How
do you get plants to grow on Mars? The first step: relieve
their anxiety.
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August 5, 2005: Anxiety can be a good thing. It alerts
you that something may be wrong, that danger may be close.
It helps initiate signals that get you ready to act. But,
while an occasional bit of anxiety can save your life, constant
anxiety causes great harm. The hormones that yank your body
to high alert also damage your brain, your immune system and
more if they flood through your body all the time.
Plants
don't get anxious in the same way that humans do. But they
do suffer from stress, and they deal with it in much the same
way. They produce a chemical signal -- superoxide (O2-)
-- that puts the rest of the plant on high alert. Superoxide,
however, is toxic; too much of it will end up harming the
plant.
This
could be a problem for plants on Mars.
According
to the Vision
for Space Exploration, humans will visit and explore Mars
in the decades ahead. Inevitably, they'll want to take plants
with them. Plants provide food, oxygen, companionship and
a patch of green far from home.
Right:
Mars, photographed by the Viking Orbiters. [More]
On
Mars, plants would have to tolerate conditions that usually
cause them a great deal of stress -- severe cold, drought,
low air pressure, soils that they didn't evolve for. But plant
physiologist Wendy Boss and microbiologist Amy Grunden of
North Carolina State University believe they can develop plants
that can live in these conditions. Their work is supported
by the NASA Institute for Advanced Concepts.
Stress
management is key: Oddly, there are already Earth creatures
that thrive in Mars-like conditions. They're not plants, though.
They're some of Earth's earliest life forms--ancient microbes
that live at the bottom of the ocean, or deep within Arctic
ice. Boss and Grunden hope to produce Mars-friendly plants
by borrowing genes from these extreme-loving microbes. And
the first genes they're taking are those that will strengthen
the plants' ability to deal with stress.
Ordinary
plants already possess a way to detoxify superoxide, but the
researchers believe that a microbe known as Pyrococcus
furiosus uses one that may work better. P. furiosus
lives in a superheated vent at the bottom of the ocean, but
periodically it gets spewed out into cold sea water. So, unlike
the detoxification pathways in plants, the ones in P.
furiosus function over an astonishing 100+ degree Celsius
range in temperature. That's a swing that could match what
plants experience in a greenhouse on Mars.
Left:
Pyrococcus furiosus, photographed by Henry Aldrich
of the University of Florida. [More]
The
researchers have already introduced a P. furiosus
gene into a small, fast-growing plant known as arabidopsis.
"We have our first little seedlings," says Boss.
"We'll grow them up and collect seeds to produce a second
and then a third generation." In about one and a half
to two years, they hope to have plants that each have two
copies of the new genes. At that point they'll be able to
study how the genes perform: whether they produce functional
enzymes, whether they do indeed help the plant survive, or
whether they hurt it in some way, instead.
Eventually,
they hope to pluck genes from other extremophile microbes
-- genes that will enable the plants to withstand drought,
cold, low air pressure, and so on.
The
goal, of course, is not to develop plants that can merely
survive Martian conditions. To be truly useful, the plants
will need to thrive: to produce crops, to recycle
wastes, and so on. "What you want in a greenhouse on
Mars," says Boss, "is something that will grow and
be robust in a marginal environment."
In
stressful conditions, notes Grunden, plants often partially
shut down. They stop growing and reproducing, and instead
focus their efforts on staying alive--and nothing more. By
inserting microbial genes into the plants, Boss and Grunden
hope to change that.
"By
using genes from other sources," explains Grunden, "you're
tricking the plant, because it can't regulate those genes
the way it would regulate its own. We're hoping to [short-circuit]
the plant's ability to shut down its own metabolism in response
to stress."
Right:
Genetically engineered plants growing in Boss and Grunden's
lab.
If
Boss and Grunden are successful, their work could make a huge
difference to humans living in marginal environments here
on Earth. In many third-world countries, says Boss, "extending
the crop a week or two when the drought comes could give you
the final harvest you need to last through winter. If we could
increase drought resistance, or cold tolerance, and extend
the growing season, that could make a big difference in the
lives of a lot of people."
Their project is a long-term one, emphasize the scientists.
"It'll be a year and a half before we actually have [the
first gene] in a plant that we can test," points out
Grunden. It'll be even longer before there's a cold- and drought-loving
tomato plant on Mars--or even in North Dakota. But Grunden
and Boss remain convinced they will succeed.
"There's a treasure trove of extremophiles out there,"
says Grunden. "So if one doesn't work, you can just go
on to the next organism that produces a slightly different
variant of what you want."
"Amy's
right," agrees Boss. "It is a treasure
trove. And it's just so exciting."
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Author: Karen Miller
| Editor: Dr. Tony
Phillips | Credit: Science@NASA
More
Information |
NASA
Institute for Advanced Concepts
-- independent, NASA-funded organization that funds
research into ambitious, forward-looking research into
space-related technologies that will take 10 to 40 years
to realize.
Wendy
F. Boss -- William Neal Reynolds Distinguished Professor
at North Carolina State University
Redesigning
Living Organisms to Survive on Mars (NIAC) -- a
report by Amy Grunden and Wendy Boss
Greenhouses
for Mars -- (Science@NASA) When humans go to the
moon or Mars, they'll probably take plants with them.
NASA-supported researchers are learning how greenhouses
work on other planets.
Green
Generations -- (Science@NASA) It looks like an ordinary
pea pod. And it is. That's what so amazing ... because
this pod lives in space.
The
Physics of Space Gardens -- (Science@NASA) It could
only happen in space: A tiny bubble of air hangs suspended
inside a droplet of water. The droplet rests in the
cup of a delicate green leaf, yet the stalk doesn't
bend at all.
Leafy
Green Astronauts -- (Science@NASA) NASA scientists
are learning how to grow plants in space. Such crops
will eventually take their place alongside people, microbes
and machines in self-contained habitats for astronauts.
Vision
for Space Exploration |
|