It’s so easy to get carried away by wishful thinking. History shows that
this has happened many times before in science. In particular, the data-
starved, emotionally charged science of extraterrestrial life has been,
and remains, vulnerable.
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Despite the good intentions behind the “value neutral” stance, scien-
tists sometimes take this position too far. It can lead to an “it’s not our
problem” approach toward the serious societal issues created by our
rapid advances in knowledge. With power comes responsibility. Science
has allowed the technical advances that have created many of the most
crucial issues facing our species, such as global warming and the
promise and peril of genetic engineering.
Maybe the fact that astrobiology is so blatantly value-laden will be
good for us, help us get over the “value free” myth that allows science
to weasel out of its share of responsibility for many challenging aspects
of modern existence. With astrobiology, there is no hiding from societal
issues that go far beyond the strict search for physical truth. In the first
paper in the new journal Astrobiology, published in spring of 2001,
NASA scientist and administrator David Morrison addressed the soci-
etal responsibilities inherent in NASA’s astrobiology program:
Astrobiology research has implications that are felt beyond the con-
fines of the laboratory. As our understanding of living systems and the
physical universe increases, we will confront the implications of this
knowledge in more than just the scientific and technical realms. To
understand the consequences will require multidisciplinary considera-
tion of areas such as economics, environment, health, theology, ethics,
quality of life, the sociopolitical realm, and education. Together we
will explore the ethical and philosophical questions related to the exis-
tence of life elsewhere, the potential for cross-contamination between
ecosystems on different worlds, and the implications of future long-
term planetary habitation and engineering.
Clearly, ethical questions are an inseparable part of this challenging
new scientific movement. This can only help, because we must some-
how learn to do science that is guided by values but not distorted by
wishes. It’s a tough but necessary distinction. If we want to survive long
enough to become a player on the galactic stage, we are going to need
to incorporate humanistic and biophilic values into our scientific cul-
ture. Only through acknowledging this can we help humanity to use
our growing technical prowess wisely. And we can help science, an
institution plagued with critics and doubters, to win friends and influ-
ence people.
The possibility of contact with ET life presents many new ethical
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quandaries. For example, what if we discover aliens who are so alien
that we cannot tell if they are “intelligent” or not? How should we
treat them? What rights would they have? In my house and yard, I’ve
used chemical poisons to kill wasps and rodents, and traps to remove
other pests. Yet chemical warfare and kidnapping are both appropri-
ately seen as criminal acts. Personally, I believe that mistreatment of
dolphins, including involuntary confinement, is criminal. Where do we
draw the lines? Are “primitive” life-forms on other planets to be exter-
minated if they interfere with our plans?
A current intersection of technical and ethical questions is in plane-
tary protection. This is the name we give to our efforts to behave like
responsible, grown-up members of our solar system, and avoid having
unprotected curiosity. While we explore the planets, we must vigilantly
guard against “forward contamination” (the accidental spreading of
Earth germs to other planets), and “back contamination” (the acciden-
tal infection of Earth with alien germs).
We know that some forward contamination has already occurred.
Earth’s Moon is littered in a few places with unsterilized spacecraft and
human waste. The documented survival of Earth organisms on our
Moon junk demonstrates that we could inadvertently infect other
worlds—like birds propagating seeds in their scat—if we carelessly
leave our shit around the solar system.
The only way to practice “zero tolerance” of accidental contamina-
tion would be to never go exploring. And one way to make sure that
you never hit anything or anybody with your car would be to never,
ever, take it out of the garage.
In the case of back contamination, the worst-case scenario is pretty
bad: by introducing alien organisms we could cause an unstoppable
global ecological disaster.* This first became a consideration in the six-
ties when we brought lunar samples back to Earth. The Moon rocks
were all dead as, well, rocks, and quite a bit deader than any Earth
rocks. Now, as we make new plans to retrieve samples of comets and
freshly picked Mars rocks, back contamination is once again on the
front burner.
NASA actually has an official “planetary protection officer.” Is that a
cool job title or what? I even thought about applying when the job
opening was announced a few years ago. Could a guy like me really
*Oh, well. You win some, you lose some.
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259
become planetary protection officer? Why not? I’ve got a Ph.D. in plan-
etary science, a bunch of NASA grants, a respectable publication rec-
ord, no criminal record to speak of, and besides, I really care about my
planet and all the others. Unfortunately the job carried one major
drawback—it was located in Washington, D.C., an understandable
place to put the NASA Office of Planetary Protection, but outside of
my habitable zone.
NASA’s current planetary protection officer, the man now responsi-
ble for protecting Earth as well as the rest of the solar system, is John
Rummel, an exobiologist with a background in ecology. Rummel is
perfect for the job. He is actively involved in astrobiology and takes his
responsibility seriously, but he is also possessed of an impish sense of
humor and is not above using the absurdity of his title for some good
laughs. I’ve heard him introduce himself at a meeting by saying, “John
Rummel, Planetary Protection Officer. I protect the planets. All the
planets, all the time.”
Some mock our concerns about planetary protection. It’s an easy
subject for ridicule because you can convincingly argue that the chances
of an interplanetary infection are so low as to seem virtually impossi-
ble. And besides, some even say, who cares if we infect other planets?
They’ll thank us later. We’ll be doing them a favor by sharing the gift of
life.
In particular, some advocates of immediate human exploration and
colonization of Mars are quite dismissive of the need for caution about
forward and/or back contamination. They see concerns about plane-
tary protection as irrational,
annoying impediments to the speedy real-
ization of our “manifest destiny” on Mars. Mars Society president Bob
Zubrin published an editorial in the July/August 2000 issue of The
Planetary Report called “Contamination From Mars: No Threat,” in
Image unavailable for
electronic edition
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which he referred to the threat of back contamination as “not only illu-
sory but hallucinatory” and said that the kindest thing that could be
said about this concern is that it “is just plain nuts.” (What is the
unkindest?) Many of his arguments, taken individually, are perfectly
sound. He notes that it is highly doubtful that Martian organisms, if
they do exist, could infect terrestrial organisms.
Further, Zubrin points out that Earth and Mars are not presently iso-
lated systems. About a ton of Mars falls upon the Earth every couple of
years, so if Mars bugs pose a threat to Earth life, it is too late. They are
already here.
Zubrin is absolutely right about these points. If our current concepts
of biological and planetary evolution are correct, then no danger of
back contamination exists. Yet he does not consider the magnitude of
the irreversible disaster that could be caused if we are wrong. We might
not get another chance. His arguments are reasonable, but they are not
iron-clad. He assures us that “it is the opinion of experts” that Mars
bugs, if they exist, have already naturally been transferred to Earth. But
should we risk it all on the “opinion of experts”? I am an expert of
sorts who basically agrees with his arguments, if not his conclusion. If I
had to guess, I’d say that further research will come closer to proving
that there is no danger. But that’s not good enough. What if we’re
wrong? Zubrin says that we should stop worrying and just go and get
the Mars rocks, set people loose on Mars without even washing their
hands, just get on with it. He concluded his editorial by saying, “Back
contamination mavens need to back off. Their warnings have no ratio-
nal basis and are being used to urge crimes against science.”
This is not the way to win folks over to the cause of Mars explo-
ration. Though I share the dream of future human expansion into
space, on to other planets and then outward to the galaxy, when I read
these arrogant, reckless, irresponsible arguments, I find myself think-
ing, “Maybe we’re not ready.”
One argument against the “back contamination mavens” is that
organisms are always uniquely evolved to take advantage of their own
environments. Thus, invaders from a different world will always be at a
competitive disadvantage and will never thrive. Yet look at all of the
places on Earth where introduced species have outcompeted native
species and run amok. In some rain forests in Hawaii, almost no
“native” species remain. And what about those vicious cane toads in
Australia, or the damn killer bees? The analogy to planetary protection
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261
is not exact: all terrestrial species are related, making it more plausible
that, even if they’ve never met, they could enjoy each other’s habitats.
But it is possible that not being related could conceivably be an advan-
tage to an invader, since we would have no defenses against it. Imagine
some unknown, tough, primitive Mars organisms that multiply like
crazy in any warm, wet environments and voraciously consume any
organic molecules they find. To them the human body, or the cells of
any terrestrial organism, might seem like an all-you-can-eat buffet.
I would place money on Mars dirt being safe. If you handed me a
spoonful of Mars and dared me, I’d take a nibble to see what it tasted
like.* I don’t think a little Mars would get me sick. In my heart, I am
not too worried about contamination from, or of, Martian organisms
because I do not think there is life on Mars. But I could be wrong.
Extraordinary risks require extraordinary caution.
Looking at the history of science, how many times have we thought
we had a complete understanding of some aspect of nature, only to find
out later that we were looking at a tiny fraction of some larger truth?
When making decisions that might affect our entire biosphere, we owe
it to ourselves, our ancestors, and our descendants to keep this history
in mind. Do we want to bet the entire farm on our belief that our cur-
rent concepts of biology are correct? We should assume that our under-
standing of biology is wrong and proceed from there. After all, we’ve
never been able to study alien biochemistry. We could be dead wrong,
so let’s proceed with caution.
To ignore planetary protection is the scientific equivalent of refusing
to use a condom. It might make it is easier or faster to get what we
want. But we’ve got to show that we’re a lot smarter, and more respect-
ful, than that if we want the public, who pay for our exploration of the
solar system, to entrust us with its protection. If we don’t want the peo-
ple mad at science, then we shouldn’t act like mad scientists.
I’m proud to say that NASA has always taken planetary protection
issues seriously. We make and follow rules designed to protect against
even remote chances of contamination. Of course implementing these
rules will involve educated guesses. Nothing is 100 percent safe. But we
can’t be paralyzed by fear. Do not fear the universe. Don’t be afraid to
leave the house in the morning, but remember your rubbers.
If any modern human enterprise could be called “applied natural
*I know researchers who have clandestinely tasted Moon dust. It tastes like dust.
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philosophy,” it would be planetary protection. In designing planetary
missions and formulating policy we cannot avoid questions like “What
is life?” “How much is new self-knowledge worth?” “What is the
intrinsic worth of preserving nature?” and “How does this change if it
is living or inanimate?” We are stepping up to our ethical responsibili-
ties as scientists, and as sentient residents of the solar system. This
could be a model for other sciences. Doctors, when they complete their
education, take a Hippocratic oath and pledge to “first, do no harm.”*
Perhaps we need a similar pledge for scientists.
S O N G O F O U R S E L V E S
Our efforts to anticipate and find life out there require us to start with
some image of what that life should be like. Seventeenth-century writ-
ers imagined men and women in European dress occupying a universe
of alternative Earths. Now the likenesses we paint out there take the
form of squirming proteins swimming in Earth-like seas.
On every evolutionary level, from the taproots to the tips of the tree
of life, our thinking about alien biology is extrapolated from the local
example. We assume that other life will be built of the same basic bio-
chemical parts, that it will need liquid water, will be carbon-based, and
may even use protei
ns and DNA. Up in life’s high canopy, we imagine
that other complex, intelligent creatures will develop mathematics, sci-
ence, and technology similar to ours and will sing songs of their own in
prime-numbered pulses of radio waves.
Everyone assumes that carbon chemistry in water environments will
be the way that our universe makes life. The justifications for this view rest on the unique qualities of carbon chemistry and the strange properties of water.
Carbon is unusual in the way it forms molecules that are endlessly
variable, so flexible, and yet so stable. Its modular self-construction
makes it the ultimate molecular shape-shifter, forming itself into the
right tool for the job, whether that happens to be building a cell wall or
facilitating a chemical reaction between two other, essential carbon
molecules, themselves optimized for the jobs they do. Water, too, has
strange properties. On Earth, all biology takes advantage of some sub-
*Rumor has it, this is being replaced with the HMO, the Hypocritic Money Oath: “First, do nothing unprofitable.”
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tle features of water that are not at all obvious from reading the peri-
odic table and predicting chemical behavior. Water’s triangular shape,
with the two H’s both pulling to one side of the O, gives it a slightly
negative charge on one end and a slightly positive charge on the other.
This makes water a “polar molecule.” The polar nature of liquid water
creates the possibility for a whole new kind of bond: “hydrogen
bonds,” which operate independently of the elaborate rules for electron
trades and collectives that most chemistry relies on. Water’s polar prop-
erties also allow it to form attractions and repulsions to small parts of
large carbon molecules, helping to orient them and shepherding large-
scale organic structures. In chapter 8, I described how the first cells
grew out of the self-organization of lipid molecules, which line up in
orderly fashion in response to water’s opposite pull on their two ends.
The polar nature of the water molecule allows these organized struc-
tures to form. The list of unusual, biofriendly properties of water goes
on. Life has evolved to make use of many of these unique features.
It’s hard to think of another chemical system having carbon-in-
water’s essential, life giving properties. I can’t think of a good substitute
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