Across
1
Path of a planet around the sun
3
The Red Planet
6
Ball of burning gas in space
7
Tissue that contracts for movement
9
Compound containing oxygen
10
Nerve cell in the brain
11
Our home planet
Down
2
Gas form of a liquid
4
Curved glass that refracts light
5
Positive particle in nucleus
8
Group of similar cells
12
Natural satellite of Earth