Astronomers have discovered seven new “dark comets” that defy explanation due to their unusual behavior. Unlike traditional comets, dark comets lack tails but exhibit non-gravitational acceleration, similar to a comet’s tail, without the characteristic vaporization of ices.
The term “main-belt comet” has become increasingly blurred with the discovery of these enigmatic objects. Dark comets are found in two distinct families: one in the outer solar system and another closer to Mercury, Venus, Earth, and Mars. Analysis suggests that dark comets contain water ice beneath their surface, sparking debate over how they formed and originated.
Researchers believe that dark comets may be outgassing at a minimal level to produce non-gravitational acceleration. The discovery of 14 identified dark comets raises questions about their properties and potential role in delivering essential materials for life on Earth.
Source: https://www.space.com/the-universe/comets/astronomers-discover-7-new-dark-comets-but-what-exactly-are-they