A relatively smooth, circular plain, possibly an ancient impact basin, in
the north equatorial region of Mars, 1,600
km (1,000 miles) across and 2.5 km (1.5 miles) below the average planetary
surface. It appears to have suffered water erosion in the past (see Mars,
water on) and was chosen as the site of the Viking
1 landing in 1976.
AND PLANETARY SCIENCE