London, November 5 NASA's spacecraft Messenger has detected rich concentrations of iron and titanium on the surface of the planet Mercury.

Previous Earth and spacecraft-based observations had detected only very low amounts of iron in the silicate minerals covering the innermost world.

Because of its immense density, scientists have already assumed much of Mercury's interior contains iron.

According to a report by BBC News, Messenger sees the surface iron bound up in oxides with titanium.

"The iron is in a form that we don't normally encounter in other planetary situations and so it's going be a volley back to our geochemists and petrologists to come up with a scenario that's consistent with everything we are measuring now at Mercury," said the mission's principal investigator, Sean Solomon.

The new data was returned on Messenger's third and final flyby of the planet in September.

The pass, just 228km from the surface, was intended as a brake manoeuvre, using the planet's gravity to help slow the spacecraft enough to enable it to enter into orbit in 2011.

The spacecraft acquired only about half the data it was expected to because of a power "hiccup" just before closest approach.

Nonetheless, Messenger's cameras and instruments collected many high-resolution and colour images, unveiling another 6 percent of the planet's surface never before seen up-close.

Messenger is on course to enter into orbit in March 2011. (ANI)