what are planet made of – I'm a Scientist 25/26

Question: what are planet made of
- Keywords:
  matter,
  planet,
  space
Asked by egos532hods85 to Tom, rebeccawarrilow, Katherine, jonathanmound, hayleylowe, Christopher, christinaschoettler, ancyannajohn, alistairglasse, Alex M on 1 Apr 2026. This question was also asked by bhut532rynd94.
- Jonathan Mound answered on 1 Apr 2026:
  
  Depends on the planet. Venus, Earth, and Mars are mostly made of rock, with iron cores. Mercury is similar, but a much larger fraction of the planet is iron core. Jupiter and Saturn are mostly hydrogen and some helium, although they might have a relatively small (compared to the size of the planet) rocky centre. For Uranus and Neptune, we have less data and so are not as sure – they are some mix of hydrogen and helium gas, water and methane and ammonia ice, and rock.

Question: what are planet made of