Mysterious 'Obscure Comets' Divide into Two Unique Categories, Research Reveals
Mysterious 'Obscure Comets' Divide into Two Unique Categories, Research Reveals
In 2017, an intriguing visitor with an unconventional shape made its way through our solar system. This interstellar object, subsequently named 'Oumuamua, was initially categorized as an asteroid—until measurements revealed its unusual behavior. It was found to be accelerating away from the Sun, much like a comet. Consequently, scientists labeled it as a dark comet: an object that shares the appearance of an asteroid but exhibits comet-like characteristics. Recent research has now increased the count of known dark comets to 28, dividing them into two distinct groups.
A study published this week in the Proceedings of the National Academy of Sciences announced the discovery of 21 dark comets, thereby boosting the total count to 28. The findings also reveal that these enigmatic celestial bodies can be classified into two distinct categories based on their orbit and size. With this latest discovery, scientists are gaining more insight into dark comets and their potential role in delivering the building blocks of life to Earth.
The first dark comet was detected in 2016 when scientists noticed an unusual trajectory in near-Earth asteroid 2003 RM. “Anomalies in the path of a celestial object typically suggest the presence of cometary vapors, propelling the object,” explained Davide Farnocchia, a researcher at NASA’s Jet Propulsion Laboratory and co-author of the new study, in a statement. “However, despite our efforts, we couldn’t locate a comet’s tail. It appeared like any other asteroid—just a faint point of light. For a short while, we were puzzled by this peculiar celestial body.”
The following year, 'Oumuamua captured everyone's attention, and scientists drew comparisons between the two objects. “The fact that the first interstellar visitor exhibited similar characteristics to 2003 RM made 2003 RM even more interesting,” Farnocchia added.
By 2023, six more celestial bodies with mixed asteroid and comet properties had been identified, leading researchers to officially recognize them as dark comets. With the discovery of 21 more dark comets, the researchers involved in the new study believed it was time to delve into the unique features of these objects. “We now had enough dark comets to consider whether there were any distinguishing factors between them,” Darryl Seligman, a postdoctoral fellow in the department of Physics at Michigan State University and the lead author of the new study, said in a statement.
By examining their reflectivity and orbits, researchers identified two distinct populations of dark comets within our solar system. The outer dark comets, analogous to Jupiter-family comets, have highly eccentric orbits and are considerably larger. The second group, referred to as inner dark comets, traverse the inner solar system in almost circular orbits and tend to be smaller.
Scientists are still in the early stages of understanding these strange celestial bodies. A recent study suggested that approximately 60% of all near-Earth objects are dark comets that might have originated from much larger bodies in the main asteroid belt, a region that lies between Mars and Jupiter, before being ejected and fractured into smaller fragments that now come closer to Earth.
Dark comets might have significantly contributed to the emergence of life on Earth. “Dark comets present a new potential source for delivering the necessary materials to Earth for the emergence of life,” Seligman said. “As we learn more about them, we can better understand their influence on Earth's origins.”
The discovery of these dark comets through advanced technology and scientific research opens up new possibilities for our understanding of the universe's formation and the delivery of life-forming materials to Earth. With the advancement of space technology, future missions could potentially investigate these enigmatic celestial bodies further, shedding light on their role in shaping the history of our solar system and possibly our planet.