THE FIRST stirring of a tiny silicon-based life form on the surface of Mars yesterday was the climax of stage one of the invasion of the Red Planet that began on July 4th.
After a day of suspense, a robot rover - designed to sort out its own problems 120 million miles from mission control - rolled its six little wheels down a ramp and parked itself on Martian soil. There it awaited the command from Pasadena, California, to begin working its way over the stones and dust at beetle-speed analysing the soil chemistry of the fourth rock from the sun.
The rover was christened Sojourner after the African-American civil war heroine, Sojourner Truth. It rolled down the petals of the Mars Pathfinder landing craft which had just been renamed the Carl Sagan Memorial Station, alter the US writer and space scientist who died earlier this year.
The mission was the first space-craft to land on a planet without orbiting it a direct hit after a journey of more than 300 million miles and eight months. It was the first spacecraft to open a parachute at supersonic speed. And it was the first to bounce to rest on airbags.
It was also the first in two decades to overcome ajinx known in NASA as the "great galactic ghoul": since 1976, when the Viking landers returned 50,000 photographs, there have been six launches to Mars. Four were lost. One has yet to arrive.
Pathfinder has broken a long run of had luck. And it did so while a British-born astronaut and two Russian cosmonauts aboard the Russian space station Mir were working to put right a ship crippled by a collision with a supply craft.
But the euphoria at the Jet Propulsion Laboratory in Pasadena, the HQ for the Mars operation, was contained. Sojourner - like a little microwave oven on wheels - began work after the Martian sunrise yesterday, analysing rocks and soil, creeping along at an inch every two seconds, powered by sunlight, and pumping data back to the lander. It is expected to last only for about seven days, and it is not likely to stray more than 100 yards from the Carl Sagan station. It will provide the close-up studies.
On the lander itself, a steroscopic camera is surveying the Ares Vail is, the ancient flood site chosen for the descent.
"We've got some great images and all the scientists are in red heaven," said Mission Manager Richard Cook.
But they will want hard data as well. Mars is a puzzle: it may once have had rivers and oceans and a much denser atmosphere. It may have - according to evidence from Martian meteorites once been home to living things.
Until the descent of the Viking landers 21 years ago, biologists and astronomers still thought of Mars as the most likely place for neighbours in a lonely solar system. Just before the landings, NASA artists fantasised about what Viking might find and drew pictures of silicon-based rather than carbon-based life forms surviving on an arid surface of a frozen planet in an atmosphere of carbon dioxide only 1 per cent as dense as Earth's
Last night, NASA which expected 30 million people to "visit" the Martian landing sites on the Internet - posted the original artist's wistful impressions of what-might-have-been.
Meanwhile, a US firm has begun marketing the Hot Wheels JPL Sojourner Rover Action Pack Set - a toy version of the real thing across the vast distances of space, a little mobile creeping thing with a silicon brain and wheels instead of feet, analysing Martian history a bit at a time.