What makes the Red Planet red? Right now the answer is iron oxide, but one
day it could be roses say NASA scientists debating the prospects for plant
life on Mars.

May 8, 2001 — It’s been nearly 25 years since NASA sent biological
experiments to Mars. Chris McKay, a planetary scientist at 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 terraforming — that
is, what it might take to make Mars fit for human habitation.

In a presentation at the conference, McKay proposed an intriguing

“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 the Red Planet 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,” he says. “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,

John Rummel, NASA’s Planetary Protection Officer, is one who has some
doubts. 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,” he cautioned.

Rummel doesn’t disagree that growing a plant on Mars could serve as a
powerful symbol. He wonders, though, what the symbolic impact might 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 could 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. 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,” he argued.

McKay has heard these arguments before, but 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
[that planet’s] 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
spacecraft, for example, contains an experiment to measure the amount of
damaging radiation that humans traveling to Mars might face.

NASA also plans to send two “Mars Exploration Rovers” to the Red Planet in
2003. Experiments performed by the rovers will help to determine whether
resources are available on Mars that will be needed to support humans living
there. The European Space Agency will launch a mission in 2003 as well — 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 will perform even more experiments to investigate the
possibilities and challenges of supporting a human outpost on Mars — a
daunting job made easier, perhaps, by oxygen-giving, food-producing plants.
NASA’s Mars-exploration roadmap contains no plan to actually send astronauts
there for the next 20 years. But one day humans explorers surely will
venture to the Red Planet, and they might want to take a few leafy green
companions with them.