The McLaughlin Crater is 57 miles across and 1.4 miles deep (2.2 km). A combination of clues suggests this deep crater once held a lake fed by groundwater. That’s deep enough to have allowed water to remain hidden and is also in the right geographical location for underground water to pool. The crater sits at the low end of a regional slope several hundreds of miles long on the western side of the Arabia Terra region, The crater is marked by small channels as well as evidence that there may have at one time been a small lake. For the first time NASA has been able to measure the age of deposits in the crater. The analysis using measurements of the rock's potassium and argon content by NASA's Curiosity Mars rover yielded an estimate that it is 3.86 billion to 4.56 billion years old.