In 2008, something unique fell from the sky over Sudan and exploded into fragments across the vast arid expanses of the Nubian desert.
This injurious object above was known as the Almahata Sitta: a collection of about 600 meteorite fragments, meticulously recovered by researchers and taking its name, “Station Six,” from a nearby train station.
What was unique about Almahata Sitta is that it represented something unprecedented in astronomy: the first time scientists successfully predicted an asteroid impact.
Since then, the fragments of this asteroid (called TC3 in 2008) have been analyzed by researchers, looking for chemical clues about the origins of this mysterious visitor.
Now, a new study unveils this intriguing story.
The fragment AhS 202. (Muawia Shaddad)
Looking at the chips, you can tell us about the 2008 TC3, which in turn can tell us where the 2008 TC3 itself came from, like an astronomical chain of overlapping Matryoshka dolls.
“Our startling result suggests the existence of a large, water-rich mother body,” says first author and planetary geologist Vicky Hamilton of the Southwest Research Institute in Boulder, Colorado.
In the new work, Hamilton and his research colleagues did not have much to work on, analyzing only the smallest part of this remarkable space rock.
“We were assigned a 50 milligram sample of Almahata Sitta to study,” Hamilton explains. “We assembled and polished the small fragment and used an infrared microscope to examine its composition.”
Spectral analysis revealed something scientists did not expect to find. Inside the fragment (a fragment called AhS 202) was found an extremely rare form of hydrated crystals, known as an amphibole.
This type of mineral requires prolonged periods of extreme heat and pressure, of a type not believed to be possible in carbonate chondrite (CC) meteorites.
Micrograph with amphibole crystals, orange. (NASA / USRA / Lunar and Planetary Institute)
The implications suggest that the 2008 TC3 probably belonged to a much larger body, in fact so large, that it would be virtually in the same class as Ceres: the dwarf planet, which represents the largest known object in the solar system. main asteroid belt, between the orbits of Mars and Jupiter.
“Most CC parent bodies are believed to be less than 100 km in diameter and therefore would not be large enough to produce the range of pressure and temperature conditions represented by the mineral assembly at AhS 202,” the authors in their article.
“As such, we interpret that the original parent body of AhS 202 was probably an unknown object, potentially of Ceres size (~ 640-1,800 km in diameter under the most likely conditions).”
Although it is believed that this mysterious giant asteroid no longer exists, the fact that it once inhabited our solar system suggests that more people of this type may have done the same, although we have not found evidence of these large rich in water. bodies in fragments of meteorites recovered before the 2008 TC3.
Just as the asteroids Ryugu and Bennu reveal some surprises in composition that differ from most known meteorites, the various splinters of the 2008 TC3 show that there is more to space rocks than current hypotheses can fully explain.
“We do not propose that AhS 202 be a spectral analog for Bennu or Ryugu; rather, AhS 202 is a source of information about the first materials in the solar system that are not represented by whole meteorites in our collections,” they conclude. the investigators.
“The difference between their mineralogy and that of known CC meteorites suggests that unique samples such as AhS 202 (and xenoliths in other non-CC meteorites) could be crucial links in our understanding of the diversity of parent asteroids.”
The findings are reported in Nature Astronomy.