Sliver of Comet Found Inside Antarctica Meteorite

An illustration showing how a sliver of cometary building block material was swallowed by an asteroid and preserved inside a meteorite, where it was discovered by a Carnegie-led team of scientists. (Larry Nittler and NASA)

(CN) – Much like the popular movie scene where scientists discover an ancient insect preserved in amber, a Carnegie Institution for Science research team announced its discovery of primitive dust particles from a comet encased inside a meteorite found on Antarctica.

The findings, published by Nature Astronomy on Monday, may offer clues to the formation and evolution of our 4.5-billion-year-old solar system. The ancient sliver of the building blocks from which comets formed was discovered inside a primitive class of meteorites called carbonaceous chondrites, thought to have formed beyond Jupiter and landed in Antarctica’s LaPaz Icefield.

Scientists describe the LaPaz meteorite as a particularly pristine example showing minor weathering since landing on Earth’s surface. By studying a meteorite’s chemistry and mineralogy researchers can reveal details about its formation and how much heating and other chemical processing it experienced during the solar system’s formative years.

“Because this sample of cometary building block material was swallowed by an asteroid and preserved inside this meteorite, it was protected from the ravages of entering Earth’s atmosphere,” Carnegie study lead author Larry Nittler explained. “It gave us a peek at material that would not have survived to reach our planet’s surface on its own, helping us to understand the early solar system’s chemistry.”

Nittler’s team described finding a very carbon-rich slice of material that bears some striking similarities to extraterrestrial dust particles that are thought to have originated in comets that formed near the Solar System’s outer edges. This object – about one tenth of a millimeter across – was captured by the growing asteroid from which the meteorite originated about 3 to 3.5 million years after the solar system formed, but long before Earth finished growing.

Scientists conducted sophisticated chemical and isotopic analysis of the material to determine that the encased material likely originated in the icy outer solar system along with objects from the Kuiper Belt, where many comets originate. Defined by NASA, the Kuiper Belt is a donut-shaped region of icy leftover bits from the early days of our solar system that astronomers are just beginning to explore.

The existence of this primordial material inside the meteorite indicates that due to the drag caused by the surrounding gas, particles like it migrated from the outer edges of the solar system where comets and Kuiper Belt objects formed, to the closer-in area beyond Jupiter where the carbonaceous chondrites formed. The material reveals details about how our solar system’s architecture was shaped during the early stages of planet formation.

Meteorites were once part of larger bodies, asteroids, that broke up during collisions in space and survived the trip through the Earth’s atmosphere. Their makeup can vary substantially, reflecting their different origin stories from parent bodies that formed throughout the solar system.

Asteroids and comets both formed from the disk of gas and dust that once rotated around our young sun, but they clustered together at different distances from the sun, each with a differing chemical makeup. Comets contain larger fractions of water ice and far more carbon than asteroids.

Carnegie scientists Conel Alexande and Jemma Davidson, now at Arizona State University, Rhonda Stroud and Bradley De Gregorio of the U.S. Naval Research Laboratory, and Josep Trigo-Rodríguez, Carles Moyano-Cambero, and Safoura Tanbakouei of the Institute of Space Sciences in Barcelona, Catalonia, made up the full research team.

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