Scientists are creating a new breed of glowing plants –part mustard and part jellyfish– to help humans explore Mars.

June
1, 2001 — 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 people.

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."

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.