This approximate true-color image taken by the panoramic camera on the Mars Exploration Rover Opportunity shows the impact crater known as Endurance, roughly 430 feet across and, from the highest point on the rim, more than 66 feet deep. When it took this photo, Opportunity was perched about 15.5 inches away from the crater's edge. A portion of one of the rover's solar panels can be seen at the bottom right-hand corner of the image. NASA/JPL/Cornell

Cornell calibrators toil to present the most spectacular Martian image yet

A spectacular Martian color panorama image of a deep, stadium-size depression named Endurance crater was created by Cornell researchers for presentation at a news conference at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., May 6.

Jim Bell, associate professor of astronomy, researcher Jascha Sohl-Dickstein and members of the Cornell Calibration Crew in the MarsLab on the Cornell campus spent long hours putting the pieces of the complex mosaic together so that the picture, taken by the panoramic cameras on board the rover, could be revealed as possibly the most graphic view of Mars yet seen.

Bell leads the panoramic camera, or Pancam, team on the twin-rover mission.

"It's the most spectacular view we've seen of the Martian surface, for the scientific value of it but also for the sheer beauty of it," said Steven Squyres, Cornell professor of astronomy, about the panoramic image at the JPL briefing. Squyres is principal investigator for the science instruments on both Opportunity and its twin rover, Spirit.

As Squyres spoke, Opportunity was standing on the western rim of Endurance, gazing down at the crater's multiple layers of exposed bedrock, after a six-week trek across Martian flatlands. In the following days, the rover began circling the rim of Endurance, observing the crater's interior from various angles and gathering images of two potential access paths just inside the northern and southwestern edges of the crater. The task for Squyres' team is to assess how difficult it would be for the rover to descend part way into the crater and climb back out.

Brian Cooper, leader of JPL's squad of rover drivers for Spirit and Opportunity, said at the May 6 briefing that the initial view of the crater doesn't settle accessibility questions. "The slope right in front of us averages 18 to 20 degrees. Getting into the crater is no problem, but we have a lot more work to do to assess whether we could get back out. That depends on soil properties and slippage, as well as slope." The planned circuit around the rim also will require careful navigation. "If you don't go close enough to the lip, you can't look in, but if you go too far, you could fall in," he said. "We're going to have a very interesting few weeks."

There is a possibility that scientists might send Opportunity into the crater with the expectation that it would not be able to climb out. "We will need to decide whether the science is compelling enough to send the rover into a crater it might never leave, or whether to explore other sites first before entering Endurance," said Orlando Figueroa, director of the Mars Exploration Program at NASA headquarters in Washington, D.C.

Specifically, the researchers' interest lies in the layers of bedrock lining the deep crater, which could reveal what the environment on Mars was like before the salty standing body of water evaporated to produce the telltale rocks that were explored in much shallower Eagle crater, where Opportunity spent its first eight weeks on Mars.

At Eagle crater, an outcrop of bedrock only about the height of a street curb yielded evidence that the site was once covered by a body of salty water deep enough to splash in. "That was the last dying gasp of a body of water," Squyres said. "The question that has intrigued us since we left Eagle crater is what preceded that. Was there a deep body of water for a long time? Was there a shallow, short-lived playa [desert basin lake]? We don't know."

The strategy for seeking answers is to examine older rocks from deeper layers, so Opportunity was sent on drives totaling about 800 meters (half a mile) to reach Endurance, the deepest crater nearby. This crater, excavated by the impact of a tiny asteroid or a piece of a comet, is about 130 meters (430 feet) wide and, from the highest point on the rim, more than 20 meters (66 feet) deep, 10 times as deep as Eagle. An exposure of outcrop in a cliff high on the inner wall across from the rover's current position reveals a stack of layers 5 to 10 meters (16 to 33 feet) tall. Other exposures around the inner slope of the crater could be more accessible than the cliff, and chunks from the same layers may have been thrown out onto surrounding ground by the crater-forming impact.

Referring at the May 6 briefing to one large rock shown in the Endurance crater panorama, Squyres said: "It looks fundamentally different from anything we've seen before. It's big. It's massive. It has a story to tell us."