than any bet in Atlantic City, since we don’t really know what kind of
game we’re playing. We have to base our strategy on educated guesses.
We want to go and look anyway because, well, how could we not? This
argument is not sufficient to sway congressional committees, or the
White House Office of Management and Budget. It doesn’t do to say,
“Okay, Madam Senator, we admit we are stabbing in the dark, but if
you give us a lot of money, we’ll certainly learn much of value, and who
knows, we might make the discovery of the millennium.” Our missions
to other planets are in part scientific experiments, but in large part they
are just poking around the neighborhood to see what we dig up. So we
ask for money for exploration and seek to justify it as science.
Now that exo has morphed into astro, is biology here to stay as a linchpin of our space exploration plans? If life continues, like quicksil-ver, to elude our grasping hands, will we stay on task? By casting our
lot in with astrobiology we are expressing faith in its longevity.
Astrobiology is hot now, but historically both scientific interest and
government support are cyclical. It remains to be seen whether we can
commit for the long haul. But for our society this is good practice at
thinking on long timescales, which as a survival skill is as essential as
learning to think globally.
W H A T A B O U T T H E R O C K S ?
And what of the little worms who started all this astrobiology fuss, the
“microfossils” in the Mars rock? In the eyes of most of the community,
they have been demoted to strange mineral deposits that were probably
not made by living organisms.
In the seventeenth century Johannes Kepler described oceans and an
atmosphere on the Moon. The excitement generated by Kepler’s reports
helped spur scientific interest in a plurality of worlds, and that interest
retained momentum long after better telescopes and more objective
observers revealed the Moon to be a dry, battered ball of rock.
Similarly, in the late twentieth century, astrobiology was given its
biggest impetus by a discovery most practitioners now regard as highly
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dubious. As with the Viking biology results two decades earlier, the
confusion underscores the difficulty of identifying, or agreeing on, signs
of life.
Personally I’m not sure. I don’t think we can entirely rule out the
possibility of some biological products in the Martian rocks, but I am
highly skeptical. One problem is that we know nothing of where on
Mars these rocks came from, since we received them as random shrap-
nel sprayed by some long-forgotten impact. Assuming we can find
more rocks with similar features on Mars, it will be much easier to
interpret them when we can examine the environments where they
formed.
There are, in fact, living and fossilized terrestrial bacteria that look
very much like these things, with the same segmented, elongated
shapes. However, the Martian “worms” are incredibly tiny compared
to any organisms we know of on Earth. They are about one hundred
nanometers long and ten to twenty nanometers wide. (A nanometer is a
billionth of a meter.) The smallest bacteria on Earth are hundreds of
times larger than this. Life-forms using our type of chemistry probably
cannot fit into a package so small. You need to have a container large
enough to hold the genetic material that describes how to make the
container.
Today, the general attitude in our field is surprisingly scornful of the
Martian fossils, even among many who are enjoying the funding and
interest in astrobiology that they sparked. Scientists agree that we need
more data from Mars. It is commonly said that we won’t be able to
answer the question definitively until we return carefully chosen sam-
ples from Mars and analyze them in our labs on Earth. Even this may
be optimistic. It is quite likely that once we do return the first Martian
samples, the answer about the “fossils” will still be “maybe.”*
The scientists who claimed that they had found fossils in ALH84001
did us all a big favor, and I don’t just mean the increased funding for
research in astrobiology. They got us all thinking. When we asked our-
selves, “Could this be real?” we realized that there is no reason why we
shouldn’t find ancient fossils on Mars, even if there are none in these
*Returning a small sample from Mars is turning out to be much more difficult, technologically, than we once thought. When I joined SSES in 1998, the central goal of our Mars program was to return Martian samples to Earth by the year 2005. Then it got pushed back to 2014, and now 2020 is looking more realistic . . .
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particular rocks. And, the reasoning continues, since the extremophiles
on Earth show us that life can adapt to a surprising range of conditions,
couldn’t this ancient life have somehow adapted to modern Martian
conditions?
Biological or not, those nanoscale wormies in that little four-pound
Mars rock made NASA and the planetary community turn and face our
true purpose. By exploring space we are embracing life, not running
away from it.
Is It Science Yet?
16
LONDON—An elaborate, 155-year-old hoax was
revealed Monday, when the Royal Astronomical
Society confessed that the planet Neptune does not
Image unavailable for
exist. “It appears to have begun in 1846, when
electronic edition
Johann Galle needed a big discovery to give his
career a jump start, so he fabricated this new planet,”
said Royal Astronomical Society president N. O. Weiss.
“Ever since, every astronomer who’s wanted some attention
has come up with some new report on ‘Neptune’ and made up some rubbish
to support it. I swear, we meant to come clean eventually, but the whole
thing just kind of snowballed.”
— The Onion
W E I R D S C I E N C E
We scientists recoil against alien stories and beliefs that ignore stan-
dards of evidence and common sense.* Yet, extraterrestrial life is
among the most difficult of subjects to approach scientifically.
Astrobiology is not just another science. It has sometimes been derided
as a “science without a subject,” or even more harshly as a pseudo-
science. I disagree. But, to recap, here are four ways in which it is weird
science:
1. We ourselves are part of the phenomenon we seek to study. Can
a camera photograph its own lens?
2. We can’t say what it is exactly that we are looking for on other
planets, but we think we’ll know it when we see it.
*Admittedly, sometimes science rules against common sense.
Is It Science Yet?
253
3. We rely entirely on a single example—life on Earth. Could you
imagine trying to develop a science of botany if you were locked in
a room with only one seed? This does not make for “good science”
the way we usually think of it. In medicine, for example, we are
suspicious o
f studies with small numbers of test subjects.
4. We are blatantly biased by an overwhelming desire to find cer-
tain answers. Life good. Dead universe bad. Science, we have been
taught, is supposed to be neutral, like Switzerland. We’re not sup-
posed to take sides or rig the game. Yet, when it comes to life in
the universe, we’ve unabashedly forsaken our neutrality. We can’t
hide our love away. We want life.
Science demands “well-posed” research questions that we can frame
as specific hypotheses for us to test. We can’t go to Mars and do an
experiment designed to “search for life, whatever that might be.”* But
we also can’t just sit here on Earth and fret over our philosophical
conundrums while Mars stares down at us licking its chops, guarding
its precious secrets. So, we make educated guesses about which aspects
of Earth life will be universal. We go to Mars and search for water, for
organic molecules, for biogenic gases, for microbial mats. We look for
signs that on Earth would point to life. We employ widely accepted, but
unproven, criteria for inhabited planets. To “do good science” we have
to pretend we know the answers to the big questions “What is life?”
and “What kinds of planets are living?” This is fine, as long as we don’t
forget that we are still following hunches.
Astrobiology is intellectually unrestrained—some would even say
flaky—compared to other fields. It is not too hard to come up with a
conjecture about the origin or early evolution of life, or the possibility
of life in some alternative planetary environment, and get a publication
(and a newspaper story). Peer review still applies, but our filters are
somewhat loosened, as there is a wide acknowledgment that outside-
the-box thinking must be encouraged, up to a point, since we don’t
really know the shape or size of the box. Inevitably, some junk slips
through. When reading astrobiology papers, you have to set your bull-
*Although simple cameras come the closest to such “open to anything” experiments, which was why Sagan was so keen on using the Viking lander cameras to look for macrofauna.
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shit detector on a slightly higher setting than you would when reading
in an older, more established field.
Lately, I’ve been thinking of astrobiology as a resurgent branch of
natural philosophy. Calling it this may help us remain mindful of the
limitations and assumptions necessary to do our science and the larger
questions that we sometimes sweep under the rug.
N A T U R A L P H I L O S O P H Y
The fence we’ve built between science and philosophy is a recent con-
struction. Up until about 150 years ago, the study of the natural world
was not called science, but natural philosophy. There were no “scien-
tists,” only natural philosophers. Many famous philosophers, including
René Descartes and Immanuel Kant, had important physical insights
that contributed to the foundations of science. Likewise, none of our
classical Western scientific heroes—(e.g. Galileo, Darwin, Newton, and
Kepler)—called themselves scientists.* They were philosophers with a
particular interest in understanding nature. Starting with Galileo, some
philosophers developed an experimental method of establishing truths.
We who inherited this approach call ourselves scientists, and we gener-
ally forget that what we assume to be the ground rules—the obvious,
unquestionable truths about nature—were part of a new and radical
philosophy just a few hundred years ago.
Bertrand Russell said that “science is what you know and philoso-
phy is what you don’t know.” Indeed, science grows at philosophy’s
expense, continually siphoning off the known to sprout new disciplines.
For example, the study of consciousness and the mind used to be part
of philosophy, but now it’s psychology and neuroscience. Studying the
heavens and pondering other worlds was once something that philoso-
phers did. When we started to learn something definite, these musings
became the science of astronomy. Only those areas in which we have no
solid answers at all are left as a sticky residue for philosophers to roll
around in.
Along with the switch to “science” came a narrowing of scope. Science
*None of them would today be considered “skeptics” either: Newton was obsessed with alchemy. Kepler practiced numerology and based his conclusions about extraterrestrial life on mystical principles. Herschel was convinced, for metaphysical reasons, that there was life on the Sun, Moon, and planets and devoted his astronomical career to finding evidence for it. Darwin was a creationist.
Is It Science Yet?
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became professionalized. It became a full-time day job and splintered into
a few, and then many, separate fields and specialties. Natural philoso-
phers did not carve up the universe like that, and they didn’t separate sci-
ence from questions about the limits of science. In becoming scientists
we’ve accepted an invisible framework. We don’t worry about the rules
about how to do science, because these seem obvious, beyond question.
Paradoxically, none of us can say exactly what these rules are. The history
and philosophy of science are not part of a scientific education. Rather,
scientists learn the stories and rules through an intuitive cultural assimila-
tion, the way a child picks up the rules of social interaction.
Philosophers of science have competing ideas about what “the scien-
tific method” is, or even whether there is one.* They argue about the
way science really works, but they all agree that no theory about sci-
ence is remotely scientific. Meanwhile, working scientists are far too
busy doing science to worry about what it is.
Scientists ask, what can we know of nature? To this, natural philoso-
phers added, how can we know this and what can’t we know? Science,
as it has grown in confidence, has lost the ability, or at least the desire,
to question its own authority. Before science became Science, think-
ers kept these questions closer in mind. A new natural philosophy
approach would rejoin science with philosophy of science as a common
area of inquiry.
In some ways our present science cannot completely handle the ques-
tion of extraterrestrial life. In this field, more than any other, we must
keep our grand ignorance of the ways of the universe constantly in
mind and be open to anything. Yet, this kind of approach flies in the
face of what is usually considered to be good science, because science
requires that we make specific predictions to test hypotheses. The odd
status of astrobiology in the suite of sciences can, I think, be under-
stood by realizing that it is not yet science, exactly, but still natural
philosophy.
An awareness of the limits of science is especially important when we
skirt close to its edges. For an honest consideration of the questions
raised in this field, we must bravely sail beyond the edge of the scientif-
*Historically, these ideas have included the empiricism (letting nature speak for itself) of Galileo, the
experimental, inductive approach of Francis Bacon, the pure reason of Kant, the provisional truths and falsification of Karl Popper, and the “normal science” and revolutionary paradigm shifts of Thomas Kuhn.
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ically mapped world back into the realm of natural philosophy where,
in addition to chipping away at some relevant, well-posed scientific
questions, we should constantly ask ourselves, “Why do we believe
what we believe?” What is the interplay between common sense, evi-
dence, intuition, and faith that forms our beliefs about life in the
universe?
None of this is meant as a put-down of astrobiology. I think natural
philosophy is a fine thing indeed and may be what science needs now.
By helping rejoin the splintered communities of science, and rubbing
our noses in the limits of science, astrobiology can help us to rediscover
the study of nature as a whole.
Another problem plaguing science these days is a sometimes deserved
reputation for arrogance. But modesty is called for when facing the
huge unknowns in studying alien life. A natural philosophy approach
could also infuse our quest with a much needed dose of humility, which
can only help science.
During the Enlightenment, science grew out of natural philosophy
and took on a life of its own. In an unconstrained field like astrobiol-
ogy, where our ignorance so outweighs our knowledge that we are not
even sure how to ask the right questions, we can benefit from hearken-
ing back to the earlier approach. Our innocence in the ways of the uni-
verse demands that we be natural philosophers again.
O U T O F T H E N E U T R A L Z O N E
We have been taught that science is largely value-free except for a sense
of integrity to the truth. We are supposed to dispassionately interrogate
nature and accept the answers, whether we like them or not. Yet, in the
past, natural philosophers often mixed their spirituality, ethics, and val-
ues in with their science.
Our neutral stance is not just a cop-out. It arises from an attempt to
maintain a high standard of objectivity—a commitment to letting
nature be the judge. Undeniably, it is methodologically dangerous to
want a certain answer too badly. When hunting wabbits on Mars we
have to be vewwy, vewwy careful not to scare them up out of nowhere.
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