Across
1
Second lightest element
3
Path of a planet around the sun
4
Mass per unit volume
6
Natural satellite of Earth
8
The Red Planet
11
Basic unit of life
Down
1
Form of thermal energy
2
Nerve cell in the brain
5
Element found in all living things
7
Curved glass that refracts light
9
Disturbance that transfers energy
10
Hottest planet in solar system