Mooning at an asteroid

US SPACECRAFT Galileo has recently sent pictures of a tiny moon orbiting 243 Ida -- a 56 km-long asteroid in the asteroid belt between Mars and Jupiter. This is the first confirmed evidence of a natural satellite kowtowing to an asteroid (Nature, Vol 368, No 6470).

The miniature moon, astronomers believe, is either a fragment of Ida or the remnant of a recent collision between Ida and another object.