Active Small Bodies as Probes of Solar System Formation

Active small bodies—including comets, active asteroids, icy minor planets, and transitional objects—occupy a unique position in planetary science. As remnants of the protoplanetary disk, these objects preserve some of the most pristine materials from the earliest epochs of Solar System formation. Their episodic activity, whether driven by sublimation, impacts, rotational instability, or more complex physical processes, provides a rare and dynamic window into their internal structure, composition, and evolutionary pathways. Studying these bodies therefore allows us to probe not only their individual histories but also the conditions and mechanisms that shaped the young Solar System.

Over the last decade, a series of space- and ground-based observations, ranging from Rosetta’s in situ exploration of comet 67P, to high-resolution spectroscopy and imaging from James Webb Space Telescope (JWST), to synoptic surveys such as Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), ATLAS, and the upcoming Rubin Observatory Large Synoptic Survey Telescope (LSST), have revealed a remarkable diversity of activity among small bodies. Active asteroids blur the classical boundary between asteroids and comets. Interstellar comets like 2I/Borisov and bodies in the trans-Neptunian region exhibit unexpected levels of volatile release. Some Centaurs undergo sporadic outbursts that challenge existing models of thermal evolution. Together, these findings highlight the need for an integrated framework that connects physical activity to dynamical evolution, composition, and source reservoirs across the Solar System.

This Research Topic aims to gather contributions that advance our understanding of how active bodies can be used as natural probes of Solar System formation and early evolution. We welcome original research articles, observational studies, laboratory investigations, modeling efforts, and comprehensive reviews. Topics of interest include, but are not limited to:

• Drivers of activity in comets, active asteroids, Centaurs, and trans-Neptunian objects.
• Compositional studies of volatiles, dust, and refractory materials as tracers of primordial reservoirs.
• Dynamical pathways, including scattering, migration, and orbital evolution, and their role in shaping observed activity.
• Comparative studies of native and interstellar active bodies, including constraints on protoplanetary disk diversity.
• Thermophysical and structural modeling that links observed activity to interior evolution.
• New insights from survey-driven discoveries, including early-phase detections of activity.
• Implications for Solar System formation models, including mixing, radial transport, and disk chemistry.

By bringing together a multidisciplinary set of perspectives, from observers, theorists, laboratory scientists, and mission specialists, this collection seeks to chart a coherent view of what active bodies reveal about the origins and evolution of our planetary system. With upcoming missions (e.g., Comet Interceptor), enhanced detection capabilities, and increasingly sophisticated modeling tools, the coming years promise transformative advances in our understanding of active small bodies. We invite researchers from all subfields to contribute to this effort and help refine our understanding of the active, and actively evolving, Solar System.

Article types and fees

This Research Topic accepts the following article types, unless otherwise specified in the Research Topic description:

• Brief Research Report
• Curriculum, Instruction, and Pedagogy
• Data Report
• Editorial
• FAIR² Data
• General Commentary
• Hypothesis and Theory
• Mini Review
• Opinion
• ... View all formats

Articles that are accepted for publication by our external editors following rigorous peer review incur a publishing fee charged to Authors, institutions, or funders.

Article types

This Research Topic accepts the following article types, unless otherwise specified in the Research Topic description:

• Brief Research Report
• Curriculum, Instruction, and Pedagogy
• Data Report
• Editorial
• FAIR² Data
• General Commentary
• Hypothesis and Theory
• Mini Review
• Opinion
• Original Research
• Perspective
• Review
• Study Protocol
• Technology and Code

Keywords: Mass loss mechanisms, Volatile delivery, Active small bodies, Comet–asteroid continuum, Volatile-driven activity, Dynamical evolution & reservoirs, Solar System formation probes

Important note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.