Spitzer Learns About Carbon's Cosmic Life SPITZER LEARNS ABOUT CARBON'S COSMIC LIFE
Astronomers may be one step closer to understanding how the ingredients
of life are processed in space, thanks to NASA's Spitzer Space
Telescope.
On Earth, the elements carbon and hydrogen dominate the chemistry of all
life. Because molecules called polycyclic aromatic hydrocarbons, or
PAHs, contain both of these elements and are abundant all over the
universe, many astronomers suspect that they may be among life's
building blocks. PAHs are also especially hardy molecules -- typically
found in hot, chaotic regions of space -- leading some to believe that
they could have survived the harsh environments of the planet's early
days.
So, how do PAHs come to be? Astronomers may be one step closer to
solving this mystery, now that a team of scientists led by Dr. Greg
Sloan of Cornell University, Ithaca, N.Y., has detected many
predecessors of PAHs in a relatively cool region of space.
"One of the grea-*test*-('") mysteries in astrobiology is the question of what
happens to carbon before it is caught up in stars, planets, asteroids,
and comets. This finding brings us one step closer to answering that
question," says Sloan.
In the case of PAHs, "polycyclic" indicates that these molecules consist
of multiple loops of carbon atoms, while "aromatic" refers to the kinds
of strong chemical bonds that exist between the carbon atoms.
For years, astronomers believed that PAHs were the by-products of
another molecule. They suspected that the predecessors of PAHs contained
more delicate "aliphatic" carbon bonds. Because PAHs are typically found
in regions polluted with intense ultraviolet radiation, scientists
thought that harsh ultraviolet light might be responsible for breaking
the fragile aliphatic bonds. Astronomers predicted that the stronger
aromatic bonds of carbon and hydrogen atoms left over after the
ultraviolet zapping became PAHs.
Now, Spitzer's infrared spectrograph instrument has finally confirmed
this hypothesis by sensing many predecessors of PAHs -- molecules with
relatively fragile aliphatic bonds -- in a cool and tranquil region of
space. These molecules do not survive for very long in the hot, chaotic
cosmic environments where PAHs are usually found. Sloan suspects that
these molecules have yet to be processed by intense ultraviolet light
and become PAHs.
Astronomers agree that almost everything on Earth once came from a star.
A few minutes after the Big Bang, hydrogen and helium made up almost all
of the elements in the universe. Other elements -- including carbon --
were formed later through nuclear fusion in the cores of stars, and
ejected into space near the end of a star's life. Much of this material
spread across space as dust. By studying the organics in the dust and
how they are processed in space, scientists hope to understand how
planets like Earth and the life on it formed.
Sloan's paper on this finding will be published in a forthcoming issue
of the Astrophysical Journal.
http://www.spitzer.caltech.edu/Media/happenings/20070426/
Forumer™ is Voted #1 Free Forum Hosting provider
Build your own community today with the largest message board hosting company.