The closest planet to the Sun is Mercury. Everyone knows that. But did you know that Mercury has the Caloris Basin which is 1,550-kilometer-wide! Mercury is the smallest planet in the solar system. It has no moons of its own. If you stand on the surface of Mercury, the Sun would appear three times larger than seen from earth. Mercury is smaller than Ganymede and Titan. It is 2400km in radius. It is a rocky world, one of the terrestrial planets, and has a weak magnetic field generated by its core. It has a very thin, almost nonexistent atmosphere. Its landscape is more cratered than any other terrestrial planets(lots of bombardment from solar debris). Are you ready to learn more about this small yet exciting planet?

Some facts about Mercury:

Radius- 2440 km

Orbital period (Length of a year)-  88 Earth days

Length of a day- 59 Earth days

Surface temperatures-  -183°C(-300°F) to 430°C(800°F)

Axis tilt- 0 degrees

Distance from the Sun- 0.39AU

Moons- none

Gravity- 0.38 Earth’s gravity

Mercury’s History

Mercury was formed from rocky materials that could withstand the high temperatures close to the Sun.  Early Mercury lost most of its original atmosphere due to the constant lashes of the solar wind. Mercury was subject to impacts from incoming solar system debris during a period called the “Late Heavy Bombardment,” which ended about 3.8 billion years ago. Mercury has retained many of the craters from that era of its history. It is assumed that, the more craters on the surface of a planet or object, the older the planet or object is. So, Mercury’s surface is quite old. The Caloris Basin was created as a result of a 100-kilometer-wide asteroid crashing into the surface, about 4 million years ago.

Missions to Mercury

Mariner 10 was the first mission to visit Mercury in 1973 and circled the planet three times. Through its specialized equipment, it measured Mercury and sent the first-ever close-up images of its surface. 

In 2011, the MESSENGER(Mercury Surface, Space Environment, Geochemistry and Ranging ) spacecraft entered into Mercury’s orbit for a multi-year mission. The data from MESSENGER is remarkable. 

Mercury’s secrets uncovered

There is strong evidence of water at the poles. Mercury’s core is larger than expected- it takes up 85 percent of the planet! The core is probably solid and surrounded by a liquid layer of molten iron, a layer of iron sulfide above that, and silicate rocks that make up the crust. Mercury is the densest of all the terrestrial planets. Volcanism helped shape Mercury’s surfaces. Its landscape is split by large cliffs called scarps, which formed as the surface broke apart. It is made up of 60 percent iron which is twice as much as Earth has, and 40 percent other minerals. Mercury’s very thin atmosphere contains- hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor. Scientists found traces of dark materials which could be organic compounds(carbon-based). It is possible that these organic compounds and the ice deposits were delivered by comets which bombarded it.

I hope you learnt something more about Mercury than it just being the closest planet to the Sun.

https://en.wikipedia.org/wiki/Mercury_(planet)
https://solarsystem.nasa.gov/planets/mercury/overview/