13 Things That Don't Make Sense (12 page)

On the positive side, as we have noted, this result again stands against the argument that some compound, probably hydrogen
peroxide, was responsible for producing radioactive gas from the nutrient—a prolonged lack of light would not affect the chemical
process. But neither does it make a lot of sense if biology was involved.

One of the strongest arguments against life existing on Mars has always been the harshness of the environment: low temperatures,
a wispy thin atmosphere, and the lack of liquid water all count against the development of living organisms. Levin counters
this by pointing to the many subsequent discoveries of
extremophile bacteria
on Earth. Microbes have been discovered thriving in some of the most inhospitable places on our planet: in the freezing wastes
of Antarctica, in the violent and scalding water around deep ocean vents, in volcanic rock, even in radioactive waste. At
the time of the Viking mission to Mars, the existence of life in such places was unthinkable, but now it seems quite reasonable
that life could take hold in Martian soil. What doesn’t seem reasonable, given the tenacity of Earth’s extremophiles, is that
the microbes had died during a week in the dark. The experiment with the second lander, where microbes were apparently thriving
under rocks, stands against that.

One possible explanation is that the sample taken from normal, exposed soil contained microbes that needed light, but there
are other organisms, living under rocks, that don’t. In the end, all we can say is that it does muddy the waters.

WHATEVER
the truth about the complex web of results, the weight of evidence against the detection of Martian life—the negative GCMS
result coupled with the hydrogen peroxide argument—was deemed compelling enough for the mission leaders to conclude that they
hadn’t found life.

Levin still remembers the shock of sitting in the first press conference to announce the outcome of the Viking experiments.
Jim Martin sat next to him, and together they reeled as their team leader, Harold Klein, made the official announcement. The
Viking mission had found “no evidence” of life on Mars, Klein stated.

“When he said that,” Levin recalls, “Jim Martin dug me in the ribs and said, ‘Goddamnit, Gil, will you get up and tell them
you detected life?’ ”

He didn’t. He says he was cowed by his relatively junior status, and that he also wanted to be conservative; he “didn’t want
to be out of step with anyone else on the team.” He maintained this silence for ten years, the first three of which he spent
trying to find alternative explanations for his own results. It was during that time that John Milan Lavoie Jr. got in touch.

Lavoie was an MIT graduate student who had performed many of the tests on the Viking GCMS. He was embarrassed at the way the
GCMS results had been appropriated to quell speculation over life on Mars; the instrument’s readings, according to Lavoie,
should be treated with extreme caution.

Lavoie told Levin that the MIT-built apparatus had repeatedly failed in tests before launch. When given a sample of Antarctic
soil, it had failed to find any organic compounds. That news was particularly striking to Levin, because all the various Viking
experiments had been given the same sample to test prior to their acceptance onto the mission. When Levin had tested the sample—it
was known as Antarctic Soil #726—his Labeled Release experiment recorded a significant rise in radioactive carbon in the air
above the sample: Antarctic Soil #726 seemed to contain life.

A few years later, one of the engineers on the GCMS project approached Levin with a story similar to Lavoie’s. Arthur Lafleur
had been brought onto the project to help it meet its mission deadline, and had coauthored the paper that reported the negative
findings on Mars. But, he said, the machine really wasn’t anywhere near as sensitive as it needed to be to refute Levin’s
results.

Levin and Lafleur published a paper together in 2000, exposing for the first time some of the preflight results from the GCMS
experiment. It had repeatedly failed to find organic compounds that were present in samples. Antarctic soils contained ten
thousand organisms per gram of soil, but even at concentrations of 3 billion organisms per gram, the GCMS would have failed
to spot organic compounds. Martian soil can probably contain no more than 10 million organisms per gram. In short, they said,
the GCMS “was unequal to its assigned task.”

By then, ironically, this was not a controversial claim. In 1996, at a NASA press conference, the associate administrator
of NASA, Wesley Huntress, had said the same. The press conference was to announce the possible discovery of the signature
of life within Martian meteorite ALH84001 (the issue remains unresolved today). The rock had arrived on Earth thirteen thousand
years ago; it was recovered from Alan Hills in Antarctica in December 1994, and NASA scientists had found what seemed to be
fossilized microbes.

A journalist asked the obvious question: Had NASA changed its tune? If this rock says there was life on Mars, how come the
Viking GCMS found no organic material? Easy, said Huntress. For starters, the rock is a hint at past life on Mars; it has
nothing to say about the present. Second, the Viking landers landed in a desert in order to find a safe place to touch down,
and that “kind of reduced the probability of finding organic material on the planet should it be there.” And third, Huntress
added, the GCMS simply wasn’t sensitive enough to rule anything out.

In 2006 the final nail was driven into the coffin of the GCMS experiment when a team of twelve researchers, including NASA’s
Mars expert Chris McKay, published a paper on the experiment in the
Proceedings of the National Academy of Sciences
. The sensitivity of the GCMS experiment, it concluded, was several orders of magnitude lower than originally thought. “The
question of whether organic compounds exist on the surface of the planet Mars was not conclusively answered by the organic
analysis experiment carried out by the Viking Landers,” the paper states.

AT
the party to celebrate the tenth anniversary of the Viking probes, Gil Levin stood up and gave a talk about all the possible
reasons the Labeled Release experiment could have gotten a false positive. He listed fifteen or so and demolished each one.
At the end of his talk he told the audience it was more likely than not that Viking had detected life. The reaction was not
favorable—Levin describes it as “close to an uproar.” He was not invited to the thirtieth-anniversary celebrations.

So how does he go forward from here? With caution, it seems. It would be easy for Levin to call for a rerun of his experiment,
but he’s not prepared to do that. He is advocating a careful approach to the case for life on Mars. As committed as he is
to the idea that his instruments found evidence for life, he is not blind to all other interpretations. Even when other scientists
come out with new arguments or evidence in support of his Viking results, Levin’s attitude is surprisingly conservative.

Joe Miller, for instance, a cell biologist at the University of Southern California in Los Angeles, thinks he has spotted
circadian rhythms in the gas emission from the Viking Labeled Release data. According to Miller, whatever was chomping on
the free radioactive lunch showed the kind of cyclic metabolism we have; the gas release was not constant but varied in a
cyclic fashion with a cycle of 24.66 hours—the length of a Martian day. Such rhythms in metabolic emissions are commonplace
on Earth, and the discovery seems to rule out the idea that reactions involving nonorganic compounds such as hydrogen peroxide
were responsible for the gas release. In 2002 Miller declared himself “over 90 percent” certain the Viking landers had found
life.

Levin is not convinced by Miller’s analysis, however. He recruited a math professor from the University of Washington to take
another look, and he didn’t find any significant pattern in the emissions data. “We didn’t think it looked so positive,” he
says. When an Italian research group started to say they had found circadian rhythms, they got a lukewarm reception from Levin,
too. “We’re not satisfied,” he says.

Levin knows how he would like to resolve the issue: he has redesigned the Labeled Release experiment to use
chiral molecules
in the feedstock. Certain molecules—glucose is one—come in two different forms. Just as left and right hands look similar
but are not identical, chiral molecules have a subtle “handedness.” While it makes no difference to their chemistry, terrestrial
organisms will process one of these chiralities, but not the other. Probe the gas emitted in the new Labeled Release test
for chirality, and you’ll see whether life is involved in the emission: if there is a massive mismatch between the chiralities,
you’ll know the emission is biological, not chemical in origin. Other scientists are keen on the idea: Wesley Huntress expressed
an interest, and NASA’s Chris McKay, the man who leads the plans to terraform Mars for human habitation, said he’d like to
copropose the experiment for a future mission. But Levin is cautious even here; the idea is not without its flaws, he says.
We don’t know whether Mars life has chirality preferences, for example. “It’s possible they are both metabolized equally,”
he points out.

For now, then, all we have is the thirty-year-old results of an experiment that took place on the alien world 200 million
miles away.

FOR
some, the Viking mission is all in the past; there is simply no point in discussing it any further. Huntress, for example,
who is now the director of the Carnegie Institutes of Washington, D.C.’s Geophysical Laboratory, still has a lot of respect
for Levin. The problem, he says, is that astrobiology has changed since 1976. Any discussion of the Viking results has been
rendered almost meaningless by the ongoing struggle to define what life is, and the conditions it needs to arise or survive—especially
in light of the newly discovered extremophile bacteria.

Robert Hazen, an expert on the evolution of life who works upstairs from Huntress, offers a similar perspective: no one can
agree on what a good detection of life would look like, he says. What’s more, the life specialists are no longer so involved;
after Viking, the biologists all left the field.

The void, it seems, was filled by geologists and atmospheric scientists. Almost everything in NASA’s armory since Viking has
been about detecting what we think are the
conditions
for life—at least life as we know it. Instead of looking for life, we are obsessed with finding out about the composition
of the surface of Mars, looking at the rocks, and the patterns they contain that might or might not indicate the past or present
existence of water. As you scroll through NASA’s list of missions to Mars, it becomes clear that the biologists had their
one chance with Viking and failed. The missions are now the preserve of other disciplines; before Viking and since, it has
all been about rocks and weather.

The Mars Observer, launched in 1992 and lost before it entered orbit, “was designed to study the geology, geophysics and climate
of Mars.” In 1996 Pathfinder took photos, charted the weather, and carried out chemical analyses of rock and soil. Mars Climate
Orbiter, lost on arrival on September 23, 1999, was designed to function as an interplanetary weather satellite. Mars Polar
Lander was meant to dig for water, though it was lost on arrival on December 3, 1999. The Mars Global Surveyor has been monitoring
the Martian surface, atmosphere, and weather, and investigating the composition of the planet’s interior since September 1997.

Then, in 2004, came NASA’s “robotic geologists,” Spirit and Opportunity. The Mars Odyssey spacecraft continues to send us
information about Martian geology, climate, and mineralogy. Mars Express is now searching for subsurface water from orbit
(the mission’s lander, Beagle 2, was lost on impact but would at least have looked for organic molecules). The Mars Reconaissance
Orbiter is providing “an astoundingly detailed view of the geology and structure of Mars.” At the time of this writing, Phoenix
is on its way to the red planet. It will look for water ice and organic molecules.

Looking for life on Mars was a blip, a onetime opportunity, it seems. By almost every reasonable measure, we found it, but
haven’t looked again. Although almost no one doubts life
could
have existed on Mars in the past, and many experts think there
is
life on Mars now, it is Carl Sagan’s conclusion—the possibility that we actually detected life on Mars is “vanishingly small,”
to borrow his phrase—that stands as the scientific consensus. And so the geologists can poke around with Mars robots, worrying
about rock formations and liquid water, and managing not to draw a conclusion. There’s no one who wants to stick their neck
out like Levin did. And no one has to.

IF
not a scandal, it seems a shame. This overwhelming caution, this softly-softly approach to looking for life beyond Earth,
is postponing a glorious moment in the story of humanity. Peter Ward, a professor of biology, earth and space sciences, and
astronomy at the University of Washington in Seattle, wrote a marvelous book about NASA’s attempts to find (and create) life.
In
Life as We Do Not Know It
, Ward is unequivocal about the importance of the quest to discover alien life. “The discovery of life beyond Earth would
be monumental,” he says. So why aren’t we looking for life, not just tiptoeing around it? Apart from budgetary prudence and
a sense that the last people who did that got their fingers burned, there is no obvious answer. It’s not like we will find
signs of microbial life beyond Earth and then stop looking for anything more. There’s an even more important path to follow
once we have made the discovery.

According to Martin Rees, the English astronomer royal and president of the Royal Society, “the prime exploratory challenge
of the next fifty years is neither in the physical sciences nor in (terrestrial) biology. It is surely to seek firm evidence
for, or against, the existence of extraterrestrial intelligence.” Rees made the statement in a book laying out what twenty-five
distinguished scientists consider to be the most important paths for science in the next fifty years. Elsewhere he argued
that if he were an American scientist testifying to Congress, he “would be happier requesting a few million dollars for SETI
[the search for extraterrestrial intelligence] than seeking funds for conventional space projects or particle accelerators.”
To Rees, the most distinguished scientist in Britain, and an international tour de force in astronomy, it really is that important.