"Gale Crater is interesting to explore because it crosses what we think is a major time boundary on Mars that's recorded in its mineral history. That boundary marks a change from an early wet, hospitable environment that would have been suitable for life to a middle period where conditions may have become more hostile. We believe that at Gale Crater, we have located that boundary where life may have sprung up and where it may have been extinguished," Brown University geologist John Mustard wrote in an email to Discovery News.
Three other sites made it to the finalists stage - Eberswalde Crater, Mawrth Vallis and Holden Crater.
The rover, nicknamed Curiosity, will touch down within a 12.4-by-15.5 mile targeted area, a relatively small patch of real estate for interplanetary travel. NASA's 1997 Mars Pathfinder lander, by comparison, had a landing target that was 200-300 kilometers long.
Being able to make a precision touchdown didn't make things easy for scientists tapped to pick Curiosity's landing spot. In the past, lots of scientifically interesting sites were eliminated because of concerns the spacecraft wouldn't be able to make a safe landing.
"(The sites) are are all like different flavors of ice cream, all delicious," said geologist John Grant, with the Smithsonian Air and Space Museum.
Image: A topological map of Gale Crater, plus proposed oval landing zone for one of NASA's Mars Exploration Rovers (NASA)