Sound of Trumpet wrote:
http://helives.blogspot.com/2006/07/martian-life.html
Tuesday, July 18, 2006
Martian Life
Life on Mars would have no impact on the strength of the cosmological
ID argument. However, the absence of such life would land in the win
column for privileged-planet type arguments. At the same time a lack of
Martian life would be an easier pill for evolutionary biology to
swallow.
This does not seem to follow, but then, a lot of what the author says
seems not to follow.
If primitive life is discovered on Mars, some will say "see, not only
is earth not privileged, not only is life not rare, but in fact it is
so common that we find it on our next-door neighbor. Any discussion of
one in a gazillion chance is clearly nonsense."
As the author implicitly notes, there are theories that asteroid
impacts could send rocks (and perhaps microbes enclosed in them)
between Mars and Earth, or between Earth and Mars. So if we found life
on Mars, the first item of business would be to see what, if any,
relationship it had to terrestrial life. If it turned out to be no
more different from terrestrial bacteria than are, say, terrestrial
archae, that would show that transport of life between (relatively)
nearby planets is fairly easy, not that abiogenesis was. If,
conversely, life on Mars shared no homologous genes with terrestrial
life, that would imply either easy and common abiogenesis, or that
simple life forms could be easily transported across not merely
interplanetary space, but over large interstellar spaces. Either
possibility would imply that life was very widespread, and count as a
point against the "privileged planet" view. Neither, of course, would
harm the cause of ID overall, since ID is so vacuous that hardly
anything could contradict it.
Bzzt. Sorry, the more sensible response is: the conditions for complex
are exceedingly rare in the universe. And given that earth had to be in
the right part of the right kind of solar system, with the right kind
of satellite, and the right kind of star, and the right planetary
companions, in the right part of the right type of galaxy, in the right
cluster of galaxies, of the right age, in a universe with the correct
laws and constants-well if I were taking bets on the next most likely
place to find life, I'd look first at earth's nearest neighbors,
reckoning that they are closest to being in the habitable zone. If I
can't live at the oasis, I'll settle for being within walking distance.
This is on a par with saying that, if the upstairs refrigerator is full
(but not of ice cream), the best place to store ice cream (or look for
it) would be the oven, not the basement freezer, since the oven is
closer.
If any place other than earth should have life, it should be Mars. If
Mars has primitive life (that didn't originate on earth-that would
have to be ruled out) then it is because of its proximity to a favored
location in the universe-not a sign that life is cheap and easy.
There are billions of stars in the arms of the Milky Way galaxy. A
small minority (still amounting to many millions of stars) are G-type
single stars more or or less like the sun. It is not known how many
of these have planets, but both current theory (such as it is) and
current observations suggests that most of them should. There should
be many planets that are closer to Earth in size, makeup, and distance
from their star than Mars is, and which are therefore closer to being
"privileged" than Mars is.
Personally, I don't think we will find evidence of non-terrestrial
primitive life on Mars. New data from the European OMEGA satellite
confirms Mar's lack of substantial water, or of any significant
hydro-activity on Mars for the last 3.5 billion years.1 So when there
was water on Mars, the solar system was at its most inhospitable-with
the inner planets subjected to frequent life-quenching impacts from
comets and asteroids.
It's fun to test the predictability of evolutionary biology by asking
those practiced in that science to predict what life on Mars will be
like, should we discover it. If you get an answer (not likely) and
distill it to its essence, it will be along the lines of "Oh, I don't
know, but whatever it is will be consistent with evolution." Can you
imagine a physicist stating "Oh, I don't know even the gross details of
the orbit of Mars, but whatever it is it will be consistent with
gravitation."
Since, as you note, we have no obvious reason to suppose that there
even is life on Mars, wouldn't a closer analogy be asking a physicist
to give the details on the orbit of an undiscovered planetoid or comet
of unknown mass whose semimajor distance from the sun and orbital
eccentricity are unknown? Pretty much all he could say about such a
planet would be that its orbit would be consistent with Kepler's and
Newton's laws, as modified by Einstein. After all, there are assumed
to be plenty of such objects, and their orbits are not at all
predictable from first principles.
As for a biological analogy, there are estimated to be millions of
animal species (mostly insects, but a few reptiles, amphibians,
mammals, etc., many in tropical rain forests) not yet discovered and
described. I doubt any biologist would dare go very far in describing
the next new species to be discovered, except, again, that it would fit
into the known nested hierarchy of life and be adapted to its ancestral
environment.
Then again, if I were an evolutionary biologist I would be hoping that
no life was found on Mars. I would not want to explain how earth
(without being privileged) supports complex life while microbes on Mars
remained microbes. I'd much rather Mars be sterile, so that I could
blame the great evolutionary scapegoat, abiogenesis. A lifeless Mars
permits the argument that "yes the origin of life is (possibly) rare,
but if life were to have started on Mars, it would have evolved (as all
life should, evolutionarily speaking) into more and more complex
forms."
Life does not seem to have evolved into particularly complex forms in,
e.g. the center of Siberia or waterless wastes of the Sahara desert,
and Mars is drier and less hospitable than either of them. Of course,
there is no evolutionary necessity that life evolve into more and more
complex forms; life adapts, over time, to local circumstances and local
niches. In some cases (e.g. many organs in parasites) this means loss
of complexity: organs becoming vestigial and vanishing entirely. In
other cases, it means undergoing very little morphological change at
all, as no major change makes a well-adapted species better-suited to a
stable environmental niche. Natural selection favors whatever works
under local, current circumstances; it doesn't have long-range goals
and a sense of mission.
It would be much harder to explain a Mars (as we know Mars to be)
crawling with banths, thoats, and egg-laying anthropoid princesses; the
latter, especially, would require a major revision of current
evolutionary theories. But the argument that, if life on Earth
includes many complex multicellular organisms, so should any life on
Mars, is exactly on a par with arguing that if tropical rain forests
exist in the Amazon basin, they ought to exist in Antarctica. It
reflects the same absurd "proximity" argument that was made above.
To summarize, and perhaps counter-intuitively, non-terrestrial microbes
on Mars would be neutral in its impact on cosmological ID.
Perhaps they would even be a point in favor of cosmological ID. After
all, if there's a case for cosmic ID, it would apparently be a case for
a very powerful Designer Who wants a universe suited for life. Such a
Designer would be expected (if competent) to produce a universe in
which life was as nearly ubiquitous as possible (and how much is not
possible for such a Designer?).
It would be
problematic for evolutionary biology, which would have to explain why
evolution was so impotent on Mars.
Well, first it would have to be demonstrated that evolution actually
was "so impotent;" as long as we're positing life, why not posit large,
elaborate multicellular organisms sufficiently different from life on
Earth that we don't even recognize them as life at first sight? But as
implied above, I'm not expecting Mars to be teeming with refugees from
the _Star Wars_ bar scene; the environments on Earth most similar to
Mars are pretty barren (and being in "proximity" to a lush, diverse
ecosystem does not mean that a place is itself a lush, diverse
ecosystem).
A sterile Mars, or a Mars whose only
life consists microbes emigrating from earth, would bolster the
privileged planet arguments, and yet provide an escape for evolution,
which could, as it always does, sweep its most difficult problem under
the
I'm-covering-my-ears-and-not-hearing-you-because-abiogenesis-is-a-different-discipline
rug.
Okay, there is no detailed theory of abiogenesis. From this, the ID
proponent would infer a Designer (for Whose nature, motives, and
methods there is no theory and no hope of one), for Whom the only
evidence is the inadequacy of known mechanisms to fully explain
abiogenesis and certain aspects of living things. Normally, it would
seem more parsimonious to invoke unknown mechanisms of limited ability
and scope than unknown Agents with abilities and interests going far
beyond the problems they are invoked to solve.
-- Steven J.
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