Sulfur dioxide (SO2) may have played a key role in the climate and geochemistry of early Mars, geoscientists at Harvard University and the Massachusetts Institute of Technology suggest in the Dec. 21 issue of the journal Science.

An asteroid could hit the planet Mars by the end of next month.

Planetary scientists have puzzled for years over an apparent contradiction on Mars. Abundant evidence points to an early warm, wet climate on the red planet, but there’s no sign of the widespread carbonate rocks, such as limestone, that should have formed in such a climate.

Inch by power-conserving inch, drivers on Earth have moved the Mars rover Spirit to a spot where it has its best chance at surviving a third Martian winter -- and where it will celebrate its fourth anniversary (in Earth years) since bouncing down on Mars for a projected 90-day mission in January 2004.

New software is helping NASA find safe places for the Spirit rover to ride out future Martian winters -- and also plan where Spirit and its companion rover, Opportunity, will explore in the future.

Scientists have gathered more evidence that suggests flowing water on Mars - by comparing images of the red planet to an otherworldly landscape on Earth.

These images taken by the High-Resolution Stereo Camera (HRSC), onboard ESA’s Mars Express imaged the Noctis Labyrinthus region, the ‘labyrinth of the night’ on Mars.

Mars, like Earth, is a climate-fickle water planet. The main difference, of course, is that water on the frigid Red Planet is rarely liquid, preferring to spend almost all of its time traveling the world as a gas or churning up the surface as ice.

Scientists scouting potential landing sites for NASA's next Mars rover mission are using new data from a powerful mineral-mapping camera to narrow the site selection.

The High Resolution Stereo Camera (HRSC) on ESA’s Mars Express orbiter has obtained pictures of the Noachis Terra region on Mars, in particular, the striking Maunder crater.

Planetary scientists on both sides of the Atlantic have tracked down a rare molecule in the atmospheres of both Mars and Venus. The molecule, an exotic form of carbon dioxide, could affect the way the greenhouse mechanism works on Venus.

A heat-sensitive camera designed at Arizona State University and flying on NASA's Mars Odyssey orbiter has led a team of Mars geologists to find seven small, deep holes on the flanks of Arsia Mons, a giant volcano on Mars. The holes may be openings, called skylights, in the ceilings of underground caves.