Moon and Jupiter

StarDate: September 29, 2009

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Walking on the Moon takes a little getting used to. The Moon's gravitational pull is only one-sixth that of Earth's, so an astronaut who weighed 180 pounds on Earth would tip the scales at only 30 pounds on the Moon. Under those conditions, the Apollo astronauts sort of waddled from side to side, or hopped like bunnies.

That wouldn't be the case on a planet that appears close to the Moon this evening. Jupiter looks like a brilliant star to the Moon's lower right.

Jupiter is the largest and most massive planet in the solar system. Because of that great heft, it has a powerful gravitational grip. So that 180-pound astronaut would weigh in at around 450 pounds on Jupiter.

Now if you're familiar with the planets, you've probably spotted a problem. Jupiter is a big ball of gas, so it doesn't have a solid surface to walk on.

To allow them to compare the conditions of all the planets and moons, though, scientists developed a definition for the surface of all the gas-giant planets. It's the depth in the atmosphere at which the pressure equals the pressure at Earth's surface.

At that depth, even with no surface to stand on, you'd still feel the crushing grip of gravity. So if you were inside a craft that was cruising through Jupiter's atmosphere, you wouldn't have much of a spring in your step. Instead, you'd want to just lie back, relax -- and enjoy the view out the window on this bone-crushing world.

Script by Damond Benningfield, Copyright 2009

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