NASA Science News
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| Above: Artists' James Graham and Kandis Elliot impression
of a more habitable Mars. |
Although Mars
may once have been warm and wet, the Red Planet today is a frozen
wasteland. Most scientists agree, it's highly unlikely that any
living creature --even a microbe-- could survive for long on the
surface of Mars.
When the first
humans travel there to explore the Red Planet up close, they will
have to grow their food in airtight, heated greenhouses. The Martian
atmosphere is far too cold and dry for edible plants to grow in
the open air. But if humans ever hope to establish long-term colonies
on their planetary neighbor, they will no doubt want to find a
way to farm outdoors. Imre Friedmann has an idea of how they might
take the first step.
Friedmann is a microbiologist who recently joined the NASA Astrobiology
Institute team at NASA's Ames Research Center. Friedmann was one
of the invited speakers at a NASA-sponsored conference, "The Physics
and Biology of Making Mars Habitable," held at Ames in October
2000. His talk focused on an organism that could be used to begin
the process of converting the Martian surface into arable soil.
Mars is covered by a layer of ground-up rock and fine dust, known
as regolith. To convert regolith into soil, it will be necessary
to add organic matter, much as organic farmers on Earth fertilize
their soil by adding compost to it.
On Earth, compost is made up primarily of decayed vegetable matter.
Microorganisms play an important role in breaking down dead plants,
recycling their nutrients back into the soil so that living plants
can reuse them. But on Mars, says Friedmann, where there is no
vegetation to decay, the dead bodies of the microorganisms themselves
will provide the organic matter needed to build up the soil.
The trick is finding the right microbe.
"Among the organisms that are known today," says Friedmann, "Chroococcidiopsis
is most suitable" for the task.
Chroococcidiopsis is one of the most primitive cyanobacteria known.
What makes it such a good candidate is its ability to survive
in a wide range of extreme environments that are hostile to most
other forms of life. Chroococcidiopsis has been found growing
in hot springs, in hypersaline (high-salt) habitats, in a number
of hot, arid deserts throughout the world, and in the frigid Ross
Desert in Antarctica.
"Chroococcidiopsis
is the constantly appearing organism in nearly all extreme environments,"
Friedmann points out, "at least extreme dry, extreme cold, and
extremely salty environments. This is the one which always comes
up."
Moreover, where Chroococcidiopsis survives, it is often the only
living thing that does. But it gladly gives up its dominance when
conditions enable other, more complex forms of life to thrive.
For clues on how to farm Chroococcidiopsis on Mars, Friedmann
looks to its growth habits in arid regions on Earth. In desert
environments, Chroococcidiopsis grows either inside porous rocks,
or just underground, on the lower surfaces of translucent pebbles.
The pebbles
provide an ideal microenvironment for Chroococcidiopsis in two
ways. First, they trap moisture underneath them. Experiments have
shown that small amounts of moisture can cling to the undersurfaces
of rocks for weeks after their above-ground surfaces have dried
out. Second, because the pebbles are translucent, they allow just
enough light to reach the organisms to sustain growth.
Friedmann envisions large farms where the bacteria are cultured
on the underside of strips of glass that are treated to achieve
the proper light-transmission characteristics. Mars today, however,
is too cold for this technique to work effectively. Before even
as hardy a microbe as Chroococcidiopsis could be farmed on Mars,
the planet would have to be warmed up considerably, to just below
the freezing point.
Friedmann, pictured left, admits that his ideas about growing
Chroococcidiopsis are, at this point, merely a thought experiment.
"I don't think any of us alive today will see this happen," he
muses. When the time does come to make Mars a more habitable place,
"the technology will be so different that everything we plan today...
will be ridiculously outdated."
Friedmann fully expects that genetic engineering will eventually
develop designer organisms to do the job. Even if Chroococcidiopsis
is ultimately used as the basis, it will be a vastly improved
version of today's microbe.
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