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Climate Cycles Could Have Carved Canyons on Mars
1. The surface is of Mars etched with ancient river valleys and lake basins.
2. Which makes researchers think that liquid water once flowed on the Red planet.
3. But why?
4. Today, Mars is too cold for much, if any, liquid water to exist.
5. And 3.8 billion years ago, When the flowing water features formed, the sun was fainter than it is today, making it even harder to imagine a balmy Martian climate.
6. That's why many researchers think Mars have gone in and out of freezes.
7. The real questions have been: for how long was it warm, and what was the mechanism for warming it up.
8. James Kasting, a geologist at Penn State University.
9. He shared his take on problem at December meeting of American Geophysical Union in San Francisco, and in the journal Earth and Planetary Science Letters.
10. Some researchers have suggested that early Mars only thawed out when large asteroid impacts or volcanic eruptions temporarily warmed the planet.
11. Bur Kasting and others think warm windows from such dramatic events would have been too brief to carve the vast canyons that exist on Mars.
12. Now, Kasting and his colleagues have come up with on alternative explanation: they think Mars have experienced series a climate cycles coursed by changes in the strength of greenhouse effect.
13. The idea goes like this: When Mars was cold and frozen, volcanoes continued to belch out the greenhouse gases carbon dioxide and hydrogen into the atmosphere.
14. There, the gas blanket trapped heat and warmed the planet up until liquid water began to flow, forming Mars' rivers and lakes.
15. However, warm temperatures and abundant water would also have sped up certain chemical reactions that consumed carbon dioxide, reducing the greenhouse effect and cooling the planet back down again.
16. Then the cycle would repeat.
17. Which is similar to what the impact people have been arguing expect that when it gets warm, it can stay warm for millions of years instead of thousands of years.
18. So far, Kasting's team has only shown that such an explanation as possible, according to climate models.
19. But the researchers say NASA's Curiosity rover and other future Mars missions could help test the idea by looking for evidence of multiple warm events, and their durations.
20. Perhaps, hidden in the dry Martian dust lie clues to a surprising soggy past.
411 words / 22 minutes
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