An international team of scientists claim that they may have traced the planet Mercury’s origin. Apparently, Mercury is formed by an extremely rare form of meteorite called enstatite chondrite.

Geologists from MIT believe that like other planets in the solar system, Mercury was the result when tiny particles of gas and dust combined into bigger meteoroids 4.6 billion years ago. These meteoroids then collided with each other, forming planets.

The meteoroid that formed Mercury was made of enstatite chondrite, which makes up only two percent of the meteorites that fall to our planet. Like other planets, Mercury’s material was not solid as it is now but actually used to be melted. They only cooled and solidified millions of years later.

Mercury

Mercury. Credit: ASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The geologists estimate that Mercury’s interior temperature decreased by up to 240 degrees Celsius. The findings are now available online in the journal Earth and Planetary Science Letters.

The researchers used data gathered by NASA’s MESSENGER spacecraft, which orbited Mercury from 2011 to 2015, taking pictures of Mercury’s lava deposits on the surface as well as measuring the planet’s radiation levels.

The spacecraft determined the chemical compositions of more than 5,800 lava deposits. Based on these, the research team believe that Mercury’s composition matched the enstatite chondrite.

Moreover, the scientists also report that some deposits are as old as 4.2 billion years old and some are 3.7 billion years old. The composition of older lava deposits was different from the new ones. The team believes that the older ones melted deeper than the young ones, about 360 kilometers deep at temperatures of 1,650 degrees Celsius.

On the other hand, the younger rocks only melted at 160 kilometers deep at temperatures of around 1,410 degrees Celsius. Mercury’s cool down took 500 million years, which occurred between 4.2 and 3.7 billion years ago.

However, according to Timothy Grove, the professor of Geology in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, the findings remains inconclusive. Since they did not actually study the rock samples,  other researchers may argue that Mercury might be made of another material besides enstatite chondrite.

“The next thing that would really help us move our understanding of Mercury way forward is to actually have a meteorite from Mercury that we could study,” concludes Grove. “That would be lovely.”