Sulfur dioxide contributed to warm climate on early Mars

December 21st, 2007 - 1:20 pm ICT by admin  

Washington, Dec 21 (ANI): Geoscientists at Harvard University and the Massachusetts Institute of Technology have suggested that sulfur dioxide might have played a crucial role in maintaining a warm climate on Mars during its early history.

This study, they say, may resolve longstanding questions about the Red Planets climate.

“There is abundant evidence for a warmer climate, perhaps even a liquid water ocean, early in Martian history, between 3.5 and 4 billion years ago,” said Daniel Schrag, professor of earth and planetary sciences and environmental engineering at Harvard and the paper’s senior author.

“However, scientists have found it difficult to reconcile this evidence with our understanding of how the climate system is regulated on Earth,” he added.

For over millions of years, the Earth’s climate has been controlled by the carbon cycle and its effect on carbon dioxide, the main greenhouse gas. On Earth, there is a balance between carbon dioxide vented from volcanoes and chemical reactions with silicate rocks on the Earth’s surface that remove carbon dioxide from the atmosphere and convert it to calcium carbonate, commonly known as limestone.

Scientists believe that this balance has helped maintain Earth’s habitability over the last four billion years.

On Mars, there is not enough volcanic activity today to maintain this cycle. But this was not true some four billion years ago, when a giant volcanic complex called Tharsis erupted from time to time. Evidence suggests Mars then had a much warmer climate.

The new hypothesis points to sulfur dioxide for maintaining the balance in the Red Planets climate .

Sulfur dioxide is a powerful greenhouse gas, like carbon dioxide, and it is more reactive with silicate rocks than carbon dioxide. On Earth, sulfur dioxide is rapidly oxidized to sulfate, and then removed from the atmosphere. The authors argue that the atmosphere of early Mars would have lacked oxygen, so sulfur dioxide would remain much, much longer.

“The sulfur dioxide would essentially preempt the role of carbon dioxide in surface weathering reactions,” said Halevy, the first author of the report. “The presence of even a small amount of sulfur dioxide in the atmosphere would contribute to the warmer climate, and also prevent limestone deposits from forming,” he added.

“We think we now understand why there is so little carbonate on Mars, and so much sulfur,” said Halevy.

“Our hypothesis may also be important for understanding the early Earth,” said Schrag. “Before the origin of life, our atmosphere may have looked much like early Mars. Sulfur dioxide may have had an important role then as well, he added. (ANI)

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