Ice oceans and little green Martians

By ANDREW LAXON

Maybe Hollywood will be proven right after all. For more than a century science fiction writers and, more recently, filmmakers have been predicting that Earth will soon colonise Mars or vice versa.

The stories range from the H.G. Wells classic War of the Worlds, published in 1898, to B-grade movies such as Mission to Mars and Red Planet only two years ago.

Along the way they have spawned little green men, fear of invasion across the United States - and occasional insights into where science may be taking us.

Last week, science fiction fans and space exploration addicts got a strong hint that their dreams could be coming true, when the US space agency Nasa reported that its Odyssey spacecraft had found oceans of ice just below the surface of Mars.

The discovery has scientists buzzing. It supports theories that life once existed on the planet and could open the way for a human expedition.

In theory, astronauts could drink the thawed ice and also use the hydrogen from it as fuel to power their spacecraft home.

The discovery quickly prompted speculation that Nasa would revive its pet project for a manned mission to Mars.

The agency has been keen on the idea for decades and even drew up plans in 1997 predicting the launch of the first crew in 2009.

A detailed scenario outlining the proposal can still be found at http://nssdc.gsfc.nasa.gov/planetary/mars/marslaun.html

All this sounded promising until the astronomer in charge of the website, David Williams, said the plan had assumed that work would start in 1997.

He described the timetable as "crazy optimistic" and said he would be surprised if Nasa landed an astronaut on Mars within the next 20 years.

Nasa then cancelled a press conference which had been tipped to announce a 20-year target. Its lead scientist for Mars exploration, Jim Garvin, now says the agency will concentrate on probes which could lay the groundwork for a human visit.

Asked about the prospects of a manned expedition, he said: "We have a decade of homework to do".

Humans have not been into deep space since the last Moon landing in 1972, he says. And no new "human-rated" craft have been developed since the space shuttle.

But Garvin has not given up all hope. "If it doesn't happen within the next 40 years I would be disappointed."

So, if and when humans ever get to Mars, how will our images of the Red Planet stack up to reality?

A review of the essential (and not-so-essential) Mars reading and viewing from the past 100 years suggests your best bet is to wait for the live broadcast of the landing - but you might miss some fun and a few interesting theories along the way.

Serious Martian literature begins with The War of the Worlds, the first major work to explore the idea of an invasion from outer space. Written at the end of the Victorian era, it describes a Martian invasion of Earth, starting with an attack on London.

People flee, helpless against the superior weaponry of the Martians, which includes a "heat ray" and poisonous black smoke.

The surprise ending has become a model for science fiction ever since. Just as the Martians' victory seems secure, they succumb to a fatal infection by germs.

The tone of the famous opening passage was also to influence generations of (mostly bad) imitators: "No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own."

The idea of life on Mars was popular in Wells' day.

In 1877 astronomer Giovanni Sciaparelli reported observations of large canali (Italian for "channels") on Mars. This was mistranslated as "canals" in English, prompting speculation about a technologically advanced race of builders.

Nasa's 1975 Viking mission finally eliminated the possibility of present life on Mars after it found no evidence of the organic compounds necessary to support life as we know it. But last week's discovery increases the chances that some form of life once existed there.

The War of the Worlds was to become even more famous when an updated 1938 radio adaptation by Orson Welles caused panic across the United States with its realistic on-the-spot news bulletins.

After H.G. Wells, pulp fiction took over. Images of Mars in the first half of the 20th century tended to come from 1938's Flash Gordon: Mars Attacks the World or The Martian Tales by Edgar Rice Burroughs.

Like many writers of the time, Burroughs envisioned a dying Mars with oceans drying up and a vanishing atmosphere. His greatest achievement may lie in using the phrase "the green men of Mars", thought to be the origin of the term "little green men", in reference to Martians or aliens in general.

Variations on little green men marched through the second half of the 20th century as Hollywood produced such classics as Mars Needs Women and Santa Claus Conquers the Martians.

The most famous, Arnold Schwarzenegger's Total Recall from 1990, has a convoluted plot about a man who may or may not be on Mars, but its ending, involving the release of subterranean water and gases, now looks surprisingly topical.

The Mars colonisation theme was picked up in 2000 by Red Planet and the woefully bad Mission to Mars.

Books also began to pay more serious attention to Mars.

One landmark work, written in the 1990s, is Kim Stanley Robinson's trilogy Red Mars, Green Mars and Blue Mars, which tackles with the utmost seriousness the colonisation of Mars and settlers' attempts to create an Earth-like world there.

Some critics say Robinson's vision has all the reader appeal of a textbook but scientists say his starting point is valid.

Nasa Mars specialist Christopher McKay says the planet has all the chemical elements needed to support life.

A Martian day is about the same length as Earth's, although its year is twice as long and gravity is only one-third of Earth's.

McKay says the first step would be to create a carbon dioxide atmosphere to support plant life.

In a plan which might sound far-fetched if it appeared in a science fiction novel, he suggests building hundreds of Volkswagen-sized solar-powered factories pumping out greenhouse gases.

These would trap solar energy on the planet, raise the surface temperature and create the thick, warm atmosphere necessary for life.

Of course there's always someone out there who wants to spoil the fun. Robert Park, a University of Maryland physics professor, says he favours Mars exploration but not by humans.

"The greatest scientific quest right now is to find life to which we are not related," he says. "The big chance to do this is Mars, but the last thing you want to do is send a human there to do it."

The problem, says Park, is that each human has a higher number of bacteria in his or her gut than there are people on Earth.

"You run the risk of contaminating the very thing you want to study."