by Charles Baum
phenanthrene to pyrene, a particularly stable diamond-shaped mol-
ecule with four interlocking rings (C H ). One thing is certain: we’ll
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10
never run out of molecules to try.
LOOKING FOR LIFE ON MARS
The most exciting, important, and potentially accessible field area to
look for ancient alien life is Mars, which, like Earth, formed some 4.5
billion years ago. A mass of new data points to an abundance of surface
water during the planet’s first billion years, dubbed the Noachian ep-
och by Mars geologists. Sunlit lakes, hydrothermal volcanic systems,
and a benign temperature and atmosphere might have sparked life and
made Mars habitable long before Earth. Perhaps fossils, molecular and
otherwise, litter the surface.
The quest for Martian life has a checkered history. A century ago,
American astronomer Percival Lowell reported observations of a net-
work of canals on the red planet—evidence of an advanced civiliza-
tion, he thought. Such speculation fueled the imaginations of science
fiction writers, but hardened the scientific community to such unsub-
stantiated claims. NASA’s remarkable Viking Mars lander of the mid-
1970s carried an array of experiments designed to find organic
compounds and to detect cellular activity, but ambiguous results
merely led to more controversy. Hot debates over purported fossils in
the Allan Hills Martian meteorite represent just one more chapter in
this contentious saga. Given such a troubled context, NASA will choose
its next round of life detection experiments with the greatest of care.
Humans aren’t going to set foot on Mars anytime soon, but that’s
what NASA’s amazing rovers are for. Sojourner, Spirit, Opportunity, and other robotic vehicles provide the experimental platform; they haul
the instruments across the desolate Martian surface to probe tantaliz-
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GENESIS
ing rocks and soils. The key to finding life (or the lack thereof) is to
design and build a flight-worthy chemical analyzer for life. That has
been the occupation of Andrew Steele throughout much of his career.
“Steelie,” my ebullient colleague at the Geophysical Laboratory, is
a microbial ecologist who got his start studying the microbial corro-
sion of stainless steel in nuclear reactors. British Nuclear Fuels Ltd.
sponsored his PhD thesis, which is still largely classified and unpub-
lished. Radioactive isotopes often contaminate the thin outer layer of
stainless steel that lines nuclear reactors—a difficult and costly clean-
up problem. Steelie invented new microscopic techniques to study the
steel surfaces, and he found that some microbes secrete biofilms that
rapidly eat away steel, thus stripping off the affected layers and greatly
simplifying decontamination. [Plate 4]
In 1996, just two weeks after defending his PhD thesis in England,
the Allan Hills meteorite story broke. The timing was perfect, and
Steelie was hooked. Setting his sights on nonradioactive ecosystems, he
became obsessed with attempts to detect ancient life from the faint
molecular traces in rocks. He contacted the NASA team, who were lack-
ing in microbiology expertise and thus eager for his help. David McKay
sent him a sample of the precious Martian rock, and within a year
Steele had applied his microscopic techniques to investigations of the
purported microbes. He made a memorable presentation at NASA’s
annual Lunar and Planetary Science Conference in Houston and
landed himself a job as a NASA microbiologist working at the Johnson
Space Center under McKay’s guidance.
Steelie’s assignment at NASA was to head the JSC Blue Team (con-
sisting of Steele and a fellow gadfly), who were to try out every possible
idea to disprove the hypothesis of Martian life in the Allan Hills mete-
orite. McKay led the significantly larger competing Red Team. McKay’s
strategy of examining both sides of the issue was laudable and in the
best tradition of scientific objectivity, but it may have backfired when
Steelie did his job too well. He performed a series of high-resolution
microscope studies and by 1998 had discovered that the Allan Hills
specimen (like virtually every other meteorite he had ever examined)
was riddled with contaminating Earth microbes. McKay was
unconvinced and continued to promote his original interpretation of
ALH84001. Discouraged at the cool reception accorded his findings,
and missing his wife and family in England, Steele left his steady NASA
employment in early 1999 for a hectic schedule of visiting professor-
IDIOSYNCRASIES
73
ships and research jobs at the Universities of Montana, Oxford, and
Portsmouth, along with more NASA consulting.
About the time that Andrew Steele’s research was making him
something of a persona non grata at the Johnson Space Center, the
Carnegie Institution’s Geophysical Laboratory found itself under new
leadership. Wes Huntress, the former associate administrator of the
NASA Office of Space Science (and the man who introduced the term
“astrobiology” to the NASA community), had been hired to shake
things up and expand Carnegie’s fledgling astrobiology effort. In a bold
and welcome move, Huntress made Steele his first staff appointment
in 2001. Steelie’s peripatetic scientific lifestyle seemed unsuited to the
traditional academic world, but his unconventional background was
just the ticket for the Geophysical Lab.
He arrived like a whirlwind, his shoulder-length blond hair and
open tie-dyed lab coat flying behind him as he dashed between office
and lab. Crates and boxes arrived by the dozen at his second-floor do-
main, two doors down from my own office. He crammed his lab space
with DNA sequencers, chip writers and chip readers (benchtop ma-
chines that prepare and read slides), and a bewildering array of other
microbiological hardware, most of which none of us geologists had
ever seen before. A small army of bustling postdocs followed and the
corridor took on new life. Chemist Mark Friese brought his collection
of orchids to grace one alcove with a forest of exotic blooms. Molecu-
lar biologist Jake Maule maintained his pro-level golf game by chal-
lenging all comers to putting contests—a regular stream of golf balls
began rolling past my open doorway.
In such an environment, new ideas fly thick and fast. Steelie had a
master plan. He wanted to build a life-detecting machine to fly to
Mars—a huge interdisciplinary project, given how much we still don’t
know. On the scientific side, he had to figure out what constitutes a
legitimate biosignature, so Steelie embarked on various paleontology
projects, principally with German postdoc Jan Toporski, who happens
to be his brother-in-law and soccer buddy. (There are also a lot of soc-
cer balls and other soccer paraphernalia in the corridor.) They focused
on a 25-million-year-old fossil lake in Enspel, Germany, where well-
preserved fish, tadpoles, and other animals are found. Studies of their
molecular
preservation would provide important hints about life’s
most stable and diagnostic molecular markers.
Then there was the detection part. It was essential to develop an
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GENESIS
unambiguous procedure to find the tiniest amounts of any target mol-
ecule. That’s where Jake Maule came in. An aspiring astronaut trained
in clinical medical technology, Jake’s job was to develop molecular an-
tibodies—proteins with specialized shapes that would lock onto only
one type of target molecule. [Plate 4]
Jake focused on producing hopane antibodies for use in a rapid
and sensitive field test for microbes. His procedure involved injecting
mice with hopanes and letting their immune systems do most of the
work. Hopanes are too small to evoke an immune response by them-
selves, so Jake attached hopane molecules to a big protein called BSA
(for bovine serum albumin). He injected 30 mice with a hopane–BSA
solution, waited a week, and gave each a booster shot. In about three
weeks, the mice manufactured a suite of hopane-sensitive antibodies.
From each mouse, Jake extracted a syringe full of blood, which was
centrifuged to separate out the red and white blood cells from the wa-
tery fluid that held the antibodies. Ultimately, each mouse yielded one
tiny, precious droplet of that antibody-rich fluid.
Armed with hopane antibodies, Maule was ready to analyze an-
cient rocks, in an elegant four-step process.
Step 1: He crushed various promising rock samples and washed
them in a solvent, which concentrated any hopane residues. Those so-
lutions were loaded into the chip writer, a sleek benchtop machine
about the size of a breadbox that placed an array of tiny dots of the
solutions (some containing hopane and others not) and various stan-
dards onto a glass slide.
Step 2: With the chip writer, he applied a tiny amount of hopane
antibody onto each of the sample spots, then rinsed. Some spots then
retained hopanes with attached antibodies, while other spots were
washed clean.
Step 3: He then treated each spot with another solution, this one
containing a second antibody that locks onto any mouse antibody and
is also highly fluorescent. All the spots with hopanes attached to mouse
antibodies would thus fluoresce.
Step 4: Finally, he took the glass slide with its array of spots and
put it into a second sleek machine, the chip reader, which, as its name
suggests, recorded which spots fluoresced and which spots didn’t. Like
microscopic lightbulbs, his antibodies glowed when hopanes were
present in the rock sample.
IDIOSYNCRASIES
75
Jake had devised a fast, automated process for identifying hopanes.
But all that work and more was mere prelude to the most crucial as-
pect of a flight-ready analytical instrument—the design and engineer-
ing. Concepts and benchtop demonstrations were one thing, but an
instrument on Mars has to be absolutely reliable, shock resistant, and
very, very small. Steelie began dealing with nitty-gritty questions of
how to collect a soil sample, how to introduce a small amount of sterile
solvent to dissolve the target molecules, how to excite a fluorescent
signal, and how to relay the information home to Earth, all in a tiny
box. Soon, armed with a million dollars of NASA funding, he planned
to fly the instrument on NASA’s 2013 mission to Mars.
Steelie’s baby is called MASSE—the Microarray Assay for Solar
System Exploration. Adapting the latest in chip writer/chip reader
technology, his team is building both flight-ready and handheld de-
vices that use antibodies to detect trace amounts of dozens of diag-
nostic biomolecules: hopanes, sterols, DNA, amino acids, a variety of
proteins, even rocket exhaust. Carnegie is not alone in developing such
an instrument, and given the intense competition of other dedicated
design teams, there’s no guarantee that MASSE will ever fly. Steelie is
also competing against a seductive sample-return mission—a techni-
cally challenging effort to return a soda can-sized canister of Martian
rock and soil to Earth on the same 2013 mission. Only one instrument
package will be selected. Even if MASSE does fly, there’s no guarantee
that it will arrive safely, and if it does arrive safely that it will find
anything of interest. Of course, Steelie and his group are learning lots
of fascinating stuff along the way. And I’ve never seen scientists have
so much fun.
In our quest to understand life’s emergence, fossils provide essential
clues. Even lacking morphological evidence, fossil elements, isotopes,
and molecules point to the nature of primitive biochemical processes.
These microscopic remains also reveal a diversity of life-supporting
environments and help to constrain the timing of life’s genesis. What’s
more, if we’re lucky, fossils from Mars or some other extraterrestrial
body may eventually provide the best evidence that life has emerged
more than once in the universe.
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GENESIS
And yet, valuable as these insights may be, all known fossils repre-
sent remains of advanced cellular organisms similar to those alive to-
day. Few, if any, clues remain regarding the emergent biochemical steps
that must have preceded cells. To understand how life arose, therefore,
we must go back to the beginning and approach the question of ori-
gins from the bottom up.
Interlude—God in the Gaps
Darwinists rarely mention the whale because it presents
them with one of their most insoluble problems. They
believe that somehow a whale must have evolved from
an ordinary land-dwelling animal, which took to the sea
and lost its legs.
. . . . A land mammal that was in the process of becom-
ing a whale would fall between two stools—it would
not be fitted for life on land or sea, and would have no
hope of survival.
Alan Haywood, 1985
This rant by Alan Haywood, and similar silly statements by his
creationist colleagues, reveals a deep mistrust of the scientific
description of life’s emergence and evolution. But he is correct in
one sense. Science is a slave to rigorous logic and inexorable
continuity of argument. If life has changed over time, evolving
from a single common ancestor to today’s biological diversity,
then many specific predictions about intermediate life-forms must
follow. For example, transitional forms between land mammals
and whales must have existed sometime in the past. According to
the creationists in the mid-1980s, the lack of such distinctive
forms stood as an embarrassing, indeed glaring, proof of
evolution’s failure. Their conclusion: God, not Darwinian evolu-
tion, must have bridged the gap between land and marine ani-
mals. But what appeared to them as an embarrassment for science
then, has since underscored the power of the scientific method.
Science differs from other ways of knowing because scientific
reasoning leads to unambiguo
us, testable predictions. As
Haywood so presciently predicted, whales with atrophied hind
legs must have once swum in the seas. If Darwin is correct, then
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78
GENESIS
somewhere their fossils must lie buried. Furthermore, those
strange creatures must have arisen during a relatively narrow in-
terval of geological time, bounded by the era before the earliest
known marine mammals (about 60 million years ago) and the
appearance of streamlined whales of the present era (which ap-
pear in the fossil record during the past 30 million years). Armed
with these predictions, several paleontologists plotted expeditions
into the field and targeted their search on shallow marine forma-
tions from the crucial gap between 35 and 55 million years ago
for new evidence in the fossil record. Sure enough, in the past
decade paleontologists have excavated more than a dozen of
these “missing links” in the development of the whale—curious
creatures that sport combinations of anatomical features charac-
teristic to both land and sea mammals.
Moving back in time, one such intermediate form is the 35-
million-year-old Basilosaurus—a sleek, powerful, toothed whale.
This creature has been known for more than a century, but a re-
cent discovery of an unusually complete specimen in Egypt for
the first time included tiny, delicate vestigial hind leg bones. That’s
a feature without obvious function in the whale, but such atro-
phied legs provide a direct link to four-limbed ancestral land
mammals.
And then a more primitive whale, Rodhocetus, discovered in
1994 in Pakistani sediments about 46 million years old, has more
exaggerated hind legs, not unlike those of a seal. And in that same
year paleontologists reported the new genus Ambulocetus, the
“walking whale.” This awkwardly beautiful 52-million-year-old
creature represents a true intermediate between land and sea
mammals.
Nor does the story end there. In September 2001, the cover
stories of both prestigious weekly magazines Science and Nature
trumpeted the discovery of a new proto-whale species that had
just been reported from rocks about 50 million years old. Nature’s
cover story, titled “When whales walked the earth,” underscores
