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relates the discovery of extremophiles—bacteria that
thrive in harsh subterranean and deep ocean environments similar
to those believed to have existed on primitive Earth.
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describes an attempt to determine when life began on Earth by
searching rock formations in Greenland for higher-than-expected
ratios of carbon 12 to carbon 13 (in ratios currently only known
to be created by life processes).
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points to the comets and meteorites that struck Earth during its
early history as possible sources for the carbon and other
ingredients necessary for life to form.
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reveals the discovery of amino acids (organic acids that form
the proteins that are essential to life) in meteorites.
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describes an experiment that simulated a comet's massive impact
with Earth to determine whether certain amino acids could have
withstood such a collision.
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indicates experimental results that show that the amino acids
not only could have survived but also may have fused into
peptides (compounds formed by linking two or more amino acids).
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speculates that life may have begun deep in Earth's crust or
oceans, where it would have been protected from harsh solar
radiation, the high temperatures of Earth's surface, and
bombardment by meteorites.
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uncovers bacteria living deep below Earth's surface that obtain
energy from methane, ethane, and propane gases and suggests that
ancient bacteria might have derived energy in the same way.
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notes that surface bacteria that emerged following the Great
Bombardment likely developed the ability to photosynthesize.
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looks at stromatolites—both modern ones built from layers
of cyanobacteria and sediment and their fossil counterparts that
may have formed the same way—and reviews the role the
cyanobacteria played in creating an oxygen-rich environment in
which complex life could form.
NOVA reports on the different ways scientists explain how life
emerged on Earth.
