Across
1
Particle of light
4
Mass per unit volume
5
Icy body with a tail near the sun
8
Preserved remains of ancient life
9
Solid with repeating atomic pattern
11
Basic unit of life
Down
2
Unit of electric potential
3
Gas essential for breathing
6
Blocking of light by a celestial body
7
Tissue that contracts for movement
8
Push or pull on an object
10
Precious yellow metallic element
12
Path of a planet around the sun
13
Naturally occurring inorganic solid