Across
1
Tectonic landmass section
2
Force that attracts objects together
4
Precious yellow metallic element
5
Blocking of light by a celestial body
7
Gas essential for breathing
9
Form of thermal energy
11
Icy body with a tail near the sun
12
Nerve cell in the brain
Down
1
Particle of light
2
Unit of heredity
3
Basic unit of life
6
Unit of power
8
Ball of burning gas in space
10
Path of a planet around the sun