MadSci Network: Astronomy |

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First of all, let me try to clarify your question. You ask what the
equivalent of 1 kilogram would be. Kilograms actually measure how
much *mass* an object has. Mass just measures how much matter
is in the object. Because the amount of matter in (for example)
your body won't change whether you are on Earth or Mercury, mass is
constant everywhere. Thus, technically, the equivalent of 1 kilogram
on Mercury is just 1 kilogram!

But I'm guessing you are asking how much one kilogram would
*weigh* on Mercury. The weight of an object reflects how
strongly gravity pulls on it. This will change, because factors other
than the mass of the object affect the pull of gravity: on Earth, 1
kilogram weighs 2.2
pounds, while on Mercury, a 1 kilogram object will have the same mass but a
different weight. The other factors that affect gravity's pull are
the mass of the planet (the more matter there is to attract you, the
stronger gravity will be) and the radius of the planet (because the
closer the matter in the planet is to you, the stronger gravity gets).
There's a formula for this, first discovered by Isaac Newton, that
describes the strength of the gravitational attraction between any two
objects, depending on their masses and the distance between them. You'll
probably learn this equation, and how to use it, in school in a few years.

The numbers you need are these: the mass of Mercury is only 5.5% that of earth, and Mercury's diameter is 38% of Earth's (you can find these numbers at The Nine Planets Web site. When you plug the numbers into the formula for gravity, you find that gravity is only 38% as strong on Mercury as it is on Earth. Therefore, a 1 kilogram object will weigh 2.2*0.38 = 0.83 pounds on Mercury.

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