| Microbes
and Mars |
Read
an excerpt from The
Secret of Life
|
| Paul
McAuley |
 A
very common early twenty-first century condition is that of disappointed or
diminished expectations. Here we are in 2001, the future of science fiction's
Golden Age, and we don't have the aircars, jetpacks, vastly ambitious space
programs, and homicidal computers we were promised. Not to mention, of course,
aliens willing to meddle in human evolution, or even their black monolithic
stand-ins.
Even so, not since
the end of the space age have there been so many science-fictional headlines
in the newspapers: planet-busting asteroids; worlds around other stars; cloning
(my favorite headline generated by the cloning of Dolly the sheep, a headline
guaranteed to falsely raise expectations, was "Soon we will be able to
raise the dead"); obsolete space stations crashing into the Pacific Ocean; and,
of course, life on Mars.
 Not
the cold, inhuman intelligences of H.G. Wells' War
of the Worlds, or the belligerent warrior-races of Edgar
Rice Burroughs, or the mournful aesthetes of Ray
Bradbury's The Silver Locusts (killed off by culture shock and McDonald's-ization);
not even the modest splotches of a few hardy lichens hugging the sunny side
of some deep equatorial canyon. No, the reality is nothing more than the fossilized
remains of incredibly tiny bacteria associated with smears of organic material
deep inside a meteorite -- famously designated ALH84001 -- that was knocked
off Mars by a glancing impact some 15 million years ago. And it is entirely
possible that the fossil "bacteria" might be nothing more than inorganic crystalline
deposits, and the organic material might be due to contamination after the meteorite
hit the Antarctic ice cap.
 The
best we can expect of life on Mars, it seems, are contentious traces of bacteria
which, even if they had existed, (1) died out billions of years ago, and (2)
were so small that most other bacteria would have no trouble kicking nanosand
in their endcap filaments.
Talk about your
basic twenty-first century diminishment of expectations. If science fiction
writers are going to spin fictions about life on Mars, they had better learn
some microbiology, and they had better find some way of making the small and
insignificant interesting. How much easier H.G. Wells, Edgar Rice Burroughs,
and Ray Bradbury had it!
But the possibility
that bacterial fossils were able to travel from Mars to Earth inside a chunk
of rock hints at an intriguing possibility: suppose live bacteria could have
traveled the same way?
 Bacteria
can be incredibly hardy. Forty-million-year-old bacteria have been extracted
-- and cloned -- from inside a bee preserved in amber. Bacterial spores were
recently isolated from water trapped in a billion-year-old salt crystal -- and
the spores produced living bacteria. The Apollo 12 astronauts recovered viable
bacteria from Surveyor 3 after it had spent two-and-a-half years on the Lunar
surface. Experiments show that bacteria, by their very small size, could survive
the 10000g acceleration needed for a rock to be blasted off Mars at escape velocity
by an asteroid impact, and that some species are very resistant to raw solar
radiation. If protected inside a layer of rock, they can survive in the vacuum
of space for up to several thousand years. The cold of space, by the way, isn't
much of a problem. Between Earth and Mars, sunlight keeps objects at about minus
50 degrees centigrade -- the temperature inside a laboratory freezer -- and
viable bacteria are often stored at even lower temperatures. And although the
outer layers of a meteorite are heated by friction when it enters the atmosphere,
rock is a good insulator and the inside remains cool.
 Suppose
that there once was life on Mars. It now seems very likely that life on Earth
arose almost as soon as the crust had cooled to acceptable temperatures. Mars,
a much smaller body, would have cooled more quickly, and if conditions were
right, life would have arisen there before it had a chance to do so on Earth.
Four billion years ago, inner solar system bodies, including Mars, were undergoing
intense meteoritic bombardment. Perhaps at that time many life-bearing rocks
were knocked off Mars and eventually fell to Earth. Only one Martian bacterium
would have needed to survive. The descendants of that single bacterium -- the
Solar System's first successful astronaut -- could have flourished here on Earth
while life on Mars died out, or retreated to a last stronghold.
 The
millions of species living on Earth could all be descendants of that microscopic
Martian pioneer. What would happen if, four billion years later, astronauts
brought back Martian life, which shares a common ancestor with life on Earth?
This notion was the seed of my novel The Secret of Life, but there are
other variations on the same theme. Perhaps there's life on Mars -- but it came
from Earth, not Mars. Billions of years before the first human colonists reach
Mars, it had already been colonized by hardy, microscopic pioneers. Perhaps
other bacterial pioneers have colonized every habitable corner of the Solar
System -- the subsurface oceans of Europa and Enceladus could harbor ecologies
derived from the same primordial ancestors as ourselves.
It is even possible
that bacteria could travel between stars. Bacteria permeate the Earth's biosphere
-- all the way up to the top of its atmosphere. Solar winds could on occasion
strip some of the wispy upper layers of the atmosphere and send the puffs of
gas -- and bacteria and bacterial spores -- into space. The same solar winds
would propel the microscopic spores outward, towards interstellar space.
It's not an original
idea: it was first proposed by the Swedish chemist, Svante Arrhenius, who called
his theory panspermia. He suggested that bacterial spores wafted through the
Galaxy by starlight could have given rise to life on Earth, and by implication,
to life on other planets of other stars.
 Needless
to say, it would be a very difficult journey. Bacterial spores would have to
survive millions of years in hard vacuum and temperatures approaching absolute
zero, and would also have to survive the drenching of ultraviolet light when
approaching another star. One possibility is that they could be protected by
something as simple as soot. G-type stars like the Sun start to eject carbon
grains as they age; like banked furnaces, they grow smoky. The microscopic carbon
grains could accrete around bacterial spores, and this coating of soot could
help the spore survive ultraviolet light as it approached a new star.
Again, only one
microscopic star voyager would need to find a new home and survive in it to
begin a new cycle of life. And even if it was dead on arrival, if its RNA fell
in a suitable prebiotic soup, it could kickstart life.
Bacteria could
have been the first
interstellar astronauts.
We could truly
be children of stardust.
The
Secret of Life
Look
for Paul
McAuley's books on BookSense.com
Read
an excerpt from The Secret of Life
Paul McAuley's
books have that ring of authority that tells you the author is not just making
this stuff up, he knows what he's talking about. He has
a Ph.D in Botany, has worked as a researcher in biology in various universities,
including Oxford and UCLA, and for six years was a lecturer in botany at St
Andrews University in Scotland.
His first novel,
Four Hundred Billion Stars, won the Philip K. Dick Memorial Award, and
Fairyland
won the 1995 Arthur C. Clarke Award for best science fiction novel published
in Britain and the 1996 John W. Campbell Award for best novel. He has also won
the British Fantasy Award, and the Sidewise Award for Alternate History fiction.
Most of the time he lives in London.
Further
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Jeffrey
Ford
Albert Goldbarth
Sean Stewart
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