Washington - NASA scientists said Wednesday that a flyby of Mercury earlier this month has sent images showing 30 per cent of the planet never seen before.

"The region of Mercury's surface that we viewed at close range for the first time this month is bigger than the land area of South America," scientist Sean Solomon said. "When combined with data from our first flyby and from Mariner 10, our latest coverage means that we have now seen about 95 per cent of the planet."

NASA's Messenger spacecraft came within just 200 kilometres of Mercury on October 6 in the second of three planned flybys for the craft. It is due to settle into orbit around Mercury in 2011, providing what scientists hope will be the most complete picture yet of the solar system's smallest planet.

The 1,200 images show the planet's western hemisphere. Researchers hope to use them to map the planet's surface.

The flyby was designed largely to pick up a gravitational boost of energy for the craft.

Data from Messenger's first flyby in January showed massive lava flows had shaped the planet and provided the first information on 20 per cent of Mercury's surface.

In 1974-75, the NASA probe Mariner 10 made three passes by Mercury, giving space scientists their first information about the planet's magnetic field. (dpa)