The Search for Life
In the 1960s, space probes took the first close-up photos of Mars. Those showed what seemed like a barren landscape. Later searches, however, revealed surprising features, suggesting previously wet, habitable environments. Such hints have revitalized the search for life (if not intelligent civilizations).
FIRST IMAGES OF MARS
1965: The American space probe Mariner 4 sent back the first photos of the Martian surface, temporarily dashing scientists' hopes of finding life by revealing a dry, barren landscape punctuated only by craters.
1972: Mariner 9 revived interest in Martian life when it sent home photos of dry riverbeds, indicating that Mars once had a very different climate that might have supported life.
1997: Thanks to satellites like the Mars Global Surveyor, which orbited Mars for nearly a decade starting in 1997, people now have extremely detailed images of virtually the entire Martian surface, including what would turn out to be the largest canyons and volcanoes in the solar system.
1999-2005: Captured by the orbiting Mars Global Surveyor, these two images reveal the same site on Mars six years apart. The image at right, taken in 2005, shows a place where liquid water seems to have burst onto the surface so recently that it left flow deposits not visible in 1999 photos, at left. If liquid water is still flowing underground, it could possibly harbor life even today.