Neptune is a gas planet, so it doesn’t have a solid surface. If you tried to walk on the surface of Neptune, you’d sink right in. But let’s say you could walk on Neptune. How strong is the gravity on Neptune? How heavy would you feel?
The surface gravity of Neptune is 1.14 times the gravity on Earth. In other words, if you could actually walk on Neptune, you would feel only a little heavier than if you were walking on Earth. If you weighed 100 kg on Earth, you would weight 114 kg on Neptune. Compare that to the much lower gravity you would feel on the Moon (16.5%) or Mars (37.6%).
Neptune has much more mass than Earth. In fact, it has a mass of 17 times the mass of the Earth. You would think that would make the gravity much more extreme. But it also has a much larger size. The diameter of Neptune is 3.8 times the diameter of Earth. This brings the gravity on Neptune down to a very comfortable 114% the gravity of Earth.
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Except for the non-solid part, walking on Neptune would feel very comfortable.
Want to learn more about the gravity on the Moon, or the gravity on Mars?
If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.
We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.