NASA's Mars Global Surveyor camera recently captured four wide-angle pictures of craters in both the northern and southern middle and polar latitudes of Mars that demonstrate how the camera is used to monitor changes in Martian weather and the seasonal coming and going of polar frost.

It is spring in the Northern Hemisphere, and frost that accumulated during the most recent six-month-long winter has been retreating since May. Examples of frost-rimmed craters include Lomonosov and an unnamed crater farther north. It is autumn in the Southern Hemisphere, and frost was seen as early as August in some craters, such as Barnard; later the frost line moved farther north, and frost began to appear in Lowell Crater in mid-October.

Lomonosov Crater. Photo: NASA/JPL/Malin Space Science Systems

This unnamed crater has a patch of frost on its floor that -- based on how it looked during the 1970s Viking missions -- is expected to persist through summer. Photo: NASA/JPL/Malin Space Science Systems

Barnard Crater. Photo: NASA/JPL/Malin Space Science Systems

Lowell Crater. Photo: NASA/JPL/Malin Space Science Systems

Mars Global Surveyor is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif. JPL is a division of the California Institute of Technology in Pasadena. Malin Space Science Systems, San Diego, built and operates the camera system. JPL's industrial partner is Lockheed Martin Astronautics, Denver, which developed and operates the spacecraft.