Scientists are creating a new breed of glowing plants - part
mustard and part jellyfish - to help humans explore Mars.
by Karen Miller and Dr Tony
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
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.
Image credit: Rob Ferl/University of Florida.
Arabidopsis thaliana - a future pioneer of Mars?
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
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 Centre.
Ferl, Schuerger, and
Chris McKay of NASA's Ames Research Centre. 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.)
An artist's concept of a full-fledged
Martian greenhouse, an essential part of any future human
colony on the Red Planet.
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."
Credit: C.E. Mills.[more]
Top: An overhead flash
reveals the outlines of Aequorea victoria. The blue
glow is reflected light, not bioluminescence.
Bottom: True bioluminescence around at the rim of the
jellyfish. The light produced by Aequorea is actually bluish
in colour, 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.
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
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 vapour to
leave, and maybe that would be a positive adaptation," says Ferl.
The plants might also be exposed to
Martian light, which could be piped into the greenhouse (inside
the lander) through fibre 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.
Note - The plant experiments described
in this story are funded by NASA's Office
of Biological and Physical Research. NASA is currently evaluating
43 Mars Scout proposals, of which this is only one.