How the origin of 90% of meteorites was lastly revealed | EUROtoday

DWhere do the meteorites that cross our sky come from? These extraterrestrial rock fragments, which you will have already picked up in a area or admired on the National Museum of Natural History, maintain fascinating secrets and techniques in regards to the photo voltaic system.

For centuries, solely the origin of 6% of meteorites discovered on Earth was decided. Today, a world staff of researchers, made up of a number of French scientists, has succeeded in elucidating 90% of this thriller, marking immense progress and opening new views for scientific analysis. This discovery is described in three research: the primary, revealed in September within the journal Astronomy and Astrophysics and two others not too long ago revealed in Naturewhich made the entrance web page of the journal.

The 6% of meteorites whose origin was identified got here from the Moon, Mars and the asteroid Vesta. Michaël Marsset, astronomer on the European Southern Observatory (ESO) and member of the scientific staff, explains: “For the Moon, the samples brought back by the Apollo missions allowed a direct comparison. For Mars, it is the rare gases trapped in meteorites which correspond to the Martian atmosphere. Concerning Vesta, its unique spectral signature, confirmed by observations, facilitated the association with certain meteorites. » On the other hand, for the majority of meteorites in the main asteroid belt, located between Mars and Jupiter, the spectral similarities complicated the identification of their true source.

To achieve this impressive result, scientists crossed five sources of information: first, spectroscopic data from collisional families, groups of asteroids resulting from the fragmentation of the same body, sharing orbital properties and a common composition ; then, the composition distribution of near-Earth asteroids, ejected from the main belt and capable of colliding with the Earth; then, pre-atmospheric data on meteors observed in the Earth’s atmosphere, making it possible to triangulate their trajectories and recover samples; finally, the characteristics of meteorites, such as their shock age, linking the fragments to their origins, and the distribution of zodiacal dust, which can be associated with asteroid families and meteorite classes. Everything was combined with extensive simulation work.

It is this meticulous and large-scale collaborative approach that made it possible to identify the origin of 84% of meteorites, in addition to the 6% already known!

A paradox to resolve

However, the researchers initially stalled. “We always came back to the same eternal paradox: our simulations indicated that the most massive families of asteroids should provide the majority of meteorites. However, it was enough to examine the characteristics of the said meteorites to see that it absolutely did not fit,” says Pierre Vernazza, astrophysicist at LAM (Marseille Astrophysics Laboratory) and co-author of this work. This inconsistency has raised many questions amongst researchers.

It was solely by observing the distribution of zodiacal mud that scientists lastly had a hunch about what was mistaken. “Apart from the dust logically concentrated in the plane of the planets’ orbit, called the ecliptic plane, we spotted individual dust bands at particular orbital inclinations corresponding to the position of young asteroid families. However, each of the families from which these bands of dust seemed to spring corresponded spectroscopically to a major class of meteorites found on Earth. It could hardly have been a coincidence,” mentioned Michael Marsset. “This is where we understood the key element: collisions generate many more small fragments than the models predicted,” factors out Pierre Vernazza.

This is how researchers managed to find out that 70% of all 70,000 meteorites listed in world collections – peculiar chondrites often called H and L varieties – got here from simply three younger households of asteroids: Karin , Coronis and Massalia. Three households born from collisions that occurred in the primary asteroid belt 5.8, 7.5 and roughly 40 million years in the past, respectively.

The solely Massalia household being recognized because the supply of 37% of all identified meteorites, the L-type chondrites. The H-type chondrites come from the Coronis and Karin households, which is none apart from a subfamily of the primary. Finally, relating to the valuable carbonaceous meteorites, which symbolize roughly 4.4% of the falls, they’d come from households of asteroids reminiscent of Veritas (sort CM), Polana (sort CI) and Eos (sort CO/CV/ CK).

Fascinating views

But why are these younger households accountable for almost all of meteorites? This is defined by their abundance of small residual fragments, which improve the chance of collisions and, because of their excessive mobility, favor their ejection out of the primary belt, doubtlessly in direction of the Earth. This can also be why the big households of asteroids, ensuing from older collisions, are now not on the origin of the meteorites that we all know as we speak.

These sources have now dried up: the small fragments that after composed them have eroded till they disappear. “Which will also inevitably happen for Karin, Coronis and Massalia within a few tens of millions of years,” underlines Pierre Vernazza. These households will then coexist with new sources of meteorites from more moderen collisions and, finally, will give approach to them.

That mentioned, a brand new collision may very properly restart the manufacturing of meteorites from an historical household. Researchers consider that is what occurred in Massalia’s household. Indeed, along with the collision that occurred roughly 40 million years in the past which is on the origin of the present L chondrite falls, one other would have occurred 470 million years in the past leading to a meteorite bathe, doubtlessly accountable of an ice age and a change in biodiversity.

“Indeed, a team of geologists in Sweden realized that, in the sedimentary rocks of this geological period, which we call the Middle Ordovician, there was the trace, in the form of micrometeorites, of a bombardment chondrite massif L”, signifies Michael Marsset. An episode to which latest analysis carried out in China has given a worldwide dimension.

This identification of the origin of meteorites opens up fascinating views: it should make it attainable to hyperlink our bodies presently circulating in house to occasions which have marked the historical past of our planet and the evolution of life. What’s extra, the scientific staff did not simply examine meteorites; it additionally examined the origin of near-Earth asteroids, these objects which cross Earth’s orbit and represent a most popular goal for house missions (OSIRIS-REx, Hayabusa 2, Dart, Psyche, Hera and shortly Ramses).

To Discover



Kangaroo of the day

Answer

“In particular, we noted that two recently sampled asteroids, Bennu and Ryugu, probably come from the same parent body, that of the Polana family. It’s perhaps a bit of a shame,” remarks Pierre Vernazza. One factor is definite: sooner or later, exploration missions for these small our bodies – true archives of the photo voltaic system – will have the ability to select their targets with extra discernment, thus making it attainable to gather new samples, doubtlessly from households of which we have no idea. we nonetheless haven’t any meteorites on Earth.

As for the scientific staff behind this advance, they intend to work on the origin of the ten% of meteorites whose provenance stays unidentified.