With the third and last flyby of Mercury by the MESSENGER spacecraft, NASA scientists have now imaged nearly 98 percent of the surface of the first planet from our sun. The photo above shows a color-calibrated view of a crescent Mercury, acquired on September 29.

This will be the last close-up color image of Mercury from MESSENGER until the spacecraft enters orbit in March of 2011. The remaining areas of Mercury to be imaged are in the polar regions, and those will be mapped at that time.

One of the previously unseen features is a large double-ring impact crater, seen above at upper left, estimated at a “youthful” 1 billion years old. (Other similar features on Mercury are 4 times that age!)

Read the official press release here.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington