Across
1
Natural satellite of Earth
4
Force that attracts objects together
5
Blocking of light by a celestial body
6
Nerve cell in the brain
12
Second lightest element
Down
2
Magnetic metallic element
3
Unit of force
7
Center of an atom or cell
8
Preserved remains of ancient life
9
Icy body with a tail near the sun
10
The Red Planet
11
Form of thermal energy