15. Inner planets are much smaller than outer planets. Most of the Outer planets are made of gas, and It is likely that they have a much smaller solid or liquid center. It would be impossible to stand on any of the Outer Planets. The inner planets have solid surfaces and little to no atmosphere. Inner planets have a greater density than than outer planets. all of the outer planets have rings while none of the inner planets have any.
16. A meteoroid is a small solid particle that travels through space, if they burn up in earth's atmosphere they are called meteor. A meteoroid that actually reaches Earth's surface is called a meteorite.
17. Earth is denser than all other planets. Earth has the largest known solid surface the other inner ones are much smaller. Earth has a predominantly nitrogen atmosphere and Venus and Mars have mostly carbon dioxide in their atmospheres.
18. I think that Pluto should be classified as a dwarf planet because It has not yet cleared the neighborhood of its orbit in space. Pluto is also super small, about the size of the moon and much smaller the the other planets!
19.The Outer planets have a thick gas and liquid layer covering a small, solid core. Mostly hydrogen and helium atmosphere and layers of liquid hydrogen. Neptune and Uranus have a core covered by ice and ammonia.