Every asteroid that falls to Earth is a potential window into the origins of the solar system, but scientists have stumbled upon something very strange when studying a fragment of the Almahata Sitta asteroid. It contains evidence of a huge, previously unknown object in our solar system – perhaps a dwarf planet destroyed long ago.
Almahata Sitta’s asteroid collection consists of about 600 fragments, all of which rained down on Sudan in 2008 when the space rock known as 2008 TC3 exploded. This was the very first asteroid impact correctly predicted by scientists, giving ground teams a chance to dive in and collect lots of material from the 4-meter-high object.
Planetary geologist Vicky Hamilton led a new analysis of the Almahata Sitta material at the Southwest Research Institute. Hamilton’s team received a 50 milligram sample from the asteroid (AhS 202) for testing. They mounted and polished the small shard and used an infrared microscope to examine its composition. In AhS 202, the team found something unexpected – an extremely rare hydrated crystal known as an amphibole. This just shouldn’t have been part of the 2008 TC3.
These silicate crystals are only formed through prolonged exposure to high pressures and temperatures, which would never happen in a space rock like 2008 TC3 or other carbonaceous chondrite meteorites of similar size. According to the study, the only conclusion that fits what we know about amphiboles is that 2008 TC3 was once part of a much larger object. Researchers estimate that the mother body was about the size of the dwarf planet Ceres, which is 939 kilometers (583 miles) in diameter.
This section shows amphibole crystals in orange.
Obviously, we have not lost sight of any rock-sized planet floating in the inner solar system. It’s theoretically possible that there is still an undiscovered asteroid the size of Ceres in the outer Solar System that spawned TC3 in 2008, but that’s an outside opportunity. The researchers think it’s more likely that the parent’s body has long since crumbled to rubble. And if that happened once, it could have happened multiple times.
The study concludes that the Almahata Sitta fragments can glimpse a previously unknown phase in the formation of our solar system. This mysterious dwarf planet existed long enough to leave its geological mark, then for some reason split up. We probably want to understand that better.
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