Mercury: A Brief Overview

Enhanced-color image of Mercury from first MESSENGER flyby.

Mercury is the smallest and innermost planet in the Solar System. Its orbit around the Sun takes 87.97 days, the shortest of all the planets in the Solar System. It is named after the Roman deity Mercury, the messenger of the gods.

Size1,516 miles
Distance To The Sun36 million miles, or 58 million kilometers, or 0.39 AU
Length of A Day On Mercury176 Earth days
Length Of A Year On Mercury88 Earth days
Temperature (Lows and Highs)Lows: -290°F
Highs: 800°F
Number Of Moons0
Number Of Rings0
Missions To The Planet3
AtmosphereHighly Variable, thin exosphere made up of atoms blasted off the surface by the solar wind and striking meteoroids. Contains hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor
Size Compared To Earth2.6x smaller than Earth
Discoverer And Discovery DateKnown By Ancients

Known since ancient times, Mercury is one of those planets that has a long history. There is a lot to talk about, and we won’t be able to cover it all, but will do our best to cover some information.

Mercury appears to have a solid silicate crust and mantle overlying a solid, iron sulfide outer core layer, a deeper liquid core layer, and a solid inner core. It is one of four terrestrial planets in the Solar System, and is a rocky body like Earth. It is the smallest planet in the Solar System, with an equatorial radius of 1,516.0 miles. The planets core has a higher iron content than that of any other major planet in the Solar System. Mercury’s surface is similar in appearance to that of the Moon, showing extensive mare-like plains and heavy cratering, indicating that it has been geologically inactive for billions of years.

Two spacecraft have visited Mercury: Mariner 10 flew by in 1974 and 1975; and MESSENGER, launched in 2004, orbited over 4,000 times in four years before exhausting its fuel and crashing into the planet’s surface on April 30, 2015. The BepiColombo spacecraft is planned to arrive at the planet in 2025.


Because Mercury is so close to the Sun and its gravity, it wouldn’t be able to hold on to its own moon. Any moon would most likely crash into the planets surface or maybe go into orbit around the Sun and eventually get pulled into the sun.

Fun Facts:

Mercury is actually the closest planet to every other planet.
Almost 85% of Mercury’s radius is represented by its enormous iron core.
Your weight on Mercury would be 38% of your weight on Earth.

Come back next week for the next article in the Planetary Bodies Category, which will be a further look into observation of Mercury.

Sources And Further Reading

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