Dynamics and Origins of Dark Comets

Recent research suggests that up to 60% of near-Earth objects may be dark comets. These ambiguous asteroids, which orbit around the sun, likely hold ice or have previously contained it, potentially serving as a source for Earth's water. This conclusion comes from a study conducted by the University of Michigan.

The study indicates that asteroids in the asteroid belt—located between Jupiter and Mars—may hide subsurface ice. This claim aligns with suspicions held since the 1980s, as noted by Aster Taylor, a graduate student in astronomy and lead author. The findings present a possible method for delivering ice to the near-Earth region, addressing the long-standing question of how Earth acquired its water.

Taylor stated, "We don’t know if these dark comets delivered water to Earth. But our work shows there’s ongoing debate regarding how the Earth got its water." This research implies another pathway for ice transfer from other solar system regions to Earth.

The study indicates that one large dark comet may originate from the Jupiter-family comets. These comets usually orbit close to Jupiter. The team presented their results in the journal *Icarus*.

Dark comets maintain a unique mystery as they exhibit traits of both asteroids and comets. Asteroids are rocky with minimal to no surface ice and typically orbit within the ice line, where ice could sublime due to proximity to the sun.

Conversely, comets are icy bodies characterized by a fuzzy coma — a cloud surrounding the comet — as sublimating ice drags dust along. These comets often experience slight accelerations, known as nongravitational accelerations, caused by ice sublimation rather than gravity.

The current research evaluated seven dark comets. It estimates that between 0.5% and 60% of near-Earth objects might be dark comets. Unlike comets, these dark comets lack comae but exhibit nongravitational accelerations. The study suggests that most dark comets trace their origins back to the asteroid belt, proteins that support the premise of subsurface ice presence among these asteroids.

Taylor elaborates, "We believe these objects originate from the inner and/or outer main asteroid belt, serving as a mechanism for introducing ice to the inner solar system." This implies potential ice exists in larger quantities in the inner main belt than previously assumed, raising questions about the existence of similar objects.

In prior research, Taylor and a team characterized a group of near-Earth objects by their peculiar nongravitational accelerations, coining the term "dark comets." Their analysis indicated this acceleration likely resulted from small amounts of sublimating ice.

In their current work, Taylor and colleagues aimed to track the origin of these dark comets. They noted that near-Earth objects do not maintain their orbits for extended periods, staying in these environments for roughly 10 million years. The constancy of these objects implies a continuous influx from translations due to larger sources elsewhere.

To pinpoint the origins of dark comets, the researchers devised dynamic models that assigned nongravitational accelerations to various object populations. They analyzed how long these objects would follow their assigned states over 100,000 years. Their findings show many end up as dark comets today, primarily implying the main asteroid belt as their likely point of origin.

For example, one dark comet, known as 2003 RM, travels in an elliptical path sharply close to Earth. This evolution parallels the expected motions of Jupiter family comets — evidencing its inward trajectory.

On a parallel note, the research revealed that the other dark comets likely originated from the inner asteroid belt where ice is also present. The inference suggests even more existent ice within the inner sections of the main belt.

The researchers then applied previously acknowledged theories to evaluate why dark comets appear extensively small and with fast rotations. Comets can be visualized as rocky formations bound with ice, similar to a dirty ice cube. When they traverse beyond the solar system's ice line, sublimation begins, propelling gas and boosting acceleration.

As these ongoing physical modifications occur, the rapid motion can seemingly propel the comets to gain higher velocities—eventually leading to fragmentation. "As they fracture, they further spin and accelerate until they break into even smaller pieces," Taylor explained. Changes lead to continual loss of ice, shrinking their fitfully until they spiral further into quicker rotations.

The team concluded that while 2003 RM likely derived from an uprooted larger instance in the outer sections of the asteroid belt, the six additional dark objects studied corresponded to inner belt creations disturbed from their initial paths, leading to fragmentation.

Earlier, SSP reported that researchers developed instant turmeric milk.