Nine places on Earth that mimic Mars terrain
Scientists say that Mars went through three ages, and the first age may have been habitable for life as we know it. Each stage on Mars can be found at nine different locations around the planet Earth today.
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In the Atacama Desert the soils are very old, up to 2 million years in age, as well as extremely dry and enriched in soluble salts similar to those found on Mars. The soils also possess very low levels of bacteria and organic materials, providing a way to study the rigors any Martian microbes might face.Skip to next paragraph
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Another way the soils in the Atacama Desert mimic Martian ones lies in how they possess levels of perchlorates nearly as high as those seen by the Phoenix lander on Mars. These were likely created by sunlight-induced chemical reactions in the atmosphere.
A contentious past
There have been decades of debate over how warm, cold, wet or dry Mars has been in the past, and not everyone agrees with the timeline that Fairen and his colleagues set forth.
For instance, during the earliest age of Mars, which Fairen and his colleagues set forward as cold and wet, "I don't think you can create the kinds of features that they see without a much warmer climate than they propose," said planetary scientist James Kasting at Pennsylvania State University, who did not participate in this study. "I don't believe in a cold, wet Mars — I think it was warm and wet in the distant past, and I think climate models for Mars bear that out. That doesn't mean that it was as warm as the Earth is today, but that mean annual temperatures were above the freezing point of water."
Fairen noted that it was "difficult is to know if the planet was warm or cold. Atmospheric models are unable to raise the temperatures on the surface over zero degrees C (the freezing point of water) whatever the concentration of carbon dioxide assumed, so additional gases must have contributed to warm early Mars.
Which gases did this, and what their concentrations were, is something that still needs to be determined, so the 'warm' model for early Mars lacks solid evidence. Alternatively, salty solutions could have kept liquid on Mars at temperatures somewhat under the freezing point of pure water, for a cold and wet Mars."
Regardless of the arguments over how warm or wet Mars was in the past, planetary scientist Victor Baker at the University of Arizona, who did not take part on this study, felt the timeline would help motivate research. "It can help us understand particular periods in Martian history and formulate strategies on where to go and search for life," he said. "They're presenting the idea that we have to think of Mars as a whole planet evolving through time, and as something that we can look at on Earth."
"If people don't like the timeline, that's a positive thing, too — they can go out and find hard data that the timeline is wrong, and then create a better one, and then science can move forward," Baker added. "This framework they propose is not absolute — it's a working idea. They're not saying this is absolutely the way Mars is, but that this is a way we can think of it as a strategy to learn more about the planet, and it's something we can revise as we move along."
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