This image from NASA Mars Odyssey shows part of the eastern flank of Ascraeus Mons, one of the large Tharsis Volcanoes. The circular pits all aligned in a row mark the collapse of the roof of a lava tube.
This image from NASA Mars Odyssey shows part of the eastern flank of Ascraeus Mons, one of the large Tharsis Volcanoes. The circular pits all aligned in a row mark the collapse of the roof of a lava tube.