A meteorite fragment indicates a dwarf planet missing from the early solar system

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Every asteroid that falls on Earth is a potential window to the origins of the solar system, but scientists came across something quite strange when they studied a fragment of the asteroid Almahata Sitta. It contains evidence of a huge object, previously unknown in our solar system – perhaps a long-destroyed dwarf planet.

The Almahata Sitta asteroid collection consists of about 600 fragments, all of which rained in Sudan in 2008 when the space rock known as the 2008 TC3 exploded. This was the first correct asteroid impact predicted by scientists, giving teams on the ground a chance to enter and collect a lot of material from the 4-meter (13-foot) object.

Planetary geologist Vicky Hamilton conducted a new analysis of the Almahata Sitta material at the Southwest Research Institute. Hamilton’s team received a 50 milligram asteroid test (AhS 202) for testing. They mounted and polished the small fragment and used an infrared microscope to examine its composition. Inside the AhS 202, the team found something unexpected – a rare hydrated crystal extraordinarily known as amphibole. This simply should not have been part of the 2008 TC3.

These silicate crystals are formed only from prolonged exposure to high pressures and temperatures, which would never happen in a space rock like the 2008 TC3 or other carbonaceous chondrite meteorites of similar size. According to the study, the only conclusion that matches what we know about amphiboles is that the 2008 TC3 was once part of a much larger object. The researchers estimate that the parent body was as large as the dwarf planet Ceres, which measures 939 kilometers (583 miles) in diameter.

Micrograph showing amphibole crystals in orange.

Obviously, we have not lost track of any planet-sized rock moving around the inner solar system. Theoretically, it is possible that there is another Ceres-sized asteroid undiscovered in the outer solar system that generated TC3 in 2008, but this is an outer chance. Researchers believe that the parent body is more likely to have collapsed for a long time. And if that happened once, it could have happened countless times.

The study concludes that Almahata Sitta fragments could provide a glimpse into a previously unknown phase in the formation of our solar system. This mysterious dwarf planet existed long enough to leave its geological footprint and then fell apart for some reason. It’s something we probably want to understand better.

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