Mercury is nearest and smallest planet in our solar system. Planet Mercury got its name from Roman messenger god “Mercury.” It’s diameter is around 4,880 km which is little-bit bigger than Earth’s moon.
Mercury is closest planet to sun but it’s not the hottest.
Discovery of Mercury
Mercury is one the five planets which can be seen by naked eyes, and we know presence of mercury since ancient time. Sumerian had first recorded observation of mercury around 3,000 BC. Ancient Greek astronomer initially believed that mercury was two separate objects because it appeared in morning and evening skies. Around 500 BC Pythagoras was first man who realized that these two objects are same. We can’t give credit to one person to discovered mercury because it has known for thousands of years.
Physical Characteristics
Diameter: Mercury has a diameter of about 4,880 Km, making it the smallest planet in the solar system.
Density: Mercury is the second densest planet in solar system after Earth, with a density of about 5.43 gram per cubic centimeter. This high density suggests a large metallic core.
Gravity: The surface gravity of Mercury is about 3.7 meters per second squared (m/s²), which is approximately 38% of Earth’s gravity. This mean your weight on mercury will be much lesser than on Earth.
Surface: Due to heavy bounds of asteroid on mercury, its surface is uneven there are many impact craters, ridges, and plains. Its surface is much similar as moon.
Temperature: Due to its proximity to sun and lack of substantial atmosphere, Mercury experiences extreme temperature fluctuations. Daytime temperature can reach up to 430 C while nighttime temperature can decrease to 180 C.
Atmosphere: Mercury has thin atmosphere called an exosphere, mainly composed by Oxygen, Sodium, Hydrogen Helium, and Potasium. The exosphere is too thin so it can’t support weather and can’t prevent surface from asteroids.
Magnetic field: Mercury has a magnetic field that is 1% as strong as Earth’s. It suggests partially molten core.
Internal Structures and Layers of Mercury
Core: Mercury has a large metallic core which covers 85% of its radius, which is proportionally larger than other planets in solar system. The core is considered to be composed mostly of iron and some lighter elements like sulfur. The core is partially liquid, which helps generate mercury’s weak magnetic field.
Mantle: A silicate mantle that surround the core, is 400 to 500 km thick. This is much thinner than Earth’s mantle.
Crust: The outer layer is thin crust, estimated to be around 35 km thick. The crust is composed primarily of silicate rocks and is heavily catered from billions of years of impacts.
Orbital and Rotational Characteristics
Orbit: Mercury has an elliptical orbit around the sun, with a period of around 88 Earth days. It has shortest orbit of any planet, making it the fastest orbiting planet in the solar system.
Rotation: Mercury rotate very slowly on its axis, taking around 59 Earth days to complete one full rotation. Because its slow rotation and fast orbiting, one solar day (sunrise to sunrise) on mercury lasts almost 176 Earth days.
Tidal Lock: Mercury is in a 3:2 spin-orbit resonance, means it rotates three times on its axis for every two orbits around the sun.
Important Events Related to Mercury
First Observation: Observed in ancient times by civilizations like Sumerian, Babylonian, and Greek.
Mariner 10 Mission (1974 – 1975): NASA’s Mariner 10 spacecraft first visited Mercury, which conducted three flybys and provided first closeup images of its surface.
MESSENGER Mission (2004 – 2015): MESSENGER launched by NASA orbited mercury and mapped its entire surface, provided detailed data on its geology, magnetic field, and exosphere.
BepiColombo Mission (2018-Present): BepiColombo is joint mission by ESA and JAXA. BepiColombo aims to study mercury’s magnetic field, magnetosphere, and surface composition. It is expected to arrive Mercury in December 2025.
Interesting Facts About Mercury
> Mercury has no moons or rings, similar to Venus
> Mercury is gradually shrinking due to the cooling of its large metallic core, causing the planet to contract.
> One of the largest impact craters in the solar system, the Caloris Basin is about 1,550 kilometers (960 miles) in diameter.
> Water ice has been discovered in permanently shadowed craters near Mercury’s poles.
> Mercury travels around the Sun at nearly 47 kilometers per second (about 29 miles per second), making it the fastest planet in the solar system.