Rates of change in surface temperatures during a martian day indicate differences in particle size in and near "Bonneville Crater." Temperature information from the miniature thermal emission spectrometer on NASA's Mars Exploration Rover Spirit is overlaid onto a view of the site from Spirit's panoramic camera. This sequence of five frames begins at the top with data from 10:15 a.m. (PIA05928) local solar time at Spirit's location inside Mars' Gusev Crater. The times of the subsequent frames are 11:49 a.m. (PIA05929), 1:35 p.m. (PIA05930), 2:35 p.m. (PIA05931), and 4:39 p.m.(PIA05932).

In this color-coded map, quicker reddening during the day suggests sand or dust. (Red is about 270 Kelvin or 27 degrees Fahrenheit.) An example of this is in the shallow depression in the right foreground. Areas that stay blue longer into the day have larger rocks. (Blue indicates about 230 Kelvin or minus 45 Degrees F.) An example is the rock in the left foreground.