WASHINGTON, Feb. 21 (UPI) -- NASA's Messenger is preparing to enter orbit around the planet Mercury, a world one U.S. scientist says has been "under-appreciated."
The spacecraft, due to settle into an orbit around Mercury on March 17, is the first visitor to the solar system's innermost planet since the Mariner 10 probe visited in 1974, sending back pictures of what seemed at the time an uninteresting planet when compared to Venus, Mars and the system's gas giants, the BBC reported Monday.
Nancy Chabot, who is Messenger's instrument scientist, says Mercury was "under-appreciated" and in fact may be unique among the planets.
It has a giant metal core unlike that any of the other inner Solar System planets, and scientists say understanding Mercury might be the key to understanding how all the inner rocky planets formed.
"What you can learn when you are in orbit is so different from when you are just flying past by gathering data as you go," Chabot said. "This is really going to revolutionize what we know about this planet."
Currently three theories have been put forward to explain Mercury's outsized metal core: that it was somehow created that way; that the planet used to be much larger and a giant impact ripped off much of the rocky crust; or, most intriguingly, that Mercury was once much larger but an early massive solar event partially vaporized its surface.
Messenger scientists will eagerly await data to start testing the competing theories.