Risky Crater Descent Planned for Mars Rover
The route followed by NASA's Mars Exploration Rover Opportunity during its exploration partway around the rim of Victoria Crater is marked on this map. The rover first reached the edge of the crater on it's 951st Martian day, or Sept. 26, 2006. This map shows travels through June 24, 2007.
Credit: NASA/JPL/Cornell/University of Arizona/Ohio State University

Updated at 2:31 p.m. ET.

The Mars Exploration Rover (MER) "Opportunity" will perform a risky descent into the red planet's giant Victoria Crater early next month.

The announcement was delivered during a NASA teleconference today, and came after months of debate about whether or not to proceed. Officials said the decision has been difficult to make because some scientists think the crater may become the aging rover's final resting place.

Alan Stern, NASA's associate administrator of the Science Mission Directorate in Washington, gave the go-ahead during the conference. 

"We've made a decision to authorize the rover to descend down into Victoria Crater," he said, noting that the move is not without risks--if it goes inside the large hole in Mars' crust, it may malfunction or not be able to climb out. "But the science could occupy us not just for days or weeks, but for months. This is why I've authorized the rover to go into the crater."

Risky maneuver

Opportunity is currently perched on "Duck Bay," an alcove on the rim of the crater from which it will descend. Scientists have deemed the site the gentlest entry point to the 800-meter-wide (2,600-foot-wide) crater. 

The rover is set to make its descent early next month. "Perhaps the 7th or 9th of July," said John Callas, MER project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. He noted that the team will first see if the rover can make the trip with a short "toe-dip" into Duck Bay.

?We chose our entry point solely on the basis of safety,? said Steve Squyres, principal scientist of the Mars Exploration Rover team at Cornell University in Ithaca, New York. Squyres explained that moving the rover only a few feet down the slope and backing it out should reveal any unpleasant surprises such as slips or slides.

In addition to slippery terrain, the Mars scientists fully accept the risk of wheel failure or other malfunction once in the crater. ?We believe we can get in and explore and get out safely, but if we were to have a wheel failure on Opportunity that would make getting out very problematic,? Squyres said.

Crater of knowledge

During the descent into Victoria Crater, however, the scientists expect to stay busy.

?It?s much farther away from our previous craters than any place we?ve been,? Squyres said. ?And this thing is a hell of a lot deeper than any other crater we?ve looked at so far. This provides us access to a much longer span of Mars? geologic history.?

But perhaps the most important aspect of the crater, Squyres said, is that it?s extremely old--possibly billions of years. Instead of a fresh impact with chaotic jumbles of rock, the crater has eroded to its current form and has exposed a clean spread of intact bedrock.

The rover team?s first objective with Opportunity is to scope out a bright band of rock in un upper portion of the crater.

?It?s different from everything else around it,? Squyres said. ?This is the layer that was in contact with the Martian surface at the time of impact, so it may have preserved information about ? the ancient Martian environment.?

Long journey

The rovers Spirit and Opportunity have been exploring the Red Planet since January of 2004 and were expected to last just 90 days on the dusty surface. Defying the odds, they have both been in operation for more than 12 times their expected mission length--but not without event. 

Spirit's right front wheel stopped moving in March of 2006, but has since proven an effective soil-digging instrument. In May of this year, it turned up a powdery white substance discovered to be 90 percent pure silica. Scientists think its presence beneath the surface is indicative of a watery past on Mars.

In addition to looking out for mechanical troubles, team members are closely watching a massive dust storm to the south of Opportunity. "We are tracking this thing daily," Squyres said. "It's a risk to us, just as driving it down into a crater is a risk to us. The dust levels are among the highest we've seen so far."

Assuming a safe journey and good weather, Squyres thinks Opportunity will make exciting discoveries while in the crater, as well as when it leaves to investigate the cobble-strewn plains in the area.

?We?ve blown by a bunch of these stones in a hurry to get to crater,? he said, and have looked at ?only a handful? of them. From meteorites to debris rocketed from distant impact sites, Squyres said investigating the rock-strewn plains will be Opportunity?s next big mission.

?Nature has delivered to us, in the form of these cobbles, exotic rocks from places we can?t sample,? he said. In addition, the team hopes to look for more evidence of surface water, which they think they discovered around Erebus crater.