April 9, 2013
Volcanic Activity Would Have Helped Mars Sustain Liquid Water
Brett Smith for redOrbit.com - Your Universe Online
A new study suggests that Earth´s atmosphere is largely the product of carbon dioxide gas moving from the mantle to the surface through volcanic activity; if similar activity were to happen on Mars — the planet would be able to sustain liquid water.
According to the study, which appeared in the early online edition of Proceedings of the National Academy of Sciences (PNAS), greenhouse gases such as methane and carbon dioxide slowly make their way to the surface after the formation of a planet.
On Earth, carbon is sequestered in magma as carbonate and vented as carbon dioxide, which allows Earth´s atmosphere to trap heat from the sun. While scientists understand how this process plays out on Earth, little is known how it functions on other planetary bodies, such as Mars.
“We know carbon goes from the solid mantle to the liquid magma, from liquid to gas and then out,” said study co-author Alberto Saal, a professor of geology at Brown University. “We want to understand how the different carbon species that are formed in the conditions that are relevant to the planet affect the transfer.”
In the study, the team of American researchers said that the mantles of Mars, the Moon and other bodies trap carbon in their magma mainly as iron carbonyl and release it as both carbon monoxide and methane gas.
The authors also noted that the volcanic activity of Mars´ early history resulted in the release of enough methane to insulate the planet — making it much warmer than it should be. On a hot summer day, temperatures along the Mars equator can reach a high of 70 degrees Fahrenheit.
One of the major differences between Earth´s mantle and those of other planetary bodies is something called oxygen fugacity, or the total free oxygen available to react with other elements in the mantle. Today, Earth´s mantle has a fairly high oxygen fugacity; in the Moon and Mars, it is very low.
To understand how oxygen fugacity affects carbon transfer within the mantle, the researchers created experiments using volcanic basalt similar to what is found on the Moon and Mars. After melting the volcanic rock at varying pressures, temperature, and oxygen fugacities, the team discovered that at low oxygen fugacity levels, carbon was trapped as iron carbonyl and degassed as carbon monoxide and methane at lower pressures.
“We found that you can dissolve in the magma more carbon at low oxygen fugacity than what was previously thought,” lead author Diane Wetzel, a Brown graduate student, said in a statement. “That plays a big role in the degassing of planetary interiors and in how that will then affect the evolution of atmospheres in different planetary bodies.”
Scientists theorize that early Mars was home to giant active volcanoes. This would mean that massive amounts of methane were released via carbon transfer. Because methane acts as a more effective greenhouse gas than carbon dioxide, the study´s findings suggest that a thin atmosphere during Mars´ early history could have created ideal conditions for liquid water on the planet´s warm surface.