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Location: UFOUpDatesList.Com > 2004 > Mar > Mar 13

Seeking Life as We Know It

From: UFO UpDates - Toronto <ufoupdates.nul>
Date: Sat, 13 Mar 2004 09:51:50 -0500
Fwd Date: Sat, 13 Mar 2004 09:51:50 -0500
Subject: Seeking Life as We Know It




[UFO UpDates thanks Greg Boone for the lead.

 Greg's message, accompanying the URL said: "Quite a suprise
 to read this. An intelligent non-confrontational story on
 searching for extraterrestrial life."]

Source: The L.A. Times

http://story.news.yahoo.com/news?tmpl=3Dstory&u=3D/latimests/20040305/ts_lat=
imes/seekinglifeasweknowit

Fri Mar 5 2004


Seeking Life as We Know It
By K.C. Cole Times Staff Writer

Albert Einstein once famously wondered whether God had a choice
in how he created the universe. His unanswered question drives
physics to this day.

The same question could be asked about the biological universe =97
especially now that the rover Opportunity has found signs of
ancient standing water on Mars.

NASA (news - web sites)'s search for alien life is based on the
strategy "follow the water," and for obvious reasons.

The only life we know is built on a scaffolding of carbon that
floats in bags of water. Bacteria or brontosaurus, we're all
made from the same basic recipe.

But did life have a choice? Could it have evolved from entirely
different ingredients? In looking for water-based life in worlds
beyond, are we making the mistake of peering into a mirror?

Why not life in ethanol? suggested Cornell University's Roald
Hoffmann, a Nobel laureate in chemistry. Or ammonia?

"Now life in liquid ammonia, that would be colorful," said
Hoffmann, explaining that metals can dissolve in ammonia,
"giving bright blue solutions."

And why does the scaffolding have to be carbon?

Why not silicon, its neighbor on the periodic table of elements?

"We're so dumb about what life is because we only have one
example," said astrobiologist Chris McKay of NASA Ames Research
Center at Moffett Field, near the Bay Area city of Mountain
View. "It may be true that we sail through the universe and
everything we find is carbon and water, but I would hesitate to
conclude that based on the one example we have."

As a practical matter, NASA's strategy of following the water
makes good sense.

"We don't know how to do anything better," McKay said. "We're
too stupid to look for things if we don't know what they are."

At $820 million, the twin rover missions have to look at what's
most likely. "If you had to bet, what would you bet on?" asked
Stanford chemist Richard Zare.

Still, one has to wonder what else might be out there.

The search is complicated by the fact that scientists aren't
even sure what life is exactly. Bizarre new species are
discovered on Earth all the time in the most unlikely places.

"We even have trouble understanding what's alive and what's
dead," Zare said. "People still wonder what a virus is."

All life as we know it is spun from carbon-based threads
swimming in water solutions. Both carbon and water have unique =97
some say magical =97 properties. Indeed, physics and chemistry
strongly suggest that life might not have had a choice.



Water is the most eccentric of liquids. "It's this elusive,
magical, mystery molecule," said James Garvin, lead scientist
for the Mars exploration program at NASA headquarters in
Washington.

On the face of it, water seems a rather silly molecule =97 two
hydrogen atoms attached to an oxygen atom in a way that looks
like the head of Mickey Mouse. Even children know its chemical
formula: H2O.

But the bonds it forms with itself and other molecules are
anything but ordinary.

Atoms normally bond by sharing the negatively charged electrons
that buzz around their positively charged nuclei, like people
sharing popcorn at a movie.

In water, the oxygen shares one electron with each of its
hydrogens, leaving four extras. These clump together as "lone
pairs" that can grab onto other molecules like prehensile feet.

At the same time, the two positive hydrogen nuclei stick out the
other side like arms. The "feet" of one water molecule grab the
"arms" of the other, forming abnormally strong networks. Where
one water molecule goes, the others tend to follow. Thus, water
can climb tall trees =97 hand over foot, as it were =97 in defiance
of gravity, carrying nutrients from the soil to the leaves.

Chemists say they would expect water to be a gas at room
temperature because it's made up of just a few light atoms. But
the strong bonds make the molecules stick together in a liquid
form.

Luckily, the bonds aren't so sticky that they form a viscous gel
=97 something that Boston University physicist Eugene Stanley
initially found perplexing. Water flows freely, he and others
discovered, because water molecules stick to each other only
briefly, let go, grab another partner =97 whirling an ever-
changing cast of partners around in a molecular square dance.

The upshot is that water stays watery over a remarkable range of
temperatures (32 to 212 degrees Fahrenheit, to be exact).

This is a liquid bonanza for life, which seems to need some form
of fluid to transport things from place to place. In solids,
molecules stick together and can't go much of anywhere. In
gases, the molecules don't get close enough to interact.

Water's unbalanced geometry =97 positive charges on one side,
negative on the other =97 also gives it a distinctively
schizophrenic personality (although chemists, like
psychiatrists, prefer the term bipolar). This makes it an
excellent solvent.

One side of a molecule grabs on to negative charges; the other
side grabs the positive. This pulls most things apart, so water
can dissolve almost anything. (If things didn't dissolve, they'd
sink to the bottom, or rise to the top =97 not good for a free
flow of chemical reactions.)

Why doesn't life just disintegrate altogether in water then?
While water is one of the most strongly bipolar molecules, it is
not the most reactive =97 meaning it can make things fall apart
(dissolve) without changing their composition (react). So the
parts can be endlessly rearranged.

And as it turns out, the few things water doesn't dissolve are
equally important in assembling life's building blocks. Water
hates fat. "It won't dissolve a spot of grease on my nice silk
tie," Stanley said.

Water herds these hydrophobic (water-hating) and hydrophilic
(water-loving) molecules into structures such as cells. The
hydrophobes point away from each other, while the hydrophiles
look inward. "It's like circling the wagons," McKay said.

Water, in other words, gives living things outsides and insides.
The hostile outside is kept at bay, while inside, the proteins
behind nearly all of life's mechanisms go about their business.

"You have 3,000 proteins, minimally, in every cell," said
University of Massachusetts biologist Lynn Margulis, "and every
reaction requires water. Everything else is negotiable."

What's the water doing with the proteins exactly? "Everything,"
Margulis said. "It's like a loom that you can do the weaving in.
It's the matrix that's holding things in place. Nothing can go
on without it."

The magical molecule does a whole lot more: For example, it
absorbs heat slowly, and holds on to it for a long time. This
stabilizes temperatures not only in the oceans, but also inside
living things =97 which, lest we forget, are made mainly of water.

Finally, water expands when it freezes, contrary to nearly every
other substance known. That's why ice floats, allowing it to
form an insulating blanket on lakes and ponds for life beneath.
Without it, fish would freeze before they hit the grocer's
shelves.

Of course, it's hard to ignore one obvious reason life may
depend on water. Hydrogen is the most abundant element in the
universe. Helium is the second, but it's inert =97 so standoffish
it doesn't bond with other atoms at all. Oxygen comes third.
Maybe life is made of water simply because it's there.

But some otherwise habitable worlds just don't have water. Are
they out of luck?

Not necessarily. "Water's a wonderful molecule," McKay said,
"but there are other wonderful molecules."

Ethanol, or grain alcohol, would probably work, concurred UCLA
chemist Ken Houk. Proteins and nucleic acids are soluble in
ethanol. But the liquid is rare in nature because the chemistry
needed to produce it is complicated.

In contrast, water "is the easiest fluid to make," Garvin said.

As for ammonia (used in smelling salts), it's scarce on Earth,
but "you could easily have an ocean of ammonia," Houk said. In
fact, scientists speculate that Saturn's moon Titan could have
such an ocean. Life could certainly exist at the cold
temperatures at which ammonia is liquid (between minus 28
degrees and minus 108 degrees on Earth). Like water, ammonia is
polar, and an excellent solvent.

Even if water does turn out to be the beverage of choice for
quenching life's insatiable thirst, does that mean carbon has to
be in the mix too?

Many scientists think it does.

"I feel more strongly about carbon than about water," said David
Des Marais, an astrobiologist at NASA Ames Research Center.

Again, there's an abundance argument. Carbon is the fourth-most
common element. And life grabs the ingredients at hand.

Carbon also has unique properties that allow it to form long
chains and rings easily.

Think of carbon as a small atom with four Velcro (actually
electronic) attachment points. One, two or three of these can
form links with other atoms, giving carbon enormous versatility.

Almost anything can find a way to attach. So carbon just
naturally makes the kinds of complex molecules life needs.

Like water, carbon is a Goldilocks substance: It forms strong,
stable bonds, but not so strong that those bonds can't break off
and attach to something else. "You have this kind of texture,"
Margulis said, "a range of properties that change in very subtle
ways."

Carbon's closest competitor, silicon, is not so subtle. Sitting
right below carbon on the periodic table of elements, it also
has four attachment points, but it's heavier and has different
chemical properties.

It can make long chains if you add oxygen, for example. But then
everything it touches turns to stone. "It locks on to things,
and folks, it's over," Zare said. "It's very hard to break the
bonds. It's like rigor mortis." So virtually any attempt at
metabolism as we know it would produce something solid.

Solid silicon compounds are already familiar =97 as rocks, glass,
gels, bricks and, of course, medical implants.

Life seems to have ignored silicon, except here and there as
structural material in rice, grasses and microscopic algae. How
ironic, Hoffmann noted, that the silicon worlds we build
ourselves (computers, electronics) now dominate our lives. "This
is silicon's revenge!"

If there were such a thing as silicon life, it would have to be
built on an entirely different biological model. It probably
would be stiff =97 unable to breathe, for example, as we do.

"You'd have to give up not just carbon but the whole pattern,"
McKay said. "We live as bags of liquid. A better model [for
silicon life] is more like computers, a rigid life form that
gets its energy from some electrochemical means directly."

Just because we do our chemistry on the inside, he said, doesn't
mean all life does. Silicon life might do its chemistry on the
surface.

But if silicon life appeared on ancient Earth along with carbon
life, as some speculate (rather wildly) that it might have, it
wouldn't stand a chance from an evolutionary perspective.

"You might be able to make living things out of different
materials," said UCLA planetary scientist David Paige. "But I'm
comfortable with the idea that the life we are is the best that
we could do given the constraints of our environment and the
laws of physics and chemistry."

Those laws of physics and chemistry apply to the entire
universe, so life elsewhere, Paige speculates, might well look
familiar. "If we find a planet that's covered with water, the
life forms are likely to look like fish, because there's a good
reason fish look like fish and dolphins and submarines."

Of course, life can't spring from carbon and water alone.

At a minimum, life also needs some form of energy =97 the kind we
use from the sun, or the heat of radioactive decay from deep
inside the Earth, or tidal friction that comes from being a
large moon (like Titan) orbiting a large planet.

Life, at its essence, is a mechanism for turning energy into
order.

Many purely physical processes do that as well: Gravity herds
stars into galaxies. The late Columbia University physicist
Gerald Feinberg and New York University biochemist Robert
Shapiro speculated that what they called "physical life" could
exist in solid hydrogen, in neutron stars, even in interstellar
clouds, living on the energy of radiation. This "radiant life"
would consist of individual beings they called "radiobes."

"It may be difficult to think of such systems of being alive,"
they acknowledged in an article included in the collection
"Extraterrestrials: Where Are They?" But our own biochemistry =97
based on proteins and nucleic acids =97 does little "to convey the
wonders, such as elephants and Sequoia trees, that ultimately
arise from it."

Would we recognize these alternative life forms if we saw them?
Probably not.

"Our imagination is biased by what we're able to see," Paige
said. "We can't be as clever as the universe. So we have to be
careful."

One of the mistakes of the 1976 Viking missions to Mars, Paige
said, was looking for life that was "too lifelike." Life, for
example, that eats familiar kinds of food, thrives in similar
environments.

Since that time, scientists have discovered bizarre new
biological worlds of so-called extremophiles on Earth, thriving
in places where life was thought to be impossible =97 such as
boiling-hot vents at the bottom of the ocean, shut off from
sunlight, subsisting on hydrogen sulfide.

These life forms (giant tube worms, for example) came as a
complete surprise. Now, many scientists believe they may be our
earliest ancestors.

More surprises are certainly in store. "We still don't
understand how life works," Houk said. "It's utterly miraculous.
Even though it's sitting there and staring us in the face, we
don't understand it."

-----






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