A NASA probe heading for Mercury is already making valuable observations although still months away from entering an orbit about the planet, scientists say.

The National Aeronautics and Space Administration's MESSENGER mission will establish an orbit around Mercury next March to start creating the most detailed maps ever made of the planet, SPACE.com reports.

As it heads toward orbit after three flybys of the planet, the probe has already beamed back views of the cratered world providing a fresh look into its volcanic past.

"Mercury is not what we thought it was even 2 1/2 years ago," principal mission investigator Sean Solomon said.

MESSENGER is the first spacecraft to examine Mercury up close since NASA's Mariner 10 mission in the mid-1970s.

In addition to new global maps, scientists hope the mission will reveal new clues to how Mercury was formed and how it evolved.

"We're trying to learn how a planet very near its host star differs from others that are more far out and more massive," Solomon said. "Exploring the inner part of our solar system is to understand our place in the solar system."