Last August, NASA scientists held up photos of a pockmarked, potato-size rock and said that, at last, they had found evidence that life once had existed on Mars.
It seized the collective imagination, this idea that scientists had coaxed one of the great mysteries of the universe from a putty-colored rock.
A flurry of speculation, questioning and rhapsodizing ensued, but eventually was supplanted by news of our own planet.
Behind closed laboratory doors, however, the din only grew louder. The questions that meteorite so forcefully posed were so seductive that it sent researchers from Chicago to Seattle, from Bologna, Italy, to Manchester, England, on what many consider the quest of a lifetime: to offer their own evidence on one of the greatest questions of science.
Now, as the Mars Pathfinder mission is on course for a July 4 landing on the Red Planet, a look behind those laboratory doors provides a rare glimpse of the intimate details of science–the bursts of creativity, the drudgery of data collection, the burdens of competition.
Researchers are working faster, rushing to publication earlier, pushing themselves and their technologies, and even testing their loyalties.
“It’s not what people think it is,” said researcher Laurie Leshin. “It’s not all dispassionate.”
After the discovery, NASA locked up all its samples of the meteorite, labeled ALH84001, until proposals for studying it could be evaluated.
The question was so alluring, though, that some scientists couldn’t leave it alone.
Some already had samples of the rock sitting on shelves or mounted on slides. Others got tiny chips through a kind of black market that emerged as researchers around the world cajoled their friends for a chance to work on the hottest topic in science.
Now, the official research channels have been reopened. NASA has just awarded $1.5 million to 16 separate teams to study the meteorite. In July, the National Science Foundation will be awarding money to another batch of scientists who submitted proposals.
The first wave of experiments neither proved nor disproved the theory.
But it has already shown how simple human curiosity about these precious flecks of Mars are driving research, as well as the researchers into new worlds.
Probing the globules
As Laurie Leshin watched NASA scientists announce that they had found evidence of life in a meteorite from Mars, she was, in her mind, already wielding her cesium ion gun, drilling microscopic holes into that rock.
Only 31 and a mere adjunct professor at the University of California at Los Angeles, Leshin had been studying Martian meteorites for years.
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As a little girl, she got chills looking at the first eerie, reddish photos from the surface of Mars. She still thinks something could have lived there.
But the NASA research? She found some of it woefully crude.
Rattling around in her top desk drawer at UCLA was a leftover fragment of the same meteorite. She had analyzed it in 1994, years before anyone thought it contained evidence of life.
Looking at it then, she had noticed small, orange spots. Carbonate globules, people call them now.
She snapped off some pictures, thinking, “I’ll have to do some work on those some day.”
These spots, the NASA scientists were now saying, contained evidence of life. They cited earlier work showing the spots had formed at temperatures low enough for life.
She had read that paper, and she thought it was wrong.
Temperature is key. If the carbonate globules were formed under great heat, nothing could have grown there. “It’s the one thing that can destroy the theory in a fell swoop,” said Allan Treiman of the Lunar and Planetary Institute.
Leshin dropped everything, even putting off work funded by another NASA grant.
She was at UCLA on a two-year teaching fellowship, in the early and uncertain stages of her career. High-profile research could help her tremendously. A high-profile goof-up could be disastrous.
Worse, Leshin and another team of scientists–including Edward Stolper, her former thesis adviser and “academic father”–were doing similar experiments.
“The whole thing is highly charged,” she said. “This is my first time competing directly with another team of scientists. It’s not all fun.”
She spent weeks at the controls of a machine called a mass spectrometer, using a stream of cesium ions to wash away layers of atoms of the meteorite the way water from a garden hose makes a hole in dirt.
With a magnet as big as a dishwasher, the machine vacuumed up the shavings from this drilling. Just as a prism breaks light into a rainbow-like spectrum, the big magnet made a sort of rainbow out of atoms–based not on color, but mass.
Not all atoms are alike, even atoms of the same element. They can have differing numbers of neutrons, making them into “isotopes” and changing their mass.
Furthermore, different ratios of these isotopes are likely to form at certain temperatures.
So by looking at the “rainbow” cast by these oxygen atoms of different masses, Leshin could determine the proportion of the isotopes in the meteorite–the ancient temperature record she sought.
Her findings, announced in a March conference, suggested just two ways the isotopes could have been made in these proportions. Both had conditions too extreme for life.
“It is very reasonable to say that life could have started on Mars,” she said. “But in my opinion, this is not the right rock to look at.”
The team she competed with, though, isn’t quite sure.
John Valley had spent much of his 25-year career probing Earth rocks to determine how hot they had been when they formed.
Valley, chairman of the geology and geophysics department at the University of Wisconsin, realized that was precisely the question scientists were asking about the Mars rock. He joined the fray, leading an experiment similar to Leshin’s.
Though NASA had slapped a moratorium on cutting more samples off the rock, there were a number of samples already out for study.
Valley asked Everett Gibson, a member of the NASA team, for a piece of the rock. At a scientific conference last fall, Gibson handed over a container holding a chunk small enough to pass through a paper clip.
Valley packed up his precious sample and flew to Scotland, where he and other scientists had been refining a process to study oxygen isotopes in Earth rocks.
The group spent 240 hours over 10 days training their beam of high-energy ions on 24 spots on the meteorite.
Their analysis revealed a pattern he recognized from low-temperature Earth environments. Their conclusion: This pattern could only be formed at temperatures low enough to foster life.
A closer look
Late one night, alone in his Georgia lab, John Bradley’s heart raced when a worm-like image appeared on the phosphor screen of his electron microscope.
In another sample of this meteorite, the NASA team had found similar worm-like structures, which they believed were micro-fossils of ancient Martian bacteria.
What he was seeing, though, had unfortunate implications for the NASA team, some of whom are friends.
Bradley was one of the few people who had known about the NASA research before publication. “For 2 1/2 months, we were sitting there thinking this is the greatest announcement of the millennium,” Bradley said.
With two colleagues who had a sample of the meteorite, he began to look for himself.
“The first thing I noticed was that it was absolutely beautiful,” he said. “It had this grayish surface with these orange carbonate regions. While looking at them, I couldn’t help but feel I might be looking at an ancient Martian colony.”
Bradley rejected the method the NASA team used to cut its samples for the electron microscope, because it tended to damage and distort them.
“A glorified salami slicer,” he said, even though he had helped develop the system.
Instead, he used a beam of argon ions to erode single layers of atoms until the sample was wisp-thin.
Then he saw them–the worm-like structures. “I thought, this is it!” Bradley said.
The NASA team had speculated that bacteria had produced the worm-like strings of magnetite crystals, just like some Earth bacteria do. The next step, even the NASA team acknowledged, was to begin looking for cell structures in these crystals.
“I had expected to see a daisy chain of crystals,” Bradley said. “What I found instead was that the worm was a single crystal, like a pencil, with a peculiar type of defect. This was real bad news.”
He recognized those crystals right away. He had done graduate work on something called “whiskers”–a shape minerals take when they are formed in volcanoes or during violent impacts.
The “fossils” had not been formed in cool temperatures inside bacteria, he concluded, but in extreme heat.
“There appear to be insurmountable problems,” he said, of the NASA thesis.
Drawn to the research
Deep in the subbasement of a 1930s building on the campus of the California Institute of Technology, back in a room that used to store fossils, Joseph Kirschvink built a nearly perfect place to measure the pull of a magnet.
A magnet freak, he built his first electromagnet from wire and foil and a paper-towel tube when he was 11.
Now he studies how magnetism is at play in the Earth, in bacteria, in fish, even in people.
“I guess you could say I was drawn to it,” he says, then laughs, as if he hadn’t said or heard that before.
The room he had built is, in fact, a massive anti-magnet. Tons of magnetized steel embedded in the walls block out Earth’s magnetic field.
Shortly after NASA announced its discovery, a member of the team called.
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“He said, `Joe, we ought to be able to answer some of the questions about this rock with magnetism,’ ” Kirschvink said.
Looking at a pebble so small he wouldn’t have felt it in his shoe, Kirschvink spied a minuscule crack, a place where he could stake an intellectual foothold.
This was his thinking:
Magnets have direction, as if they are filled with arrows, all pointing the same way.
Rocks lose their magnetic direction when they are heated, but may regain it when they cool.
Kirschvink wondered: What if the direction of the magnetic field is different on either side of the crack? That would mean the magnetic field was there before the rock cracked, and that the crack knocked the arrows out of alignment. More important, it would also mean the rock had not been heated since it cracked.
On the other hand, the magnetic field might be aligned on either side of the crack. That would suggest that the rock had cracked, then heated up; as it cooled, its magnetic direction would have realigned.
As the data came in, it was clear the magnetic fields were out of alignment.
That meant that since the crack appeared in the rock billions of years ago, it has never been heated above 350 degrees Celsius, and probably not above the boiling point of water.
“We have a rock, sitting on the table, that we know could have brought bacteria from Mars to Earth,” Kirschvink said.
Narrowing the age
Before any claims had been made that the meteorite held evidence of life, Meenakshi Wadhwa had spent months trying to figure out how old it was.
Wadhwa, now the 29-year-old curator of meteorites at Chicago’s Field Museum of Natural History, had earlier measured the decay of radioactive isotopes to date the carbonate globules at about 1.4 billion years old.
That would mean they had formed when Mars was thought to have been cold, dry and less hospitable to life.
She reported her findings at a conference in Berlin last summer. Just weeks later, NASA made its announcement, citing another study that dated the carbonate globules at 3.6 billion years. Mars probably was warm and wet then, like Earth is today.
“That is not the age of those carbonates,” Wadhwa said.
She could not immediately run the tests again. Her tests had dissolved her sample.
Instead, she rechecked her old data and came up certain that she was right.
“Certainly a younger age makes the case for life more improbable, but it doesn’t rule it out completely,” she said.
The view from NASA
The last 10 months have been difficult for the NASA team, and their lab time has been limited.
Lead author David McKay underwent quadruple bypass surgery and still cannot work full time. A key member of the team, Kathie Thomas-Keprta, had her first baby.
“I was pregnant throughout this whole thing, so I don’t know if my hormones were acting up, but I would have days where I was absolutely convinced we were right and other days when new information would come out and I would be doubting it,” she said.
In her view, the most potentially damning evidence comes from John Bradley, who could not find evidence of cell structures that would indicate life.
Team member Everett Gibson has taken on the job advancing, and defending, the work.
Much of the opposing research has been flawed or off point and has not taken the entire body of evidence into account, Gibson said.
“So far, everything that has been thrown at us we can explain, and I am not being boastful,” he said.
For his part, Gibson has grown even more convinced that the meteorite once harbored life and that the pursuit of the question has enlivened science.
“This is a situation where science wins,” he said. “We are going to be better prepared in the decade ahead so that when we do get samples from Mars we will know how to attack them and understand them.”
What has been good for the profession has been hard on some individuals, though.
“I’ve seen the jealousy,” he said. “I’ve seen people go into depression because they didn’t do it, that they were crushed because they had dedicated their whole life to finding life on Mars.”
The next wave
One day soon, five tiny pieces of Mars are expected to arrive on the desk of University of Wisconsin researcher Bill Barker.
That will be plenty.
“You can work the rest of your life on a piece of rock the size of a black-eyed pea,”said Barker, a geomicrobiologist.
Normally, Barker studies the traces left behind by creatures that lived in moist cracks inside Earth rocks. That’s just the kind of environment in which the Martian bacteria are believed to have developed.
Barker will begin his extraterrestrial fossil hunt by buffing each piece until it is “way thinner than a human hair.”
Barker will then descend to the basement of the geology building in the dead of night and enter a dark, stuffy room, home to a 9-foot tall microscope.
Fewer vibrations shake the high-resolution microscope in the off-hours, because virtually no one walks the halls or drives by.
By beaming electrons through the sample, the microscope will give a minutely detailed look at structural and chemical makeup.
If the rock harbored life, it likely also was shaped by water, which would lead to the creation of clay minerals. Like a vandal etching “Kilroy was here” into a monument, bacteria living in rock lend a distinctive texture and chemistry to clay minerals.
Such work is only for the patient.
“You almost have to adopt it as a religion,” he said.