Across
1
Second lightest element
5
Blocking of light by a celestial body
6
Reddish electrical conductor
8
Mass per unit volume
10
Our home planet
Down
2
Path of a planet around the sun
3
Curved glass that refracts light
4
Molten rock beneath Earth surface
7
Absolute temperature scale unit
9
Unit of energy
11
The Red Planet
12
Compound containing oxygen
13
Particle of light