Across
1
Natural satellite of Earth
4
Biological catalyst
5
Blocking of light by a celestial body
7
Chemical element in table salt
10
Nerve cell in the brain
11
Curved glass that refracts light
Down
2
Element found in all living things
3
Hottest planet in solar system
6
Preserved remains of ancient life
8
Icy body with a tail near the sun
9
Measure of matter in an object
12
Gas essential for breathing
13
Group of similar cells