NASA announced two years ago strange dark streaks on Mars might be formed by liquid water. But a new study led by a Flagstaff geologist says that’s not the case. KNAU’s Melissa Sevigny reports.
Colin Dundas of the U.S. Geological Survey examined NASA images of the dark streaks. He discovered they form on Martian dunes that slope at a particular angle.
"What we found in this paper is that they end on slopes that match the “angle of repose” for dry sand, which is the slope that you get if you heap up dry sand and it slides under its own weight," he explains.
So, the streaks behave like tumbling sand grains, not like flowing water. Dundas says this doesn’t rule out liquid water on Mars, but it supports the idea of a cold, dry planet.
There are still unanswered questions, such as why the streaks appear and vanish with the seasons, and what makes them dark in color. The paper appeared in Nature Geoscience this week.