 miles (100 km), Mars Express took images in five HRSC channels…I combined those to create this. 🙂 The top of Phobos was cropped a bit the original data, hence the flat-top.
Did it form with Mars as a planet? Is it a captured asteroid, now trapped in orbit? Or is Phobos a chunk of Mars flung into orbit from an impact? (Or…maybe it’s an ancient alien spacecraft?? :P) Wherever it came from, as a moon Phobos really is an oddity. In addition to its small size – only 16 miles across at its widest – and irregular shape, it also orbits its parent planet at a very low altitude, only 5,840 miles (compare that to our own Moon’s 248,000 mile distance), and thus needs to travel at a very high speed in order to stay in orbit. It is actually orbiting Mars over three times faster than Mars rotates, and thus appears to rise in Mars’ western sky. And its orbit is so low that it can’t even be seen from the polar regions on Mars. Clearly something is unusual about Phobos. Hopefully these flybys will help scientists figure out the history of this little world!
Read more on ESA’s Mars Express site here.
Image credits: ESA/DLR/FU Berlin (G. Neukum). Animation by J. Major.