Across
1
Icy body with a tail near the sun
4
Center of an atom or cell
5
The Red Planet
6
Gas essential for breathing
9
Path of a planet around the sun
Down
2
Smallest unit of an element
3
Absolute temperature scale unit
5
Measure of matter in an object
6
Compound containing oxygen
7
Tissue that contracts for movement
8
Particle of light