The US space agency's robotic Mars explorer Opportunity has arrived at Endurance Crater, where it has been travelling to for about three weeks.
The rover has now sent back a spectacular image from the western rim of the 130m-wide depression.
Patches of thick rocky outcrop can be seen exposed all over the interior of the impact crater.
Nasa scientists now have to decide whether it is safe to send the rover in to explore the crater's geology.
On Saturday, Opportunity completed a 50m (164ft) drive, followed by a final approach of 17m (56ft) to the crater.
The western side of the crater rim slopes down in front of Opportunity with an angle of about 18 degrees for about 17m (56ft).
On Tuesday, the rover is due to take high-resolution miniature thermal emission spectrometer readings of the far crater wall to pick out interesting rock targets for possible further investigation.
Opportunity has uncovered evidence that its landing site at Meridiani Planum was once the shoreline of a salty lake or sea. This came from examination of a rocky outcrop in that crater.
Those rocks are thought to have been laid down in sediments beneath a gently flowing body of water.
The outcrops in Endurance crater are thought to be much thicker than those at Opportunity's landing site.
They could reveal an even more detailed picture of the history of liquid water on the Red Planet.