- Mercury is the smallest planet in the solar system. It is approximately 4,876 km in diameter, making it about as wide as the United States and only slightly bigger than Earth’s moon.
- Mercury speeds around the sun every 88 Earth days, going at nearly 47 km per second – faster than any other planet in the solar system. Mercury’s orbit is not only very fast but also highly elliptical. The planet gets as close as 47 million km to the sun and as far as 70 million km from the sun.
- In 2012, NASA’s MESSENGER spacecraft discovered water ice in Mercury’s craters. In 2017, it was confirmed that Mercury has much more ice in its north polar region than previously thought.
- The planet has very little axial tilt, meaning that the polar regions receive very little direct sunlight, and some places remain constantly in the dark. And Mercury has no atmosphere, so its temperatures rise and fall dramatically during the day and night.
- NASA’s MESSENGER probe orbited Mercury for more than four years and came back with some amazing images of Mercury. Scientists used those images to create the first-ever complete map of Mercury’s surface.
- Scientists have discovered that Mercury has streams of particles sliding off its surface, much like a comet. photographs taken by astrophotographers on Earth can capture these tails.
- In a very, very slow process, Mercury is getting smaller every day. It is estimated that the planet is about 9 miles smaller than it was four billion years ago (told you it was a slow process). Astronomers believe this is happening because it’s iron core is cooling, which is making it solid, therefore reducing the planet’s volume.
| Diameter – 4880 kilometers |
| Distance from sun – 0.4 astronomical units |
| Rotation period – 58d 15h 30m |
| Orbital Period – 88 days |
| Surface temperature – −173 ℃ to 427 ℃ |
