The mission of the European Space Agency (ESA) Rosetta has obtained the first images of asteroid 2867 Steins. Pictures taken by both cameras of the OSIRIS instrument show that the asteroid has an unusual diamond-shape, with an effective diameter of 5.3 kilometres and a large crater near the south pole of the asteroid of 2.1 km in diameter. The study is published in the journal Science.
Staff | 8 January 2010
The international team of researchers suggest that it is the sunlight that has shaped this diamond, through what is called YORP: the sun's radiation can alter the asteroid's rotation on its own axis. OSIRIS images are the first visual evidence of YORP on an asteroid of the main belt.
One of the authors of the work, the researcher from the Consejo Superior de Investigaciones Científicas (CSIC) Luisa Maria Lara, says: "In this case, everything seems to indicate that the thermal effect of the sun on the asteroid has changed the direction of the body rotation, which could cause the slippage of material from the asteroid's south pole to the equator, a phenomenon that would give it the form of Steins´ diamond”.
The large crater that is located in the asteroid's south pole in turn provides information about the internal structure of the body. "If you compare the size of the crater with the overall size of the asteroid, and this value with those of other asteroids with large craters [Matilda Vesta], one can conclude that Steins was already a heap of rubble by the time it suffered the impact which resulted in a crater of 2.1 kilometres across, "explains the researcher of the CSIC.
