Recent times have been very favorable for people who are fond of astronomical genealogy. In fact, the results of several projects interested in unearthing the origins of meteorites. And their results have revealed that the families of origin of the meteorites that have rained down on us throughout our history are, in reality, quite small.
The meteoritesthose fragments of celestial objects that, after passing through our atmosphere, collide with the ground, are truly mysterious objects. In fact, they are the easiest way to have with us something extraterrestrialand always have been, long before we did everything possible to bring lunar or asteroid fragments to Earth, as happened with the lunar missions, from Apollo to Chang’e 6, or the Osiris-Rex missions or Hayabusa 2, respectively. The study of meteorites is one of the most valuable methods we have to understand our solar system and its evolution, a study that is sometimes fascinating because of the stories that revolve around the discovery and characteristics of these space samples. The search for the origin of meteorites It is framed in this context and takes as its starting point the fact that for a long time practically nothing was known about them.
How to study the origin of meteorites
In fact, as pointed out by the US National Scientific Research Center (CNRS), one of the protagonists of the latest research on the subject, until now only the origin of 6% of the 70,000 meteorites that we “own.” And the “family tree” pointed in that case to the Moonhe asteroid Vesta and Mars as a homeland. But how to trace these ancestors, that is, how was it possible to find out where the ancestors came from? meteorites? It is above all a question of chemistry: The composition of terrestrial samples is compared with that of celestial bodies (for example, by spectroscopic analysis). But not only that, chemistry by itself is not enough, because there is no unique correspondence between the meteorites we have here on Earth and the objects out there, the researchers behind the discoveries clearly write, from the pages of Naturealso with this other article, and those of Astronomy & Astrophysics (A&A). To get to the bottom of this enterprise, other data is needed, such as those relating to the dynamics of collisions between asteroidsthe analysis of the orbits of these objects and the age of the meteorites themselves, which can be deduced from values such as exposure to cosmic rays, as the researchers continue to explain.
A few families of origin
Proceeding in this way, the researchers were able to trace the origin of most of the meteorites and the events that would have generated them; collisions that occurred between 6 and 40 million years ago. The big picture suggests that three families of main belt asteroids gave rise to most meteorites: Karin, Koronis and Massalia. The origin of the meteorites would be attributable to collision events and destruction of bodies more than 30 km in diameter, but the shower of bodies falling on Earth would ultimately come from asteroids smallthe product of relatively young collisions.
This, the authors write, would also explain the abundance we observed of ordinary “chondrite” meteorites of type H and Lhigh and low iron content, respectively. L-type chondrites, in particular, would have originated from asteroids of the Massalia family, the researchers say. However, experts were also able to trace the origins of less common meteorites, such as carbonaceous chondritesin this case from the Veritas, Eos and Polana families (the latter, the authors point out, is possibly the mother of the very famous asteroids Ryugu and Bennureached by the Japanese and American space missions).
The origin of 90% of known meteorites (maybe)
It interesting of these investigations, which would allow us to explain where more than 90% come from of meteorites on Earth, is precisely their restricted origin. They come from just three asteroid families, and taking into account that asteroid families are a set of celestial bodies with similar orbital characteristics that are probably linked by birththat is, with a common origin, the bodies of origin of the meteorites would be few, as pointed out, among others, by Trevor Ireland, from the University of Queensland, in The Conversation.
Although, adds scientist Mikael Granvik, from the University of Helsinki, an expert in near-Earth objects (Neo), in an article on the same pages of Nature“the devil is in the details”, those of the complexes calculations and models carried out by researchers, who may not be able to capture in the most adequate way the dynamics that govern the evolution of collisions between asteroids. New experimental observations, both from small asteroids and meteorites, could perhaps support the researchers’ models, Granvik hopes.
Article originally published in WIRED Italy. Adapted by Mauricio Serfatty Godoy.
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