To the surprise of researchers, Hubble is showing that the Martian climate has changed considerably since the unmanned Viking spacecraft visited Mars in the mid-1970s, which was the last time astronomers got a close-up look at weather on the Red Planet for more than just a few months.
Hubble images of fleecy clouds, and spectroscopic detection of an ozone abundance in Mars' atmosphere, all indicate that the planet is cooler, clearer and drier than a couple of decades ago.
The neighboring planets are grand natural laboratories for testing computer models that will lead to a general theory of the behavior of planetary atmospheres. In the case of Mars, being able to predict the weather will be critical prior to human exploration and, perhaps eventually, colonization.
Photos : NASA HST Philip James (University of Toledo) Steven Lee (University of Colorado)