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It can be slow going to get to a destination. Just look at the driving record of the twin Mars rovers, which took months to trek several miles.

“You could eat up a substantial portion of your mission just driving where you want to go,” said Ruff, who called it an unnecessary risk.

Astronomer Jim Bell of Arizona State University, who goes back and forth between favoring Gale and Eberswalde craters, agreed it was chancy, but thinks it’s worth it.

“We won’t be putting on blinders and heading east or west without stopping,” said Bell, who is part of the mission’s camera team. “There’s a clear pot of gold at the end of the rainbow, but there are also some neat things to do along the way.”

Planetary geologist John Mustard of Brown University was disappointed when the site he was rooting for, the Nili Fossae region, a series of deep fractures in the Martian crust, was rejected because it was deemed too dangerous to land.

He now supports going to Mawrth because he thinks it’s the most diverse.

“It’s not a one-trick pony. You’ve got more than enough compelling outcrops that one can test,” he said.

After the community input, the team will meet in private to mull over the pros and cons of each site and eventually recommend one to NASA. The space agency has the last say, but it usually follows the advice of its researchers. A final decision is not expected until late June or July.

Smithsonian geologist John Grant, who is co-chairing the meeting, said he hopes there’s more clarity about the strengths and weaknesses of the final four.

“There’s a big investment in this rover. We want to make sure that it goes to the best possible site.”

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Online:

Mars mission: http://www.nasa.gov/mission_pages/msl/index.html

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Alicia Chang can be followed at http://twitter.com/SciWriAlicia