By Craig T. Kojima, Star-Bulletin
Edward Scott, left, and J. William Schopf said
the life-on-Mars question is exciting but needs more proof.

---

Martian signs
of life disputed

The 'real hunt' starts with water,
say a UH scientist and a noted
California researcher

By Helen Altonn
Star-Bulletin

No hard evidence has been found for life on Mars despite claims of NASA researchers two years ago, says a noted California scientist.

"If there is life on Mars, or has been in the past, we'll get the answer," says J. William Schopf, who discovered the oldest known fossil organisms on Earth. "It's a scientific question. We can figure it out but it has to be right."

NASA scientists stirred excitement in 1996 when they announced they had found remains of ancient bacteria in a 16 million-year-old piece of Martian meteorite.

Schopf of the University of California-Los Angeles said then that the evidence wasn't conclusive.

University of Hawaii planetary scientist Edward Scott and his colleagues also disputed the findings.

The two discussed the life-on-Mars issue in an interview while Schopf was here to give talks in the University of Hawaii's distinguished-lecture series.

Schopf cited three categories of evidence to address such a question: neutral, negative and positive.

Almost all evidence cited for Martian micro-organisms in the rock ALH84001 is neutral, he said, "which is consistent with biology and nonbiology and will never answer the question."

The argument made for fossil-like organisms is based on negative evidence, such as, "We've never seen any minerals like this, so they must be fossils," he said. That is "just guessing -- an argument from ignorance that is likely to be in error," he said. Positive evidence is needed, he said, such as organic material or other characteristics of life, and none has been found so far.

Schopf, whose research has focused on ancient fossils and evolution of life on Earth, said he'd like to see evidence of cell walls and cell division on Mars.

A life cycle can be constructed even with dead cells, he said. "We can do it with microscopic fossils on Earth. We ought to be able to do it with microscopic fossils anywhere."

Schopf also cites reasons given by Scott's team to counter claims that ALH84001 contains evidence of life on Mars. The UH team said most likely it's a "shocked rock."

Scott said the carbonates appeared to form at high temperatures in a powerful impact on Mars 4 billion years ago and couldn't be remains of ancient bacteria.

He said scientists who believed they found fossils of ancient Martian life "have retreated on most lines of evidence."

Now they're saying presence of iron oxide "is their strongest and weakest evidence -- the weakest because some oxides are not made by organisms," Scott said.

A few bacteria are able to make little iron oxide crystals, but there's no difference between those formed biologically and geologically, Schopf added.

"The lesson from all of this is that science is self-correcting," he said. "These (NASA) fellows had an interesting idea, an important idea, doing very difficult science. . . . But within two years, a whole lot of other information has come out. . . . There is no hard data, no smoking gun. Guesses don't count."

Schopf said there are "several steps to the real hunt for life on Mars," and the first is to find water, essential for life.

Although Mars has a cold surface, its interior is hot like Earth's and may melt ice to produce liquid water, he said. "We know organisms can live on Earth in cracks and crevices in rocks down a mile. If they can live here, they can live there."

Scott said the possibility of life "has stimulated a remarkable renaissance of research on Mars" with space missions and laboratory work. "The match that lit the explosion was this one rock."