Mars CallingWho knows what secrets lie in its soil?
Unscrewing the cap from an Advil-bottle-sized container with a NASA logo on it, Samuel P. Kounaves, associate professor of chemistry, shakes out a small gray and black rock, part of a large meteorite discovered in Antarctica in 1979. Trapped inside, he says, are gases just like those that make up the atmosphere of Mars, which means that Mars is in fact where this fragment came from.
So far, handling that rock has been Kounaves’s most meaningful encounter with Martian soil, but a spacecraft now on its way to the Red Planet will change all that. NASA’s Phoenix Mars Lander, launched in August, is due to touch down in the planet’s icy arctic region on May 25, 2008. When it does, it will scrape up silt with its spindly robotic arm and dig down as far as a meter to extract soil and ice below the surface. The samples will then be analyzed in four onboard mini-labs that Kounaves and his team at Tufts helped develop.
Kounaves is one of the scientists who designed and proposed the Phoenix project, which NASA selected from a field of competing concepts, including a remote-controlled plane and a hot-air balloon. Phoenix, with its down-and-dirty approach to science, “turned out to be the lowest risk with the highest scientific return,” Kounaves says.
The mission of the Phoenix Mars Lander, according to NASA, is to “uncover clues to the geologic history and biological potential of the Martian arctic.” Among other things, it will look for evidence of long-evaporated seas, creeping glaciers, and maybe, just maybe, a hint about whether Mars ever harbored life.
Aiding in the search will be a bank of instruments developed by institutions such as NASA’s Jet Propulsion Laboratory, the Canadian Space Agency, and the University of Arizona. An atomic force microscope will examine soil particles. Tiny ovens will heat soil samples so that scientists can measure the elements given off. A meteorology station will track daily weather and measure the distribution of dust and ice particles in the atmosphere. A “surface stereo imager” will act as the mission’s eyes. The four Tufts mini-labs will do much of the dirty work.
“Laboratories in a teacup,” Kounaves calls them. One such unit will add a cubic centimeter of surface soil to 25 milliliters of water and stir it up like a glass of Tang. Then the unit’s 26 sensors will spring into action, looking for ions (charged atoms or molecules) of calcium, potassium, and chloride—which could be residues of biochemical reactions—and measuring soil properties such as pH and conductivity. The three other mini-labs will repeat the process on samples dug from different depths.
Back on earth—at the University of Arizona, to be precise—research teams, including Kounaves’s group, will pore over the data beamed back from 171 million miles away. Will the results show a planet hospitable to life? It depends on whether the mission detects adequate concentrations of the six elements that are indispensable for life on our own planet: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. And whether the mass spectrometer on board picks up signs that the soil contains organic compounds such as amino acids, which may have been produced by living organisms. And whether there is indeed permafrost—frozen H2O—just below the surface, as scientists believe. Evidence from earlier missions suggests that water flowed in canyons and sat in lakes on Mars billions of years ago and froze at the poles, but scientists have never had their hands—or robotic arms—on a real-life sample. Now they will.
But what if Phoenix reveals none of those things? Would that rule out the existence, now or in the past, of life on Mars? Not for Kounaves. In recent years, our concept of locales that can support life has expanded dramatically, he explains. “We have been astonished at where life on earth has been found.” For example, some microbes are “capable of living in boiling hot deep-ocean vents and in frozen Antarctic rocks.” Scientists are not even sure life has to be based on carbon chemistry, as terrestrial life is, Kounaves says. “We don’t know if life on another planet would follow the same evolutionary path as life on earth, ending up with the same biochemistry and metabolism.”
If life did arise on Mars, it could be there still. “When Mars’ surface became cold and desiccated, life could have continued to evolve underground,” Kounaves speculates. And with that, a tantalizing prospect opens up. “Finding subterranean microbial life on Mars would be an earth-shattering event in human history.”
DEBORAH HALBER was a science writer at MIT for seven years before turning to freelancing. She is also the former editor of the Tufts Criterion, an earlier incarnation of Tufts Magazine. Among her favorite writing assignments: a story on using spinach to generate power.