Planetary scientists have wondered for decades why the surface of Mercury reflects so little of the Sun’s light . This planet, the smallest in the Solar System – in 2006, the International Astronomical Union considered that Pluto was not, and integrated it into a new category of objects, called “dwarf planets” – is only 58 million kilometers away. of the star king, that is, it is about two and a half times closer to it than the Earth.
However, it reflects much less sunlight than the Moon . Astronomers know that iron-rich compounds present on the surface of our satellite contribute to “darkening” it, but this does not appear to be the case for Mercury.
One of the strongest hypotheses that have been held so far stated that the cause was, in reality, the gradual accumulation of carbon , deposited in this world by the impacts of comets and asteroids. Now, a team of researchers from the Johns Hopkins University Applied Physics Laboratory in the US has confirmed the presence of carbon.
However, in a recent study published in the journal Nature Geoscience , they indicate that it did not arrive aboard space rocks, but originated deep within Mercury. In fact, they claim that it could have been part of its primitive crust, rich in graphite, which cracked and was buried during the formation process of what it looks today.
To determine this, physicist Patrick Peplowski, from the aforementioned US institution, which has coordinated the research, and his collaborators, carried out a thorough analysis of the data collected by NASA’s Messenger probe between 2011 and 2015. Measurements from the spacecraft, in orbit around Mercury, reflected a significant presence of low-energy neutrons , which, according to scientists, points to the presence of carbon , specifically, in the form of graphite .
The models developed by these planetologists reveal that when Mercury was young, most of it was covered by an ocean of magma . When it cooled, a good part of the minerals that solidified sank. The graphite, however, remained “afloat”, in such a way that it would give rise to the first crust of the planet . What remains of it would be found mixed with the rocks of volcanic origin and the remains of impacts that make up what we can see today.
Image: NASA / JHUAPL / Carnegie Institution
