May 20, 1997: As two NASA spacecraft speed toward a mid-year rendezvous with Mars, astronomers using the Hubble telescope are providing updated planetary weather reports to help plan the missions.
Hubble's new images show that the "Martian invasion" of spacecraft will experience considerably different weather conditions than seen by the last U.S. spacecraft to land on Mars 21 years ago. Martian atmospheric conditions will affect the operation of both the Mars Pathfinder landing on July 4, 1997 and the September 11 arrival of the Mars Global Surveyor, which will map the planet from orbit. These two Hubble snapshots were taken barely three weeks after another Hubble observations of the Red Planet. The differences in the two sets of images are striking, revealing dramatic changes in some local conditions and show overall cloudier and colder conditions than the Viking orbiter encountered two decades ago.See the rest: