NASA's Opportunity rover will be sent into a big impact crater on Mars despite the risk that it may not be able to get out, the space agency said Friday.
The potential scientific value of exploring Endurance Crater outweighs the risk that the six-wheeled rover may not be able to drive back up its inner slopes, mission officials said.
The decision was made after extensive study of the crater as the rover moved along its rim. Images have shown layered rock, which could offer important clues about the past history of water on Mars.
The decision was "crucial and careful," said Edward Weiler, NASA's associate administrator for space science.
"Layered rock exposures inside Endurance Crater may add significantly to the story of a watery past environment that Opportunity has already begun telling us," Weiler said in a statement.
Operation planned next week
The earliest Opportunity could be sent into the 140-yard-wide (130-meter-wide) crater would be early next week, NASA said.
The rover will first go to a proposed entry point and make a final check of the slope. If it's no greater than what test runs at NASA's Jet Propulsion Laboratory show the rover can handle, Opportunity will be given the go-ahead.
Richard Cook, rover project manager at JPL, said that one exposed rock layer at a site called Karatepe will require driving only 16 to 23 feet (5 to 7 meters) down into the crater on a 25-degree slope.
"We'll take an incremental approach, edging our way down to the target," Cook said.
Several days on the bottom
Opportunity will use its instruments to study the layers for several days, and then will be ordered to reverse back up the slope and exit the crater.
Back in January, at the very beginning of its mission, Opportunity landed in a smaller depression known as Eagle Crater and found evidence of a vanished salty sea within the layered rock there. Endurance Crater is much deeper, and may shed additional light on the question of how long liquid water persisted on Mars.
Finding out what Mars was like before the era documented at Eagle Crater is "the most significant scientific issue we can address with Opportunity at this time," Cornell University's Steve Squyres, the lead scientist for the rover missions, said in Friday's statement.
"We've read the last chapter, the record of the final gasps of an evaporating body of water. What came before?" Squyres asked. "It could have been a deep-water environment. It could have been sand dunes. It could have been a volcano. Whatever we learn about that earlier period will help us interpret the upper layer's evidence for a wet environment and understand how the environment changed."
Opportunity and its twin, Spirit, have been working on opposite sides of Mars since landing in January. Both rovers completed their primary missions and are now on extended missions.
Spirit has been rolling through a vast depression called Gusev Crater toward a rise in the terrain called the Columbia Hills. It is expected to arrive at its first destination in the hills by the middle of this month.
This report includes additional information from NASA.