Mars’s dust bowl image may need a makeover. Dark streaks seen forming in summer and fading in winter might be signs of water flowing just beneath the surface.
The sudden appearance of streaks on sloping ground have been attributed to present-day liquid water before, although their origin is still debated. Light streaks have been seen appearing on steep slopes in images taken years apart by NASA’s Mars Global Surveyor spacecraft. And seasonal dark streaks have emerged in the north polar region.
Liquid water flowing downhill might explain both types of events, but dust or sand avalanches could also be to blame.
Now, new images have revealed a previously unknown population of seasonal dark streaks in Mars’s southern hemisphere, with characteristics that seem to tie them to liquid water.