The research also indicates asteroids in the main belt may contain higher amounts of water than previous estimates.
Illustration of a Dark Comet. (Image Credit: University of Michigan).
New Delhi: Classically, the small objects in the Solar System were categorised either as asteroids or as comets. Asteroids are rocky objects that are in close orbits around the Sun, within what is known as the ice line. Within the ice line, the heat from the Sun is sufficient to sublimate any ice on the asteroid, that is changing it directly from solid ice to a gaseous form. Comets are icy bodies that develop a tail whenever they come close to the Sun, because of the breakup of icy material from the heat.
Comets also have slight accelerations that cannot be explained by gravity alone, caused by the sublimation of the ice, known as nongravitational accelerations. There are some small Solar System bodies that share characteristics with both asteroids and comets, called centaurs and active asteroids. Now, scientists have proposed a new type of small Solar System body, known as dark comets.
What are dark comets?
Dark comets are mysterious asteroids that likely contain ice, or could have previously contained ice. The researchers investigated seven dark comates, and determined that as much as 60 per cent of all near Earth objects could be dark comets. Near Earth objects or NEOs are small Solar System bodies that orbit the Sun in the same neighbourhood as the Earth. This population is highly unstable, with the objects maintaining these orbits for only about 10 million years. The Sun is 4.6 billion years old, which indicates that the existing NEOs are being constantly replenished.
The researchers traced the origin of the dark comet population by creating dynamical models that accounted for the nongravitational accelerations to objects from different populations of asteroids dispersed throughout the Solar System. The researchers then modelled the trajectories that these objects would follow over a period of 100,000 years, and determined that the most likely origin of the dark comets were the asteroids from the main belt.
Main belt asteroids may contain more water than previous estimates
Most of the asteroids in the Solar System occupy the main belt between Mars and Jupiter. The new research suggests that many of the rocky asteroids in the main belt, have subsurface ice. There has been mounting evidence since the 1980s suggesting that asteroids indeed contain more water ice than previously believed. While comets were believed to be the objects that delivered water to an ancient Earth, allowing life to spring up, the new research suggests that the water could have been delivered by dark comets as well.
A paper describing the research has been published in Icarus. Lead author of the paper, Aster Taylor says, “We don’t know if these dark comets delivered water to Earth. We can’t say that. But we can say that there is still debate over how exactly the Earth’s water got here. The work we’ve done has shown that this is another pathway to get ice from somewhere in the rest of the solar system to the Earth’s environment.”
Shambhu Kumar is a science communicator, making complex scientific topics accessible to all. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
