Secret To Water On Mars: Greenhouse Gases Hydrogen and Carbon Dioxide
Mars, the fourth planet from the sun, has been a huge enigma for scientists for decades. There is no life on Mars, yet there is unmistakable evidence that everything needed to create the condition for life exists on the planet. The latest discovery made by NASA's rover Curiosity shows unambiguous signs of not just water but also several other elements to sustain life on Mars. "When we send people, they could scoop up the soil anywhere on the surface, heat it just a bit, and obtain water," according to a statement made in a press release by Laurie Leshin, dean of science at Rensselaer Polytechnic Institute
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However, the Red Planet's surface is even more intriguing. Its surface has valleys deeper than the Grand Canyon, and there are braided river channels to be found on Mars, in addition to a level sea shore reaching around the northern third of the planet. These are distinctive signs that there was a lot of water on Mars during the planet's early history. However, the planet is at present too cold for liquid water.
The enigma of Martian water for the scientists is that how could this planet have rivers and oceans 3.8 billion years ago, at a time when the sun was colder and dimmer, and yet now that the sun is hotter, the planet is too cold to host H20? A team of scientists from Penn State and NASA suggest the presence of hydrogen in the atmosphere might be the answer. "A CO2 -H2 greenhouse could have done the trick," writes Ramses Ramirez, lead author of a new paper appearing in the Nov. 24 Nature Geoscience.
Jim Kasting, a Penn State professor and fellow author on the paper says, "You just need a little nudge. On early Mars, you can almost make it warm enough with carbon dioxide and water vapor, but not quite. You need something to push you over the edge."
In the 1970s, valleys were discovered on Mars and scientists began to form different hypotheses to explain running water in the cold and minimal environment of the planet. Some scientists, for example, have suggested the possibility of a series of "transient" atmospheres. According to this explanation, big meteor impacts could have possibly delivered enough material into Mars's sky to cause a brief warm spell on the planet lasting long enough to melt huge chunks of ice into catastrophic floods.
Ramirez and Kasting, however, refute this argument claiming flash-in-the-pan transient atmosphere is incompatible with the amount of water required to carve and shape enormous valleys and channels on Mars. So, Ramirez and Kasting set out to model a stable, warm climate on early Mars.
In their opinion, the hydrogen-rich atmosphere of the outer planets might well have done the trick. Hydrogen in itself is too stable and symmetrical to be excited by passing the sunlight. However, on Earth and on Titan (Saturn's largest moon), hydrogen can trap massive amount of heat with support from nitrogen. Under the impact of nitrogen, hydrogen loses its stability and symmetry to become an effective greenhouse gas.
However, the mechanism that works on the Earth and Titan to create a warm environment by trapping heat seems problematic in case of Mars because the planet does not have enough nitrogen. So Ramirez and Kasting hypothesized that the presence of methane and carbon monoxide on Mars can interact to create carbon dioxide which works as well as nitrogen to knock hydrogen off-balance. The computer models of the early hydrogen atmosphere that Ramirez made along with even conservative estimates for the effective carbon dioxide-hydrogen collisions made all the difference.
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