Across
1
Curved glass that refracts light
3
Icy body with a tail near the sun
6
Center of an atom or cell
9
Force that attracts objects together
10
Substance with pH below 7
11
Molten rock beneath Earth surface
Down
2
Unit of electric potential
3
Basic unit of life
4
Preserved remains of ancient life
5
Measure of matter in an object
7
The Red Planet
8
Biological catalyst