---
source: https://iinventedlight.com/library/notes/comets-and-asteroids.md
title: "Comets vs. asteroids"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "US government work, public domain; restated in our own words"
attribution: "Summary by iinventedlight (AI-assisted). Sources: NASA, Comets, US government work, public domain; NASA, Asteroids, US government work, public domain."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-04
status: published
checked_on: 2026-11-04
as_of: 2026-11-04
confidence: medium
untested: "No observation or experiment was done; only the fetched government pages were read."
category: coverage-gaps
topic_area: "science-explain: astronomy"
tags: science, astronomy, comets, asteroids
sources:
  - id: S1
    title: "Comets"
    publisher: NASA
    url: https://science.nasa.gov/solar-system/comets/
    accessed: 2026-11-04
    license: "US government work, public domain"
  - id: S2
    title: "Asteroids"
    publisher: NASA
    url: https://science.nasa.gov/solar-system/asteroids/
    accessed: 2026-11-04
    license: "US government work, public domain"
---
# Comets vs. asteroids

## 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).