Mercury is the smallest and nearest planet in the solar system at a distance of 59.8 million km (0.4 AU) from the sun. it is only slightly larger than the earth’s moon but even smaller than the largest natural satellite in the solar system- Ganymede and Titan. Mercury is one of four terrestrial planets in the Solar System and is a rocky body likewise the Earth. It is named after the Roman deity Mercury, the messenger of the gods. Mercury is closest to the sun, in spite of this, it is not the hottest planet in the solar system; this title belongs to Venus.
Day and year
Mercury’s highly eccentric, egg-shaped orbit takes the planet as close as 29 million miles (47 million km) and as far as 43 million miles (70 million km) from the Sun. Its axis has the smallest tilt of any of the Solar System’s planets. It is just 2 degrees tilt with respect to the plane of its orbit around the Sun. It takes 87.97 earth days to complete orbit around the sun and 59 earth days to spin or rotate with respect to the star. One mercury solar day (one full day-night cycle) equal to 176 earth days.
It rotates in a way that is unique in the Solar System. It is tidally locked with the Sun in a 3:2 spin – orbit resonance, meaning that relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun.
Structure and Surface
Mercury is one of four terrestrial planets in the Solar System, and is a rocky planet and has a solid, cratered surface, much like the earth. Mercury consists of approximately 70% metallic and 30% silicate material. Mercury’s density is the second highest in the Solar System at 5.427 g/cm3, only slightly less than the Earth’s density of 5.515 g/cm3. It has a large metallic core with a radius of about 1,289 miles (2,074 km), about 85% of the planet’s radius. It’s outer shell, comparable to the Earth’s outer shell (called the mantle and crust), is only about 250 miles (400 km) thick.
It’s surface is similar to the earth’s moon showing heavy craters resulting from collisions with meteoroids and comets. In the solar system’s history, many asteroids collide from the mercury surface. The largest known crater is Caloris Basin, with a diameter of 1,550 km. Mercury has large areas of smooth terrain, and there are also cliffs, some hundreds of miles long and soaring up to a mile high.
Most of Mercury’s surface would appear greyish-brown to the human eye.
Size and Distance
Mercury is an average distance of 59.8 million km (0.4 AU) from the sun. From this distance, it takes sunlight 3.2 minutes to travel from the Sun to Mercury. The mean diameter of Mercury is 4880km (0.3829 the earth’s diameter), little more than 1/3 the width of the earth and contains 3.3011×1023 kg mass (0.055 the earth’s mass).
Mercury has a thin atmosphere, mostly made of oxygen, sodium, hydrogen, helium, and potassium. Its surface temperature is very from -173oc at night and 427oc during the day across the equatorial region. It is too small and hot for its gravity to retain any significant atmosphere over long periods of time.
Orbital and escape velocity
Mercury’s orbital eccentricity is the largest of all known planets in the Solar System. It’s average orbital speed is equal to 47.362 km/s. and equatorial rotational speed is 10.892 km/h.
Escape velocity of mercury is 4.25 km/s i.e. if you want to escape some object from the mercury’s gravitational area; you have to through the object at minimum speed of 4.25 km/s.
The magnet field on mercury is generated by dynamo effect (circulation of planet’s iron rich liquid core), similar to the magnetic field of the earth. But the strength of magnetic field at surface of mercury is just 1 percent of the earth’s magnetic field.
Magnetic field of this planet is strong enough to deflect the solar wind around the planet, creating a magnetosphere. The planet’s magnetosphere, though small enough to fit within Earth, is strong enough to trap solar wind plasma. This contributes to the space weathering of the planet’s surface.
Mercury has no moon.
Mercury has no rings.
Mercury’s environment is not conducive to life as we know it. The temperatures and solar radiation that characterize this planet are most likely too extreme for organisms to adapt to.
Two spacecraft visited mercury till now. The first was Mariner 10; it flew by Mercury three times during 1974 & 1975 and mapped 45 percent of Mercury’s surface. Mariner also discovered its thin atmosphere and detected the magnetic field.
The second spacecraft was Messenger; it flew by Mercury three times during 2008-2009 and orbited the planet 4000 times in four years (2011-2015) exploring lots of images, compositional data, and scientific discoveries. In 2015 Messenger crashed into the planet’s surface on April 30, 2015 after exhausting its fuel.
The on-going first mission of the European Space Agency “BepiColombo” launched in 2018 with a target date for Mercury orbit insertion of 2025.
In Roman Mythology, Mercury the son of Maia Maiestas (Daughter of the Titan Atlas) and It was a major god of trade, profit, Travelers, and commerce. He is commonly identified with the Greek Hermes, the fleet-footed messenger of the gods. Mercury’s temple in Rome was situated in the Circus Maximus, between the Aventine and Palatine hills, and was built in 495 BC. The temple was regarded as a fitting place to worship a swift god of trade and travel since it was a major center of commerce as well as a racetrack. Since it stood between the plebeian stronghold on the Aventine and the patrician center on the Palatine, it also emphasized the role of Mercury as a mediator.
In Hindu Mythology, Mercury is known as Budha Graha, the son Soma (moon god Chandra) and Tara (wife of Brhaspati, Jupiter god). Budha is also the root of the name for the week day Wednesday.
Quick Discover :
Distance from the sun:
0.4 Astronomical unit
Average orbital speed:
Equatorial rotational velocity:
88 Earth days
176 Earth days
Potential for Life:
Image credit :
Image5: universe discover/aniket kumar