Across
1
Tissue that contracts for movement
2
Compound containing oxygen
7
Fourth state of matter
9
Second lightest element
Down
2
Gas essential for breathing
3
Mass per unit volume
4
Path of a planet around the sun
5
Icy body with a tail near the sun
6
Blocking of light by a celestial body
8
Center of an atom or cell
10
Solid with repeating atomic pattern