Scientists have doubled the number of known enigmatic “dark comets” and report for the first time two such varieties, one in each of the inner and outer reaches of the solar system. These results, presented on December 9 in the Proceedings of the National Academy of Sciences, provide new avenues toward tracing the origins of life-giving materials on Earth.
The so-called dark comets, discovered back in 2016, are asteroid-like objects showing typical cometary behavior due to their volatile outgassing, which affects their orbits. Such bodies lack the usual comet tail, hence remaining as some kind of “cosmic chameleon.” The first steps in dark comet research began with asteroid 2003 RM: its unpredicted change of orbit indicated it was actually a comet masquerading as a simple point of light.
By 2023, seven dark comets had been classified new class of celestial objects. The latest study revealed another seven dark comets, and for the first time, astronomers could separate two different subgroups of dark comets:
Outer Dark Comets: These are larger bodies, hundreds of meters across, residing in the outer solar system on eccentric, elliptical orbits, just like Jupiter-family comets.
Inner Dark Comets: tens of meters in diameter, located within the inner solar system, and usually travel in nearly circular orbits.
This discovery not only helps explain their physical and orbital properties but also raises important questions about their origins and possible composition. Could these objects harbor ice and other raw materials that might have seeded the emergence of life? Researchers like lead author Darryl Seligman say that dark comets may have played a role in delivering the elements of life to Earth during its early formation.
The implications go beyond the study of dark comets themselves but also hint at a greater understanding of celestial mechanics and how dark comets can serve as delivery systems for organic compounds. As NASA and other agencies continue observing these unique objects, the insights gained may provide a clearer picture of Earth’s earliest building blocks.
With this doubling of known dark comets, scientists are now ready to explore their role in the solar system and their possible connections to the origins of life on Earth.
