Across
1
Group of similar cells
5
Measure of matter in an object
6
Second lightest element
7
Unit of heredity
10
Biological catalyst
11
The Red Planet
Down
2
Disturbance that transfers energy
3
Unit of force
4
Blocking of light by a celestial body
8
Hottest planet in solar system
9
Molten rock beneath Earth surface
12
Ball of burning gas in space