Valuable
clues
Our planet is warming up, and experts warn that the consequences
will be serious. To see precisely how the process works, scientists
need as much information as possible and from many different
sources.
There are valuable clues out in space. ESA's missions to
Venus, Mars, and Saturn's moon Titan will soon provide useful
information to understand how our own planet's climate is
regulated.
The Earth's climate seems to be changing much more quickly
than it used to do. We are altering one of our planet's natural
'temperature regulators' - the greenhouse effect. The greenhouse
effect determines the flow of energy arriving at and leaving
from Earth.
The Sun's energy heats the Earth's surface and the planet
radiates energy back into space. However, certain atmospheric
gases trap some of the outgoing energy, retaining heat. Without
this natural phenomenon, average temperatures on Earth would
be 30 degrees lower than the current 15 degrees Celsius.
Unfortunately, fossil-fuel combustion and deforestation release
large amounts of greenhouse gases to the atmosphere, strengthening
the greenhouse effect. Global temperatures have increased
more than half a degree in the last century as a result.
A look at Venus
For a strong greenhouse effect, we should look at Venus.
Venus is similar to Earth in terms of size and mass, but
its surface temperature is about 460 degrees Celsius. This
is hot enough to melt lead! The Venusian atmosphere is
mainly made up of carbon dioxide, a greenhouse gas. On
Earth, carbon dioxide makes up only a tiny fraction of
the atmosphere.
However, man-made emissions have caused carbon dioxide concentrations
here to increase by about 30% since pre-industrial times.
Why is there so much carbon dioxide in the Venusian atmosphere?
What made Venus evolve so differently from Earth? "Good
questions. That is precisely one of the things we want to
find out,” says Hakan Svedhem, Project Scientist for
ESA's mission Venus Express, due for launch in 2005.
Is Venus a mirror that reflects how the Earth will be if
global warming continues at its current speed? "Venus
will help us understand what happens when the greenhouse
effect is really extreme. However, it's not a good example
of what will happen to Earth due to human activities. Life
on Earth would disappear due to the extreme temperatures
much before reaching even half of the concentrations of carbon
dioxide on Venus!" says Svedhem.
Mars & Titan
As a complete contrast to Venus, there is Mars. The Red Planet
displays hardly any greenhouse effect. Mars does have some
atmospheric carbon dioxide, but almost no atmosphere! The
existing atmosphere is so thin that it cannot retain energy
from the Sun. There are therefore extreme temperature contrasts
between day and night and sun or shade. However, most scientists
agree that Mars was much warmer in the past and even had
oceans, which means that the atmosphere was also very different.
About 3600 million years ago, something happened and the
planet evolved towards its current state. What could have
triggered such a huge change in climate? "We will answer
this question with Mars Express,” explains Agustin
Chicarro, Project Scientist of ESA's mission to Mars, due
for launch in May 2003.
Finally,
if we look at Titan, Saturn's largest moon, we see a moderate
greenhouse effect mostly due to the large concentrations of
methane, another greenhouse gas, in its atmosphere. Astronomers
have compared Titan with the early Earth. It would be a suitable
place for life if it were not so cold: its surface is extremely
cold at about -180 degrees Celsius. Understanding which factors
influence Titan's climate would be enormously helpful to us,
on Earth. "What we learn on Titan will certainly be useful
to understand the other planets", confirms Jean-Pierre
Lebreton, Project Scientist of Huygens, ESA's probe to Titan.
Reprinted courtesy of ESA
© Copyright 2003. Galt Western Personnel
Ltd. Unless otherwise specified, you may reprint this article,
quote from it, use it in research or projects, duplicate it or
distribute it. Credit of authorship and source MUST be given to
galtglobalreview.com. Ownership of Copyright remains with Galt
Western Personnel Ltd.
