1) Unit of mass 
Earth mass (M⊕) is the unit of mass equal to that of the Earth. 1 M⊕ = 5.97219 × 1024 kg. Earth mass is often used to describe masses of rocky terrestrial planets. The three other terrestrial planets of the Solar System, Mercury, Venus, and Mars, have masses of 0.055, 0.815, and 0.107 Earth masses respectively. One Earth mass can be converted...