Astronomers announced the discovery of seven new ‘dark comets,’ which they suggest might be the means through which water is transported into the inner solar system.
NASA has announced the discovery of seven additional ‘dark comets,’ bringing the total count to 14. These dark comets represent a newly identified category of near-Earth objects, existing somewhere between asteroids and traditional comets.
Planetary scientists classify them as both comets and asteroids due to their orbits around the sun that bring them near Earth. While they resemble asteroids in appearance, their ability to accelerate unexpectedly hints at the possibility of emitting gas jets akin to those of comets.
A recent study by the National Academy of Sciences highlights the fascinating differences among these objects.
New comets detected in two distinct populations
Scientists have reported the detection of these seven dark comets within two separate populations. They claim that larger dark comets are found in the outer solar system, whereas smaller ones are located in the inner solar system.
Darryl Seligman, the lead author and a postdoctoral fellow in the Department of Physics at Michigan State University in East Lansing, stated, “We had accumulated enough dark comets to start investigating if there were any distinguishing characteristics among them.”
He further explained, “By examining the reflectivity, or albedo, and their orbits, we discovered that our solar system hosts two distinct types of dark comets.”
The authors propose that dark comets may have delivered essential materials for the development of life on Earth. This idea aligns with a paper published in Icarus in July, which suggests that dark comets are far more prevalent than previously believed and could have brought water to Earth long ago.
Scientists estimate that between 0.5% and 60% of all near-Earth objects could be dark comets originating from the asteroid belt between Mars and Jupiter. These dark comets, unlike asteroids, also contain ice, similar to traditional comets.
Asteroid that wanted to be a Comet
The initial discovery of a dark comet occurred in 2016 as scientists monitored the orbit of asteroid 2003 RM. This object exhibited a slight deviation from its orbit, a behavior previously attributed only to comets propelled by gas jets.
Davide Farnocchia, a co-author from NASA’s Jet Propulsion Laboratory in California, explained, “Such perturbations in a celestial object’s path generally indicate that it’s a comet, with volatile materials outgassing from its surface and providing a small thrust.”
“Despite our efforts, we couldn’t detect any signs of a comet’s tail. It resembled any other asteroid—merely a pinpoint of light. Thus, for a brief period, we had this peculiar celestial object that remained a mystery,” he added.
Dark Comets: Potential source of water and life
Determining how and when dark comets delivered water to Earth will be challenging to prove. The main asteroid belt is likely the source of near-Earth objects, which typically remain in their current orbits for only about 10 million years. Considering that the solar system is approximately 4.5 billion years old, this adds a layer of complexity to the investigation.
Seligman remarked, “Dark comets represent a new potential source for delivering the materials essential for life’s development on Earth. The more we uncover about them, the better we can comprehend their role in our planet’s origin.”
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