“In fifty or a hundred years, we will know whether today’s climate models were right but if they are wrong, by then it will be too late,” according to David Grinspoon, astrobiologist and one of the world's leading authorities on Venus.
To help increase confidence in the computer models of global warming on Eatrth, Grinspoon believes that scientists should look at our neighboring planets. “It seems that both and Venus started out much more like Earth and then changed. They both hold priceless climate information for Earth,” says Grinspoon.
Modeling Earth’s climate to predict its future has assumed tremendous importance in the light of mankind’s influence on the atmosphere. The climate of our two neighbors is in stark contrast to that of our home planet, making data from European Space Agency's (ESA) Venus Express and Express invaluable to climate scientists.
The atmosphere of Venus is much thicker than Earth’s. Nevertheless, current climate models can reproduce its present temperature structure well. Now planetary scientists want to turn the clock back to understand why and how Venus changed from its former Earth-like conditions into the inferno of today.
They believe that the planet experienced a runaway greenhouse effect as the Sun gradually heated up. Astronomers believe that the young Sun was dimmer than the present-day Sun by 30 percent. Over the last 4 thousand million years, it has gradually brightened. During this increase, Venus’s surface water evaporated and entered the atmosphere. “Water vapor is a powerful greenhouse gas and it caused the planet to heat-up even more. This is turn caused more water to evaporate and led to a powerful positive feedback response known as the runaway greenhouse effect,” says Grinspoon.
Data from the European Venus Express spacecraft now orbiting Earth's twin planet have been piecing together an understanding of why the climate on both worlds is so different.
In the early stages of the Solar System, Venus seems to have evolved very rapidly compared to the Earth. Data from Venus Express supports the theory that the Earth’s twin once had significant volume of water covering the surface but it appears that these oceans were lost in a very short geological timescale.
As a result of the loss of water, the geological evolution of the surface of Venus came to a geologically abrupt halt because it was unable to develop plate tectonics like the Earth, which completely stymied Biological evolution.
'They may have started out looking very much the same,' said Professor Fred Taylor of Oxford Universit, 'but increasingly we have evidence that Venus lost most of its water and Earth lost most of its atmospheric carbon dioxide.'
Here, the CO2 is locked up in minerals in the crust, in the oceans, and in plant life. The release of some of this back into the atmosphere is the source of current concern about global warming and climate change. On Venus, most of the CO2 is still in the atmosphere and the surface temperature is a scorching 450 degrees Celsius, slowing or stopping geological as well as biological evolution -much too hot for life as we know it.
'The interesting thing is that the physics is the same in both cases' said Prof Taylor. 'The great achievement of Venus Express is that it is putting the climatic behavior of both planets into a common framework of understanding.'
The job is not finished yet - Venus Express is currently due to operate until May 2009, and the scientists involved are busy applying for an extension until 2011.
Posted by Casey Kazan. Adapted from materials provided by Royal Astronomical Society.
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