Across
1
Disturbance that transfers energy
3
Particle of light
6
Gas form of a liquid
7
The Red Planet
8
Nerve cell in the brain
11
Preserved remains of ancient life
13
Biological catalyst
Down
2
Gas essential for breathing
4
Ball of burning gas in space
5
Positive particle in nucleus
9
Form of thermal energy
10
Force that attracts objects together
12
Natural satellite of Earth