Did life begin when meteorites crashed into the planets and scattered across their primative surfaces the amino acids that are the building blocks of life?

Evidence for this belief lies with the remains of several meteorites that have fallen to earth in recent years, one of which contained 18 of the 20 amino acids basic to life.

But if this is the way began on earth, why didn't it start the same way on Mars? Why are there no signs of life on Mars or any other planet? Or did life begin on Mars at the same time it did on earth . . . only to perish before it could flourish?

So urgent are these questions that scientists have gone to bizarre lengths to find the answers.

Four years ago, a University of Rochester biologist, Wolf Vishniac, fell to his death in a ravine in the Antarctic looking for the kinds of tough microbes that might be growing on Mars.

Another time, three scientists from the California Institute of Technology on a similar search in the High Sierras suffered frosbite and almost died when they were trapped at 12,000 feet by a freak blizzard.

"We had no food," recalled chief Viking scientist Gerald Soffen. "We got through on a bottle of bourbon."

The Viking instruments that cost the United States $100 million found no sure signs of life on Mars. Does that mean there is none, was none? "Dig deeper on Mars," Harvard University's Dr. Elso Barghoorn said at a meeting at Boston Universtiy to plan future strategy. "Find the fossils."

Viking found that the big difference between Mars and the earth is that Mars doesn't have enough of an atmosphere to screen out the sun's blistering ultraviolet exposure very long. But Mars once had an atmosphere 10 times thicker than it is today and not much different from earth's early atmosphere.

"Mars should have been teeming with the same organic molecules found in most meteorites and it was not," the National Aeronautics and Space Administration's Dr. Ichtiaque Rasool said the other day. "The problem on Mars may have been the preservation, the sustaining, of those organics. Mars may have lost whatever life began there."

The space agency has abandoned the idea of going back to Mars to look for the life Viking didn't find.The strategy emerging now is to land a robot on Mars in about 10 years that will dig deep into the soil and fly 200 pounds of Mars back to earth for analysis. To find Barghoorn's fossils. To find what happened to life. The mission has hints of "The Andromeda Strain." The rocks will be examined in earth orbit, to prevent any possible contamination of our planet.

Ambitious as it all sounds, the return of a sample of Mars is one of the lesser missions being contemplated by the U.S. space community to seek out the origin of life.

Scientists want to rendezvous with a comet and bring pieces of it back to earth. They want to land on Io and Callisto in Jupiter's orbit, for samples of the two most beguiling moons in the solar system. They would like to sample the dazzling rings of Saturn. They want a piece of Titan, the brilliant moon of Saturn with an atmosphere almost as dense as earth's.

"The reasons for going there are simple," said Dr. Andrew Ingersoll of the California Institute of Techology. "The origins of life, the origins of the solar system and everything in it."

Put another way by Dr. Bruce C. Murray, director of the Jet Propulsion Laboratory in Pasadena, Calif: "The most important question still is . . . has biological life evolved elsewhere in the solar system? We may never find it, we may never get to the top of that glass mountain, but we've got to look . . ."

The search is under way. Two years hence, Pioneer 11 will become the first spacecraft to reach Saturn. Two Voyayer spacecraft left earth this summer for Jupiter, Saturn, Uranus and even Neptune, if their batteries last.

In the works is a nameless spacecraft that will fly in 1981 to Jupiter. It will be the first to orbit the giant planet, probe its atmosphere and make detailed observations of five of Jupiter's 13 moons.

Of growing importance are the moons and rings of the outer planets. If life exists anywhere in the solar system, it might be on the moons striking difference in the solar system is the difference between the brilliant rings of Saturn and the freshly found rings of Uranus, which are so dim that scientists are calling them "The Black Rings of Uranus."

Dazzling as they are, the rings of Saturn are one of the great celestial mysteries. There's a gap (called Cassini's Division) between the two brightest rings that's probably caused by the pull of the nearest of Saturn's nine moons. But the rings are in such precise balance they make perfect circles around Saturn's equator, moving with the equator even when the planet tips on its own axis.

The innermost of the two brightest rings moves around Saturn at more than 45,000 miles an hour, making it the fastest moving body in the solar system. Astronomers see a third ring closer to the planet and some think they see a fourth ring beyond the outer ring. There must be spaces between whatever makes up the rings, because distant shines through the rings.

The biggest mystery is what the rings are made of. Radar echoes suggest they could be swarms of tiny iceballs, spheres of silver or giant shards of some jagged metal. One thing is sure - the rings reflect radar signals from earth more strongly than any other body in the solar system.

Alongside the mysteries of Jupiter's four biggest moons, called the Galilean moons because they were discovered by Galileo in 1610 with his first telescope. Galileo also discovered Saturn's rings, which he first described as "queer appendages" on either side of the planet.

Io, Europa, Ganymede and Callisto extend out from Jupiter "like a miniature solar system," said JPL's Dr. Fraser Fanale. Io is the closest and densest, just like Mercury is the closest planet to the sun and appears to be made mostly of iron. Callisto is farthest from Jupiter and is two-thirds water. Just like Uranus and Neptune. Each is made up of the flimsiest gases, having formed far from the sun's influence.

Io and Callisto arouse more interest among scientists than many planets do. Unique among moons, Io looks like the salt flats of Utah or the nitrate deserts of Chile. It's covered and streaked with sulfates and nitrates that percolated to the surface in the first 20 million years of creation. That's when Jupiter was hot enough to boil Io's water away.

Io is encircled by a cloud of sodium so bright it looks like a yellow halo, so close is Io to Jupiter and its fear-some radiation belts that a current, which Fanale estimates at 1 million volts, forever brushes against the moon. The magnetic field sweeping by Io is moving so fast (40 miles a second) that it sputters the salts off the surface to form the equal of a sodium atmosphere. This is the yellow halo seen in photographs this year for the first time.

While Io is too close to Jupiter's radiation fields to support any life, Callisto might be far enough away to have a primeval kind of life.

As big as Mercury, Callisto is covered with a dark crust of ice, but no more than a few miles below the crust is a subterranean ocean that could be as deep as 1,000 miles. The temperature of this underworld ocean might go as high as 1,000 degrees because the radioactive uranium and thorium in its core are still hot enough to warm the moon.

The ice on Callisto's surface is strangely dark, suggesting comets might have left their ash on its surface. Another explanation is that the land masses on top of the subterranean seas broke up aeons ago, sinking like Atlantis but leaving traces of themselves to freeze as the moon cooled.

Beyond Callisto and all of Jupiter's moons lies Titan the moon of Saturn that has an atmosphere half as dense as earth's. Titan's glow stands out in telescopes like a seachlight beckoning from the sea. Nobody has seen its surface which is one reason why Voyager will make a special pass close to Titan to photograph it.

Titan is far from the radiation belts that might be lethal to life on Jupiter's moon, which is why Cornell University's Carl Sagan once said that life could have emerged on Titan.

Finally, there is Jupiter. Now thought to have been the sun's companion at the time of creation expect that it banked its fires when the sun was stoking its. Cal Tech's Ingersoll says that probing Jupiter's atmosphere will be "like sampling the sun."

Probing Jupiter comes in 1963 when a small spacecraft is dropped into the Red Spot, the mysteriously moving part of the upper atmosphere believed to be a permanent hurricane. Wherever it falls the probe will answer a host of mysteries.

Take just one, the one that may hold clues to why droughts occur on earth. Earth has a wet zone at the tropics and zones north and south of the equator with air so dry it is the cause of most of our deserts. Jupiter has at least 10 zones that are alternately wet and dry. On Jupiter you don't run out of weather patterns like you do on earth.

"We've never been inside we've just seen the top skin." Ingersoll says of the chance to sample Jupiter's atmosphere. "It's the most important thing we can do at Jupiter."