Across
1
Path of a planet around the sun
4
Unit of electric potential
6
Element found in all living things
7
Blocking of light by a celestial body
9
Substance with pH below 7
Down
2
Unit of power
3
Particle of light
5
Substance with pH above 7
8
Curved glass that refracts light
10
The Red Planet
11
Hottest planet in solar system
12
Mass per unit volume