Mercury is the planet closet to the sun having almost no atmosphere and no water. It is the smaller planet of the solar system . Its outer layer consists of rocks. beneath the rocky layer, most of the planet comprises of iron.
Size of Mercury
How big is Mercury? Mercury is the smallest planet in the Solar System by surface area, volume, and equatorial diameter. Surprisingly, it is also one of the most dense. It gained its ‘smallest’ title after Pluto was demoted. That is why older material refers to Mercury as the second smallest planet. The aforementioned are the three criteria that we will use to show the size of Mercury in relation to Earth.
Some scientists think that Mercury is actually shrinking. The liquid core of the planet occupies about 42% of the planet’s volume. The spin of the planet allows a small portion of the core to cool. This cooling and shrinking is thought to be evidenced by the fracturing of the planet’s surface.
The surface of Mercury is heavily cratered, much like the Moon, and the continued presence of those craters indicates that the planet has not been geologically active for billions of years. That knowledge is based on partial mapping of the planet(55%). It is unlikely to change even after NASA’s MESSENGER spacecraft maps the entire surface. The planet was most likely bombarded heavily by asteroids and comets during the Late Heavy Bombardment about 3.8 billion years ago. Some regions would have been filled by magma eruptions from within the planet. These created smooth plains similar to those found on the Moon. As the planet cooled and contracted cracks and ridges formed. These features can be seen on top of other features, which is a clear indication that they are more recent. Volcanic eruptions ceased on Mercury about 700-800 million years ago when the planet’s mantle had contracted enough to prevent lava flow.
Diameter of Mercury (and the Radius)
The diameter of Mercury is 4,879.4 km.
Need some way to compare that to something more familiar? The diameter of Mercury is only 38% the Earth’s diameter. In other words, you could put almost 3 Mercurys side to side to match the diameter of Earth.
In fact, there are two moons in the Solar System which actually have a larger diameter than Mercury. The largest moon in the Solar System is Jupiter’s moon Ganymede, with a diameter of 5,268 km and the second largest moon is Saturn’s moon Titan, with a diameter of 5,152 km.