Space trip to Mars Your mass remains the same wherever you are, Earth, Mars, Space the Moon and so on. Your weight changes depending on where you are. If you are in space, well away from any planets (or the Sun), there is very little gravity and so your weight is very small. If you are on the surface of a planet, it's gravity pulls you down (towards the centre) and it is this that you feel as weight. The greater the amount of gravity, the greater your weight. So someone who weighs 550N on Earth, will weigh only 208.5 N on Mars. This is because Mars only pulls with 0.38 as much gravity as Earth. This is because Mars is a much smaller planet than Earth. The gravity on Jupiter is 2.7 times more than Earth gravity (Jupiter is much bigger) so you would weigh 550 x 2.7 = 1485 Newtons on Jupiter! Weight is a force. Search the internet for more information about Mars and spaceflight: Back to mass and weight main page.