NASA in the sky with diamonds
An ESA spacecraft has flown by an asteroid, and imaging has shown it to be a diamond worthy of King Kong’s wedding ring:
It’s asteroid 2867 Steins, as seen by the Rosetta spacecraft when it passed only 800 kilometers away on Friday. It’s a diamond in the rough – asteroids of this size range (~5km across) can theoretically be pretty much any shape, as the gravity of an object that size isn’t strong enough to form the rock into a sphere. However, collisions with other asteroids generally tend to make them roundish so most of the ones we see are either spherical due to random collisions, or potato-shaped (known as “spuds”).
The diamond shape extends all the way around the visible half of Steins – as Rosetta passed the asteroid imaging as it went by, so more than half of Steins was mapped. The shape appears to hold up and It is shaped like a diamond.
Steins has a massive crater on it, spanning 1.5 km of its surface. That’s quite big, and the impact that made it must have been of an impressive scale. If Steins were a solid chunk of rock, an impact that large would have likely shattered it (or covered the body with cracks). It could be that Steins is instead a “rubble pile” – a body made of loose pieces of rock, held together by it’s weak gravity.
Some asteroids have very low density, and astronomers think that these used to be solid bodies, but several collisions has made them a looser body of fragments and empty space – lowering its density.
The Rosetta mission was launched in 2004 and it’s main science goal is to study the comet 67P/Churyumov-Gerasimenko. Rosetta consists of two elements: the Rosetta space probe and the Philae lander, which will be used to make contact with the comet’s surface. The spacecraft will also flyby and examine the asteroid 21 Lutetia in 2010, before making it’s approach to the comet in 2014.