Our solar system once had a fiery planet. The surface of Mercury was once covered in oceans of magma, a new study suggests.

Based on data collected from NASA's Messenger spacecraft, which has been in orbit around the closest planet to the sun since March 2011, scientists believe the planet was most likely covered by a huge ocean of magma shortly after the planet's formation 4.5 billions years ago, Space.com reported.

The fiery conclusion was drawn after scientists were at a loss to explain two types of rocks present on Mercury's surface, leading them to deduce that the rocks must have been formed as a result of some very hot seas.

"The thing that's really amazing on Mercury is, this didn't happen yesterday," Timothy Grove, a professor of geology at MIT, said in a statement, according to Space.com. "The crust is probably more than 4 billion years old, so this magma ocean is a really ancient feature."

The $446 million Messenger spacecraft has an X-ray spectrometer which is able to distinguish the chemical compositions of material's on Mercury's surface, the article said.

Back on Earth, scientists re-created the the chemical makeup of the spacerocks and began to speculate on what sort of conditions must have been present in order to rocks with such a particular chemical makeup to have been formed.

The analysis pointed to only one possible origin of the two types of rock: An ancient ocean of magma created two layers of crystals, which eventually solidified and re-melted into magma that was spread onto the surface of Mercury through volcanic eruptions, the report stated.

"We're gradually filling in more blanks, and the story may well change, but this work sets up a framework for thinking about new data," said Larry Nittler, a researcher at the Carnegie Institution of Washington about studying the history of Mercury, according to the report. Nittler led the team that originally identified the two rock types on Mercury, but was not involved in the MIT laboratory study. "It's a very important first step toward going from exciting data to real understanding."

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