Environmental Engineering Reference
In-Depth Information
greenhouse effect. Though the cause of the runaway on
Venus is not fully understood, we do know the conse-
quences. Today the Venusian atmosphere is about
times
denser than ours and it consists almost entirely of CO .The
greenhouse effect is huge and so is the surface temperature.
Mars is smaller than Earth. Its diameter is
% of ours
and its surface gravity is
% of ours. The person
weighing
pounds on Earth, and
pounds on
Venus, would weigh only
kg) on Mars.
This low gravity is what makes Mars lifeless today. Mars
has an orbit that is one and a half times as large as ours
and so receives much less sunlight. Its surface temperature
in the absence of any greenhouse effect would be about
pounds (
C). However, from the data trans-
mitted from the Martian Rovers that traveled its surface in
F below zero (
, we think that the red planet once had
liquid water. It could only have had that if a greenhouse
effect had once kept the temperature above the freezing
point of water,
and
C). Unfortunately for Mars, its
low gravity let its atmosphere (now only
þ F(
% of the density
of Earth
s atmosphere) diffuse away into space and with it
went its greenhouse effect.
My science-
'
ction Martians knew their fate and
mourned it; my Venusians ignored their fate and regret
it, but this is science, not sci-fi,
, and the moral to be drawn
about our activities and the greenhouse effect is that if you
do not understand what you are doing, changing things
on a global scale can be dangerous. Just how dangerous is
the subject of Chapter
. For now, remember that the
Earth has been hotter and the Earth has been colder than
it is today. Human existence has spanned many ice ages.
The transition fromNeanderthal man to Homo sapiens (us)
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