It would be a suitable place for life if it were not so cold: its surface is extremely cold at about -180 degrees Celsius. Astronomers have compared Titan with the early Earth. 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.įinally, 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. About 3600 million years ago, something happened and the planet evolved towards its current state. 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. There are therefore extreme temperature contrasts between day and night and sun or shade. 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. The Red Planet displays hardly any greenhouse effect. 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.Īs a complete contrast to Venus, there is Mars. However, it's not a good example of what will happen to Earth due to human activities. 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. 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. Why is there so much carbon dioxide in the Venusian atmosphere? What made Venus evolve so differently from Earth? "Good questions. However, man-made emissions have caused carbon dioxide concentrations here to increase by about 30% since pre-industrial times. On Earth, carbon dioxide makes up only a tiny fraction of the atmosphere. This is hot enough to melt lead! The Venusian atmosphere is mainly made up of carbon dioxide, a greenhouse gas. Venus is similar to Earth in terms of size and mass, but its surface temperature is about 460 degrees Celsius. Titan's murky atmosphere with the Huygens probe descending on the leftįor a really strong greenhouse effect, we should look at Venus.
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