Mercury, Nine Planets in Universe

Mercury, Nine Planets in Universe is the closest planet to the Sun but, perhaps surprisingly, it does not have the highest temperatures.

Mercury, Nine Planets in Universe

Mercury, Nine Planets in Universe

Mercury is the closest planet to the Sun but, perhaps surprisingly, it does not have the highest temperatures. It is the second densest planet of the Solar System, but also the smallest planet. The structure of Mercury makes it the most similar planet to Earth.

Mercury, Nine Planets in Universe

One of the earliest known recorded observations of Mercury is the Mul.Apin tablets. It is believed that these observations were made by an ancient Assyrian astronomer around the 14th century BC. The name used in these tablets is translated as “the jumping planet”.

Some Babylonian records date back to the 1st millennium BC. They called the planet Nabu, after the messenger to the gods in their mythology. The ancient Greeks knew the planet as Hermes while the Romans named it Mercury and it remained as such to this day.

Credits cannot be given to a single civilization or person because the planet has always been easy to spot on the sky. What we can do is to give credit to those who first studied the planet by more “modern” means such as Galileo Galilei in the early 17th century and Giovanni Zupi who in 1639, observed that the planet had phases just like Venus and the Moon.


It is theorized that Mercury was formed about 4.5 billion years ago when gravity pulled swirling gas and dust together to form the small planet. Its small size but the enormous core is theorized to be the result of a collision with another giant object that stripped much of its surface.

Distance, Size, and Mass

Mercury is the closest planet to the Sun, at a distance of 57.91 million kilometers / 35.98 miles or 0.4 AU away. It takes sunlight 3.2 minutes to travel from the Sun to Mercury.

Mercury has a radius of 2.439 km or 1516 mm, and a diameter of 4.879 km or 3.032 mi. It is about the size of the continental United States, slightly bigger. It has a mass of about 3.285 × 10^23 kg or about 5.5% that of Earth.

Despite being the smallest planet from the Solar System, it is the second densest planet in the Solar System, with a density of 5.43 g/cm³ after Earth. For comparison, Mercury’s size is about a third of Earth, and Earth has a density of 5.51 g/cm³.

Orbit and Rotation

Mercury’s highly eccentric, egg-shaped orbit takes the planet as close as 29 million miles or 47 million kilometers, and as far as 43 million miles or 70 million kilometers from the Sun. It takes a trip around the Sun every 88 days thus 1 orbit/year is the equivalent of 88 Earth days. Mercury travels through space at nearly 29 miles or 47 kilometers per second, faster than any other planet.

Future plans for Mercury

Because of Mercury’s closeness to Earth, it will always be a target for missions and further observations. The third spacecraft set to arrive on Mercury is called BepiColombo, and it is planned to arrive at Mercury in 2025.

Did you know?

– From the surface of Mercury, the Sun would appear more than three times as large as it does when viewed from Earth, and the sunlight would be as much as seven times brighter.

– NASA’s spacecraft Mariner 10 was the first mission to explore Mercury in 1974-1975.

– NASA’s spacecraft MESSENGER was the first to orbit Mercury in 2008.

– Mercury’s apparent distance from the Sun as viewed from Earth never exceeds 28°.

– You could fit approximately 21,253,933 Mercuries inside the Sun.

– In ancient China, Mercury was known as “the hour Star” – is associated with the direction of the north.

– Modern Chinese, Korean, Japanese, and Vietnamese cultures refer to the planet as “water star.”

– Hindu mythology used the name “Buddha Graha” to refer to Mercury. This god was thought to preside over Wednesday.

– The god Odin or Woden of Germanic paganism was associated with the planet Mercury and also Wednesday.

– Maya people may have represented Mercury as an owl that served as a messenger to the underworld.

– Mercury can, like several other planets and the brightest stars, be seen during a total solar eclipse.

– Even though Mercury is a planet, it is even smaller than the largest natural satellites in the Solar System: Ganymede and Titan, albeit Mercury is more massive.

– Mercury’s core has a higher iron content than that of any other major planet in the Solar System.

– Your weight on Mercury would be 38% of your weight on Earth as Mercury has a gravity of 3.7 m/s², while Earth has 9.807 m/s².

– The most cratered planet in the solar system is Mercury.

– NASA has mapped the entire surface of Mercury.

– It is believed that Mercury has a tail: it streams of particles sloughing off its surface.

– The naming and discovery of Mercury cannot be attributed to anyone.

– The crater Caloris Basin is large enough to fit in the state of Texas.

– An event called a “transit” occurs 13 times every century making it possible to see Mercury from Earth, as it crosses the Sun’s face.

– Mercury is about 50% larger in diameter than Earth’s Moon.

– It would take about 18 Mercury’s to match Earth.

– Mercury doesn’t experience any seasons.

– It is one of the most popular planets in our imagination.

– Mercury is about twice as large as Pluto.

To know about Earth,