Across
1
Basic unit of life
3
Our home planet
5
Group of similar cells
7
Precious yellow metallic element
8
The Red Planet
11
Gas essential for breathing
12
Unit of force
Down
2
Blocking of light by a celestial body
4
Curved glass that refracts light
6
Magnetic metallic element
9
Particle of light
10
Disturbance that transfers energy