Scientists studying a meteorite that fell to Earth from Mars have identified organic compounds and certain minerals that they conclude "are evidence for primitive life on early Mars."
The discovery of the first organic molecules ever seen in a Martian rock is being hailed as startling and compelling evidence that at least microbial life existed on Mars long ago, when the planet was warmer and wetter.
The molecules found in the rock, which left Mars some 15 million years ago, are being described as the fossil trace of past biological activity.
In a statement issued yesterday, as unofficial word of the discovery spread, NASA Administrator Daniel S. Goldin confirmed that scientists had "made a startling discovery that points to the possibility that a primitive form of microscopic life may have existed on Mars more than 3 billion years ago."
He added: "I want everyone to understand we are not talking about 'little green men.'
"These are extremely small, single-cell structures that somewhat resemble bacteria on Earth."
A detailed description of the research, conducted at the Johnson Space Center in Houston, is to be given at a NASA news conference at 1 p.m. today in Washington.
The journal Science is publishing a full report on the work in its Aug. 16 issue.
A draft of the Science paper, written by a team led by Dr. David S. McKay of the Johnson Space Center, identified the telltale compounds as polycyclic aromatic hydrocarbons, called PAHs, which often have biological origins and are associated with coal and diesel exhaust, and the minerals magnetite and iron sulfide, both of which are related to bacterial action on Earth.
In addition, they found some carbonate globules that are similar in texture and size to materials produced by bacteria on Earth.
"The PAHs, the carbonate globules and their associated secondary mineral phases and textures could thus be fossil remains of a past Martian biota," the researchers concluded.
Although the authors of the paper were under orders from NASA not to talk before the news conference, scientists familiar with the research spoke in unusually enthusiastic terms about the work.
One scientist called the results "unequivocal."
Another said it was one of the most stunning discoveries in the solar system in recent decades.
But they cautioned that it would take more research to assess the discovery's full implications for the longtime quest for extraterrestrial life.
Dr. David C. Black, director of the Lunar and Planetary Institute in Houston, praised the research as being "very, very cautious" work that would not have been possible two or three years ago, before new analytical instruments for electron microscopy were available.
"The signs are all consistent with biological activity," Black said.
"But what makes the case much more interesting is that the compounds are found all together in proximity within the meteorite," he said. "That is really suggestive."
Reservations about the interpretation of the discovery were expressed by Dr. Jack D. Farmer, a geologist and paleobiologist at the Ames Research Center in Mountain View, Calif.
He said the meteorite, as one of the oldest rocks ever identified in the solar system, contained evidence that Mars had water early in its history and that this environment, with liquid water and organic molecules, was one where life could have existed.
"We didn't know this about Mars until now," Farmer said. "It gives us a lot of compelling reasons to go back to Mars.
"But it doesn't tell us anything definite about life. It's interesting, but not convincing."
Because of its possible scientific and philosophical ramifications, Goldin briefed President Clinton and Vice President Al Gore last week about the discovery.
They were reported to be "excited" about the research.
After the space agency makes its formal announcement, White House officials said, Clinton is likely to call for more study of the question of fossil life on Mars.
Officials said he may propose adding resources to continuing NASA projects to place unmanned spacecraft and roving vehicles on the planet.
Pub Date: 8/07/96