Has pieces of mercury already fallen on earth? Two mysterious meteorites sow doubt

No one has ever walked another planet. And yet some people visit us. Meteorites, these fragments of asteroids or planets torn off by violent impacts, are messengers of the solar system. Thanks to them, we were able to study Mars pieces, who fell on earth there are millennia. But what about mercury, this planet so close to the sun that it becomes almost inaccessible? A new study relaunches an old mystery: what if two meteorites found in the Sahara were actually from the burning surface of Mercury?

Mercury, the prohibited planet

With an average temperature of around 167 ° C (and much more extreme peaks), Mercury is not really a dream destination. Located just 58 million kilometers from the sun, the planet is a real mineral hell, beaten by intense radiation. The rare probes having attempted to approach him – like Mariner 10 or Messenger – had to deal with extreme conditions. And no machine has yet arose on its surface.

So, while waiting for the European-Japanese Bepicolombo mission to do it (in 2026), our best chances of analyzing Mercury may rest … on pebbles that have fallen here, on earth.

Desert meteorites that intrigue scientists

It is in the Sahara, a large desert and hunting ground ideal for meteor hunters, that two intriguing specimens were discovered. Called Ksar Ghilane 022 (Tunisia) and Northwest Africa 15915 (Morocco), these meteorites are not like anything known.

They are classified as achondrites, that is to say meteorites without chonders (these small spheres characteristic of many primitive meteorites), rich in silicates such as olivine or pyroxene. Until then, nothing abnormal. But it was their similarities with the data collected on the Mercury crust by the Messenger probe that caught the attention of the team led by Ben Rider-Stokes, planetologist at the Open University (United Kingdom).

Pebbles from Mercury… or almost?

So can they really come from Mercury? The answer is: maybe. But it’s complicated.

Because if their chemical and mineralogical composition seems compatible with the mercurian crust, a detail does not stick: isotopic signatures of oxygen and the content of iron -poor silicates. These properties are close to those of the Aubritis, another class of meteorites that we think from asteroids rich in Enstatitis – but no mercury, the surface of which is much richer in metals and displays a very different light spectrum.

So why this resemblance? This is where the theory of “proto-mercure” comes into play.

What if they came from an old mercury, now disappeared?

Several billion years ago, Mercury was perhaps very different. Its primitive surface, before being riddled with impacts and modified by volcanism, could have presented a composition closer to that of these mysterious meteorites. These fragments – aged approximately 4.5 billion years – could therefore be vestiges of an old crust, disappeared since.

Another possibility: they do not come from mercury, but from a celestial body today disappeared, a distant parent, a “pre-mercor” of the internal solar system. A hypothesis which, if confirmed, would offer an unprecedented window on the very early stages of our solar system.

Bepicolombo: the justice of the peace

For the moment, no formal evidence makes it possible to assert that these two meteorites come from Mercury. But with the upcoming arrival of the Bepicolombo mission in orbit around the planet, scientists hope to be able to compare in detail the spectral data of the surface of Mercury with those of these mysterious terrestrial samples.

If direct correspondence was found, this would change our understanding of the geological history of Mercury-and would confirm that it is possible, although extremely rare, that a piece of this ultra-proctrocal planet of the sun has succeeded in us.

A pebble of the sun under your feet?

Whether they come from Mercury or not, Ksar Ghilane 022 and NWA 15915 are exceptional. They remind us that each meteorite is a fragment of cosmic history, and that our planet, far from isolated, regularly receives the visit of stones that fell from the heavens – sometimes from worlds that we have never approached.

The next time you come across a strange pebble in the desert, who knows? Perhaps there is a secret of 4.5 billion years old-and coming straight from solar hell.