University of Oulu

Active Asteroids

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Author: Penttilä, Jenna1
Organizations: 1University of Oulu, Faculty of Science, Physics
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 8.5 MB)
Pages: 31
Persistent link:
Language: English
Published: Oulu : J. Penttilä, 2022
Publish Date: 2022-08-05
Thesis type: Bachelor's thesis
Tutor: Schmidt, Jürgen


Asteroids and comets have been thought to be two separate kinds of objects in our solar system. In recent years, however, evidence has been found that there is a continuum of objects that have both asteroid-like and comet-like properties.

Active asteroids are objects with typical asteroid orbits that eject dust almost like comets, forming dust tails. They can lose mass by different mechanisms, which include ice sublimation, impact ejection, rotational instability, electrostatic forces, thermal stresses, dehydration, sodium volatilization, and radiation pressure.

There are some challenges in observing asteroid activity, but two dozen mass-losing asteroids have been found. Examples of active asteroids are the main-belt comet 133P/(7968) Elst-Pizarro where ice sublimates, the large main-belt asteroid (596) Scheila that collided with a smaller body, and the near-Earth asteroid (3200) Phaethon whose mass-loss is likely related to thermal stresses and sodium volatilization.

In the future, more research is needed in active asteroid observations, models, and laboratory experiments. Space missions with active asteroids as their targets have also been planned.

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Copyright information: © Jenna Penttilä, 2022. Except otherwise noted, the reuse of this document is authorised under a Creative Commons Attribution 4.0 International (CC-BY 4.0) licence ( This means that reuse is allowed provided appropriate credit is given and any changes are indicated. For any use or reproduction of elements that are not owned by the author(s), permission may need to be directly from the respective right holders.