NASA on Tuesday released the first picture taken of Mercury's surface by the US space agency's orbiting Messenger craft.

"Early this morning, at 5:20 am EDT (0920 GMT), Messenger captured this historic image of Mercury," NASA said.

"This image is the first ever obtained from a spacecraft in orbit about the solar system's innermost planet."

The spacecraft snapped 363 images over the next six hours, and more were expected to be released Wednesday in conjunction with an expert press conference to discuss the findings.

The upper part of the image shows an unusual, dark-rayed crater called Debussy, while the lower part reveals a portion of Mercury near its south pole that has never before been witnessed by spacecraft, NASA said.

NASA's Messenger craft -- which stands for MErcury Surface, Space ENvironment, GEochemistry, and Ranging -- became the first vehicle to orbit Mercury on March 17.

Messenger was launched more than six years ago, traveling through the inner solar system and embarking on flybys of Earth, Venus and Mercury.

The first NASA craft to study Mercury since the Mariner mission more than three decades ago, Messenger has already been able to return a partial map of the planet's crater-filled surface after just a handful of flybys.