Across
1
Gas form of a liquid
4
Tissue that contracts for movement
6
Nerve cell in the brain
7
Blocking of light by a celestial body
8
Fourth state of matter
11
Mass per unit volume
Down
2
Preserved remains of ancient life
3
Amplified beam of light
5
Center of an atom or cell
9
Unit of energy
10
The Red Planet
12
Hottest planet in solar system