An animation of Mars showing four hemispheric views at 90 degree intervals as seen by the Hubble Space Telescope between April 27 and May 6, 1999. The telescope's Wide Field and Planetary Camera 2 snapped these images between April 27 and May 6, when Mars was 54 million miles from Earth. From this distance the telescope could see Martian features as small as 12 miles wide. The telescope obtained four images, which, together, show the entire planet. Each view depicts the planet as it completes one quarter of its daily rotation.
Winds move sand and dust from region to region, often in spectacular dust storms.
Over long timescales, many of the larger bright and dark markings remain stable, but smaller details come and go as they are covered and then uncovered by sand and dust. The four hemispheric views of Mars obtained by the HST are striking for their clarity and detail. In the gallery above, hemisphere A is centered near the location of the Pathfinder landing site. Dark sand dunes that surround the polar cap merge into a large, dark region called Acidalia. This area, as shown by images from the Hubble telescope and other spacecraft, is composed of dark, sand-sized grains of pulverized volcanic rock.