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Nifty essay about issues surrounding exobiology!
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July 19, 2005
Hunting for Life in Specks of Cosmic Dust
By DENNIS OVERBYE
In astronomy, the race is on to the bottom.
Teams of astronomers are staying up all night in the breath-fogging cold of the
high-altitude desert of Chile and in the oxygen-starved heights of Hawaiian
volcanoes, deciphering downloaded pixels from the Hubble and Spitzer Space
Telescopes over soggy pizza, and then upstaging one another's news conferences,
all in the search for the smallest, dimmest crumbs of creation, the most
mundane specks of dust that may be circling some garden-variety star.
It is here, in boring, peaceful meadows of the galaxy, far from fountains of
lethal high energy particles, swarms of killer comets or hungry black holes, we
are told, that we should look if we want to find habitable abodes and possibly
life.
And that, of course, would be the most exciting and wonderful result in the
history of science, one of the few in astronomy that would probably rebound
beyond science, affecting our view of our own status as tenants in this strange
house of stars.
Last spring the quest ratcheted another notch downward (or upward) when a team
of astronomers announced the detection of a planet only seven times the mass of
the Earth circling a dim star named Gliese 876 in the constellation Aquarius.
This was the first alien planet that astronomers were unabashedly able to
identify as a ball of rock, like the Earth, rather than a bag of gas like
Jupiter or Neptune.
Its discoverers estimated that the new planet was made of iron and silicate and
was about 70 percent larger in diameter than Earth. Moreover, as in our own
solar system, there are larger Jupiter-size planets orbiting Gliese 876 at
greater distances.
Never mind for the moment that it was so close to its home star, Gliese 876,
that you could bake a lasagna on its surface. The planet was hailed as yet
another sign that the cosmos was basically friendly and that sooner or later
planet hunters would find worlds as small as Earth out there, another step on
the road to finding out whether or not humanity is alone in the universe.
"We are beginning to find our planet's kith and kin among the stars," said
Geoffrey Marcy of the University of California, Berkeley, leader of the team
that discovered the Gliese planet.
And the joy of family reunion has resounded throughout the cosmos of
astronomers for more than 10 years now.
It was on the night of July 4, 1995, that Michel Mayor and his student Didier
Queloz woke up their wives at 4 a.m. to drink Champagne and eat raspberry pie
at an observatory in the south of France. The astronomers, based at the
University of Geneva, had just confirmed that an invisible object about half
the mass of Jupiter was sailing around the star 51 Pegasi, tugging it to and
fro every four days. It was the first planet ever discovered around another
Sun-like star.
Dr. Mayor and his student were using a humble little-used reflector a mere 76
inches in diameter, way small compared with the 320-inch behemoths then being
planned and built for cosmology. Their rivals, Dr. Marcy and Paul Butler,
professors at San Francisco State, had to make do with similarly unglamorous
circumstances at Lick Observatory. "We were typically assigned only two nights
per year, exactly when the Moon was full and no one wanted the telescopes," Dr.
Marcy recalled in an e-mail message.
Most of the 150 so-called exoplanets subsequently discovered have been found
using the "wobble" technique that Dr. Mayor's group and Dr. Marcy's group
pioneered. This consists of looking for a to-and-fro motion in the star,
induced by the gravitational tug of an orbiting planet.
In retrospect, it seems only natural that the first planetary systems these
astronomers discovered were psychotic beasts unlike anything previously
imagined. The more massive a planet is and the more tightly it circles its
star, the bigger the wobble and thus the easier it is to detect. As a result,
the first planets were so-called "hot Jupiters," orbiting their suns in a
matter of days instead of years, lethally searing and dense.
As time has gone on and they gather more data on various systems, the observers
have been able to detect smaller planets and ones that are farther and farther
from their stars, an effect astronomers refer to as "drawing back the curtain."
Last week astronomers announced the discovery of a planet with three suns, in a
configuration the theorists had thought was unlikely, if not impossible. Dr.
Marcy said in an interview that when the dust finally settled he expected that
planetary systems with architectures like our own - with Jupiter-mass planets
in circular outer orbits, leaving space for smaller planets in closer orbits
protected from comet showers - would be rare, "but not that rare."
Whether those planets will be suitable for life and intelligence is a different
matter, however, and one that reaches beyond astronomy into metaphysics and
theology. The requirements for Life As We Know It, some astronomers argue, are
so exacting that Goldilocks planets like Earth might be rare or even
nonexistent.
The list of astronomical requirements for life gets longer and more exacting
every year: the home star has to be far enough from the galactic center to be
away from lethal black hole pyrotechnics, for example, but not so far into the
galactic sticks that stellar evolution has not yet produced enough of the
heavier elements like oxygen and iron needed for planets and life.
Among other things, its planet has to have liquid water, a magnetic field to
keep away cosmic rays, plate tectonics to keep things stirred, a giant outer
planet to keep away comets and asteroids and perhaps a big moon to stabilize
its rotation axis.
Of the 200 billion or so stars in the galaxy, what fraction have the lucky
combo to win this cosmic lottery? Faced with the same paltry data, different
astronomers get vastly different conclusions, ranging from hundreds of
thousands to one, namely our own.
Among the various members of the planetary posse, Frank Drake, an astronomer at
the SETI Institute and a pioneer of the practice of listening with radio
telescopes for alien broadcasts, is one of the most optimistic.
"It may well be that there are far more habitable planets orbiting M dwarfs
than orbiting all other types of stars combined," he said on the institute's
Web site recently, referring to the dim red stars like Gliese 876. The SETI
Institute is holding a conference this week on the habitability of planets
belonging to such stars.
On the other hand are pessimists who argue that planets like the Earth and
therefore even simple life forms are rare. One is Ben Zuckerman, an astronomer
and exoplanet hunter at the University of California, Los Angeles, who admitted
in an e-mail message, "Frankly, the correct answer remains anyone's guess, and
the range of guesses is very wide indeed."
But, he emphasized, the question can actually be answered by future spacegoing
experiments like the Terrestrial Planet Finder and Kepler, which will find and
count habitable planets in our corner of the galaxy.
A null result would suggest that humans might be alone in the galaxy or the
universe.
This would merely be an interesting academic argument except for a film that is
going around, and which I recently viewed, called "The Privileged Planet,"
which suggests that the Earth's nice qualities are no accident.
The film, produced by Illustra Media in California, is based on a book of the
same name by Guillermo Gonzalez, an astronomer at Iowa State, and Jay W.
Richards, a philosopher and vice president of the Discovery Institute in
Seattle.
It argues that Earth is so special and unlikely that it must be the work of an
intelligent designer. "What if it's not a cosmic lottery?" Dr. Richards asks in
the film.
The Discovery Institute advocates "intelligent design," a notion that posits
the intervention by a designer, whether divine or not, in the origin and
history of life, as an alternative to standard evolutionary biology. Illustra
Media has produced a series of videos in support of this idea.
The showing of the film at the Smithsonian Museum of Natural History last month
exacerbated the worries of many astronomers that the Big Bang would be next on
the hit list of creationists.
Thoughtful cosmologists have long wondered about the apparent friendliness of
the universe to carbon-based life forms like us. The notion that the fix must
be in from a creator, however, has always been rejected as unscientific
thinking.
It's the job of scientists, after all, to pursue natural causes and
explanations, not settle for supernatural ones.
One such explanation for the specialness of the Earth, for example, comes from
theories of modern particle physics and cosmology, which seem to suggest that
there have been many, many Big Bangs resulting in a plethora of universes. We
live in one that is suitable for us the same way that fish live in the sea.
A prominent cardinal in the Catholic Church, Christoph Schönborn, recently
criticized this idea, along with evolution, in a July 7 article on the Op-Ed
page of The New York Times. He said the church needed to "defend human reason"
against "scientific claims like neo-Darwinism and the multiverse hypothesis in
cosmology invented to avoid the overwhelming evidence for purpose and design
found in modern science."
But the argument from design, many scientists say, is circular. Charles
Stevenson, a planetary scientist at Caltech, said that it was no surprise that
the Earth appears suited to our needs. "That's what Darwinian evolution tells
us should happen. We are adapted to our world," Dr. Stevenson said.
Who knows what powers atoms in their collective and complex majesty have to
respond to their environments over time?
Lacking anything approaching a final theory of physics, or of how planetary
systems form, and of more than one example of life - the biosphere on Earth -
scientists have no way of actually knowing how unlikely various properties of
life and the universe are. In science the smart money is always on surprise.
Everybody agrees that intelligent technological life is a much greater leap,
but it might be instructive to consider who is laying down bets on at least
looking for it. Among the financial angels of the search for extraterrestrial
intelligence, or SETI, have been people like Paul Allen, the co-founder of
Microsoft; the late Barney Oliver, William Hewlett and David Packard, leaders
of Hewlett-Packard; Gordon Moore, the founder of Intel; and the novelist Arthur
C. Clarke, who invented the idea of the communications satellite.
The smart money isn't always right, but this is certainly smart money.
a.. Copyright 2005 The New York Times Company
b..
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