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The uncertainty of science: An analysis of five years of data from Mars Odyssey suggests that the dark streaks flowing down Martian slopes might contain very little and possibly no water at all.
This year, planetary scientists Christopher Edwards and Sylvain Piqueux took a closer look at the feature using a thermal imaging instrument on board Mars Odyssey, another orbiter. They found no temperature differences between the dark RSL streaks and surrounding terrain — which suggests that the streaks aren’t really patches of wet sand streaming down a slope. At best, they say, the RSLs could contain no more than 3 percent liquid water — making them more like mildly damp, slightly salty dirt. And that’s an optimistic interpretation, Edwards said; it’s possible the RSLs contain no water at all. “Why this process is happening in this area, or what is causing this darkening, I don’t think is exactly obvious at this point,” he continued. “But to say it’s flowing liquid water, I don’t think it’s the whole story. It’s not necessarily even the right story.”
This data once again illustrates why we must be very careful with our conclusions when looking at features on an alien world that seem to resemble things we are familiar with here on Earth. Just because they might look alike is not evidence that they are the same. Mars has a very different gravitational field (one-third of Earth’s) and a significantly different make-up. We might be witnessing processes we’ve never seen before that produce features that mimic Earthlike forms.