Supporting the theory that water on Earth originated on asteroids like these

Oct 11, 2013 10:21 GMT  ·  By

Spotting asteroids in our solar system is rather difficult. Even relative large ones, which could cause some damage if it they hit populated areas, can't be seen until they're very close to Earth and many times are only spotted once they enter the atmosphere.

So you can imagine that spotting an asteroid in another solar system, let alone one 170 light years away, is much harder. But a team of astronomers used Hubble's spectrograph to spot the tell-tale signs of one asteroid as it crashed into its parent star, GD 61. The results of the study are published in Science.

Astronomers have a tough time surveying most stars and it's even harder to find out anything about the planets that orbit around them. In fact, very few exoplanets have actually been seen, most are just inferred by the effects they have on their stars. So spotting an asteroid is quite an achievement.

In fact, astronomers don't only know that the asteroid existed, but also that it had a huge amount of water attached to it. Actually, they determined that the asteroid was 26 percent water. The Earth is only 0.02 percent water, for comparison.

The find is great support for the theory that water was brought to Earth and possibly other planets like it by asteroids since our planet formed too close to the sun for water to have formed naturally, in the early days.

But things aren't clear cut. The astronomers didn't actually see any water; instead, they found a lot of oxygen which they believe is tied up with hydrogen in water molecules. They were able to spot the oxygen on the surface of the star, after the asteroid got too close and broke apart because of the massive gravitational forces.

GD 61 is a white dwarf, the remnants of a star like the sun, which has shed its outer layers and is now as big as the Earth and only has hydrogen and helium on the surface. So the oxygen spotted by the astronomers could only have come from an external source.