Across
1
Icy body with a tail near the sun
4
Basic unit of life
5
Curved glass that refracts light
6
Blocking of light by a celestial body
8
Substance with pH below 7
Down
2
Preserved remains of ancient life
3
Biological catalyst
4
Element found in all living things
7
Absolute temperature scale unit
9
Second lightest element
10
Unit of electric potential