How do you get plants to grow on Mars? The
first step: relieve their anxiety.
by Karen Miller
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.
photographed by the Viking Orbiters.
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.
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.
furiosus, photographed by Henry Aldrich of the University
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."
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
"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."
agrees Boss. "It is a treasure trove. And it's just so exciting."