There is a chill in the air today. The sun is bright but the temperature is dropping and the wind is gusting from the south. Otherwise it is another perfect day on Mars.

Such is our knowledge of the red planet, courtesy of two unmanned Nasa space rovers beaming pictures 300m miles back to Earth. Sulphuric acid, frozen lakes, rippled rocks, ice floes, mini-tornadoes — the pictures that the two robots, Spirit and Opportunity, are transmitting are revolutionising our view of this alien planet.

So great is the volume of data that Nasa scientists are encountering a problem. There are not enough rocket scientists to go around. It’s like waking up every day to a giant jigsaw puzzle when there are not enough people to figure it all out.

Why does Mars show evidence of water? Why are there lakes of sulphuric acid? How do the swirling dust devils, or mini-tornadoes, occur? These sightings are challenging conventional wisdom.

“We used to think that Mars was cold, dry and desolate,” says Steven Squyres, professor of astronomy at Cornell University in New York state and head of the Nasa team of 170 scientists.

“Now we can see that billions of years ago there was water on the planet because it has left ripples on the sand. We can see salt flats and shallow pools of sulphuric acid. The colours are extraordinary. If you went there you would see pools of ruby red water under a pink Martian sky.”

The significance of the findings from the robots, which landed in January last year, brings scientists full circle. Our ideas about Mars are reverting to those of the 1950s and before. When Giovanni Schiaparelli, the 19th-century Italian astronomer, viewed Mars he thought he saw channels, or “canali” as he put it.

Later astronomers wrongly translated this as “canals”, with the implication that they were man-made. Dark patches were interpreted as vegetation. No wonder that many people at the beginning of the 20th century, including authors such as H G Wells and Edgar Rice Burroughs, imagined life on Mars.

However, later probes, such as Mariner 4 in 1965 and two Vikings which landed in 1976, found little to support this idea. Mars studies languished while Nasa continued with its Apollo moon programme. But the July 4 landing by Pathfinder in 1997 changed all that. Its detailed pictures revealed mountains, canyons and contoured valleys and, once again, speculation about simple life forms on Mars was rife. Now the stuff of science fiction seems less fictional.

As Dava Sobel, whose book The Planets has just been published, says: “It’s starting to seem more and more likely that there was some kind of life on Mars. The presence of water shows us that. Whatever happened here on Earth three billion years ago might well have happened there. It’s amazing what is possible.

“Of all the planets Mars is a place where humans could make themselves at home. Early explorers could create a change in the climate to make it warmer — it’s about 40C below. Scientists could put a mirror in space to melt the ice caps. No one thinks life on Mars is out of the question.”

Coping with the data is a constant battle for Squyres’ team: “Spirit and Opportunity were predicted to last 90 days before they ran out of energy, but this is day 628.”

He knew that the dust storms on Mars might eventually disable the robots, clogging up their solar panels. “We got lucky. We encountered gusts of wind that cleaned the dust off the rovers,” he explains.

He also believed that the coming of the Martian winter would disable the craft: “By winter Spirit had reached a range of hills so we were able to drive into the northern slopes and tilt the solar panels to the sun. We went sunbathing and survived. Both rovers are really hopping.”

The same cannot be said of the team. At 24 hours, 39 minutes and 35 seconds, the Martian day is longer than ours. So when the team conducts experiments for days or weeks at a time, its members become completely disoriented. “We’re all exhausted,” says Squyres. “It’s Martian jet lag.”