Gravity differs depending on what planet you are on. This is because the planets vary in size and mass.
Mercury is the smallest planet with the least mass and the least density. The gravity on Mercury is only 38% of the gravity on earth. Considering Mercury only has a radius of 4,879 km, which is barely any larger than the Moon, the gravity is high. The high gravity is due to the high density of the planet.
Venus is similar in size to the Earth, which is why it is often called Earth’s twin. Its mass, density, and volume are all slightly less than Earth’s. This means that the gravity on Venus is slightly over 90% of the Earth’s gravity. Although you would weigh less on Earth’s twin than you would on Earth, you would not want to visit Venus because of its toxic, burning atmosphere.
The promise of life on Mars has intrigued people for centuries, but what would living on Mars really be like. Well, Mars has a smaller density and mass than our planet, which means that it has lower gravity. In fact, you would weigh less on Mars than you would on any other planet in our Solar System. The gravity of Mars is 38% the gravity of Earth.
Jupiter is the most massive planet in our Solar System, meaning it also has the highest gravity. If you stood on Jupiter – you cannot because it does not have a solid surface – than you would weigh two and a half times what you would on Earth.
A gas giant, Saturn is more massive than Earth, but it also has the lowest density of all the planets in the Solar System. If you were able to stand on Saturn’s surface, you would experience about 91% of the gravity you would on Earth.
Like Saturn, Uranus is massive, but has a very low density. Because of this combination, Uranus has a low gravity about 89% of the gravity that you would feel on Earth. This is very close to Venus’ gravity although Uranus is more than 14 times larger than Venus is.
Neptune is much more massive than Earth – 17 times Earth’s mass – but it is also much larger than Earth, so it has a lower density. This means that Neptune’s gravity is only slightly more than Earth’s gravity – 14% more. It would not be too uncomfortable walking on Neptune if you could walk on it, which is impossible because it does not have a solid surface.
Astronomy Cast also has an episode on gravity.