To get a sense of how big Mercury is, let’s take a look at Mercury compared to Earth.
The diameter of Mercury is 4,879 km. That’s approximately 38% the diameter of Earth. In other words, you could put three Mercurys side by side and they would be a little larger than the Earth.
What about surface area? How much room is there to live on the surface of Mercury (who’d want to, of course, it would be incredibly hot). The surface area of Mercury is 75 million square kilometers, which is approximately 10% the surface area of Earth. If you could unwrap Mercury, it would be almost twice the area of Asia (44 million square km).
How about volume? The volume of Mercury is 6.1 x 1010 km3. That sounds like a big number, but it’s really only 5.4% the volume of Earth. In other words, you could fit 18 objects the size of Mercury inside Earth.
Mass? The mass of Mercury is 3.3 x 1023 kg. Again it sounds like a big number, but it’s really only 5.5% the mass of Earth.
Finally, let’s look at the gravity on its surface. If you could stand on the surface of Mercury (with a nice spacesuit), you would experience 38% the force of gravity that you experience on Earth. In other words, if you weighed 100 kg on Earth, you would weigh 38 kg on Mercury.
We have written many stories about Mercury on Universe Today. Here’s an article about the possibility of snow on Mercury, and here’s an article with some nice color pictures of Mercury captured by the MESSENGER spacecraft.
We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.