Martian temperature changes. Five images taken in the course of a Martian day (early morning at top and afternoon at bottom), showing the changes in temperature of the rocks in Bonneville crater. This allows an analysis of particle sizes, as the smaller particles (sand and dust) absorb heat more quickly. The temperature varied from 270 Kelvin (red, -3 degrees Celsius) to 230 Kelvin (blue, -43 degrees Celsius). Larger rocks stay blue during the day (one at left), and craters are filled with sand (heat-absorbing, red, upper, lower right). Local solar times (from top) are: 10:15, 11:49; 13:35; 14:35 and 16:39. Data relayed by the Spirit rover, which reached this crater in March 2004.