NASA is releasing these images to commemorate the second anniversary of the Mars Pathfinder landing. 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. These Hubble telescope snapshots reveal that substantial changes in the bright and dark markings on Mars have occurred in the 20 years since the NASA Viking spacecraft missions first mapped the planet. These images show that the Martian surface is dynamic and ever changing.
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. See the full caption for more information.