The other day I told you that this gif was the best thing I had seen on the Internet recently. Well, I was wrong. I apologize.
Because the gif below is just amazing. It shows the moment NASA’s Hubble Space Telescope, while looking at Mars, also saw its moon Phobos in orbit around the Red Planet.
The gif is stitched together from 13 images taken by Hubble over 22 minutes. Astronomers hadn’t planned to capture Phobos too, it just happened to dance into view.
These images were actually taken a little while ago, back on May 12, 2016, but they’ve just been released by NASA. At this time, Mars was 80 million kilometers (50 million miles) from Earth, which is about as close as it gets. At its furthest, it can be up to 400 million kilometers (250 million miles), which is where it is at the moment, on the other side of the Sun relative to Earth.
Owing to the small size of Phobos, it appears like a star in the images, just a small speck of light. But the fact that Hubble saw it at all is hugely impressive.
Phobos is a tiny irregular shaped moon, roughly 24 kilometers (15 miles across), and it completes an orbit of Mars in just 7 hours and 39 minutes. Its orbit is so close to Mars, just 6,000 kilometers (3,700 miles) above the surface, that in 30 to 50 million years astronomers think it might break apart, and possibly form a ring system. Phobos is moving about 2 meters (6.5 feet) closer to Mars every 100 years.
We’ve actually seen evidence of this happening from spacecraft in orbit around Mars. They’ve seen long, shallow grooves on the moon, which are thought to be signs that the gravitational pull of Mars is actually tearing it apart.
Quite where Phobos came from, along with its companion moon Deimos, is still up for debate. They have a similar composition and shape to asteroids, but as their orbits are nearly circular, the idea they are captured asteroids seems unlikely.
“Phobos may be a pile of rubble that is held together by a thin crust,” notes NASA. “It may have formed as dust and rocks encircling Mars were drawn together by gravity. Or, it may have experienced a more violent birth, where a large body smashing into Mars flung pieces skyward, and those pieces were brought together by gravity. Perhaps an existing moon was destroyed, reduced to the rubble that would become Phobos.”
Whatever its origin, there’s no debate that Hubble’s view of this weird little moon is definitively awesome. This’ll be a tough one to beat. Your move, Internet.