Phobos makes surprise appearance in Hubble Mars photo

NASA's Hubble Space Telescope recently captured a time lapse of Phobos, a tiny rock-like moon, orbiting around Mars. The resulting composite image of the 13 total exposures shows what appears to be a bright dot of light near looks something like a spec of dust that reflected light back at a camera. That 'speck of dust,' though, is a great look at one of the Red Planet's two small moons.

Phobos, as far as moons go, is very small and shaped somewhat like a rocky football. The moon measures only 13.5 x 16.5 x 11 miles in size, making it positively speck-like when viewed next to the celestial behemoth that is Mars. NASA explains that Phobos is so small, it could 'comfortably' fit within the District of Columbia's beltway. The image above underscores its tiny size.

The moon is notable for a certain oddity, namely it orbits around the planet faster than a full planet day — it only takes a bit under 8 hours for Phobos to complete an orbit, whereas Mars' days are a tad over three times that length. Though Phobos was discovered in the late 1800s by Washington DC's US Naval Observatory, we didn't get our first proper (read: photographic) look at the space rock until the late 60s.

Photos of the moon have been increasing in quality since, the most recent being the ones you see in the video above. NASA explains that Phobos is in rough shape and is expected to be obliterated one way or another in the next 30 – 50 million years — whether that'll happen by it breaking up to form a ring around Mars or crashing into the Red Planet's surface isn't clear.

Overall, NASA managed to get the photo you see above by snapping exposures a little over a minute long each — the entire process took only 22 minutes. The photos are all from a single Phobos orbit; be sure to watch the video above to see them combined together into a single animation showing the moon in motion.