NASA Discovers Seven More Puzzling 'Dark Comets', Unveiling Unknown Details
NASA recently announced the discovery of seven new "obscure comets," bringing the tally of this unusual celestial category to 14.
Obscure comets represent a fresh category of near-Earth objects, lying between asteroids and typical comets. As explained by astronomers, these celestial bodies share characteristics of both comets and asteroids. Their orbits around the sun bring them close to Earth, yet they exhibit unexpected acceleration, akin to comets that release gas jets.
Despite this similarity, obscure comets differ from typical comets in that they lack a cloud of dust, known as a coma, surrounding their nucleus. Furthermore, they bear a resemblance to 1I/'Oumuamua, the interstellar object detected in 2017 that traversed our solar system.
Obscure Comets: Two Populations in Our Solar System
A new report, published today in the Proceedings of the National Academy of Sciences, reports the detection of seven obscure comets in two distinct populations. The researchers propose that larger obscure comets reside in the outer solar system, while smaller ones are found in the inner solar system.
"With a sufficient number of obscure comets, we began exploring the possibility of distinguishing features between them," stated Darryl Seligman, the lead author and a postdoctoral fellow in the Department of Physics at Michigan State University, East Lansing. "Analyzing the reflectivity and orbits revealed that our solar system hosts two distinct types of obscure comets."
Obscure Comets: More Abundant Than Previously Thought
The researchers suggest that obscure comets, containing volatile substances and organics, may have supplied materials necessary for the development of life on Earth. A study published in July in Icarus argued that obscure comets are more common than previously believed, potentially delivering water to Earth in the past.
This study examined seven obscure comets but estimated that between 0.5 and 60% of all near-Earth objects could be obscure comets from the asteroid belt between Mars and Jupiter. Since obscure comets contain ice, like comets but unlike asteroids, they could serve as the primary means for water to enter the inner solar system.
Obscure Comets: The Asteroid Pretending to be a Comet
The first obscure comet was discovered in 2016 when researchers noticed an anomaly in the trajectory of an asteroid called 2003 RM. Its path appeared to deviate slightly, a phenomenon typically associated with comets propelled by gas jets.
"When you discover such perturbations in celestial objects, it's usually a sign of a comet with gas expelling from its surface, providing a slight boost," explained Davide Farnocchia, a co-author from NASA's Jet Propulsion Laboratory in California. "However, despite our efforts, we failed to identify any indications of a comet's tail. It simply looked like any other asteroid, just a spec of light. For a while, we had this peculiar celestial object whose true nature remained elusive."
That discovery, dubbed "The Asteroid That Felt Like a Comet," was followed a year later by the discovery of 1I/'Oumuamua, the interstellar object whose behavior was reminiscent of 2003 RM, moving like a comet but appearing as a solitary point of light, similar to an asteroid. "The resemblance between the first extraterrestrial object we encountered and 2003 RM made 2003 RM even more intriguing," said Farnocchia.
Obscure Comets: A Potential New Source of Water—And Life?
Determining how, when, and to what extent obscure comets delivered water to Earth will be challenging to prove. The main asteroid belt is the most likely source of near-Earth objects, but such objects only maintain their current orbits for approximately 10 million years. Our solar system is over 4.5 billion years old.
"Obscure comets represent a new potential source of the materials necessary for the development of life on Earth," stated Seligman. "By learning more about them, we can better understand their role in Earth's origins."
Wishing you clear skies and curious minds.
- The newly discovered obscure comets belong to two distinct populations, with larger ones residing in the outer solar system and smaller ones in the inner solar system.
- The study suggests that obscure comets, rich in volatile substances and organics, could have contributed to the development of life on Earth by delivering water.
- The first identified obscure comet, 2003 RM, presented an anomaly in its trajectory, showing slight deviations similar to comets but without any visible tail.
- The behavior of 1I/'Oumuamua, the interstellar object detected in 2017, shared similarities with 2003 RM, moving like a comet but appearing as a solitary point of light, leading to its classification as an obscure comet.
