Across
1
Path of a planet around the sun
3
Center of an atom or cell
4
Mass per unit volume
6
Substance with pH above 7
10
Natural satellite of Earth
12
Force that attracts objects together
Down
2
Group of similar cells
3
Nerve cell in the brain
5
The Red Planet
7
Unit of power
8
Unit of energy
9
Tectonic landmass section
11
Naturally occurring inorganic solid