Active Asteroids

Active asteroids are small rocky objects in our Solar System that have asteroid-like orbits but comet-like appearances. Active asteroids can have visible tails and comae - halos of debris. These visible features suggest that these asteroids are rich in water. It is even possible that active asteroids supplied some of the water that became Earth’s oceans! Join the Active Asteroids project and search for these unusual asteroids to help map the distribution of water in the solar system and inform future space mining!        

WHO: All Ages 
WHERE: Online

ActiveAsteroids Subject 84515629.png

Go to Project Website

What you’ll get to do:

  • Help answer unsolved questions about how much water was delivered to Earth after it formed, and where that water originated.
  • Search images captured by the 4-meter Blanco telescope in Chile to find active asteroid candidates.
  • Connect with professional scientists and other citizen scientists in the project Talk forums.


  • Time: Minutes
  • Equipment: Internet connected mobile device or computer
  • Knowledge: None. In-project training provided.

Get started!

  1. Visit our project website.
  2. Click the “Get started” button and complete the short Tutorial to learn how to identify an active asteroids in the images. 
  3. Use your new skills to look for evidence of active asteroids in telescope images.
  4. Communicate with other volunteers!
A dark blob at the center of the image is surrounded by a paler shadow that is roughly spherical on the left of the blob and spreads out on the right, as if the blob was moving through something from right to left.

A coma is the fuzzy glow that forms around some orbiting bodies (like comets or active asteroids) when they approach the Sun.

a tight dark spot in the middle of the frame has a tail of grey material extending down to the bottom left. The tail is darkest near the dark spot, getting increasingly faint with distance.

The tails of active asteroids or comets consist of vapor and dust, and can vary in shape, length, and intensity. They may even have multiple tails extending in different directions!


A big, slightly oblong, dark and light grey asteroid is moving from the upper right to the lower left, shedding smaller chunks of material and a cloud of dust.

Fewer than 30 active asteroids have been discovered since 1949. Maybe you will help discover the next one!

Learn More:

If you’d like to learn more about our project and active asteroids, check out our project website at

A cartoon asteroid is staring straight out of the frame, with beads of sweat springing off its forehead and a weight in each arm. With eyes wide and mouth open it looks surprised to see you.

Get to know the Active Asteroids science team!