NASA BRIEFING ON
DISCOVERY OF POSSIBLE EARLY MARTIAN LIFE

Opening Statements 

A team of NASA and Stanford scientists discussed its findings showing strong circumstantial evidence of possible early Martian life, including microfossil remains found in a Martian meteorite, at a news conference at 1:00 p.m. EDT, August 7, at NASA Headquarters, 300 E. St. SW, Washington, DC. The team's findings were published in the August 16 issue of Science magazine. 

Panelists were: 
- Dr. Wesley Huntress, Jr., NASA Assoc. Administrator for Space Science, Washington, DC 
- Dr. David McKay, principal author, NASA Johnson Space Center (JSC), Houston, TX 
- Dr. Everett Gibson, NASA JSC, Houston, TX 
- Dr. Richard N. Zare, Professor of Chemistry, Stanford University, CA 
- Kathy Thomas-Keprta, Lockheed-Martin, JSC, Houston, TX 
- Dr. William Schopf, Professor, Department of Earth and Space Sciences, Univ. of California, Los Angeles 

BEGIN TRANSCRIPT 

DAN GOLDIN, NASA ADMINISTRATOR 

I'd like to welcome everyone here today. It's an unbelievable day, its very, very exciting for me, and I hope you feel the same excitement that I feel. First I want to congratulate the team members who brought these exciting results to the American public and the people of the world: Dr. McKay, Dr. Gibson, Miss Thomas-Keprta, Dr. Zare, and Mr. Vali, thank you all. I'm so proud of you, words can't describe it. I'd also like to introduce a numbers of the memberships of the leadership of NASA science. We have Dr. Neil Lane, the head of the National Science Foundation with us; Dr. Bruce Alberts, the head of the National Academy of Sciences; Dr. Snow, of the National Institutes of Health, representing Dr. Harold Varmis, who couldn't be with us today; and we have Dr. Jerry Soften, the scientist from the Viking mission, upon whose shoulders we all stand today. There are other scientists in the audience, and I'm sure you'll have a chance to talk to them later. Their dedication, knowledge, and painstaking research have brought us to a day that may well go down in history for American science, for the American people, and indeed, humanity. 

First, the results today are not conclusive, or there is not yet scientific consensus. We are not hereto establish as in a courtroom, beyond a shadow of a doubt, that life existed on Mars. But we are here today, to open the door, just a little bit, to provide exciting scientific findings, to tell us fascinating detective stories, and to lay out compelling clues that lead us the direction we think life might have existed at some point on Mars 

As a scientist and engineer, and all of us, are skeptical but thrilled and humbled by this prospect. As a small boy, my father took me to the Hayden planetarium in New York City. And I'll never forget that first view of the heavens that was interpreted to me. And last night, I called my father in Florida, who isn't feeling too well lately. And when I told him what was about to happen today, I could hear the vibrancy in his voice. And if this meeting did anything, it helped my father feel better. 

We are now on a doorstep to the heavens. What a time to be alive. In the last year we've discovered planets around nearby stars, we've probed to the depths of the universe, to see the formation and birth of galaxies. And today, we are on the threshold of establishing, is life unique to planet earth. I want to tell you it is privilege to lead this great agency and the wonderful people, and I thank the President of the United States for giving me this opportunity. And I really want to thank the people here for the work that they have done. And we may see the first evidence that life might have existed beyond the confines of this small planet, the third rock from the sun. 

That could be a breathtaking conclusion, and I know the possibility of this took my breath away when I was with these scientists for two and a half hours; I gave them an unbelievable quiz personally, last week. In a few moments you'll hear the detective story. The scientists again are not here to say they found ultimate proof, or evidence -- but the evidence they present will be exciting-- but a chain of circumstantial events. And to man's further scientific investigation, we must investigate, evaluate, validate this discovery. And it is certain to create lively scientific debate and controversy to which the administrator says, outstanding, that's what makes American science and world science great -- peer review. We want this to go through time and time again; we have skeptical optimism, and we hope to force to further research. And in fact today we invited Dr. William Schopf of UCLA, an eminent scientist in the field that is not part of this team, that doesn't share all the views of this team, to get a point-counterpoint on the day we opened the door. 

We want these results investigated, and we are prepared to make samples of the rock available to meritorious proposals that go through the scientific process. We want to take the time to do this, and if it takes a year or two years, so be it. If the scientists tell us we have to restructure our program to get additional evidence, we will do it, but we will be government by scientific thought and principles, and not by emotion. 

The president asked me to make sure the discovery is subjected to the methodical process. He also announced that the Vice President will call a space summit in November to address the over arching questions, and how this finding should be addressed, and all the other issues of the nation's space program, in the context of science, and the quest for knowledge and enriching life here on the planet. And finally, he repeated the commitment to an aggressive plan already in place for the robotic exploration of Mars. I want to thank the president for his unwavering support of the nation's space program, his vision and his leadership. He asked us to do something hard: he didn't say let's give you extra money; he held NASA accountable to reshape our program within a tighter budget, and I think, with his leadership, we have been. 

I want to thank the Congress for the consistent bipartisan support of this program. And yesterday I had the privilege of talking to the Congressional leadership to tell them what might happen today, and some of the members were almost childlike in their excitement about the possibilities, and very humbled about what they heard. And today I spoke to the world space leadership, and there's an unbelievable excitement around the world about the possibilities -- I invited the world space leadership to work with us, to see if this is really the case. 

We're going to develop a process -- and I've asked Wes Huntress to provide the leadership --we're going to be concerned about how we take spacecraft to Mars, and not contaminate the samples there. We are going to be concerned about that contamination if we return samples to Earth. But we will be driven by a scientific process and not a rush to go to Mars. We will not do anything irresponsible. As you know, NASA's working on an origins program. We are asking fundamental questions about how did galaxies, stars, solar systems, planets and planetary bodies form and evolve, and is life unique -- life, however low, carbon-based or not, is it unique to this planet. 

We have a program that seeks to send an armada of small spacecraft to Mars and other planets in our solar system. There are over 10 spacecraft on the books right now, and in the next decade, within ten to 15 years, it is our objective to be able to directly detect earth-sized planets if they exist around stars within 50 to a hundred light years of earth, and to be able to remotely sense their environment to see what the makeup is, to see if there's oxygen and water vapor, and carbon dioxide, and perhaps even methane, so we can reach out even further. It's a bold, exciting program, and I know we'll have some knowledge, but I can't guarantee results. 

But now, let's move today's exciting story, a detective story. The scientists will lay out for you how an ancient rock, found its way from Mars and it got to earth, after billions of years, to have this rock, tell the people of American and the world an amazing story.

Dr. Huntress? 

HUNTRESS: Thank you very much Dan. I know you are all anxious to get right down to it, so my privilege this morning is really to introduce the team, and to let them kind of tell you their story. I mean, this is the result of over 2 1/2 years of very intensive, meticulous and difficult detective work on this particular meteorite, and most of what you are going to hear today has been peer-reviewed by the scientific community, and will appear in one of this nation's most science publications, Science Magazine, but we are also going to give you some new results, that have come out just recently, as well. So if I could introduce the team: first, the team leader is Dave McCay, to my immediate left, from the Johnson Space Center, he is a geochemist with over 27 years of work, in -- particularly with lunar sample investigation. Next to him Everett Gibson, also of Johnson. He is also a geochemist with over 20 years of investigations in geochemistry and lunar sample work. 

Next to Everett is Kathy Thomas-Keprta, she's also from JSC, and she's been studying meteorites and lunar samples with transmission electron microscopy, for about 12 years. Next to Kathy is profession Richard Zare, he's professor of Chemistry at Stanford University. He's also chairman of the National Science Board of the National Science Foundation; an expert in laser analysis -- this is a guy who can detect single molecules. 

Next to him is Bill Schopf, he's professor of paleobiology at UCLA. He's the discoverer of fossil evidence for the oldest life on this planet. He's not a member of the investigative team, as Dan told you, but he's here as an independent investigator to provide a balancing view on the data you are about to see. 

Next to bill is Professor Hojitola Vali from McGill University in Montreal, one of the members of the investigative team. And we have two investigators, also in the audience over here, on the left, Dr. Simon Clement of Stanford University's department of Chemistry, and Dr. Chris Romanek of the University of Georgia. 

And so at this point, I would like to turn it over to Dave McKay. 

MCKAY: Thank you, Wes. What I would like to do this afternoon is lead you through our story, which is a bit of a detective story, on why we think we have found evidence for past life on Mars. Now I want to warn you, that this is a controversial story, and there'll be a lot of disagreement, but the team itself has spent two and a half years with this sample, and we're in consensus view that we're along -- going along the right track. 

What we've dealt with here is a single rock, and you can see a piece of this rock in front of me, and the first slide is on your screen, showing a picture of the rock, or will be on your screen soon, but this rock came from Mars, we argue, it was found in Antarctica, it was brought back to Houston, and some of it to the Smithsonian -- this happens to be the Smithsonian chunk, which is 170 grams-- the total rock is about 4 and a half pounds, 1.9 kilograms, and is about the size of a small potato. We couldn't bring the part that was in Houston, but this is a very good sample of the actual rock that we analyzed. 

What I'm going to do, what our team is going to do is look at our data, and our data has 4 different lines of evidence, and these lines of evidence -- each one of these lines of evidence can be interpreted in various ways. However, we think that a reasonable interpretation for each one of these is that the evidence is pointing toward biologic activity in early Mars, and we'll tell you why. 

The lines of evidence that we'll develop are that, first, the meteorite came from Mars, and contains carbonate -- calcium carbonate, the same thing as found in limestone -- which was formed on Mars, and it is within and associated with this calcium carbonate, that we see much of our evidence. The mineralogy and the chemistry of the carbonate globules, we call them, we believe are compatible with a biologic origin. 

That's our second line of evidence. The third line of evidence is that the rock contains organic compounds, organic material, which we believe comes from Mars, and we'll talk about that. 

And our last bit of evidence, are pictures of strange structures within this rock, within the carbonate, some of which we have interpreted as micro-fossil forms, micro-fossil-like forms, and we'll show you those. This is perhaps the most controversial part of our presentation, but we'll show you those anyway. 

Now, as I said, there are alternative explanations for each of the lines of evidence that we see, but taken it -- when you look at them individually there are alternative explanations, but when you look at them all together, collectively, particularly in view that they all occur within a very small volume-- every sand-sized chip has most of these kinds of evidence in it -- we conclude that taken together, this is evidence for early life on Mars, and we'll tell you why. Now I want to turn the discussion over to Dr. Everett Gibson, who will show an overview of our story, its an animation, and he will walk through it and tell you what it means. This is an interpretation based on our data. 

GIBSON: Thank you David. Let me explain to you a little bit of what you're going to see. We have placed -- put together two and a half to three minutes of animation on the history of this sample. We feel this will assist you in understanding the evolution of this sample, the materials we are studying, and what we are looking at in particular. This information was gathered from a variety of colleagues, through the communities who made specific measurements, but we feel it all points to the important story that we are here to tell. If I can have the animation, we'll go through this. 

Early in the history of the inner solar system, we knew the planets were solidifying in this period of time of 4 1/2 billion years ago. The sample which we have before us is 4 1/2 billion years in age. It appeared about 4 billion years, the inner solar system bodies were undergoing an intense bombardment, and the surface of Mars was no exception, it underwent this intense bombardment. And 4 billion years ago, we knew the surface was fractured, the planet was probably warmer and wetter. Water was more abundant, it filled these cracks and fractures, and as time evolved, we feel that the solutions may have resulted in the formation of these carbonate globules which we see within these fractures in this meteorite. And as these carbonate globules were growing, there was probably a presence of a microbiota?, what it exactly is, we do not know, but we see the forms which you'll see later today. And as these carbonates grew from these solutions and filled these fractures and voids in this sample, they begin to entrain these organisms which you'll see in the photography shown later,. So these carbonates were present on the surface of Mars and growing. We know this from the actual topic chemistry from these materials. 

Then Mars went through a period when it became older and drier, and so up and from the 3.6 billion years age of the carbonates up to the interval of 16 million years ago, we know a large object slammed into the surface of mars, knocked material from the surface. This material traveled through space for 16 million years. Thirteen thousand years ago, it came under the influence of Earth's gravity, and fell on the Antarctic ice sheet. It was lying on the Antarctic ice sheet, it was resided there for 13,000 years. A joint national science foundation field meteorite collecting program, which was supported by NASA and the Smithsonian Institution, this material was collected by the field team, and brought back to the Johnson Space Center, where it was cleaned and processed. You see the sample with the dark fusion? crust, which is the blighted surface as it came through the Earth's atmosphere, and you look in the interior and see the orthopyroxene minerals. And highlighted, we see an area of weathering and alteration, and then we look into theses mall cracks above, you see another area where we have these orange-brown globules. They are in the highlighted area in this film. To understand and see these a little better, we're showing an image from our colleague Monica Grady of the British Museum. And you see these 250 micron-sized carbonate globules with their black and white rims. These are approximately five times the diameter of a human hair. They are very small in size, but they are very unusual to be in a meteorite. And the study of these, and the chemistry that's going on in these rims of these globules, is basically the story which we have today, to tell you. 

I'd like to pass the microphone to my colleague Kathy Thomas-Keprta, and she'll explain the chemistry.

KEPRTA: Hi, if I could have the first slide please. What we're going to concentrate on now is taking a closer look at these carbonate globules that Everett just described. Now this is a cartoon, on your video, if you could back it up one please. Back up one slide please. Back to the cartoon. We'll have it for you in a moment. There we are. And what you're seeing -- what Everett just showed you, he showed you the golden-colored carbonate globules. What we're looking at here is just an edge of one of the carbonates, in cartoon form. And you can see, as you saw in the previous picture, these globules contain black-white-black rims. We've been calling them our Oreo cookie rims. Anyway, as you approach the rim, if you see the tiny dark spots, the rims are composed of very fine grain minerals. One of the minerals is called magnetite, and its composed only of iron and oxygen. The other one is composed of pyrrhotite, which is composed only of iron and sulfur. That's located in the rim area. Now in another area away from the rim, within the carbonate, we get a closer look at another region, which shows more smaller grains, the Magnetite, again, present -- its composed of iron and oxygen -- and supposed greigite, that is composed of iron and sulfur. Now, these particles, these metal grains are very, very tiny. And so what we had to use to image these is a transmission electron microscope, and we'll call that from now on a TEM. And we can take a very small area with the magnetite and pyrrhotite and zoom in on that. Next slide. 

... Dark splotchy regions are magnetite. Now let's get a closer look at the magnetite. Next slide. These magnetite -- you can see one has a cuboid shape, the other is in a teardrop shape -- these magnetite are roughly about 40 to 50 nanometers wide. You can fit about a billion of these on the head of a pin, that's how small they are. So -- and they have a very unique shapes. Next slide. 

Now to determine -- we can actually determine, based on the literature, based on three criteria, if this magnetite that we are seeing is biogenic or not -- whether it has been produced by bacteria --based on the distinctive shape, based on the chemistry and based on the environment. Now these shapes -- next slide -- these shapes are very similar to magnetite that's produced from bacteria on the Earth. They are also very similar in size, they are the exact same composition, they have a very pure crystal structure, there are no defects, and both types of magnetite that are produced by microorganisms on the earth, and that that we find on mars, have been produced in a low-temperature, fluid environment. Next slide. 

And these are magneto fossils found on earth, and as you can see, we can compare the shapes to what we saw previously. The one on the top left is a cuboid shape, and the one on the bottom right is a teardrop shape -- just exactly what we had seen from our Martian images. Next slide. 

We can also take a closer look at some of the iron sulfides. The two images that you see on the left are rectangular, probable greigite particles from our Martial sample. The sample on the right is a terrestrial sample. Now these greigite samples -- the greigite sulfides, are -- they're very similar to what we see on earth as far as chemistry, as far as the shape, the surface morphology, and it is very common on earth for greigite to be produced by bacteria. Next slide. 

Last we'll take a look at the puretite, which was also associated with the magnetite. And again you can see two different types of shapes for the pyrrhotite. This type of pyrrhotite, which again is an iron sulfide, can be produced inorganically. However, it can also be produced by certain types of microorganisms on earth. 

In summary, we feel that even though there could be very complicated inorganic explanations for the presence of these mineral grains, the simplest explanation is that these are products from microorganisms that were produced on Mars. And now I will hand you off to Dr. Richard Zare, who will discuss the organic chemistry. 

RICHARD ZARE: Thank you Kathy. Organic chemistry: by this I mean molecules that contain carbon. The Viking lander mission, two of them, went, looked, scooped up the surface of mars, looked with a mass spectrometer, and really came up a little empty handed, didn't really find the organics that one might have hoped to find. And there's been increasingly a feeling that grew, that somehow the planet was all dead. We can return later to examine that conclusion. What we've done is take pieces, fractures from this meteorite, and pop them in a high vacuum system. We then shine in a laser, a bunch of laser systems -- pardon me? No audio. Let's try another, thank you. 

So let me start again. We take these pieces of the meteorite sample, freshly cleaved, put them into our vacuum system in less than two minutes, high vacuum system, and analyze what type of organic molecules they have. We do this in a method that I will show you later, and if I might have the first slide, let me show you the results. We find certain types of hydrocarbons, things that contain carbon and hydrogen, this shows some peaks, these are so-called, polycyclic aromatic hydrocarbons -- Pasha. PAHs are really a pretty common substance on earth. It's found, for example, in diesel exhaust, or in sooting of a flame, or it's found when you overcook steak on the barbecue, or it's found in such things as when you fossilize various organic matter, like in petroleum products and such. The PAHs can also be made in a purely inorganic manner, for example by somehow polymerizing acetylene. So finding PAHs in themselves doesn't tell you whether something is alive or dead -- not in itself. The particular figure, though, that we have, if I could come back to showing you that slide, is unusual compared to other carbonaceous chondrites-- we've looked at other meteorites that have PAHs -- this distribution is much simpler, and I could go on and explain in some detail how it's much simpler -- it very much resembles what you'd expect when you have simple organic matter decay. We have indeed studied these PAHs and we've done them as a function of depth from the fusion crust inside the rock, we find them more inside of the rock than in the fusion crust. We believe that means that they're indigenous, they belong to the rock. If they came from a contamination -- if they came through the rock while it was on earth, it would really expect to be more on the outside working its way in. It's completely backwards as to what we find. 

If I could have the next slide. I'll show you that we're also able to make a map, and as you look at this, you'll see in the upper right-hand corner, this is the A, B, C, D, and each one, you'll find what I call "hot spots" -- this is where there's a bigger signal, that's what I mean by hot spot. And of these different simple PAHs, they are not only correlated with each other, but they are correlated with the carbonate globules which you've already heard about. 

Let me now explain how the method works by asking you to take a look at the animation that we've prepared for this setup. This is a system that has a very immense sensitivity. It is able to look at only a few thousand molecules of material. First we have an infrared laser, which we'll turn off, hit the sample shown below, heat it up, and cause it to evaporate. This will produce a plume of gas cloud. Here we go -- there's the plume. Next the UV laser shines in, excites some molecules that can absorb it, produces ions, knocks on an electron to produce ions, and this electric field with a battery, they go and hit the detector. Now we move the laser around, hit another spot, fire it again, and we make a map, as we, indeed, make these ions. Notice there's two types of ions, those that are fat and those which are thin. It's like a race, and I'm sorry to tell you, the thin ones always beat the fat ones, and so by looking at the arrival time, we determine the weight of the molecule --that's the mass spectrum. And by this means, we've been able to look and see the first organic molecules that we believe come from Mars. Let me now turn this microphone back to Dave and hopefully we're going to see some pictures. 

DAVID MCKAY: Okay, moving on, if I could have the first slide, please. This is simply the same picture you saw earlier of the carbonate globules with the black and white rims around them. This picture was provided to us by Monica Grady of the British National Museum, who took this very nice picture. Next slide please. 

We're going to discuss now some of the features that we see in the scanning electron microscope, features which occur on the surface of those carbonate globules. This is a typical picture of an area rich in iron, it's one of the iron-rich rims. And we see that the scale is not on this, but the biggest object in this picture is about 500 nanometers across. That's roughly 1/500th the size of a human hair. We see that the carbonate globule is covered in areas with this kind of very fine-grained material -- and you can see that there's one rod shape, there's kind of a one with a dark line up the center of it -- many of these are probably the magnetite iron-oxide crystals that we saw earlier --we're looking at them with a different technique now -- and many of them are probably the iron-sulfide grains that we saw earlier. But some of these don't look like either magnetite or iron sulfide -- they may be something else. And we're not quite sure what that is. Next slide please. 

Again, at very high magnification in the area of the carbonate globules we see this kind of feature. These are elongated forms, structural forms. We think that matrix that they appear to be eroding out of is probably a clay mineral. We're confirming that, but we do have indication now that there's a water-containing clay mineral in this area. The features that you see may be any number of things; for example, they could be dried-up parts of that clay, or they could be microfossils from Antarctica or microfossils from Mars. It is our interpretation, the one that we favor, is that these are, in fact, microfossil forms from Mars. But keep in mind that is an interpretation, we have no independent data that these are fossils, we don't have pictures showing cell walls, or internal material characteristic of cells. It's simply an interpretation at this point. Next slide, please 

As we look in other areas of the carbonate, we see these forms which are elongated, they have rounded ends on them. Are these strange crystals? Are they dried-up mud? We believe, we interpret that these are indeed microfossils from Mars. They are extremely tiny, the longest one is about 200 nanometers, this is very high magnification. One of the techniques that we're using, by the way, is high-resolution scanning electron microscope. We're looking at rocks and minerals at a scale that has really not been used before. These are extremely high-magnification, high-resolution pictures. Next slide please. 

Just for comparison, these are some tiny bacteria, nano- bacteria on an Earth rock, on calcite, calcium carbonate, the same kind of material we're looking at on Mars, and the scale their shows 500 nanometers. These are interpreted by the authors of this particular paper, which includes none of our team, they are interpreted to be nanobacteria. And these things are the same size and shape as many of the forms that we're seeing in the Mars sample. Next please. 

As we move on, we see a few of these elongate forms, which appear to be segmented. This one is about a half a micrometer long, which is still about a 1/100th the diameter of a human hair, which is very tiny, but now we're getting up into the size range of a common terrestrial microbes and bacteria, and whether this is a microfossil or whether its a dried up mud crack, we can't really say because we have no data other than what you see, which is simply the photograph, but again, it is our interpretation that this and similar features have a high probability of being martial microfossils. Next, please. 

Now, Dr. Vali of our group, and his laboratory in Canada, using a different technique, a totally different technique, took these pictures of the same rock, and he found very similar elongated, somewhat curved structural features, and again we don't know what these are, we don't have chemistry on these, but one possible interpretation is that they are similar kinds of Martian microfossils to what we saw in the scanning electron microscope. Next slide, please 

And finally, I want to finish up with a slide of some real bacteria, that we know are bacteria, which turn out to be about the same size and about the same shape as the things that I've been showing you in the Mars sample. These are from the Columbia River basalts from the state of Washington, and they're from volcanic rocks, and they're buried deep within the ground. They're a couple kilometers deep, these come from a drill core, and it turns out that within the samples from this drill core, there are subterranean, subsurface bacteria, and some of them -- there are larger ones-- but some of them are these very small kind of bacteria. 

So in conclusion then, in terms of the photography, we have a number of forms, which are --which it is very tempting for us to interpret as Martian micro-fossils. But, we have no confirming evidence, and you'll hear more about the pitfalls of identifying such things based on appearance alone. We don't have the chemistry of these, we don't know if they have cell walls or not -- we will find that out, that will be part of our future work -- but for now we have to use these images and interpret them the best way we can. And so I want to finish up here by simply saying that we have these lines of evidence, and none of them in itself is definitive, but taken together, the simplest explanation to us is that they are the remains of Martian life. And Everett is going to sum it up in terms of a checklist of what you would look for if you were looking and trying to prove early Martian life. 

EVERETT GIBSON: Thank you David. Very clearly, the only record we have, our criteria that we can use to judge our data against, is that of the own geologic record here on the earth. And what we have chosen to do is go into the literature and pull out those data points which other investigators have used to establish the criteria of the authenticity of microfossils here on the earth, they are evidence of early living systems here on the Earth. 

And what are they? If I could have the next slide of view graph. We have essentially eight criteria for establishing credible evidence of past life within geologic column. One: do we know the origin of the sample? Do we know the age of the sample? Are there presence of microfossils in this sample? Are there remains of potential colonies where these microfossils have begun to multiply or replicate? Are there biomineral markers present? Is there some organic material as a organic biomarker present? And then we turned to a technique of the stable isotope pattern, that may give us evidence, because we know from living systems the isotopes of carbon and other elements are fractionated[?], that we can use these as fingerprints to identify evidence of living systems. The last one is, are these features indigenous to the samples? 

And lets go to the next slide, and look at our data, and review that again. What is the origin of the sample? We know the sample is from Mars, we feel, from several lines of evidence, primarily, the oxygen isotopic composition is unique, for materials from Mars, because the materials were formed from a different reservoir. 

What is the age of the sample? Three different independent geochronometry techniques have determined the age of this rock as 3.5 billion years old -- I mean, sorry, 4.5 billion years old, from the early crust of Mars. The age of the carbonates that are in this rock have been dated at 3.6 billion, this also may have a slightly younger age, but this is the age that's published, that we must go at. 

Are there presence of microfossils? Yes, you've seen from the evidence that's presented, there are the ovoids, or the spherical objects, that down, in the range, of individual units. Some of these appear to be dividing, or they're doublets, or things of this type. 

Are there any structural remains of colonies, or perhaps these carbonate globules are a larger colony there. 

Are there any biomineral markers? Yes, we have the evidence, the magnetite, and the pyrrhotite, and possibly the greigite, which are suggestive of disequilibrium assemblages[?] that must be present within minerals to support the energy source for organisms to thrive. 

Are there any organic biomarkers? The organic biomarkers we've seen from the organic chemistry of Dr. Zare shows that yes, there is evidence of organic material -- and a reduced organic material carbon material, reduced carbon -- within these samples from Mars. 

Are there any unique stable isotope patterns which we use here on earth, this is an area where clearly we need more work in, but we saw from the initial discovery of the unusual carbon composition of these carbonates, there is another story there, which we have a lot to be done in this area. 

And are the features indigenous to the sample? I think we can say yes, from what we've seen today, and the tests that we've done, these features appear to be indigenous to these samples. 

So from the criteria we have, we come to the conclusion that we meet a large number, if not all, of these criteria which we use to establish evidence of past life in our own terrestrial geologic column, and perhaps they can be applied to this material believed to be from Mars. Thank you. 

DR. HUNTRESS: Okay, I think what you've seen here is a very compelling case for the possibility of life on early Mars, and it's been built on several lines of evidence: evidence involving the organic chemistry of this sample, mineralogical evidence, and even structural evidence of this sample and their close association together. I think you've also seen some pretty astounding imaging that is very, very suggestive of early life on Mars. The agency's attitude is, as Mr. Goldin suggested, and that is of skeptical fascination with this result, and the point is it is now time for this to move into the scientific community, and for the discussions to begin as to the conclusions that these investigators have come to as a result of having taken all this data, and so here to kind of represent and begin that debate, is Bill Schopf of UCLA. 

BILL SCHOPF: Thank you. I would prefer to refer to my comments as part of a discussion rather than a debate. I would like to thank Mr. Goldin and NASA for inviting me to be here. I am not a member of this science team. I have been invited here to do a preliminary analysis, publicly, of the paper that is coming out in Science Magazine in about ten days. Mr. Goldin referred to me as the optimistic skeptic, or perhaps I'm a skeptical optimist, I really don't know. Could I have the first slide, please? 

I do think this is a fine piece of work, and this is not easy science. This is multi-disciplinary science, these folks have tried to bring to bear on an important problem many different areas of the science, and to bring them into a coherent whole. I personally regard this as a preliminary report. I quote on this slide a quote attributed to Carl Sagan: "Extraordinary claims require extraordinary evidence," and I happen to regard the claim of life on Mars, present or past, as an extraordinary claim, and I think it is right for us to require extraordinary evidence in support of that claim. And so I guess my job here, principally, is to sound a note of caution. 

If I could have the next slide, I have been involved in searching for ancient life on this planet for the past three decades. I wrote my first scientific paper in 1964, and so I have been in this game for a long time. And during that period of time a set of seven criteria have evolved, and that is, those are the criteria we use to test such claims on earth, and those criteria, in my opinion, must be met on Mars as well. We want to know the source of the material -- the age of the rock, the environment in which it was formed, and the history of that rock -- has it been pressure cooked, for example. With regard to claims of organic matter, or of fossil-like objects in such ancient rocks, there are three tests: one, are they within the rock; two, are they as old as that rock, rather than having been introduced somewhat later; and thirdly and most importantly, are they demonstrably, assuredly, certainly biological? 

Let us remember that the mere presence of organic matter by itself does not say it's part of life, because we know on this planet, prior to the origin of life, organic matter was synthesized non-biologically; we know that there are lots of -- there are meteorites called carbonaceous chondrites that contain large amounts of organic matter that is of non- biologic origin. So we want to know, is that organic matter demonstrably biological, and secondly, with regard to fossil-like objects, we'd like to know they are assuredly fossils, not mineralic pseudo-fossils, or what we used to call "foolers," things that fool you and you'd prefer they didn't. 

So let me have the next slide and I'll show you the oldest evidence of life on this planet to give you an idea of the sort of thing that we're looking for elsewhere. These are microscopic fossils, 3.465 billion years in age, that is, nearly three and a half billion years in age -- roughly three-quarters the age of the earth. They are demonstrably cellular, as you can see, and they are composed of organic material. Their cell walls are made of organic matter. On the next slide, at the far upper right-hand side of the -- no, lets, this is another set of fossils from this deposit; they have conical end-cells, they have rounded end-cells[?], they have demonstrable cells, and all that. These are demonstrably fossils. Now, up in this slide at the upper-right-hand side, I want to draw your attention to a very minute strand. And that strand, at the upper right-hand side, is one-half of a micron in thickness. This is a bacterial strand, it's three and a half billion years in age, it comes from this Earth, and it is 100 times larger than these microscopic objects that we have just seen from Mars. And that is one of the smallest, shown in the slide, one of the smallest fossils that has been found on Earth. Let me finish up now, by going to the last slide, which is a subjective confidence rating comparing evidence of life on Earth to evidence of life on Mars, as here presented. I want to emphasize this is subjective; it says "subjective"; it is italicized "subjective." It is my opinion. And I want to go through these seven lines of evidence and tell you what I think about them; I've been asked to do that and I'll be as honest and as rigorous as I can. 

With regard to the geology: it seems to me that it is quite probable that this meteorite is from Mars. We should remember that there are only 12 such Martian, alleged Martian meteorites known, only two of them, to my knowledge, contain inclusions in which there is direct evidence that they are like the surface chemistry of the Martian atmosphere. Nevertheless, I give that a confidence rating of 9. The Olympics are just over, I'm using a one-to-ten scale -- this is a 9. 

The age, I think, is also pretty well established, the age of these carbonates at about 3.6 billion, that's a little more uncertain. I give that a confidence rating of 8. But I think that's pretty good stuff. 

Now with regard to the environment and history it is only fair to point out that there is a debate, scientifically, regarding such matters. There was, in fact, a paper published in the July issue of Nature Magazine, by Ralph Harvey and Harry McSween, of Case Western Reserve and the University of Tennessee, respectively, in which they argue that these carbonate in the fractures in this Martian meteorite were not formed at low temperature, that in fact they argue that they were formed at 450 degrees Celsius; if that is true, there is no expectation of these things harboring life. 

Similarly, there is a question as to the time the carbonate formed within this rock. One argument presented here is that this was before the body was lifted off the Martian surface. A second interpretation in the paper I just referred to was that those fractures were caused during the impact that lifted that off the Martian surface. If Harvey and McSween were correct and the NASA group were to be incorrect, I think those two interpretation would rule out the presence of life in the sample. Let me only point out, I am not taking sides in this matter, I am simply saying that this is not a resolved issue as yet in the minds of some people. 

Finally: with regard to the organic matter and the fossil-like objects. I think that it has been established certainly to my satisfaction beyond any doubt that I have, that both the organic matter --that is, the polycyclic aromatic hydrocarbons[?] -- and the fossil- like structures are -- occur within the rocks. I think it's very likely, that even though they occur in fractures, where ground water can introduce things, I think the data are good, I give it an 8 or 9 rating that, in fact, those things are a sold as the fractures in that rock. 

With regard to the biology, however, I take a rather different view. With regard to the polycyclic aromatic hydrocarbons, I note that such compounds are found in interstellar dust grains. I note that PAHs are found in interplanetary carbon grains. I note that PAHs are found in other sorts of meteorites, like carbonaceous chondrites. In none of those cases have they ever been interpreted as being biological. This is, after all, a meteorite, and so, the first approximation, I'd look at those PAHs and say, assuming that they're not contamination from industrial pollution on this planet, I'd say that the first guess would be that they're probably non-biological, just like PAHs that occur in other meteorites. The burden of proof is on those who claim that they are biological. 

And secondly, with regard to these fossil-like objects, I note that they are 100 times smaller than such fossils that have been found on this planet. I note that there is no evidence of their composition. The best guess at this point would be that they are made of mineralic material. At least, there are no data -- and it's because they are so small, there are no techniques at present to analyze their chemical composition -- but there's no evidence that they're made out of carbonaceous material; we don't know that yet. 

Thirdly, there's no evidence that there is a cavity within them, a compartment, a cell. Why do you need that? Well, that is where the juices of a living organism reside, that's where the chemistry that makes things live works. We've got to look inside these things -- see if they have cell walls, see if they are compartmentalized, see if they are cellular, see if they are composed of organic material. There is no good evidence as yet of life cycles, or of cell division -- tests that we also apply to, in the fossil record. So all I am saying is that there is additional work here to be done. I give the biological interpretation at this point, I claim that in my opinion it's probably unlikely. But it's possible to do additional science, to answer these questions, to test this and move it up the confidence scale. 

I finally come back to Sagan's, Carl Sagan's quotation, which I think is applicable: extraordinary claims require extraordinary evidence. We know the sort of evidence that we need to obtain regarding these samples. Personally I think that this is exciting, I think it's very interesting, I think they're pointing in the right direction. But I think a lot more, or a certain amount, of additional work needs to be done before we can have firm confidence that this report is of life on Mars. Thank you. 

DR HUNTRESS: Well, I think you've seen that this is a result that is going to be very controversial. That's not a surprise to us at all. We've given you a kind of a taste of the scientific discussion and how this process will proceed. We'd like you to keep in mind that a fair amount of this has been peer-reviewed by the scientific community, although much more work needs to be done to confirm or deny this, as you just heard from Bill Schopf. But the agency certainly felt that it was very important to make the results of this work, the data, and the conclusions of these investigators, public. And so I now turn it over to Laurie Boeder to handle Q & A.

Corrections made by David M. Seidel, JPL