Question: do other planets have cores

Charlie Ryan answered on 17 Mar 2011:

hi richard it matters what you mean by cores…. but lets look at metal cores like the earth has.
It’ a little hard to tell because you obviously can’t look directly at the core of a planet but there are generally a few clues that it might be metallic. One of the best clues is whether it has a magnetic field. These are created by the movement of iron within the planet. So from the inner planets mercury and earth have a strong magnetic field, so probably have a moving (kind of swirling – convection movement) metal core.
It’s believed that mars and venus also probably have metal cores even though they don’t have a strong magnetic fields. I’m not really sure why people believe this though! I guess they were probably formed from the same material as the earth (from a disc of material that used to surround the sun), so it is reasonable to assume that they also have metal cores.
For the outer planets i believe (but again i’m not sure – i’m no astrophysicist!) that scientists are just not sure what the core is made from and if it’s metallic. And they might not even have cores (this can be found out by measuring the strength of gravity but the accurate measurements haven’t been done on jupiter yet). It seems that generally it is thought they probably have rocky cores!!
Hope that helps!