NASA has announced the discovery of seven more “dark comets,” doubling the previously known number to a total of 14. These celestial objects blur the distinctions between asteroids and comets, challenging long-standing perceptions about near-Earth objects (NEOs). Their study could provide valuable insights into the origins of Earth’s water and the development of life.
According to a recent study in the Proceedings of the National Academy of Sciences, dark comets are divided into two distinct groups based on size, reflectivity, and orbital patterns. Larger dark comets are located in the outer solar system and follow elliptical orbits similar to Jupiter-family comets. In contrast, smaller ones reside in the inner solar system, near planets like Earth and Venus, and travel in more circular paths. These differences suggest varied origins and evolutionary trajectories within the solar system.
Dark comets are a unique category of NEOs that appear asteroid-like in their lack of a visible coma but exhibit comet-like behaviors, such as unexplained accelerations. This behavior hints at the possibility of gas emission, although no visible evidence of outgassing, such as tails, has been observed. These objects are also extremely dark, akin to the interstellar visitor ‘Oumuamua, which passed through the solar system in 2017 and exhibited similar traits.
The first dark comet, asteroid 2003 RM, was identified in 2016 when its trajectory showed deviations typically associated with gas-emitting comets, despite lacking visible signs of outgassing. This led scientists to consider a new classification, reinforced by the subsequent discovery of ‘Oumuamua. Together, these findings underscore the existence of a mysterious type of celestial body.
Dark comets are thought to have played a crucial role in Earth’s formation, potentially delivering water and organic materials essential for life. Recent studies estimate that a significant proportion of NEOs could be dark comets originating from the asteroid belt. Their icy composition supports theories that such objects, rather than traditional asteroids, may have brought water to the inner solar system.
Studying dark comets poses significant challenges due to their low reflectivity and unusual accelerations, which defy conventional orbital mechanics. However, their potential role in delivering the building blocks of life to Earth makes them an exciting area of research. Each new discovery brings scientists closer to understanding these enigmatic objects, their influence on Earth’s history, and their broader role in the dynamic processes shaping the solar system.
