Across
1
Natural satellite of Earth
4
Substance with pH below 7
6
Measure of matter in an object
7
Blocking of light by a celestial body
10
Center of an atom or cell
11
Precious yellow metallic element
Down
2
Preserved remains of ancient life
3
Naturally occurring inorganic solid
5
Absolute temperature scale unit
8
Fourth state of matter
9
Form of thermal energy
12
Second lightest element