NASA announced a year ago mysterious dark streaks on Mars might be caused by liquid water. But a new study out of Northern Arizona University says those features are actually dry.
The streaks — called recurring slope lineae — appear seasonally on slopes of Mars and then vanish again. Christopher Edwards of NAU’s astronomy department measured their temperature with an instrument on the Mars Odyssey orbiter.
Wet soil would heat and cool differently than the surrounding landscape. But Edwards found no temperature difference between the streaks and nearby areas.
That means the features can’t contain more than 3 percent water by weight.
“So these features are as wet as the driest deserts on Earth, no more wet than that!” Edwards said. “And they are in fact entirely consistent with dry surface materials. So that was the big finding of this study.”
Edwards said scientists need to consider other processes that could create the seasonal streaks.
The study appears in Geophysical Research Letters .