The weight of anything is
(the thing's mass) times (gravity in the place where the thing is located).
Gravity on Earth is 9.8 m/s² .
90 kg of mass weighs (90 kg) · (9.8 m/s²) = 882 Newtons on Earth.
Gravity on the Moon is 1.62 m/s² .
The same 90 kg weighs (90 kg)·(1.62 m/s²) = 146 Newtons on the Moon.
Gravity on Mars is 3.7 m/s² .
The same 90 kg of mass weighs (90 kg)·(3.7 m/s²) = 333 Newtons on Mars.
