In 1997, a National Research
Council report on sample return from Mars concluded, "While the probability
of returning a replicating biological entity in a sample from Mars is judged
to be low and the risk of pathogenic or ecological effects is lower still,
the risk is not zero." That will be quite enough for forces already mustering.
"Not zero" equates in their eyes to a certainty.
Knowing this, NASA has agreed
to Chicken Little protocols to contain, sterilize, or -- if there’s any
chance the container has leaked into the rest of the spacecraft -- abandon
the mission entirely. You need not be a science fiction writer to expect
the usual opponents to even be joined by the Mars First! activists -- who,
conversely, didn’t want Earth to contaminate Mars. Both groups will want
the two planets to stay strictly apart, for opposite reasons.
You can hear the rhetoric
now: At their press conference today, the Protect Earth Party (PEPA)
lashed out against NASA’s plans. "Genocide, that’s what it is," their spokeswoman
exclaimed. "The so-called ‘discovery’ of the New World all over again.
European explorers brought diseases like measles, syphilis and flu to the
Indians, who died by the millions. Now we’re doing it again, to a whole
planet!"
They will cite Ray Bradbury,
whose fictional
Martians died from earthly diseases. That it was fiction was a fine
point they won’t appreciate.
Traditional menace-from-space
scenarios assumed an Earth-centric attitude. Earth attacked! Outer space
invaders! The Andromeda Strain, the Triffids, various evolved Martians,
and lots of squishy aliens.
And what was the fate of
the fictional menaces from space? The Andromeda strain was done in by the
pH of earth’s ocean after being rained out of the clouds. H.G.
Wells’ Martians succumbed to local microbes within a few days. The
authors had reasonably assumed that a planet with a lively biosphere could
put up a good fight.
But that was only fiction.
Is there any real data to suggest that Earth could be at risk from an incoming
Mars microbe?
~
Anaerobic naugahyde
First, Martian microbes would
have evolved in an oxygen-free, carbon dioxide-rich atmosphere -- anaerobic.
Earth’s oxygen-rich atmosphere would be the first challenge, vastly reducing
where it could live. Oxygen is a potent poison to many organisms on Earth,
after all.
Mars has lain beneath a thin
skin of carbon dioxide, thicker in the past but always carbon dioxide,
for four billion years. Even so, it still contains much more carbon dioxide
than Earth’s atmosphere. Even if Martian metabolism were not immediately
poisoned by our air, there might not be enough carbon dioxide to sustain
it.
And finally, Mars has been
delivering rocks to Earth for billions of years, without any resulting
Mars plagues. Several kilograms per year have been splashed out by incoming
meteors, and found their way to Earth. But so far, Earthly diseases have
all been from Earth. And that’s reasonable, because vastly different life
forms wouldn’t pose a biological threat to earth life anyway.
Remember the Nauga? A stuffed
monster toy invented by some ad agency to push a particular type of leather-like
vinyl cloth. The really interesting thing about vinyl was that it had been
created in the lab by chemists, a novel arrangement of atoms, a new molecule.
After it was introduced, it was found to be inedible to all earthly life.
There simply were no digestive enzymes that could attack the vinyl configuration
of atoms.
To truly alien life, Earth
is filled with Naugas.
And there is infinitesimal
chance that any life can survive on the peroxide-rich surface. Peroxides
formed by the ultraviolet sunlight make the dust of Mars as antiseptic
as bathroom cleansers.
But what about those Mars
First! people?
NASA had always tried to
avoid cross-contamination. Spacecraft are assembled in a clean environment:
an interplanetary condom.
Any microbes accidentally
sent to Mars on the various landed robots should have succumbed to the
aerobraking heat, then the cold, dry and chemically hostile surface.
I once wrote a short story
about the first manned mission finding traces of microbial life on Mars,
and then tracking it back to...a crashed Russian probe! NASA tried hard
to prevent that coming true.
But a manned mission is different.
In their habitats they will support a
microcosm of earth, humans with all their tiny fellow travelers. Although
we think we are individuals, we play host to colonies of bacteria, from
our skin to the inner recesses of our gut. Not to mention the little creatures
living happily between our eyelashes.
Each expedition member will
be a mobile Earth colony -- not to mention tons of food, frozen or dehydrated,
carrying different microbes.
Even being careful, it will
be impossible to keep from liberating some organic material. Airborne dust
blowing out of the habitat will include shed hair, skin flakes, human commensal
bacteria, tiny mites that feed on human detritus, their waste pellets,
and their own bacteria. The built-in vacuum system in a habitat will keep
up with most of the dirt, but there was no way to eliminate it all. The
crew can’t operate like a clean room for 18 months.
~
Landing on the distant
shore
Mars will greet these ambassadors
with a reactive, peroxide-rich covering of busted up crustal rock, sand
and dust that is essentially sterile. Microbes will be torn apart by vigorous
chemical jaws. If the Martian surface is indeed lifeless, this will definitely
be the unwelcome mat to any bacterial life form attempting a landing --
apart from the cold and dryness.
A hostile shore for life,
indeed. Even if, as many suspect, Mars harbors life within, there is that
rusty, defensive skin.
And what kind of life could
exist on Mars? Something fearful of deadly oxygen -- anaerobic. But could
we harm it?
We still think of Earth as
the water planet, the blue planet, the planet of the oxygen-breathers.
"All life is ultimately dependent on the sun," children are still taught.
"Food chains begin with energy from the sun that is harvested by the green
plants."
But once again, that’s our
ignorance speaking.
Late in the twentieth century
biologists found hydrothermal vents teeming with life deep on the ocean
floor. The basis for the food chain was chemosynthetic bacteria, that had
never seen the sun and couldn’t use its light. Soon after came discoveries
of life in boiling hot springs, very acid water, coal mines, and even microbes
living inside rocks. Life permeates Earth, not merely crawling its surface
or swimming in its seas.
All of the underground microbes
were anaerobes, but the biggest surprise was their DNA. Their genes were
only 60% similar to all other life on the planet. They are the ancient
bacteria, the archaea, persisting underground billions of years after the
rise of the oxygen lovers.
But did they retreat underground
as the only refuge free from the deadly oxygen atmosphere? Is Earth’s deep
underground a refuge, or the cradle of life?
There may be more life below
ground than oxygen users on top. They have the whole interior of Earth,
while we are confined to the thin biosphere on the surface. After all this
time, billions of humans haven’t touched the anaerobes on our own planet.
How can space-suited explorers
going to invade and destroy such forms? They might be lurking in the ancient
thermal vents of Mars, which geologists suspect we shall soon find by satellite
studies.
It would be damned difficult.
But settling the issue of whether life on Mars ever arose, or still persists,
demands that sometime in the next few decades, an astronaut ventures down
such a passage.
Maybe they’ll only bring
back fossils of what once was. But maybe they’ll find hearty life still
holding out in the rocks and fissures of that dry, ancient world.
Then will be the time to
worry about contaminating it, or back-contaminating Earth.
But the specifics will have
to make the case -- not lawyers. We need to get more hard evidence before
we can speculate about the vastly improbable harm that might come from
mingling two biospheres. After all, they’ve been swapping
rocks for 4 billion years.
NASA has already allocated
$60 million to the legal defense of the sample return mission. This is
a "small" but characteristic waste. Best to retain our sense of proportion,
educate the public, and use the money for a positive goal -- MARS
IN OUR TIME.
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