The Red Planet Mars never ceases to surprise scientists. The Mars Global Surveyor spacecraft has found patterns of surface rock which are magnetised. These are stripes of magnetic material which point alternately in one or the other direction. These patterns resemble the patterns observed at mid-ocean rift zones on Earth. On this planet, these signify the change in the Earth's magnetic field due to the activity of the tectonic plates which sit above the molten core. This has led scientists to conclude that Mars may also have experienced tectonic activity in the past ( Science , Vol 284, p790, April 30, 1999).