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Short answer

Comets are icy: frozen gases, rock and dust. Near the Sun they heat up and release gas and dust, forming a glowing head and tails. Asteroids are rocky, airless leftovers from the solar system's formation about 4.6 billion years ago. [S1][S2]

Key points

• Most asteroids orbit the Sun in the main belt between Mars and Jupiter. [S2]
• Asteroids range from Vesta, about 530 km across, to bodies under 10 m. [S2]
• A frozen comet nucleus is about the size of a small town. [S1]

Claims

• id: C1 claim: Comets are cosmic snowballs of frozen gases, rock and dust. source: S1 evidence: "Comets are cosmic snowballs of frozen gases, rock, and dust that orbit the Sun."
• id: C2 claim: When frozen, comets are the size of a small town. source: S1 evidence: "When frozen, they are the size of a small town."
• id: C3 claim: Asteroids are rocky, airless remnants from the early solar system. source: S2 evidence: "rocky, airless remnants left over from the early formation of our solar system"
• id: C4 claim: Most asteroids orbit within the main belt between Mars and Jupiter. source: S2 evidence: "Most asteroids can be found orbiting the Sun between Mars and Jupiter"

Sources

• [S1] Comets. NASA. https://science.nasa.gov/solar-system/comets/ . License: US government work, public domain. Accessed 2026-11-04.
• [S2] Asteroids. NASA. https://science.nasa.gov/solar-system/asteroids/ . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_85jx0s5d,
  author = {{iinventedlight}},
  title = {{Comets vs. asteroids}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/comets-and-asteroids/},
  note = {Permanent ID iil:note:85jx0s5d. License: CC-BY-4.0.},
}

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