This 360-degree view shows Opportunity’s last stop on Meridiani Planum before reaching Victoria Crater. In the center of the picture is Beagle Crater, an impact crater about 115 feet wide. Opportunity took this false-color mosaic of images on the rover’s 901st through 904th Martian days (Aug. 6 through Aug. 9, 2006); the false colors emphasize differences in rock and soil materials.

NASA

An artist’s concept portrays a NASA Mars Exploration Rover on the surface of Mars.

Image Credit: NASA/JPL/Cornell University/Maas Digital

Send a message to Mars: Dig. Drill. Search for signs of life.

It’s just another day at the office for Michael Wyatt.

Every day for nearly three years, the assistant professor of geological sciences at Brown University participates in a conversation over millions of miles with two Mars rovers that just keep going and going. Spirit and Opportunity, which Wyatt calls “robotic geologists,” were supposed to survive 90 days in the planet’s dusty and metal-cracking cold climate. They’ve lasted more than 10 times that.

“There’s no doubt the extended lifetime of those rovers has shed new light on the history of Mars,” Wyatt says.

Water was once there, and, maybe, life, too. The search is on — not for Martians, although that would be exciting, but for rocks.

“Rocks record the geological history,” Wyatt says.

The deeper you dig, according to Wyatt, the more history you see. Although maybe you can see the past without digging, which is what scientists may soon discover. Opportunity, which has moved 5.6 miles since it landed in January of 2004, is now within meters of a crater that would make the Grand Canyon appear much less so.

“Scientists are extremely excited about this crater,” says Greg Mehall, NASA’s instrument and mission manager at the Mars Space Flight Facility at Arizona State University.

But scientists haven’t decided if the rover should enter the crater.

“Getting in is easier than getting out,” Wyatt says.

When Michael Wyatt joined the Brown faculty this school year, he joined the legacy of the university’s department of geological sciences, which has long been involved in the exploration of Mars. The late Thomas Mutch, a former professor who died in 1980 while climbing the Himalayas, was involved in NASA’s 1976 Viking probe to the planet, which sent back the world’s first pictures taken from its surface.

Since then, much of the research and engineering of subsequent Mars projects has involved current Brown faculty members in the geosciences, including professors James Head and Carle Peters, and associate professor John Mustard.

“It’s the opportunity of a lifetime for me to be joining a group such as the one here,” Wyatt says.

Before coming to Brown, Wyatt performed post-doctoral work at Arizona State, where one of the rovers’ key instruments, the mini-thermal emission spectrometer was designed. Every day Wyatt communicates by phone, videoconference or e-mail with scientists at Arizona State who send commands to the two rovers: Analyze soil. Grind rocks. Take pictures.

And every day, by satellite transmission, the rovers send back results, which Wyatt studies.

“When you’re doing field work, you don’t just like to go to one particular place,” Wyatt says. “You like to travel around.”

Victoria Crater wasn’t on the 90-day travel itinerary.

“It was our wildest dream early on,” Wyatt says. “People used to joke how great it would be if we could go there.”

This was before the rovers’ engineering proved so successful, and before the arrival of a couple of cyclones that completely cleaned the rovers’ dust-covered solar panels.

The rovers’ longevity, Mehall says, can be attributed to two things: “Engineering and the planet cooperating with us.”

Dust is deadly, particularly to solar panels. Most of Mars is covered with dust; after a few months, so were the six-wheeled one-ton rovers that are roughly 8 feet long, 5 feet wide and 7 feet high.

“Solar power was dropping as the dust was accumulating,” Mehall says. “Over one night, the dust we saw on the solar panels was gone. We made it through winter.”

At that time, the sun isn’t strong, and the temperature is a circuit-killing minus140 degrees Fahrenheit.

But that’s not the worst part, according to Mehall. It’s the daily change in temperature, from generally 20 above to 100 below.

“Unlike on earth where temperatures are seasonal, here it’s day to day,” he says.

The rovers are made of special materials to withstand severe temperature swings. And the rovers use solar energy captured during the day to withstand the night, which it does by charging batteries, which run heaters.

“When temperatures swing in a large range, the batteries will fail,” Mehall says. “Then the rovers will die, which is probably what will kill them.”

The two rovers landed on opposite sides of the planet. Both survived, which pleased NASA officials who designed one as a backup for the other.

Opportunity landed in a crater and immediately detected chemicals that could only have been created in the presence of water. Wyatt calls this NASA’s “hole in one.”

Spirit landed respectably, but not notably on the fairway. However, it has since entered what scientists call the Columbia Hills.

“In those hills is where we are now beginning to find all this evidence of aqueous activity and alteration of rock,” Wyatt says. “If the rover had not lasted as long, we never would have made it to the hills.”

Those hills, Wyatt says, are “turning out to be a gold mine of diversity.” For months prior to that, Spirit crossed an area of plains, which, according to Wyatt, were “pretty much the same.”

Now, after traveling 4.3 miles, Spirit is hunkered down for winter, parked on a hill with its solar panels facing the sun.

“We’ve been doing science, but restricted science,” Mehall says. “We’re not allowed to drive.”

Spirit, Mehall says, must conserve energy until the season changes. Then it will rove again, within its limits. Spirit’s right front wheel is malfunctioning and not moving, so scientists drive the vehicle backward to reduce its drag. Meanwhile, Opportunity is having trouble with its robotic arm.

Such is life, for man and machine.

“They’re geriatric rovers,” Mehall says. “They have achy joints. Their arms get stuck. They are beyond their prime 20s. Every day, they may wake up with a sore wheel.”

Still the rovers roam, and will until they can’t.

“Once the assets are on Mars, the last thing you want to do is turn them off,” Mehall says. “We spent so much money on them.”

The project costs $840 million, with presumably more projects to come.

What is going on now on Mars, Mehall says, is “baby steps” in an exploration that will involve more landings in an ambitious endeavor.

“NASA’s goal is the search for life,” he says. “If Mars had life on it, that philosophically changes everything.”

Are we alone in the universe?

“If you find other forms of life, the existence or absence can tell us a lot about Mars as a planet,” Wyatt says. “It can also give us a bigger, broader understanding of ourselves and how life may have started on earth.”