Across
1
Our home planet
2
The Red Planet
4
Mass per unit volume
5
Blocking of light by a celestial body
10
Solid with repeating atomic pattern
11
Force that attracts objects together
Down
2
Tissue that contracts for movement
3
Form of thermal energy
6
Nerve cell in the brain
7
Ball of burning gas in space
8
Group of similar cells
9
Second lightest element
12
Molten rock beneath Earth surface