1. The Mercury | Smallest Planet in our Solar System

The Mercury

The first, nearest to the Sun and the smallest planet in our Solar System. The Sun appears three times bigger / larger than compared from the earth when viewed from its surface, also the Sunlight is seven times brighter than that of Earth. Despite, Mercury being in the closest arena to the Sun, it is not the hottest planet in our Solar System. Venus being the second closest planet to the Sun holds the title for the Hottest Planet in our Solar System.

For in-depth information on planet Venus please read our article: “Venus (Hottest Planet in the Solar System)”

As an Inferior planet, It orbits around the sun just like Venus and Earth. Also, it does not have any Moons, just like Planet Venus. Mercury telescopically displays the complete range of phases, as the planet moves in its inner orbit relative to Earth and similar to Venus and the Moon which recurs over its synodic period of approximately 116 Earth days. The planet may usually appear as a bright star-like object but is more difficult to observe than Venus. Although it is just like several other planets can be viewed during a total Solar eclipse.

Dimensions and Distance

Mercury is more than 1/3rd the width of Earth. It has a radius of 2,440 kms (1,516 miles).

It is 0.4 astronomical units i.e. An Average distance of 58 million km (36 million miles) away from the Sun. [Astronomical Units are abbreviated as AU]. The distance from Sun to Earth is One AU (Astronomical Unit). The Sunlight takes about 3.2 minutes (192 seconds) to travel to Mercury from the Sun.

As observed from Earth, its apparent distance from the Sun never exceeds 28° degrees in proximity. This means the planet can only be observed / seen near the western horizon after sunset or eastern horizon before sunrise; to be precise in twilight due to the planet’s close proximity to the Sun.

Brain Gym: – Do you know after whom the planet is named “Mercury”? And how much do we weigh on Mercury? Find out!!!

Structure and Formation

Mercury has a large metallic core with a radius of about 2,074 km (1,289 miles) i.e. almost 85 percent of the planet’s radius. It is also the second densest planet in our Solar System after Earth. There are theories and evidence that the radius of its partly molten or liquid. Also, it 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’s outer shell (crust and mantle) is only about 400 km (250 miles) thick as compared to Earth’s outer shell.

When gravity pulled swirling gas and dust together, the planet was formed. It was formed about 4.5 billion years ago. The planet has a solid crust, a central core, and a rocky mantle.

Did you know: – The BepiColombo Spacecraft is expected to arrive at Mercury in 2025?

Rotation and Orbit

Mercury rotates around the Sun in a 3:2 spin-orbit resonance in a way that is unique in our Solar System. Mercury is egg-shaped and is highly eccentric and its orbit takes the planet as far as 70 million km (43 million miles) and as close 47 million km (29 million miles) from the Sun. It orbits the Sun travelling in space at a breath-taking speed of 47 km (29 miles) per second every 88 days, faster than any other planet in our Solar System.

It spins slowly on its axis and completes one revolution around the Sun every 59 Earth days. When Mercury is on fastest pace in its elliptical orbit around the sun i.e. when the planet is closest to the sun, for every rotation a sunrise and sunset aren’t accompanied as of other planets in our Solar System. The sunrise is brief; sets and raises again in few parts on the planet’s surface. Also, sunset is just vice-versa for the rest of the parts on the planet’s surface.

Did you know: – 176 Earth days is equal to One Mercury Solar day (a complete day & night cycle) -just over two years on Mercury!!

The planet does not have seasons like other planets as it spins nearly perfectly upright because the planet’s axis of rotation is tilted just about 2 degrees with respect to the plane of its orbit to the Sun, also the orbital eccentricity is the largest of all known planets in our Solar Systems.

Surface and Atmosphere

Its surface resembles that of Earth’s moon. It has many impact Craters due to collisions with comets and meteoroids. There are cliffs, some hundreds of miles long and ranging up to a mile high, while there are large areas of smooth terrain too. They are formed at the planet’s interior cooled and contracted over the billions of years since it was formed.

Mercury’s most of the surface appears greyish-brown in color to the naked human eye. The big basin like structures also known as ‘bright streaks’ are called “Crater Rays”. They are formed when a huge Comet or Asteroid hits the planet surface. Due to the impact of the same, tremendous amount of energy releases which creates or digs a huge hole in the ground leaving a basin like structure called Crater. This impact also crushes a large amount of rock under the core or point of impact.

Few crushed materials due to impact are bounced back far from the Crater and lands back on the surface resulting in the form of rays. The rays look brighter because very Fine particles of the crushed rock are more reflective than larger pieces. The rays appears to darken with time due to the Solar-Wind particles and the Space Environment-Dust.

Did you know: – Large Asteroids have made impacts which has created large Craters just as basin like structures on the surface of Mercury, including Caloris [1,550 kms (960 miles) in diameter] and Rachmaninoff [306 kms (190 miles) in diameter].

Mercury’s temperature is on an extreme level (both Hot and Cold) on the surface. During the day, the temperature on the surface of the planet reaches up to 430 degrees Celsius (800 degrees Fahrenheit), and during the night the temperature on the surface of Mercury drops down to minus 180 degrees Celsius (minus 290 degrees Fahrenheit). This huge fluctuation in temperature is caused due to the absence of atmosphere to retain the Heat on the planet. Mercury may have iced water caps inside deep craters at both of its North Pole and South Pole where it’s available only in the regions of permanent shadow. Despite the high temperatures on sunlit parts of planet there could be cold enough iced water to preserve.

Speaking of Atmosphere on Mercury, the planet, instead of Atmosphere possesses a thin exosphere made of atoms blasted off the surfaces by the Solar Wind and striking Meteoroids. This exosphere is mostly composed of Helium, Hydrogen, Oxygen, Potassium and Sodium.

Brain Gym: – What are the names of the Spacecraft’s which have visited and orbited the planet Mercury? And when? Find out!!!

Magnetic Field

Mercury’s Magnetic field is relatively offset to the planet’s equator. Its Magnetic field strength is just one percent when compare to the Earth’s Magnetic field strength. Although it interacts with the Magnetic field of the Solar Wind to create intense Magnetic tornadoes that spins / funnels furiously fast, hot Solar Wind Plasma down to the surface of the planet. When the ions strike the surface, they knock off neutrally charged atoms and send them on a high loop into the sky.

Fun Facts: – A year in Mercury is 88 days, yet One Mercury Day is 176 Earth Days!!! Confusing right?!

Expectancy of Life Forms

Theories and Researches have proved as of now that Life on Mercury is highly impossible as there is no atmosphere present on the planet and the Temperatures and Solar radiations are extreme to withstand and adapt for organisms.