Across
1
Smallest unit of an element
3
Nerve cell in the brain
5
Mass per unit volume
7
Unit of power
8
Gas form of a liquid
10
The Red Planet
11
Preserved remains of ancient life
Down
2
Path of a planet around the sun
3
Center of an atom or cell
4
Tectonic landmass section
6
Icy body with a tail near the sun
9
Blocking of light by a celestial body