Across
1
Unit of heredity
4
Second lightest element
7
Biological catalyst
8
Fourth state of matter
11
Hottest planet in solar system
12
The Red Planet
Down
2
Molten rock beneath Earth surface
3
Mass per unit volume
5
Preserved remains of ancient life
6
Our home planet
9
Tissue that contracts for movement
10
Curved glass that refracts light