The first colonists on Mars probably won’t be humans. More
likely, they’ll be plants. And the prototypes of these leafy pioneers are
under development right now.

As part of a proposed mission that could put plants on Mars as soon as 2007,
University of Florida professor Rob Ferl is bioengineering tiny mustard
plants. He’s not altering these plants so that they can adapt more easily to
Martian conditions. Instead, he’s adding reporter genes: part plant, part
glowing jellyfish — so that these diminutive explorers can send messages
back to Earth about how they are faring on another planet.

The plants can be genetically wired to glow with a soft green aura when they
encounter problems. Within a garden grouping, some plants could report (by
glowing) low oxygen levels, while others might signal low water or, say, the
wrong mix of nutrients in the soil.

“Just like humans, plants must learn how to adapt to any new environment,”
Ferl says. On Mars they would encounter extreme temperatures, low air
pressure, exposure to harsh ultraviolet light, and generally inadequate
soil. “We are using genetics to create plants that can give us data we can
use to help them survive.”

Learning to grow plants on Mars will be an important precursor to humans
living there. Future explorers will need oxygen, food, and purified water —
items too costly to ferry from Earth to Mars on a regular basis. But plants
can help provide those essentials inexpensively and locally as part of a
self-contained “bioregenerative” life support system.

Bioregenerative life support means humans, plants, and microbes working
together in a renewable system. Humans consume oxygen and produce carbon
dioxide. Plants take carbon dioxide and turn it back into breathable air.
Human waste (after processing by suitable microbes in bioreactor tanks) can
provide nutrients for growing plants, which will, in turn, produce food for

Such life support systems on Mars will probably involve growing crop plants
in Martian soil within specially designed greenhouses, says Andrew
Schuerger, a manager of Mars projects with Dynamac Corporation at the NASA’s
Kennedy Space Center.

Ferl, Schuerger, and Chris McKay of NASA’s Ames Research Center want to test
the greenhouse concept by sending bioengineered plants to Mars on board a
small NASA spacecraft — a “Mars Scout.” They envision a seed-bearing lander
that would scoop up a portion of Martian soil, add buffers and nutrients,
then germinate the seeds to grow within a miniature greenhouse.

Thriving plants won’t glow at all. They’ll look like normal mustard. But
plants struggling to survive will emit a soft green light, a signal to
researchers that something is amiss. A camera onboard the lander would
record the telltale glows and then relay the signal back to Earth. No humans
are required on the scene — a big advantage for such a far away experiment.

The plants’ designer genes consist of two parts: a sensor side to detect
stress and a reporter side to trigger the glow.

The sensor side of the gene comes from the plant itself — Arabidopsis
thaliana, a member of the mustard family also known as thale cress. Ferl and
his colleagues picked Arabidopsis because three attributes suit it well for
a Mars mission: Its maximum height is about 6 inches, so it can fit inside a
small greenhouse, its life cycle is only six weeks, and its entire genome
has been mapped. (For these same reasons Arabidopsis plants are already
orbiting Earth on board the International Space Station as part of an
independent experiment to learn how plants react to free fall.)

The reporter side of the gene comes from Aequorea victoria, a jellyfish
common along the Pacific coast of North America. Aequorea live about six
months, grow to 5 or 10 cm, and can glow soft-green along the rim of their
bell-shaped bodies. Scientists aren’t sure why they glow — Aequorea
victoria do not flash at each other in the dark, nor do they glow
continuously. But the touch of a human hand, for example, can stimulate the
jellyfish to “light up.”

Right above: An overhead flash reveals the outlines of Aequorea victoria.
The blue glow is reflected light, not bioluminescence. Credit: C.E. Mills.
Right below: True bioluminescence around at the rim of the jellyfish. The
light produced by Aequorea is actually bluish in color, but in a living
jellyfish it is emitted via a coupled molecule known as GFP, or green
fluorescent protein, which causes the emitted light to appear green to us.

Once the sensor and the reporter gene fragments are stitched together, Ferl
uses a bacteria to move the newly-constructed gene into the plant.

Because plants are sessile — that is, they can’t get up and walk away from
stressful situations — they can survive only by adapting to whatever their
environment offers. So, they’ve developed an exquisite variety of sensing
mechanisms to monitor their surroundings and trigger appropriate responses
to stressors. By adding phosphorescent reporters to those sensors, Ferl
says, “we can learn not just whether the plant is surviving, but whether
it’s struggling to survive, and whether it’s surviving because it’s mounting
specific responses to the Mars environment.”

Ferl offers this example of an adaptive response to hard times: Here on
Earth when plants are flooded by water, they have access to less oxygen. The
plants respond by changing their metabolism to generate energy anaerobically
(without oxygen) — a less efficient pathway, but one that is available to
them. On Mars plants might adopt the same response to survive in the thin
oxygen-poor atmosphere.

Water on Mars will also be very scarce, and plants will need to conserve
every bit. The leaves of all plants contain stomata, little holes that let
gas molecules in and out. Plants have the ability to open and close stomata
as conditions demand. “One can imagine plants [living on the surface of Mars
in the distant future] that might adapt by means of fewer stomata in their
leaves: that means fewer opportunities for water vapor to leave, and maybe
that would be a positive adaptation,” says Ferl.

The first wave of Martian plants envisioned by Ferl and his colleagues would
sprout inside a very small and protected greenhouse. We don’t know exactly
how big it’s going to be,” says Schuerger, “but we’re shooting to fit a foot
print of about 10 inches by 10 inches, and weighing about 15 to 20 pounds.”
The greenhouse, he expects, could hold as many as 20 to 30 plants. “We can
grow a single plant,” he says, “in one or two grams of soil, in a tiny glass
or steel or Teflon container.”

The plants might also be exposed to Martian light, which could be piped into
the greenhouse (inside the lander) through fiber optics, and to a
moisture-added, oxygen-enhanced version of the Martian atmosphere. But the
project’s primary goal is determining whether plants can thrive in Martian
soil — an experiment best done on Mars itself!

As important as it is to know whether plants can actually grow on the Red
Planet, this project also has a philosophical purpose, says Chris McKay, the
principal investigator of the proposed Scout mission. “It will be a symbolic
step,” he says, “of life from Earth, leaving Earth, and growing somewhere
else.” And when this little plant grows on Mars, he believes, it’s going to
be a major awakening of our interest in our future in space.