MassLet's look at one more way of describing the size of a planet, its mass. Mass is a measure of how much matter an object is made of. We say that heavy objects have a lot of mass. Light objects have less mass. The size (diameter or volume) of an object is certainly an important part of figuring how massive something is. However, the kind of material something is made of is very important too. Imagine you had a ball of styrofoam twelve inches in diameter and a hard ball of concrete 10 inches in diameter. The styrofoam ball would be pretty light and easy to lift. However, you would have a much harder time lifting the concrete ball. Even though the styrofoam ball has a bigger diameter than the concrete ball, the concrete ball has more mass. The Earth has a mass of about 6 and a half trillion billion tons. Let's compare that with the mass of the other planets. Once again, we'll use the Earth to measure by. Take a look at the table below. | Mercury | Venus | Earth | Mars | Jupiter | Saturn | Uranus | Neptune | Pluto | | 0.055 | 0.86 | 1.0 | 0.11 | 318 | 95 | 14.5 | 17.2 | 0.002 | From this table we can see that Jupiter has 318 times as much mass as the Earth does. We can also see that some planets are less massive than the Earth. Check it out!
Look at the table above. Which planet has the least mass? Click your answer below.
| Intro | Diameter | Volume | Mass |
| Surface Gravity | And Beyond... | NASA Educator Resource Center Content and Web Development: Brian H. Day
Responsible NASA Official: Donald James |