A Galactic Warrior, With Hypothetical Enemies
April 24, 2004
By CLIVE THOMPSON
When NASA's Spirit and Opportunity probes landed on Mars
recently, they were carrying some of the most sophisticated
technology ever sent to that planet. But they might also
have been carrying some illicit stowaways: microbes.
That is what John Rummel worries about every day. He is
NASA's planetary protection officer, a sort of cosmic
border guard, and his job is to keep the planets safe from
each other's contagions: to prevent Earth from being
infected with extraterrestrial bugs and to make sure Earth
bugs don't stow away on space probes and infect other
"The best way to find life on Mars," Mr. Rummel said, "is
to bring it from Florida."
In the last few years his work has heated up as probes zip
with increasing frequency through a solar system that seems
more and more likely to harbor extraterrestrial life.
NASA's Stardust probe collected dust from a comet and will
bring it to earth in 2006. This summer a probe will be
launched for Mercury, and others are planned for Jupiter's
icy moon Europa, which is potentially ripe with water in
liquid form, considered essential for creating life. And in
January, President Bush proposed building a lunar base to
be used eventually as a launching pad for a manned mission
In a little more than 10 years, Mr. Rummel will face his
biggest task when NASA launches a probe that is to bring a
chunk of Martian soil to Earth, a contamination risk so
significant that exobiologists - people who study life
outside the atmosphere - say that NASA will need the decade
to build a facility airtight enough to handle the sample.
One might expect that the subzero environment of space
would be enough to kill any life. But as exobiology studies
have shown, microbes can withstand punishing conditions. In
April 1967, NASA landed the Surveyor 3 probe on the moon;
when astronauts brought parts of the probe back almost
three years later, they discovered still-viable microbes
that had survived the launching, a lack of oxygen and
bombardment with radiation. Many scientists believe that
the radiation on Mars would instantly kill any Earth
microbes, but there is no way to be absolutely sure, Mr.
"Microbes are pretty much about as tough as silicon," he
said. "Your average run-of-the-mill microbe can take as
much as your average run-of-the-mill microchip. Some of the
microbes are even tougher than those chips."
To rid a probe of life, NASA engineers assemble it in clean
rooms where filters pump out bacteria; many parts are baked
at 233.1 degrees Fahrenheit - what technicians call the
casserole technique - to sterilize them. Before Mr. Rummel
can approve a launching, his team must verify that it meets
standards set by the Committee on Space Research, an
international space-exploration group: it can have no more
than 300,000 spores on its exposed surface, an amount so
tiny it would fit on the head of a pin.
At its heart, though, planetary protection is a weirdly
philosophical task, simply because there is no proof that
life exists anywhere else. What precisely are we protecting
against? Mr. Rummel will bend over backward to keep alien
life from harm, while cheerfully admitting he is not sure
there actually is any. Planetary protection is thus like an
Xtreme form of environmentalism. When Galileo finished its
mission to explore Jupiter last fall, NASA chose to destroy
the probe by flying it into the planet, so it wouldn't
accidentally crash on Europa and infect it.
But this caution, Mr. Rummel notes, is not merely about
protecting life. It is about protecting science. If a probe
were to accidentally seed Mars with Earth microbes,
scientists might later mistake them for natives. "The point
is to be able to tell" that there is nothing there, he
But that poses yet another existential puzzle: if alien
life is sufficiently alien, will we know when we have found
it? "If there's life up there, how would we recognize it?"
asked Margaret Race, an ecologist whose
planetary-protection research for the Search for
Extraterrestrial Intelligence Institute is financed by
NASA. "It's an interesting scientific, social and religious
For the public, the truly hair-raising danger comes from
bringing alien material to Earth. "What your body might
take as a little lump of dust might actually be alive," Mr.
Rummel said. "It might actually find our bodies to be a
useful resource," or cause environmental damage.
Nonetheless, Ms. Race and Mr. Rummel support a
sample-return mission, because they believe it is possible
for NASA to build a sufficiently well-quarantined facility
to study Martian samples. "We know we can do this," Ms.
Race said, though it will take years and years.
This glacial pace angers critics. They say planetary
protection, with its neurotic level of caution, is slowing
Martian exploration to a crawl. If NASA didn't have to
laboriously remove microbes from probes, it could afford
many more projects and execute them more quickly, says
Robert Zubrin, president of the Mars Society, a group that
lobbies for a manned mission to Mars.
Mr. Zubrin takes a contrary position: Mars and Earth do not
need protection, he says, because they have already
contaminated each other via naturally occurring space
debris. Asteroid impacts regularly send bits of the planets
flying off into space, and those chunks often reach other
planets. Scientists estimate that 88 pounds of Martian
rocks land on Earth every year, Mr. Rummel says. There is
even a theory, called panspermia, which contends that life
was originally carried to Earth from elsewhere, possibly
Mars, by interplanetary debris.
"The arguments for planetary protection stem from an
earlier belief that the planets were originally quarantined
from one another, and they're not," Mr. Zubrin said. "It's
like having the customs people using quarantines to stop
people from bringing Canadian geese across the border.
They'll fly over anyway. You can stop the tourists, but you
can't stop the geese." Because humans are more resourceful
and adaptable than robots, he says, only a manned probe can
settle the question whether life currently exists on Mars.
The idea of sending live astronauts to Mars makes
planetary-protection advocates shudder. "When you talk
about sending people, you're talking about spewing
fountains of bacteria," said Norine Noonan, chair of NASA's
Planetary Protection Advisory Committee and dean of
sciences and mathematics at the College of Charleston.
And while Mr. Zubrin's theory sounds neat, Mr. Rummel says,
it is ultimately just a theory. There is no scientific
proof that any Martian rock has carried life to Earth, and
NASA should proceed cautiously.
Even those who devoutly believe in panspermia, like Chandra
Wickramasinghe, director of the Cardiff Center for
Astrobiology in Britain, say their theory ought to make
planetary protection more important, not less. If it is
true, Mr. Wickramasinghe said, that "the basic genetic
basis of life is constantly raining down on planets" and
that the solar system shares a common heritage, then
Martian microbes would be able to infect genetically the
human ecosystem. (Mr. Wickramasinghe became controversial
last year for his much-ridiculed suggestion that SARS might
have had extraterrestrial origins.)
In the end Mr. Rummel's art is one of managing ignorance,
not knowledge. He safeguards against surprises. And, he
says, the thing Mars is doing best lately is surprising us.
"What worries me about Mars is that it appears to be
listening," he said, half-joking. "You have Mars saying,
`Oh you want water? O.K., I'll give you water.' It's a very
interesting place. It's much more interesting than we could