Across
1
Icy body with a tail near the sun
4
Positive particle in nucleus
5
Mass per unit volume
8
Preserved remains of ancient life
10
Biological catalyst
11
Solid with repeating atomic pattern
Down
2
Substance with pH below 7
3
Nerve cell in the brain
6
Group of similar cells
7
Magnetic metallic element
8
Push or pull on an object
9
Our home planet
12
Naturally occurring inorganic solid