Two Distinct Populations of Dark Comets Delineated by Orbits and Sizes

Abstract

Small bodies are capable of delivering essential prerequisites for the development of life, such as volatiles and organics, to the terrestrial planets. For example, empirical evidence suggests that water was delivered to the Earth by hydrated planetesimals from distant regions of the Solar System. Recently, several morphologically inactive near-Earth objects (NEOs) were reported to experience significant nongravitational accelerations inconsistent with radiation-based effects, and possibly explained by volatile-driven outgassing. However, these "dark comets" display no evidence of comae in archival images, which are the defining feature of cometary activity. Here we report detections of nongravitational accelerations on seven additional objects previously classified as inactive (doubling the population) that could also be explainable by asymmetric mass loss. A detailed search of archival survey and targeted data rendered no detection of dust activity in any of these objects in individual or stacked images. We calculate dust production limits of $\sim 10$, $0.1$, and $0.1$ kg s${}^{-1}$ for 1998 FR${}_{11}$, 2001 ME${}_1$, and 2003 RM with these data, indicating little or no dust surrounding the objects during the observations. This set of dark comets reveals the delineation between two distinct populations: larger, "outer" dark comets on eccentric orbits that are end members of a continuum in activity level of comets, and smaller, "inner" dark comets on near-circular orbits that could signify a new population. These objects may trace various stages in the life cycle of a previously undetected, but potentially numerous, volatile-rich population that may have provided essential material to the Earth.

12 pages, 11 figures, Author's version of Proc. Natl. Acad. Sci. Vol. 121 No. 51 published at https://www.pnas.org/doi/10.1073/pnas.2406424121

References in corpus (10)

• Interstellar Interloper 1I/2017 U1: Observations from the NOT and WIYN Telescopes
• Origin and Evolution of Short-Period Comets
• 1I/2017 U1 (`Oumuamua) is Hot: Imaging, Spectroscopy and Search of Meteor Activity
• Hayabusa2 Extended Mission: New Voyage to Rendezvous with a Small Asteroid Rotating with a Short Period
• Constraining the Physical Properties of Near-Earth Object 2009 BD
• Physical Properties of Near-Earth Asteroid 2011 MD
• Establishing Earth's Minimoon Population through Characterization of Asteroid 2020 CD${}_3$
• Radiation pressure detection and density estimate for 2011 MD
• SXDF-ALMA 2-arcmin^2 Deep Survey: Stacking of Rest-Frame Near-Infrared Selected Objects
• Seasonally Varying Outgassing as an Explanation for Dark Comet Accelerations

Cited by in corpus (1)

• Covertly Active Comet (139359) 2001 ME1