Across
1
Unit of energy
2
Icy body with a tail near the sun
3
Hottest planet in solar system
7
Mass per unit volume
8
Unit of heredity
9
Group of similar cells
10
Blocking of light by a celestial body
12
Naturally occurring inorganic solid
Down
2
Solid with repeating atomic pattern
4
Gas essential for breathing
5
Biological catalyst
6
Tectonic landmass section
11
Ball of burning gas in space
13
Fourth state of matter