THE latest analysis of pictures taken by NASA鈥檚 Stardust probe during its headlong plunge through comet Wild 2 on 2 January has revealed a big surprise: the comet鈥檚 icy nucleus is covered in what look like impact craters.
In its first bulletin last week on the mission鈥檚 findings, the Stardust team reported that the jets of gas producing the comet鈥檚 spectacular coma and tail appear to be emanating from pits on the surface of the nucleus (快猫短视频, 10 January, p 11).
Now the team has studied more detailed pictures from the probe and found that as well as sinkholes apparently caused by ice vaporising below the surface, the nucleus is covered in what look like well-preserved impact craters. That is completely unexpected because comets are believed to be loose aggregations of dust and ice that would shatter on impact.
Advertisement
鈥淚 don鈥檛 think any of us ever really considered the possibility of impact craters,鈥� says Ray Newburn of NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California. If the pits are craters, the surface of the comet nucleus must be much stronger than experts thought. 鈥淚t may be a well-cemented rubble pile, but it鈥檚 definitely not a loose powdery surface,鈥� he says.
