NASA's Opportunity and Spirit Mars rovers are on the prowl. Science teams are plotting out new escapades for the twin robots--new destinations certain to reveal more secrets from the red planet.
Within Meridiani Planum, the Opportunity rover is relaying great pictures of Victoria Crater and its walls, said Steve Squyres, lead scientist of the Mars Exploration Rover (MER) project from Cornell University in Ithaca, New York.
So far, the story at Victoria is surprisingly similar to what rover scientists saw at Endurance Crater, a feature they closely studied for months back in 2004.
Squyres told SPACE.com that the rover's Panoramic Camera (Pancam) is telling Mars researchers that the rocks in the crater are mostly "fossilized dunes"--with layering that preserves clear evidence of ancient transport by wind.
Opportunity's Mini-Thermal Emission Spectrometer (Mini-TES) has revealed that this material is sulfate-rich all the way down, Squyres said. Mini-TES characterizes the martian terrain by using thermal infrared spectroscopy.
"So the picture we got back at Endurance, with a sulfate-rich dune field and lots of acidic groundwater, seems to apply here as well...several kilometers to the south," Squyres added. "This was a big, long-lived dune field and there was lots of water here."
Into Victoria Crater
What rover scientists may learn when Opportunity steers down inside the crater is anybody's guess. But first finding a driveway into Victoria is high on the priority list.
"So far we have found two safe entry routes into Victoria. Those are Duck Bay and Bottomless Bay. We have not yet confirmed that either is a safe exit route, but they both have potential," Squyres advised.
Opportunity is continuing with its scenic tour of the rim of Victoria Crater, said William Farrand, a research scientist at the Space Science Institute in Boulder, Colorado. He is also a member of the MER science team.
"We have been getting some spectacular panoramas of the promontories and inner rim of Victoria. We are also in the process of building up images for a fabulous stereo model of the crater," Farrand told SPACE.com.
It is still a bit early, Farrand said, for rover science team members to assess the totality of the geologic story contained in the walls of Victoria. Doing so calls for detailed inspection of the stratigraphy of the walls--an assessment of strata, or layers.
"We are really taking a methodical approach to mapping out the stratigraphy exposed in the walls of the crater. Once we've gotten further around I think we will have a better understanding of what that stratigraphy is telling us," he said.
Spirit: back to Home Plate
On the other side of Mars at Gusev Crater scientists are preparing to steer the Spirit Mars rover back to a region called "Home Plate"--a still baffling formation near the Columbia Hills.
At the moment, Spirit has been busy looking at a target tagged "Esperanza"--the first "vesicular" basalt that has undergone detailed scrutiny.
Vesicular basalts form when dissolved gas in a lava comes out of solution, "like bubbles in soda," Squyres tutored, creating little Swiss-cheese-like voids within the rock.
"We've seen lots of vesicular basalts at Gusev, particularly around Home Plate, and this is our first chance to really find out what they are made of and how they may or may not be related to Home Plate," Squyres explained.
Squyres said that Spirit is likely to stay in the vicinity of Home Plate for a long time.
From overhead, NASA's Mars Reconnaissance Orbiter has used its High Resolution Imaging Science Experiment (HiRISE) camera to sharp-shoot the site that Spirit is now appraising.
"The recent HiRISE image of the Spirit site has shown us that there are many more scientifically interesting targets around Home Plate than we realized. Some of these features are difficult to spot from ground level," Squyres pointed out.
The powerful HiRISE camera has found things that Mars rover scientists hadn't realized were there before. "So, having found our way with much difficulty to such a target-rich environment, we're going to work it for all it's worth."
New field season
Spirit packed up winter camp and started out on a new field season over the past couple of weeks, said Larry Crumpler, a MER science team member based at the New Mexico Museum of Natural History and Science in Albuquerque.
"It was a very long winter," Crumpler said, "but the Sun is getting high enough now that Spirit can survive with no tilt," a parking position used to glean more solar energy to keep the rover healthy.
Spirit has scrambled off the ledge it has been sitting on since last April. The rover has started a new field season on Mars...even as winds starting to pick up and dust in the air started going up, Crumpler noted, "just like a spring day in New Mexico."
"Hopefully, we will have a solar panel cleaning event somewhere in the future. That will make the power situation better even as the atmosphere becomes dustier and the Sun's rays are dimmed," Crumpler added.
Spirit is limping a bit. The rover's front right wheel is not working. So the robot is dragging it, using its five other wheels to move about.
"It makes approaches for studies of targets with the instruments tricky, requiring a crab-like motion to put targets within the instrument work space," Crumpler told SPACE.com. "So the first drives are tentative and very carefully considered for their value in learning anew how to drive on Mars."
Driving Spirit onward, the plan is to make it back to the edge of Home Plate. Spirit will then pick up where it left off last martian fall, and continue a drive clockwise around the south edge of Home Plate, Crumpler said.
Another goal of the traverse around the margin will be to see if there are any indicators of Home Plate's geologic origin - be it volcanic or just a product of wind action.
"Although it is clear that the materials that make up the outcrops are volcanic, it is not clear whether the deposition was volcanic in origin--air fall or ballistic--or whether it was just blown into a low spot by normal wind processes," Crumpler explained.
This is probably the first place where real field geology has come to the fore, Crumpler points out. "Chemical analysis of the rocks can tell us many things, but it can't tell you in every case how the rocks got where they are...that's the job of field geology," he said.
Beyond Home Plate
"We should begin exploring the unseen southern margin of Home Plate in the New Year," noted Jim Rice, a science team member of the Mars Exploration Rover Project at Arizona State University in Tempe.
"I am personally looking forward to seeing new cross sectional views of the layered rock outcrops along the southern margins of Home Plate," Rice said. "How long we will stay at Home Plate is unknown...it sort of depends on what we find there. This is the nature of exploration."
After Home Plate, Rice is voting for study of features nicknamed "von Braun" and "Goddard", after the two great rocket pioneers.
"These are very high priority targets in my opinion," Rice told SPACE.com. "Von Braun looks like some of the classic layered buttes and mesas one would see here in Arizona. Goddard could be either an impact crater or volcanic vent. The only way to know is to go."
How these two features fit into the overall, complex story of the Columbia Hills is yet to be determined, Rice said.
Enter the Promised Land
Rice said he's longing for a look at another big target labeled the "Promised Land", a region he first pointed out and named some three years ago shortly after Spirit landed in January 2004.
The origin of this material is unknown and this region would in effect constitute a new landing site, Rice suggested.
But the start of the Promised Land is about 3,000 feet (800 meters) away.
That's a long haul given Spirit's mobility issues: its balky right front wheel. "But we should at least try. It would be a shame if we only see it from afar. We will not know what possible geologic treasures the Promised Land holds until we enter its domain," Rice concluded.