Across
1
Measure of matter in an object
4
The Red Planet
5
Curved glass that refracts light
6
Second lightest element
9
Blocking of light by a celestial body
11
Element found in all living things
Down
2
Ball of burning gas in space
3
Center of an atom or cell
4
Molten rock beneath Earth surface
7
Path of a planet around the sun
8
Hottest planet in solar system
10
Gas essential for breathing
12
Icy body with a tail near the sun