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MINUTE traces of specially designed greenhouse gases could heat up Mars and
make the Red Planet habitable much faster than anyone thought possible.

鈥淥n Earth these gases may be pollution, but on Mars they鈥檇 be medicine,鈥� says
Chris McKay, who organised last week鈥檚 meeting on terraforming at the NASA Ames
Research Center in California.

No terrestrial life can survive the bitterly cold and harsh environment on
Mars. So terraformers hope to warm the planet in the same way humans are warming
Earth鈥攂y producing greenhouse gases. These gases let through most of the
Sun鈥檚 radiation, but trap the infrared wavelengths that radiate back from a
planet鈥檚 surface.

The most infamous family of greenhouse gases, chlorofluorocarbons or CFCs,
also destroy ozone that blocks harmful ultraviolet radiation. So Margarita
Marinova of the Massachusetts Institute of Technology and her colleagues looked
at so-called supergreenhouse gases, including fluorocarbons such as CF₄
and C₂F₆, which strongly absorb infrared but don鈥檛 destroy
ozone. She says that 20 nuclear-powered factories could produce enough of these
gases to warm Mars by 5 掳C in a century.

That could be enough to melt the polar ice caps and release carbon dioxide
and water, triggering much stronger warming. Marinova says more powerful
greenhouse gases could cut the timescale to as little as a decade. 鈥淭here鈥檚 no
physical reason to think this couldn鈥檛 be done,鈥� she says.

Mimi Gerstell of the California Institute of Technology has already started
designing gases. With the help of Joe Francisco at Purdue University in West
Lafayette, Indiana, Gerstell鈥檚 team calculated the optical properties of
hypothetical gases such as CF₃SCF₂CF₃ and
CF₃OCF₂NFCF₃.

The researchers found that a cocktail of six gases at a concentration of less
than one part per million could trap 95 per cent of infrared. 鈥淭he chemicals we
looked at are sci-fi right now, but chemists say they should be easy to make,鈥�
Gerstell says.