KEY POINTS:
Scientists are using a Mexican volcano as a test bed to see if trees could grow on a heated-up Mars, part of a vision of making the barren red planet habitable for humans.
Planetary scientists at Nasa and Mexican universities believe if they warm Mars using heat-trapping gases,
raise the air pressure and start photosynthesis, they could create an atmosphere to support oxygen-breathing life - including humans.
Getting trees growing would be crucial. The scientists' quest has taken them to the snow-capped Pico de Orizaba - a dormant volcano and Mexico's tallest mountain - to examine trees growing at a higher altitude than anywhere else on Earth.
"It sounds like science fiction, but we think it's feasible," said research professor Rafael Navarro-Gonzalez, who has spent nine years examining Pico de Orizaba's pine forests. "We have experienced warming our planet with greenhouse gases, but on Mars we could do it faster with more powerful gases."
Nasa scientist Chris McKay said the first human mission to Mars was 10 to 15 years away and the warming-up process could start 50 years later.
By pumping in highly insulating gases such as methane or nitrous oxide, the scientists think they could heat Mars to 5C from minus 55C now. That would match temperatures where trees grow at 4200m on Pico de Orizaba.
The scientists are studying what makes trees refuse to grow above a certain point, where temperatures drop and the air becomes thinner, to see how easily they could grow on Mars.
"Things don't really start cooking from a biological point of view until trees start growing. Trees are the engines of the biosphere," McKay said. "It's possible Mars could have trees in 100 years."
Despite Mars' lifeless rocky surface, burning ultra-violet radiation and its extremely thin, carbon dioxide-loaded air, humans have long been obsessed with finding life there. Scientists believe Mars has ice at its polar caps that could melt into seas and that its subsoil contains the key elements needed for life.
The scientists on the Pico de Orizaba project believe it would be straightforward to pump greenhouse gases into Mars' atmosphere, introduce bacteria to start photosynthesis and finally send up tree seeds with a human mission.
"Nothing that we know rules it out," McKay said. "There's still a lot of uncertainty, but nothing that's a showstopper."
The project would be called off if life was found to already exist on Mars.
"The idea is to explore the possibility of colonising Mars. If there is life, we have no right to destroy it. But if Mars is barren we could take life from Earth to Mars," said Navarro-Gonzalez.
At first, anyone braving the six-month flight to Mars would have to live in a pressurised dome, suffer violent dust storms and be cut off from earthlings too far away to easily speak to.
And in the long term Mars' low gravity could have odd effects on settlers, causing people to grow alarmingly tall, and cosmic radiation could cause cancers and mutations.
McKay ruled out anything more permanent than short-term research bases for the next century. "I don't have this vision of people moving to Mars the way people settled the New World, setting up homes and bringing their families."
- REUTERS
