Every asteroid that falls to Earth is a potential window into the origins of the solar system, but scientists have stumbled upon something quite 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 long since destroyed dwarf planet.
The Almahata Sitta 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 first-ever asteroid impact correctly predicted by scientists, giving teams on the ground the chance to swoop in and collect a great deal of material from the 4-meter (13-foot) 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 of the asteroid (AhS 202) for testing. They mounted and polished the tiny shard and used an infrared microscope to examine its composition. Inside AhS 202, the team found something unexpected — an extraordinary rare hydrated crystal known as an amphibole. This simply should not have been part of 2008 TC3.
These silicate crystals only form from prolonged exposure to high pressure and temperatures, which would never happen in a space rock like 2008 TC3 or other similarly sized carbonaceous chondrite meteorites. According to the study, the only conclusion that fits with what we know about amphiboles is that 2008 TC3 was once part of a much larger object. Researchers estimate the parent body was about as large as the dwarf planet Ceres, which measures 939 kilometers (583 miles) in diameter.
Micrograph showing amphibole crystals, in orange.
Obviously, we haven’t lost track of any planet-sized rocks drifting around the inner solar system. It’s theoretically possible there is still an undiscovered Ceres-sized asteroid in the outer solar system that spawned 2008 TC3, but that’s an outside chance. The researchers believe it more likely the parent body has long since crumbled into debris. And if that happened once, it might have happened numerous times.
The study concludes that the Almahata Sitta fragments could provide a glimpse of a previously unknown phase in the formation of our solar system. This mysterious dwarf planet existed long enough to leave its geological mark, and then it went to pieces for some reason. That’s something we probably want to understand better.
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