Exotic ‘never-seen-before’ crystals found in 21st century’s biggest meteoroid to fall on Earth

Unique and miniscule carbon crystals in a variety of unusual shapes and having “unique morphological peculiarities” have been found in dust from a space rock that had exploded in Russia nearly a decade ago.

The exploding space rock – known as a superbolide – fell on 15 February 2013 in the Southern Urals region and is the biggest meteoroid to have exploded on Earth in the 21st century to date.

It exploded about 23km above the city of Chelyabinsk – about 1,440km east of Moscow – causing immense public concern, as over 1,000 people were injured and 3,000 buildings were damaged.

Space experts called the event an immense wake-up call to the dangers posed by asteroids and other space rocks to the planet.

But the event also generated significant scientific interest as it brought with it unique materials from space that cannot be reproduced in even advanced labs.

The superbolide’s disintegration in the atmosphere as it entered the planet was accompanied by the formation of a gas-dust plume at altitudes of about 80-27km which subsequently settled down on Earth, as detected by several satellites.

Scientists have now found micrometre-sized carbon microcrystals in the Chelyabinsk dust, said a new study published recently in the journal EPJ Plus.

The crystals take up a variety of unusual shapes such as closed, almost spherical shells, and hexagonal rods, it pointed out.

“We focused on unique morphological peculiarities of carbon crystals from the meteoroid’s dust component,” said scientists, including those from the South Ural State University in Russia.

“The first carbon crystal was found during an investigation of the dust using an optical microscope, because its facets happened to be in the focal plane,” they added.

Researchers also found several other similar microscopic fragments in the meteoritic dust.

Further tests using other chemical analysis methods and X-rays revealed that the carbon crystals were made of layers of exotically-shaped forms of graphite surrounding a central nanocluster at its heart.

The most likely candidates for these nanoclusters are suspected by scientists to be buckminsterfullerene (C60), a cage-like ball of 60 carbon atoms, or polyhexacyclooctadecane (C18H12), a molecule made from carbon and hydrogen.

The microscopic structures likely formed from repeatedly adding graphene layers to closed carbon nuclei created by the extreme temperature and pressure conditions when the meteor broke apart.

In future studies, researchers hope to track down and analyse other meteorite dust samples to understand if these exotic crystals generally form via meteor break-ups, or if they are unique to the Chelyabinsk superbolide.