-> Exobiology -> Homeclick!

Cette page en franÁaisCliquez!

Life on Mars:

News from the ALH84001 Martian meteorite, 2002:

Controversy Continues: Mars Meteorite Clings to Life - Or Does It?

By Leonard David
Senior Space Writer
20 March 2002

Dating of Meteorite Mineral Leaves Mars-Life Hypothesis Alive

Infamous Mars rock purported to carry signs of Martian biology. Years later, debate continues to swirl around meteorite ALH84001 and whether or not biological processes in the rock of ages are truly evident.

HOUSTON, TEXAS Ė Following years of rigorous study, the inside story of whether meteorite ALH 84001 Ė the so-called "Mars rock" Ė harbors evidence for past Martian biology remains steeped in debate.

It was a NASA-led research team that announced in August 1996 that the potato-shaped meteorite found in Antarctica might sport fossilized bacteria. They argued that "lines of evidence" pointed to the likelihood that a primitive form of microscopic life that flourished on the red planet three billion years ago had been found.

Now, fast-forward from 1996 to five-and-a-half years later.

It turns out that rock-solid evidence is hard to come by.

Creature features

The scene is the 33rd Lunar and Planetary Science Conference, held here March 11-15, and sponsored by NASA and the Lunar and Planetary Institute. Over the past few years, this annual gathering of top-notch space scientists has played court to a kind of scientific tennis match about ALH 84001.

This year was no exception, with pro and con volleys about the true "message" of the Mars rock still being hotly contested.

"Itís a definite maybe," said one meteorite expert, after listening to over a dozen scientific papers in a session focused on ALH 84001.

The on-going debate now centers on carbonate globules and the presence of nano-size magnetites within the Mars rock Ė a purported "biosignature" of Martian biology. Those opposing this view contend that creature features in ALH 84001 are not evidence for biogenic activity. Rather, they have been formed through inorganic means.

Others suggest that any "living proof" of biology in ALH 84001 is little more than terrestrial contamination Ė stuff that eked its way into the meteorite after it came to rest on Earth.

Never the Twain shall meet

"We have concluded thereís no way to transport the magnetite into the Martian carbonates after it fell on Earth," said David McKay, a senior scientist at NASAís Johnson Space Center. He led the team that first claimed ALH 84001 had a special story to tell.

McKay said that no plausible scenario could be found that allows any of these features to be formed in the Antarctic. "We conclude that we cannot justify the hypothesis that any of the biogenic magnetite is terrestrial contamination," he said.

Kathie Thomas-Keprta, a research scientist for Lockheed Martin, is also part of the science team who first brought ALH 84001 to world attention.

Thomas-Keprta began her talk with a power point quote from Mark Twain: "The scientist will never show any kindness for a theory which he did not start himself" Her overall message conveyed a "this is my story and Iím sticking to it" attitude.

"No single process, either inorganic or biogenic, can explain the full distribution of magnetites observed in ALH 84001 carbonates. We propose that the origins of magnetites in ALH 84001 can best be explained as the product of multiple processes," Thomas-Keprta reported.

"This is a dangerous thing to say in this audience... we continue to stand by our hypothesis," Thomas-Keprta said, reemphasizing her belief that ALH 84001 is rife with biogenic proof of Martian organisms.

Lines of evidence dissected

But for skeptics, ALH 84001 as a showboat of Mars life is a dead issue.

"I think itís over," said Harry McSween, noted space geologist in the department of geological sciences at the University of Tennessee in Knoxville.

"Each of the lines of evidence have been systematically dissected. The only thing that was left was the magnetites. There are just too many inorganic ways to make the magnetites now... ways that look just like the magnetites in the meteorite," McSween said.

"Iíd love for this life hypothesis to be right. It may well be right for Mars. I just donít think itís right for this meteorite," McSween told SPACE.com.

McSween said that the years of debate have been beneficial. Identifying what kinds of signatures of life are real and can be depended upon is crucial, particularly when spacecraft missions return the first Mars samples, or in trying to make on-the-spot judgements via instruments on the planet.

The Mars rock saga has shown how tricky it is to figure out biosignatures, McSween said. "A lot of people, including the McKay team, have done some exquisite work. This is going to be really useful to the community. This is all valuable stuff," he said.

Scientific punches

ALH 84001 is a very complex rock, loaded with multiple sets of data, said Everett Gibson, senior scientist and co-leader of the Mars research team at the NASA Johnson Space Center.

Gibson was also part of the original team that linked the Mars rock with possible Martian microfossils.

"We think thereís a small percentage of the processes recorded in the rock Ė twenty-five percent Ė that may represent the end product of biological processes. So you have to sort out what the vast majority of the signatures are, which are the inorganic, normal production of a rock and other processes on Mars. Biology is a small ingredient in the life of a planet. And in the case of Mars, itís only a small component, yet it leaves trace signatures," Gibson said.

Gibson said those who see meteorite ALH 84001 as holding compelling evidence for Mars life remain on firm footing.

"This is an argument thatís difficult for the person on the street to sort out and understand the subtleties. This is the way science works. Any radical idea in science is not accepted quickly," Gibson said.

Egos of those studying the Mars rock are getting bruised and scientific punches and counter punches are being thrown. And still the debate continues. In terms of being better prepared for handling Mars return samples in the future, itís a "win-win situation for science," Gibson said.

But at the end of the conference day, following another rally of research papers the detective story that is ALH 84001 remains incomplete.

"The evidence for its biological nature is still there. Itís strong. It hasnít been refuted. This hypothesis has been out for five-and-a-half years. Itís still standing," Gibson said.


I will now tell you what the skeptics cannot or do not want to tell you.

The issue is indeed terribly complex. It cannot be explained in all its richness to the laymen.

But one thing is simple. Maybe scientists will argue for ages about this, that, or the other evidence of biological traces in the meteorite. Thy may find a process to explain this, that or the other feature with a non-biological explanation. For example, they now found an artificial process that creates the magnetites in a rock.

But the main aspect of the plot gets forgotten: what non-biological process can explain the complete set of the different biological evidence in the Allen Hill meteorite?

When taken apart, out of context, each evidence may be dismissed, but as a whole, they can be simply explained as of biological nature, and hardly by a complete collection of alternate non-biological explanation.


The skeptic line of reasoning is quite obviously similar than when applied to UFO evidence by UFO skeptics: take each evidence of a case separately and find a possible commonplace explanation.

Take a case such as the Bentwaters multiple radar and multiple ground/air visual sightings of 1956 for example. Dismiss the ground witness by claiming they saw Venus. Dismiss UFO that paced the jet fighter by claiming it was some sort of plasma. Dismiss the UK ground radar set by claiming it was a temperature inversion. Dimiss the confirmation by the US radar set by claiming it was an interference with the UK radar set. Dismiss the visual observation from above by an aircraft crew as a confusion of some sort. Basically, isolate all the numerous feature of the case, ignore quantitative factors such as the meteorological data or the flightpath of the UFOs and other data of the circumstance and as a skeptic you may be satisfied that the case is explained.

But any serious researcher that has studied the case as a whole, as a series of continous events occuring under precise conditions knows that the explanation obtained by providing separate commonplace explanation to isolated features of the case is worthless. For example, serious researchers have learned that the US and UK radar set could not interfere because the two crews communicated by radio and did set their gear to different frequency to be sure that no radar interference could coul occur.


Research for evidence of life in the martian meteorites is an accepted scientific topic. Of course, many scientist find the idea that life existed or exists on Mars "hard to believe" but many other now think that the contrary would be more surprising - as long as "little green men" are not involved.

Research for evidence of intelligent and technological extra-terrestrial presence of some sort in the skies of our planet is an accepted scientific topic only to the few scientists who dedicated time and efforts to the matter. For the larger part of the scientific community, it is not a valid scientific problem and still qualifies as pseudo-science.

I am pleased that scientists of the LPL for example, regular visitors of my site, may start to understand the parallel between their confrontations with skeptics reasoning and the confrontation between serious ufologists and UFO debunkers.

Valid XHTML 1.0 Strict

 Feedback  |  Top  |  Back  |  Forward  |  Map  |  List |  Home
This page was last updated on March 23, 2002.