Across
1
Nerve cell in the brain
4
Preserved remains of ancient life
6
Second lightest element
7
Molten rock beneath Earth surface
9
Hottest planet in solar system
10
Curved glass that refracts light
12
Fourth state of matter
Down
2
Biological catalyst
3
Naturally occurring inorganic solid
5
Center of an atom or cell
7
The Red Planet
8
Substance with pH below 7
11
Amplified beam of light