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Life on Earth may have roots in air
early atmosphere capable of assembling life’s ingredients
By Ron Cowen
When it comes to determining exactly
where in the solar system life began,
things have never been so up in the
air. Over the past decade, scientists
have suggested deep-sea hydrothermal
vents (SN: 2/2/08, p. 67), underground
aquifers, partially frozen lakes (SN:
10/23/10, p. 11) and even comets as locations for the origin of life.
Now an experiment that simulates
chemical reactions in the atmosphere
of Titan, Saturn’s haze-shrouded moon,
adds a new location to the list of unexpected places where the chemistry of life
could have developed — in the sky.
Using radio waves as an energy source
to bombard a mix of gases in a steel reaction chamber, researchers simulated
ultraviolet radiation from the sun striking the top of Titan’s thick atmosphere
and breaking apart gas molecules such
as methane and molecular nitrogen.
The experiment is the first to produce,
without liquid water, the basic chemical ingredients of life — the amino acids
found in proteins and the nucleotide
bases that make up DNA and RNA.
The results suggest that Titan’s upper
atmosphere, about 1,000 kilometers
above the frigid moon’s surface, could
produce chemical precursors to life,
planetary scientist Sarah Hörst of the
University of Arizona in Tucson reported
October 7. And because planetary scientists believe that Titan provides a
snapshot of the early Earth, the study
also indicates that building blocks for
terrestrial life might have formed within
a primordial haze high above the planet
rather than in a primordial soup on the
surface, Hörst said.
Planetary scientist Jonathan Lunine,
also of the University of Arizona but not
part of the study, notes that the com-
pounds found in the experiment “are
relatively simple precursor molecules
to life, and so there are a lot of addi-
tional steps between such molecules
and life itself, most of which will likely
require a liquid, such as water or meth-
ane.” However, he adds, everything that
forms high in Titan’s atmosphere does
eventually end up in the moon’s lakes
and seas of methane.
The atmosphere of Titan, a Saturn moon
thought to resemble early Earth, could
contain chemical building blocks for life.
To confirm that amino acids and
nucleotide bases are actually produced
in Titan’s atmosphere will require
another orbiter that can carry instruments 100 to 200 kilometers deeper
than Cassini does into Titan’s haze
layer, Lunine says. s
Saturn moon may
sport seltzer sea
Fizzy ocean could be source
of eruptions on enceladus
By Ron Cowen
Eau my! Things could be really popping
on Saturn’s moon Enceladus. A fizzy
ocean, similar in carbonation to Perrier,
may feed the plumes of water vapor, gas
and ice that erupt from the moon, a new
model suggests.
Since 2005, when the Cassini space-
craft first observed icy plumes spewing
from the south pole of Enceladus (SN:
5/6/06, p. 282), researchers have specu-
lated that an ocean may lie buried tens
of kilometers beneath the moon’s frac-
tured, icy surface. Now Cassini scientist
Dennis Matson of NASA’s Jet Propul-
sion Laboratory in Pasadena, Calif., and
his colleagues propose adding a bit of
effervescence to that watery hypoth-
esis. A bubbly ocean containing 1 or
2 percent dissolved carbon dioxide and
other gases could supply water, gas, dust
and heat to Enceladus’ polar plumes,
Matson reported October 5. Carbon-
ation could also explain why some of the
ice grains expelled by the plumes carry
sodium and potassium salts.
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November 6, 2010 | science news | 15
