Growing Glowing Martian Mustard

Arabidopsis thaliana
Arabidopsis thaliana. This plant has three attributes that make it ideally suited for the Mars mission: Its maximum height is 8 inches, its life cycle is only one month and its entire genome has been mapped.
Credit: arabidopsis.org

A team of University of Florida scientists has genetically modified a tiny plant to send reports back from Mars in a most unworldly way: by emitting an eerie, fluorescent glow.

The scientists have proposed an experiment that would send 10 varieties of the plant to the Red Planet as a Mars "Scout" mission. Scout missions are focused high-priority science experiments that can be achieved for less than $300 million apiece.

The plant experiment, which is funded by NASA’s Human Exploration and Development in Space program, may be a first step toward making Mars habitable for humans, said Rob Ferl, assistant director of the Biotechnology Program at UF.

Christopher McKay, a planetary scientist at NASA Ames Research Center and a member of the NASA Astrobiology Institute, is the principle investigator for the Scout mission proposal. "I think this has a very good chance of working," says McKay, "and thereby addressing one of the key goals in the Astrobiology program: ‘What is the potential for survival and biological evolution beyond the planet of origin?’" McKay is a strong advocate of sending biological experiments to Mars as an initial step toward eventual human exploration of the planet.

Ferl and a team of molecular biologists chose as their subject the Arabidopsis mustard plant. They picked it, Ferl said, because of three attributes that make it ideally suited for the Mars mission: Its maximum height is 8 inches, its life cycle is only one month and its entire genome has been mapped. (In December 2000 it became the first plant to have its genetic sequence completed.)

To create the glow, the team will insert "reporter genes" into varieties of the plant, which will express themselves by emitting a green glow under adverse conditions on Mars. Each reporter gene will react to an environmental stressor such as drought, disease or temperature. For example, one version will glow an incandescent green if it detects an excess of heavy metals in the Martian soil; another will turn blue in the presence of peroxides.

In fact, one of the reporter genes itself is somewhat otherworldly, having come from the depths of the ocean.

"What makes the plants glow blue is a protein derived from an incandescent jellyfish whose DNA is spliced into the mustard plant," Ferl says. "The implanted DNA then synthesizes the iridescent blue protein in the plant, which expresses itself under stress."

It wouldn’t be possible, of course, to directly see the plants glow from Earth. The camera onboard the Mars lander would record the glow and then relay this signal back to Earth.

In 1999, Ferl sent 40 reporter-gene plants into orbit aboard the space shuttle. On that flight, the lack of gravity had an adverse effect on the plants’ ability to utilize water, a condition called "space adaptation syndrome." The scientists are using that experience to engineer smarter plants.

"Just like humans, plants must learn how to adapt to a new environment," Ferl says. "We are using genetics to create plants that have the ability to give us data we can use to help them survive."

Tissue-cultured Arabidopsis thaliana
Tissue-cultured Arabidopsis thaliana. After arriving on Mars, a robot would plant Arabidopsis seeds in modified martian soil. The plant would then be grown in a miniature greenhouse.
Credit: USDA

In addition, says McKay, the scientists have to ensure that any seeds brought to Mars are completely free of any contaminating bacteria. "All missions to Mars must abide by the Planetary Protection regulations," McKay says. "This would require that the plant growth experiment be carefully controlled so as not to inadvertently contaminate Mars."

The mission would work like this: The seeds of the plant would make the trip aboard a small NASA spacecraft, which would land on the Martian surface. Upon arrival, the landing vehicle’s robot would scoop up a portion of Martian soil, which the scientists would analyze using the robot and a specialized camera. After modifying the soil with fertilizers, buffers and nutrients, the scientists would germinate the seeds and grow the plants in a miniature greenhouse on the landing vehicle.

Despite working with alien soil they know little about, the biologists are optimistic about the experiment.

"I’m confident we can grow plants if we know the pH levels and the oxidizing agents in the Martian soil," Schuerger says. "We’ll test the soil before planting, and then we can raise or lower pH, flush excess salts and add nutrients as needed."

As for long-term plans, Ferl and Schuerger have worked together on a concept called "terraforming" or "ecosynthesis," which would use plants to produce oxygen for life processes. Although the plants are genetically engineered to detect — and then adapt to — certain environmental stressors, terraforming presents additional obstacles.

Schuerger says that on Mars, daily temperatures range from a high of 7 degrees Celsius (45 degrees Fahrenheit) at noon to a low of minus 112 C (minu 170 F) at night. Also, the planet’s moisture content is 0.3 percent, which is extremely low.

Terraformed Mars
An artist’s rendition of Mars after terraforming the Red Planet. Researchers like McKay express strong enthusiasm for bringing life to Mars.
Credit: Thinkquest

Because of the cold, arid conditions on Mars, McKay says that alpine plants would be best suited for future terraforming projects. But first, scientists would have to try to grow such plants under more Mars-like conditions. Because the current project would use greenhouses to grow the plants on Mars, it is not directly related to terraforming.

"In this project, the plant is growing under comfy, Earth-like conditions in terms of temperature and water activity," says McKay. "But this experiment is directly relevant to future greenhouses on Mars that would provide food and oxygen for human exploration. It’s hard to imagine there will ever be greenhouses on Mars for life support if an experiment like this is not done first."

"I have no doubt that we can get plants to survive on Mars," Ferl says. "When we do, we will have shown that Earth-evolved life is capable of thriving in distant worlds, and we will have set the stage for human colonization."

A workshop being held this week at NASA’s Jet Propulsion Laboratory will review the dozens of proposed Scout missions. Six to ten will be funded for further study. The first Scout mission could fly as early as 2007.