For the first time ever, a European space probe performed a flyby of an asteroid. In the evening of 5 September 2008, the European Space Agency ESA’s Rosetta space probe passed the small celestial body at a distance of just 800 kilometres.
The first images which have been received show an irregularly shaped asteroid with a diameter of 4.6 kilometres, which confirms calculations made in the run-up to the observations. In Steins’ north polar region, a circular impact crater of about one and a half kilometres in size is visible; north is at the top of the image.
Relative to the asteroid’s overall size the crater is so large that is very likely that the collision which created it was so severe as to almost shatter Steins. Also striking is a chain of at least six smaller impact craters, which, decreasing in size, extends from north to south across Steins' day side. Such a chain of craters has never before been observed on any other asteroid. Through investigating the small celestial bodies of our solar system, such as asteroids and comets, the researchers hope to gain insight into the first few million years in the history of our Solar System, which is 4.6 billion years old.
ESA ©2008 MPS for OSIRIS Team MPS/UPM/LAM/IAA/RSSD/INTA/UPM/DASP/IDA.