Robotics experts are getting a next-generation rover ready to hunt for life in the driest place on Earth. The two-month-long dry run in Chile's Atacama Desert could help set the stage for a similar search someday on Mars.
The four-wheeled, solar-powered rover, named Zoë, was created at Carnegie Mellon University in Pittsburgh. It's designed to cover up to 1.2 miles (2 kilometers) a day, at speeds of up to 2.2 mph (1 meter per second). That's 20 times as fast as the top speed for the twin rovers currently working on Mars.
But raw speed isn't the point of this experiment. Rather, the researchers want to see whether highly mobile robots could do a better job of looking for life in alien environments.
"We're testing a hypothesis here, that the way to search for life is actually to look in a lot of places," said David Wettergreen, a Carnegie Mellon robotics professor who heads the NASA-funded research project, known as Life in the Atacama.
Dyeing for life
Instead of taking microscopic-scale images of rocks and making hours-long spectroscopic observations, as the Mars Exploration Rovers do, Zoë will test a novel life-detection strategy: Samples of rock and soil will be sprayed with a series of fluorescent dyes that light up in the presence of life's chemical building blocks. A camera equipped with special filters then would look for the glow associated with DNA, proteins, carbohydrates or lipids.
"Those are four of the key components of living systems," Alan Waggoner, director of Carnegie Mellon's Molecular Biosensor and Imaging Center, explained. "If you had these four dyes and you looked in a microscope or some kind of imaging device, and you saw all four colors of fluorescence coming from a region of a rock or soil, you'd be pretty sure that there were living organisms there."
Dye-based detection systems have long been used in medicine and forensics — in fact, the procedure often pops up as plot devices in crime shows like "CSI." But the technique has never been applied to the search for extraterrestrial life, Waggoner said.
Using it in the Chilean desert, where life exists in forms ranging from microbes to mice, won't be easy: Zoë's predecessor, a rover called Hyperion, was sent to the Atacama in April 2003 for a similar test. Scientists on the scene saw ample evidence of the flora and fauna, but the readings that Hyperion sent back weren't enough for remote scientists to reach the same conclusion.
Putting Zoë to the test
Researchers are in the final stages of preparation for this year's expedition. A demonstration of Zoe was scheduled for last week, but had to be canceled due to rain — an unfavorable turn in the weather that the team will almost certainly not see in the Atacama.
The Atacama is a favored site for Mars research as well as ground-based telescopes because it's considered the most arid place in the world: The desert's average annual rainfall is measured in fractions of a millimeter, and some areas are said to have gone centuries without seeing a droplet of rain.
Carnegie Mellon's operations will be based at Salar Grande, a salt flat near the city of Antofagasta.
"It's quite barren," Wettergreen said. "It's not like the Sahara Desert, where you have shifting sands. There's really just soil and rock. It is sort of reddish in color, so I guess in some regards it may be Marslike. ... Actually, when the light is good, early in the morning and in the evening, it's quite beautiful there — but it is profoundly empty."
This year's expedition begins in early September and should finish up around Oct. 20, Wettergreen said. Researchers will put Zoë through its paces at two Atacama sites. One is about 30 miles (50 kilometers) from the Chilean coast; the other is farther inland, about 375 miles (600 kilometers) away, where organisms are much sparser.
A big part of the test is just seeing whether Zoë can manage itself autonomously and roll through the desert as quickly and surely as robotics researchers hope.
"We're designing for about eight to 10 hours of rover operation a day," Wettergreen said. "To a large extent that's tied to being able to see. But we are going to do some experiments with operations at night."
Zoë will be programmed to do spot checks of target sites, as well as inch-by-inch surveys of a stretch of desert. For this year's test, Waggoner will be standing behind Zoë, spritzing the fluorescent dyes onto rocks and soil for Zoë to check with its camera. Eventually, the spritzers will be built into the rover.
The road ahead
The resulting data and imagery will be sent to Carnegie Mellon's mission control, back in Pittsburgh, and will also be interpreted by the researchers in the field. Samples will be brought back from the Atacama for further analysis, providing another level of what geologists call "ground truth."
"What we're doing at this point is early technology development," Wettergreen said. "It's a long and complicated process."
He hoped that the technologies being tested on Zoë would mature over the next few years — and perhaps be considered for a mission tentatively planned in 2013, which could bring samples from Mars back to Earth.
Zoë's handlers acknowledge that the technology might have to be adapted for operations on Mars. For example, most astrobiologists think the best bet for finding extant life on Mars would involve drilling deep underground. In that scenario, core samples could be ground up, then sprayed with fluorescent dyes for analysis by Zoë's grandchildren, Waggoner said.
Life as we may not know it
Then there are the deeper issues associated with searching for life as we may not know it.
"This is fine for detecting life on Earth, but is life on Mars or somewhere else out in the universe really structurally close enough so that these dyes will work with that kind of life?" Waggoner said. "If you talk to the theoreticians and read the literature, just so much of the evidence and the theory suggests that you're not going to have the kinds of life we think about."
Alien life, if it exists, could have a chemical makeup different from that of life on Earth. But even in that scenario, Waggoner believes the system can be tweaked for alien environments.
"There are going to be biopolymers — things like protein, like DNA, like complex carbohydrates. Even if they don't have exactly the same structure, they'll be similar," he said. "And certainly there are going to be lipid membranes. So we're on the right track, I think, for having generic life-detection technologies."
But those kinds of questions are far down the road. For now, it'll be enough if Zoë can detect life in the Atacama.
"I'm kind of a watch-and-see person at this stage," Waggoner said. "I want to see some of these basic tools really working before I start pushing hard for them to be incorporated in some mission."