By TODD ACKERMAN
October 24, 1999
But Richard Zare's lasting renown is likely to be for pioneering laser devices and techniques, now common in laboratories around the world, that detect and identify molecules in unimaginably small concentrations, whether inside meteorites or inside cells.
But Zare's biggest splash came with the Mars rock and his laser's determination that organic matter in it was not scattered randomly but clumped together in globules of carbonate.
Johnson Space Center, TX
Oct 1, 1999
This study doesn’t directly address the possibility that life once existed on Mars. But “It’s another piece in the puzzle,” said Larry E. Nyquist of the Planetary Sciences Branch of Johnson Space Center’s Earth Science and Solar System Exploration Division. Nyquist, one of the authors of an article in Science, a weekly publication of the American Association for the Advancement of Science, was the principal investigator.
Researchers at Johnson Space Center in Houston and the University of Texas at Austin did the study, using different techniques. Both produced similar results, establishing the carbonates’ age within comparatively narrow limits.
The 4.2 pound meteorite is believed to be part of an igneous rock formation formed about 4.5 billion years ago as Mars solidified from a molten mass. The meteorite probably was blasted from the planet when a huge comet or asteroid struck Mars 16 million years ago.
It fell in Antarctica about 13,000 years ago, and was found in 1984 by an annual expedition sponsored jointly by NASA, the National Science Foundation, and the Smithsonian Institution. Called ALH84001, after the Allan Hills in Antarctica where it was found, it was returned to Johnson Space Center, and has been preserved at the Meteorite Processing Laboratory there.
It subsequently was recognized as one of more than a dozen meteorites with unique Martian characteristics.
Just how the carbonates were deposited within this igneous rock is the topic of lively debate. Some scientists believe water saturated with carbon dioxide from the atmosphere seeped down to the subsurface site where the igneous rock formed and created the carbonate deposits. On Earth, living organisms often play a role in carbonate formation. In 1996 scientists at Johnson Space Center and Stanford University examined the carbonates in ALH84001 using electron microscopy and laser mass spectrometry, and reported evidence suggesting primitive life may have existed in them.
Other scientists believe the carbonates formed when hot, carbon-dioxide-bearing fluids were forced into cracks in the rocks when a meteor struck Mars. The 3.9-billion-year age of the carbonates eliminates neither possibility.
The carbonates themselves are tiny deposits, reddish globules, some with purplish centers and many surrounded by white borders. The different colors are due to variations in the compositions of the carbonates: purplish manganese-bearing calcium carbonate, reddish iron carbonate, and white magnesium carbonates. The globules were found along fractures in the meteorite and make up about 1 percent of its volume.
The JSC-UT team, using a binocular microscope and tools resembling dental picks, over a period of months painstakingly separated out enough of the carbonate material for their analyses. After experimenting with terrestrial calcium, iron, and magnesium carbonates, they developed a way to selectively dissolve carbonate material of differing compositions, enabling them to separate different elements from the carbonate solutions.
The study established the age of the carbonate deposits by measuring the decay of rubidium to strontium and of uranium to lead. The techniques are similar to carbon dating, which is used for much shorter time periods. The investigators used the dual approach because “we wanted to make sure we had a result we could believe in and that other people could believe in,” Nyquist said.
The leading author of the Science article is Lars E. Borg, formerly of the National Research Council and Johnson Space Center and now at the University of New Mexico in Albuquerque. Other authors are James N. Connelly of the University of Texas at Austin, Chi-Yu Shih, Henry Weismann, and Young Reese, of Lockheed Engineering and Science in Houston. K. Manser of the University of Texas contributed to the investigation.
The age of the carbonates, said Everett K. Gibson of Johnson Space Center and an author of the 1996 study that reported evidence of microbial life in the carbonates, had been “one of the real mysteries” of indications of life on Mars. Had the carbonates been formed more recently, when the planet’s surface was devoid of water, it would have been unlikely they were associated with primitive life on Mars. Dating them at 3.9 billion years, when there apparently was surface water on Mars is, Gibson said, very important, and could “suggest events were very similar in the inner solar system” as primitive life arose.
University of California-Los Angeles
June 22, 1999
"Cradle of Life" recounts the discovery over the last three decades of a vast, ancient fossil record, unknown and thought to be unknowable. This immense fossil record fills in gaping holes in our knowledge of the earliest 85 percent of the history of life on Earth, and changes our understanding of how evolution works. In addition to writing about this remarkable success story, however, Schopf also details two of science's stunning failures.
Schopf, director of UCLA's Center for the Study of Evolution and the Origin of Life, cites the "discovery" in the early 1700s of a skeleton of a human said to have drowned in Noah's flood -- taken for many decades as proof of Biblical truth. The claim was made by Dr. Johann Jacob Scheuchzer, a highly respected Swiss physician and naturalist. In 1725, Scheuchzer uncovered the partial skeleton of a large vertebrate animal in limestone, and dubbed the specimen Homo diluvii testis -- "Man, a witness of the Deluge."
Hailed as irrefutable evidence of Noah's flood, it was shown -- almost a century later -- to be a misidentified huge fossil salamander.
Another distinguished scientist from the early 1700s, Johann Bartholomew Adam Beringer, reported the discovery of "perfect" fossils of many animals, Including butterflies, birds with freshly laid eggs, spiders with webs, and "fossilized imprints" of the moon, sun and stars. However, Beringer was duped into falling for a hoax; the stones had been carved, hidden, and dug up -- a plot to disgrace Beringer by scholars who despised him.
"Beringer thought he had discovered a Rosetta stone, and Scheuchzer was certain he had unearthed a Rosetta stone," Schopf says. "Yet who are we to smugly sit in judgment? Though it is now harder to be fooled since so much more is known, it's a sure bet that some of what passes as 'known' today will eventually turn to dust. Like Beringer's and Scheuchzer's, our most glaring errors will also be cast aside." Following his account of Scheuchzer and Beringer, Schopf concludes with a chapter on the NASA scientists who claimed in 1996 that they had found evidence of life on Mars in a meteorite (ALH84001) that landed in Antarctica 13,000 years ago. His implication is that these respected scientists may be modern successors to Scheuchzer and Beringer.
"I want there to be life on Mars more than anyone else -- but it doesn't matter what I want!" Schopf says. "The evidence isn't there. Possibly, perhaps, maybe are not good enough."
In "Cradle of Life," Schopf recounts his involvement in evaluating the evidence for life on Mars, and the events that led to the life on Mars NASA press conference. NASA administrators asked him in January 1995 to assess what geologists at the Johnson Spacecraft Center (JSC) in Houston believed might be microfossils in a chunk of a meteorite thought to have come from Mars. The focus was on tiny, orange pancake-shaped globules of carbonate material. The scientists thought these globules might be Martian "protozoans," but Schopf's analysis showed that their guess was wrong.
"Many of the objects merged one into another in a totally nonbiologic way," Schopf says. "Their overall size range also did not fit biology, and they lacked any of the telltale features -- pores, tubules, wall layers, spines, chambers, internal structures -- that earmark tiny protozoan shells. In addition, the 'lifelike' traits they did possess could be explained by ordinary inorganic processes.
"I raised these points with the JSC scientists. They seemed to agree. I thought the matter was closed. But more than a year later, at the August 1996 news conference, the same little pancakes were again proffered as evidence of Martian life, this time of bacteria rather than protozoans. Evidently the scientists' minds were set -- the facts hadn't changed, only the meaning attached to them."
Several weeks before the press conference, NASA again asked Schopf to evaluate the findings. He studied the evidence three times, and was not impressed.
"Crucial questions had not been asked," he writes. "Articles published earlier and critically relevant to the authors' contentions had been ignored. More plausible ways to explain the findings were given short shrift. The claim of 'evidence for primitive life on early Mars' seemed overblown, ill-conceived."
At the press conference, the JSC scientists presented their findings with the aid of "high-tech cartoon videos," says Schopf, who spoke after them.
"I was wearing my best suit -- the one I got married in -- looking at hundreds of reporters who wanted me to say there was life on Mars," he says. "I had no doubt my words would prove unwelcome. On a scale of one to 10, I gave each piece of their evidence a score. Some, such as the suggested Mars source of the meteorite, I ranked high. But the evidence for life was weak; I gave it a two. A number of scientists later called me to task for being too generous. One Nobel laureate said I should have ranked the evidence zero!
"This attempt failed to find life at Mars. That does not mean Mars contained no life -- just that these scientists didn't find any."
How do respected scientists, from Scheuchzer and Beringer to the JSC team, Make such blunders? One answer, Schopf says, is that scientists have the same "strengths, fears and foibles as everyone" and are not so different from our neighbors. They have great successes and, sometimes, great failures. Mostly, "Cradle of Life" addresses one of science's great successes.
What significant events occurred in that first 85 percent of the Earth's history? Among other things, the first living organisms, the modern food chain, photosynthesis, the ability to breathe oxygen, the development of the atmosphere and oceans, various types of cell division, and sexual reproduction all date from this enormously long period of time, Schopf says.
In "Cradle of Life," Schopf tells an "even more mind-boggling tale," scaled in millions and billions of years, dealing with "all of life, over all of time, over the entire globe" -- a tale that reveals "where we have come from and who we are."
The tracing of life's earliest history is an acrimonious story of false starts, embarrassing mistakes, and ultimately, dogged persistence and remarkable success. Schopf shows why it took so long for the hidden record to emerge.
The early fossil record is richly complex and full of surprises. One such surprise: Evolution itself evolved.
"Everyone had expected early organisms would be smaller, simpler, perhaps less varied, but they were universally thought to have evolved in the same way and at the same pace as later life," Schopf writes. "This turned out not to be true. That evolution itself evolved is a new insight."
The pivotal point in evolution's own evolution turned out to be the advent of sex about 1.1 billion years ago. The origin of sex caused monumental change. Sex increased variation within species, diversity among species, and the speed of evolution and genesis of new species -- and brought not only the rise of organisms specially honed to particular settings, but because of this specialization, the first appearance of life-destroying mass extinctions.
The first organisms to engage in sexual activity were single-cell floating plankton. They started to appear about 1.1 billion years ago with a porelike mechanism that permits the release of sex cells into the environment. Before this time, organisms reproduced by asexual division, as do human body cells. Data from the fossil record clearly show that there appeared many new types of species at about 1.1 billion years ago, evidently when sexual activity first began.
"The start of sexuality," Schopf says, "had an enormous effect on the world's biodiversity. The pre-sex world was monotonous, dull, more or less static, but every organism born from sexual reproduction contains a genetic mix that never existed before."
Among the lessons Schopf draws is one that might surprise many high school students: "Science is enormous fun, and the greatest adventure ever devised. The past, present, even the future of life, Earth and all beyond are within its scope. There's hardly anything better than having a novel idea and finding that it makes sense."
March 22, 1999: Do nanobacteria rule Earth and Mars?
Ultrasmall structures within deep rock could change view of life on Earth, Mars
University of Queensland
Brisbane, Australia
20 March 1999
At 20 to 150 nanometres (billionths of a metre) in length, the organisms, which they call nanobes, are much smaller than the smallest certified terrestrial bacteria ever found on the planet.
Researchers discovered the living colonies of organisms in ancient sandstones retrieved from an oil drilling site 3-5 km below the Australian seabed. The finding has been reported in a recent issue of American Mineralogist.
The researchers behind the investigation are senior research fellow Dr Philippa Uwins and senior research officer Richard Webb of the University's Centre for Microscopy and Microanalysis (CMM), and PhD student Anthony Taylor of the CMM and Microbiology and Parasitology Department.
They believe they may be the only research group in the world with actively growing nano-organisms.
While studying sandstone samples from exploration wells several years ago, Dr Uwins discovered strange filaments on the rocks.
"They were very small -- in the nano range, but we didn't know what they were," Dr Uwins said.
In unfunded research, and exercising their scientific curiosity, they performed numerous tests using state-of-the art ultra high-resolution scanning electron microscopy, transmission electron microscopy, X-ray spectroscopy and DNA staining.
The Lilliputian organisms were in the same size range but distinctly different from controversial fossil nanobacteria reported by NASA scientists in a Martian meteorite in 1996 and by other scientists in various rock types on Earth.
Testing by the three Australian researchers has shown that the nanobes fulfil many criteria to qualify as biological life.
Their colonies grew spontaneously, they contained genetic material (DNA) and their chemical and biological structures were consistent with life. For example, they were composed of biological materials such as carbon, oxygen and nitrogen, and they were membrane-bound structures surrounding a possible cytoplasm and nuclear area.
In true scientific fashion, the scientists tried to disprove themselves by seeing if there could be another, plausible and non-biological explanation for the nanobes.
They discounted many non-biological materials such as crystalline minerals, carbonates, fullerenes, carbon nano-tubes and non-living polymers and concluded it was difficult to propose any known non-biological materials which could account for the observed structures.
Funding -- if only at a shoestring level -- was required to advance the project to the next level of investigation.
In December, the project received $19,000 Australian Research Council small grant support for further molecular and structural analyses to determine whether the organisms were related to bacteria or fungi, or belonged to a different evolutionary tree altogether.
"We will be the first group to perform DNA sequencing on a new life form with important and significant implications in many areas of research including molecular and cell biology, earth planetary sciences, environmental microbiology, medical microbiology, biotechnology, chemical engineering and many others," Dr Uwins said.
"If it is proven beyond doubt scientifically that such small organisms exist, it will be a major contribution to the controversial debate concerning extra- terrestrial life and the origin of life on Earth and other planets."
The debate was triggered in 1996 when NASA scientists in Houston reported the existence of fossil nano-organisms in a 4.5 billion-year-old, potato-sized Martian meteorite which crashed to Earth in Antarctica about 13,000 years ago.
They suggested that the meteorite, known as ALH84001, showed evidence of extra-terrestrial ancient life on Mars. The egg-shaped fossilised objects observed in the Mars meteorite were 20 to 100 nanometres long.
The announcement caused U.S. Vice-President Albert Gore and then House Speaker Newt Gingrich to agree on the need for more government spending and put Mars exploration on the front burner. One of the goals of the Mars exploration program now is to determine whether life started on Mars early in its history.
Critics of the NASA discovery argued that such nano life forms were too small to exist, because they had insufficient volume to contain the enzymatic and genetic material essential for life. They argued that the small size would not allow the supposed nanobacteria to contain RNA and a cell wall.
The same criticisms were levelled at a number of scientists, including geologist Dr Robert Folk of the University of Texas who in 1993 reported that they could see the fossilised forms of ultrasmall microbes in many rocks and minerals found on Earth.
Dr Folk argued that nanobacteria may have escaped biologists' notice because they eluded the conventional tools used to study bacteria.
He said that 200 nanometres was both the smallest size visible with an optical microscope, and the mesh size of the filters commonly used by microbiologists to strain out bacteria from liquids.
It became standard microbiological thought, he said, that because no bacteria smaller than 200 nanometres were seen, that none existed. The smallest known bacteria to date are mycoplasma, minute bacteria which cause a common form of pneumonia, and which can be as small as 200 nanometres.
Since their announcement, NASA scientists have searched for living nanobacteria on Earth.
Dr Uwins said until now, there have been no living representatives for the Martian nano-organisms or other fossil nanobacteria described on Earth in various rock types.
"Therefore it has been hard to convince the scientific community that the fossil Martian nanostructures could be remnant life forms," she said.
Dr Uwins said factors that had made a big difference to the University of Queensland investigations had been the multi-disciplinary nature of the Centre for Microscopy and Microanalysis, and access to the $750,000 ultra high resolution Jeol 890 scanning electron microscope. The instrument is capable of one million times resolution, and is one of only a handful of such microscopes in the world.
She said while the researchers did not yet have conclusive evidence for reproduction and metabolism in nanobes, and while they had not determined their evolutionary development, their evidence strongly suggested the existence of nanobes as biological organisms.
March 19, 1999: Evidence of fossilized bacteria found in Mars meteorites
March 18, 1999
NASA scientists offered new evidence that fossilized microbes could be present in at least three meteorites from Mars. NASA Johnson Space Center's Kathie L. Thomas-Keprta showed that the controversial stone known as ALH 84001 contains many microscopic crystals of the iron-rich mineral magnetite. One-fourth of these are perfectly shaped, same-sized hexagonal prisms free of chemical impurities. Certain bacteria routinely produce such ultrapure magnetite crystals as a means of orienting themselves to Earth's magnetic field. They cannot be formed by any known inorganic process.
David S. McKay raised the possibility that two other Martian meteorites, Nakhla and Shergotty, contain fossilized microbes. His scanning-electron-microscope views show a variety of round and oval forms found in tiny cracks within a Nakhla stone. McKay could not say for sure that they are microfossils. But he did note that the blobs are enriched in iron oxides. This is a common occurrence when a microbe dies and its cell becomes mineralized. Moreover, the suspect features are a few tenths of a micron across, comparable in size to many bacteria. (Many of the putative fossils in ALH 84001 were much smaller "nanobacteria" and according to too tiny to have been viable lifeforms.)
The NASA team will attempt to examine the blobs' interiors for hints of cellular structure and to determine whether they resulted from terrestrial contamination. Unlike ALH 84001, which sat on the ice fields of Antarctica 16,000 years before its discovery, many pieces of Nakhla were recovered almost immediately after falling in Egypt on June 28, 1911. McKay's sample came from a fragment with an intact "fusion crust" that was opened in sterile, clean-room conditions last year.
McKay also showed suspicious features from the interior of Shergotty, though the study of those is just getting under way. Shergotty crystallized from molten rock a mere 165 million years ago, whereas Nakhla is about 1.3 billion years old and ALH 84001 is 4 billion years old. Thus, if microbial fossils really exist in all three of these meteorites, it means that life has existed on Mars throughout much of the planet's history and could be there today. NASA hopes to obtain samples of the red planet via spacecraft as early as 2008, and the agency is currently wrestling with how best to isolate and study the Martian material once it reaches Earth.
March 2, 1999
Some of the researchers who claimed in 1996 to have found evidence for past life in a Martian meteorite now say they have further evidence to support their theories in one, possibly two, other rocks.
They will reveal their findings at a forthcoming conference in America. The announcement will once again arouse great controversy in the scientific community, which was far from convinced by the 1996 evidence.
Read the article by Dr. David Crawford on BBC News Sci/Tech.
University of Hawaii
August 14, 1998
One year ago, UH scientists Ed Scott, Sasha Krot and Akira Yamaguchi announced that the carbonates they studied in a sample of the Martian meteorite ALH84001 appeared to have formed in an impact at temperatures that were too high for organisms. Scientists at NASA and Stanford University, who argue for life in the Martian meteorite, countered that the disk-shaped grains they studied were diffferent from the grains examined by Scott and his colleagues.
Since then Scott and his colleagues have used electron and optical microscopes to study carbonates of all shapes and sizes in over a dozen samples of the Martian meteorite. They wanted to know how the rock had been deformed, fractured and heated by impact and how and when the carbonates had formed in the fractured rock.
The UH scientists found that the disk-shaped carbonates, like the grains they had studied earlier, appeared to be completely enclosed in the rock. Detailed studies of the carbonate shapes and compositions showed that they had grown in fractures as the rock had been squeezed and the fractures closed. The shapes and heterogeneous distribution of carbonates in the sealed fractures indicated that the carbonates grew rapidly from a hot fluid that was present in the rock when the fractures were opened and then closed by impact. The carbonate shapes and distribution could not be explained by growth from a fluid that was slowly percolating through fractures at low temperatures, as the NASA scientists inferred.
"Our study should help to resolve the controversy over the formation temperature of the carbonates," says Scott. "We conclude that the existing carbonates formed at high temperatures by impact heating of carbonates that had formed earlier at low temperatures in pores between crystals."
Two additional teams of scientists using electron microscopes report on their studies of the famous Martian meteorite in the current issue of Meteoritics and Planetary Science. They also conclude for entirely different reasons that NASA scientist David McKay and his colleagues were mistaken in claiming to have discovered evidence of Martian microorganisms.
"The evidence against life in the Martian meteorite has been steadily accumulating during the past year," says Scott. "At the same time, more scientists than ever before are studying Martian meteorites for clues to past conditions on Mars." Were there once oceans and rivers on Mars? What was the composition of the early atmosphere on Mars? Could life have evolved on Mars? Not since astronauts landed on the Moon has there been so much excitement about rocks from space.
"Mars mania" is apparent in the current issue of Meteoritics and Planetary Science, which contains 19 papers on Martian meteorites by 50 scientists working in six countries. Even though McKay's group is probably wrong about life in the Martian meteorite, their work has started an explosion of interest in the possibility of life on the red planet and elsewhere in the solar system, says Ed Scott.
Scott and Sasha Krot both work in the Hawai'i Institute of Geophysics and Planetology, which is part of the School of Ocean and Earth Science and Technology at the University of Hawai'i at Manoa. Akira Yamaguchi, formerly with HIGP, now works at the National Institute for Research in Inorganic Materials in Tsukuba, Japan. Their work at UH was partly supported by a grant from NASA to HIGP Director Klaus Keil, and a grant from the National Science Foundation.
Life on Mars? Read "Planetary Sciences Research Discoveries" on line.
Last year's news release about the work of Scott, Yamaguchi and Krot is on the web.
ASTRONET's previous news on the debate over life on Mars
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