The persistence of life on Earth
Questions on habitability of the rocky planets
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Hypothesis: An object with twice the
mass of Mars collided with a planet in Earths orbit 4.5 billion years ago.
The core of the proto-earth stayed intact, the core of the lesser planet
was assimilated but the rocky mantle and the atmospheres of both planets
would have been completely destroyed . Part of this mantle material was
blown into space and formed the moon. Most volatiles condensed on earth.
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This cataclysmic event is relevant
to explaining the origin of earth's present kinetics. It explains the dynamics
of the planet; the 24 hour day, the continuing volcanism , plate tectonics
and most important, the recycling of carbon every two hundred million years.
It is this carbon cycle that has maintained the green house gases as well
as supplying the main nutrient for life.
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Radioactive decay, gravitational contraction,
phase shifts and other impact events are also major sources of internal
energy.
See Scientific American July 1994 "The
Scientific Legacy of Apollo" by G.
Jeffrey Taylor
Intelligent Life in the Galaxy
The evidence so far seems to agree with the hypothesis that
given a suitable environments, we can expect life to exist on many planets
in our galaxy. The Drake Equation popularized by Carl Saigon is that intelligent
life such as ours occurs regularly on a small percentage of planets that
produce life. This however does not convey the uniqueness of self conscious
intelligent life! Nature is more likely to produce the sea horse or the
platypus duck than anything like the human brain. All of these structures
are unique or exceedingly rare. Normal life in the universe consists mostly
of sausage shaped organisms metabolizing simple molecules or photons.
Humans are very strange creatures, there is nothing in
nature that came before with abilities anything like hominids. Whereas
other organisms use variations on physical themes such as swimming or more
efficient digestion, Humans have been successful by thinking. This is a
strange and unique ability. Yet it seems to be just a chance outcome. A
creature similar to modern chimps had the need to carry stuff and throw
rocks. These abilities are all that is needed to explain human anatomy.
Intelligence followed much later. Try running a computer simulation that
ends in intelligent life as we know it!
Let us never forget that most (80%) of life on this planet
is bacteria. Statistically the strangest part of all is that life in any
form has persisted for over 3.5 billion years on this planet Earth without
a cataclysmic event making the planet inhospitable for all life. Or even
more likely, an environmental change that destroyed all complex life forms.
For life to exist liquid water is required over this entire period.
Life is common and cheap and we will find many planets
just like Mars, where life existed at one period in time, but not for most,
or even a significant fraction of these planets histories.
