Jellyplants on Mars

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 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.