Across
1
Nerve cell in the brain
4
Natural satellite of Earth
5
Our home planet
7
Curved glass that refracts light
8
Group of similar cells
9
Fourth state of matter
Down
2
Icy body with a tail near the sun
3
Unit of energy
6
Second lightest element
9
Particle of light
10
Unit of heredity
11
Form of thermal energy
12
The Red Planet