It has been nearly 25 years since NASA sent biological experiments to Mars. Chris McKay, a planetary scientist with the Space Sciences Division of NASA's Ames Research Center and a member of the NASA Astrobiology Institute, thinks it's time to try again.
McKay helped organize a NASA conference last year on what it might take to make Mars fit for human habitation. While the general tone of the conference was speculative—all of the participants agreed that humans aren't likely to begin terraforming the Red Planet any time soon—McKay maintains that it was important nonetheless to begin now to assess Mars's biological potential.
"Some of the research questions that were raised at the conference," McKay says, "would be questions that could influence near-term missions. For example, one of the key questions about Mars in the context of a biosphere, is 'Is there enough nitrogen on the planet'" to support life? He would like to see experiments performed in upcoming missions that help to answer this question.
In a presentation at the conference, McKay proposed a more intriguing experiment. "I'd like to see NASA send a seed to Mars and try to grow it into a plant." It would be important, he stressed, to "use the sunlight, the soil and the nutrients that are available on Mars." McKay suggested that growing a flowering plant on Mars might serve both as a valuable biology experiment and as a powerful symbol of humanity's expansion beyond Earth.
"One of the things that I'm very interested in is the notion of Mars as a home for life, both distant in the past, maybe now dead, but also in the future. And if we think of life as being the main thread of the Mars exploration program, then I advocate that we should get serious about sending life to Mars."
Not everyone at NASA shares McKay's immediate enthusiasm for the project, however.
John Rummel, NASA's Planetary Protection Officer, is one who has doubts about the advisability of implementing McKay's suggestion in the near-term. Rummel believes that to try "to grow plants on Mars would take power and other resources" that could be put to better use. "We would need to do a lot of analysis of Mars surface material before sending a biological experiment there."
Rummel doesn't disagree that growing a plant on Mars could serve as a powerful symbol. He wonders, though, what the symbolic impact would be if the experiment failed. "If we want to think of Mars as a place where Earth organisms can grow, we want to know it will work."
Rummel suggests a more pragmatic approach to finding out whether plants could grow in Martian soil: bring the soil back to Earth. "If we're going to challenge Earth organisms with Mars soil," he says, "we'll do it with returned samples."
Mike Meyer, NASA's Astrobiology Discipline Scientist, agrees with Rummel. He believes that it's important to take a step-by-step approach to understanding the potential for life on Mars. "If we learn enough about the soil on Mars," Meyer argues, "we can simulate Mars here and do experiments here. Then we'd know what we want to test. Otherwise, we'd end up saying, 'Golly, it died, now what?'"
Meyer also makes another point. Until there is a concrete plan to send humans to Mars who will need to grow plants for food, there's no particular hurry to find out whether the plants could grow there. "We would need some reasonable commitment that we'd be sending humans to Mars before we'd do such an experiment."
McKay has heard these arguments before. He's not swayed. "There are many logical reasons not to send a plant to Mars on a near-term mission," McKay concedes. But, he counters, "it is a bold and dramatic step that will, in my humble opinion, push the biological agenda for Mars ahead significantly."
"If we're going to send humans to Mars," he adds, "we need to begin studying its ability to support human life." And the sooner the better.
NASA does have funding in its budget to investigate some questions relevant to possible future human exploration of Mars. The 2001 Mars Odyssey, for example, an orbiter launched on April 7, 2001, contains an experiment to measure the amount of damaging radiation that humans travelling to Mars would need to protect themselves against.
Two Mars Exploration Rovers (MERs) will be launched by NASA in 2003. Experiments performed by the MERs will help to determine whether resources are available on Mars that will be needed to support humans living there. The European Space Agency will also launch a mission in 2003, a combined orbiter/lander. Current plans are for its lander, Beagle 2, to contain biological experiments designed to search directly for evidence of life on Mars.
Future missions to Mars will perform additional experiments to understand better the possibilities and challenges of supporting a human mission. And astronauts living aboard the International Space Station will improve NASA's understanding of the effects of long-term exposure to microgravity. But NASA's Mars-exploration roadmap for the next 20 years contains no plan to actually send human explorers there.
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The Greening of the Red Planet (NASA Astrobiology Institute)
Thawing Mars (NASA Astrobiology Institute)
Bring Mars to Life - Chris McKay (Mars Society)
Mars Exploration: Planetary Protection (Mars Now Team and the California Space Institute)
Planetary Protection Provisions for Sample Return Missions (Astrobilogy Web)