SCIENCE FICTION APPROACHES FACT WITH MARS DISCOVERY

Life on Mars!

It is an idea that has pricked imaginations since long before Orson Welles scared America silly with the Halloween 1938 radio broadcast "The War of the Worlds."

Now, science fiction approaches fact with the revelation last week that orange-colored particles found inside a meteorite may be evidence of bacteria-type organisms that lived on Mars 3.6 billion years ago.

Other scientists aren't so sure, and even the NASA brain trust who made the discovery aren't saying the evidence is conclusive. But in a press conference conducted last week, space agency scientists described their find as the most exciting of their careers, and President Clinton called for a summit in November that would determine the nation's response.

The occasion was especially happy for those who have advocated undertaking a manned mission to the red planet.

But if they existed, these organisms would be far from the little green men people were afraid of in 1938, or even the octopus aliens of this summer's hit movie, "Independence Day."

The evidence is of single cells, and the fossils are 1/1000th the diameter of a human hair.

"They found ovoid and bar-shaped bodies that resemble nano-bacteria we have on Earth," says Dr. Peter Roopnarine, a biologist at Southeast Missouri State University whose specialty is paleontology.

But, Roopnarine cautions, that doesn't mean the fossils were formed by bacterial organisms. "It means they were similar to the simplest and oldest organisms we have on Earth."

Most exciting at this point is the discovery of magnetite -- a common iron compound -- deep inside the meteorite.

Scientists have come to the conclusion that most of the magnetite found on Earth was deposited by the activity of bacteria over the eons.

"No other physical process we know of is capable of doing that," Roopnarine says. "Only living organisms can."

Scientists know that this 4.1-pound meteorite and 11 others they have identified originated on Mars because they are unusual igneous (formed by intense heat) meteorites. They are much younger than igneous meteorites from asteroids and also have higher contents of so-called volatiles.

Scientists can tell if a meteorite is from Mars by matching its trapped gasses with those measured in the Martian atmosphere by the Viking space probe.

Currently there are three hypotheses accounting for the past existence of organisms on Mars:

-- That they were indigenous to Mars.

-- That they originally came from Earth, and traveled to Mars during a time when the solar system was intensely bombarded by asteroids. Roopnarine says this possibility is slim because it's unlikely the organisms could have survived.

-- That life on Earth was seeded by life on Mars.

Whatever conclusions are reached, confirmation of the existence of organisms on Mars would change everything.

"In my opinion, it is possibly one of the most profound discoveries in human history," Roopnarine said.

"It implies that we are not alone."

Humankind has pondered the question of whether anyone else is out there for as long as men and women have been self-aware. The answer may be forthcoming.

"If in our solar system life could have appeared in early history twice, given the fact that there are hundreds of million of galaxies, it's likely there is an abundance of life," Roopnarine says.

He cautions that the existence of single-celled organisms would not necessarily imply intelligent life or sentience elsewhere. But if life did exist on Mars in the past, the probability that we are the lone sentient beings in the universe is "exceedingly small," Roopnarine says.

"Then the chances for sentient organisms is exceedingly high."