Across
1
Hottest planet in solar system
2
Fourth state of matter
4
Nerve cell in the brain
9
Reddish electrical conductor
11
Path of a planet around the sun
12
Icy body with a tail near the sun
Down
2
Particle of light
3
Mass per unit volume
5
Force that attracts objects together
6
Element found in all living things
7
Magnetic metallic element
8
The Red Planet
10
Preserved remains of ancient life