Mercury
Mercury is the smallest of the four terrestrial planets in our solar system and the closest planet to our sun which was first observed by Galileo Galilei and Thomas Harriot in 1631. Since it is so close to our star, it is also subjected to extreme temperature changes during its rotation. This little ball is no joke, and this page looks at some of the facts about the most inner rocky planet in the system.
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Size
Mercury is about 2.5 times smaller than Earth having an Equator circumference of 9524 miles (15,329Km) and a Radius of 1516 miles (2440km). When comparing this to the earth of 24,901 miles (40,075km) at the equator and a radius of 3985.75 miles (6371km).
Mercury is the smallest planet in the solar system since Pluto was degraded to a dwarf planet (we aren’t going there! I’m unhappy about it also).
Mercury is about 2.5 times smaller than Earth having an Equator circumference of 9524 miles (15,329Km) and a Radius of 1516 miles (2440km). When comparing this to the earth of 24,901 miles (40,075km) at the equator and a radius of 3985.75 miles (6371km).
Mercury is the smallest planet in the solar system since Pluto was degraded to a dwarf planet (we aren’t going there! I’m unhappy about it also).
Orbit and rotation of the planet
Mercury orbits very close to the sun but has an egg-shaped orbit giving different distances depending on the whereabouts it is in the orbit. At its closest, Mercury is 29 million miles (47 million km) from the sun, and 43 million miles (70 million km) at its furthest point, with an overall average distance of 36~ million miles (58 million km) from the sun. Because of this eccentric orbit and how close it is to the star, Mercury’s year is only 88 Earth days, with the planet moving at 105943mph (170,500km/h) or 29 miles per second, making it the fastest planet in the solar system.
An average day on Mercury is 59 Earth days, while the one day/ night cycle is significantly longer at 176 days. This means one complete day-night cycle is just over two years on the planet.
This extreme day-night cycle is because the planet has only a 2-degree tilt concerning the plane of its orbit. Its slow rotation speed and fast movement around the sun give the extremely large day/ night cycle. Because of the lack of tilt, Mercury doesn’t experience seasons, like other planets which means parts of the planet, some deep craters especially will never be in the sun’s light and could technically hold ice.
Because of the distance from the Sun, its orbit and its rotation, the sun appears to rise and set twice from some parts of the planet.
Mercury orbits very close to the sun but has an egg-shaped orbit giving different distances depending on the whereabouts it is in the orbit. At its closest, Mercury is 29 million miles (47 million km) from the sun, and 43 million miles (70 million km) at its furthest point, with an overall average distance of 36~ million miles (58 million km) from the sun. Because of this eccentric orbit and how close it is to the star, Mercury’s year is only 88 Earth days, with the planet moving at 105943mph (170,500km/h) or 29 miles per second, making it the fastest planet in the solar system.
An average day on Mercury is 59 Earth days, while the one day/ night cycle is significantly longer at 176 days. This means one complete day-night cycle is just over two years on the planet.
This extreme day-night cycle is because the planet has only a 2-degree tilt concerning the plane of its orbit. Its slow rotation speed and fast movement around the sun give the extremely large day/ night cycle. Because of the lack of tilt, Mercury doesn’t experience seasons, like other planets which means parts of the planet, some deep craters especially will never be in the sun’s light and could technically hold ice.
Because of the distance from the Sun, its orbit and its rotation, the sun appears to rise and set twice from some parts of the planet.
Atmosphere, Magnetosphere and Geology
The Surface of Mercury is terrestrial comprising Silicate rocks and metals, which are primarily Iron. The surface resembles the moon, by the means of heavy impact craters across the surface. Two of the larger known craters are called Caloris (960 miles in diameter) and Rachmaninoff (190 miles in diameter) along with several others to note. The surface has large smooth areas and large cliffs which span hundreds of miles and up to a mile high which was created as the interior cooled and contracted over billions of years. The core itself is a metallic core which has a radius of 1289 miles and is about 85% of the planet’s total radius. There is evidence of the core being partly molten or liquid. Its shell is comparable to Earth’s mantle and crust, which is approximately 250 miles (400km) thick making Mercury the Second dense after Earth. |
The Atmosphere is comprised of atoms blasted off the surface by solar wind and meteors striking the surface. The atmosphere is very thin and small but comprises Oxygen, Sodium, Hydrogen, Helium, and potassium. Because the atmosphere is so thin meteorites are not slowed, nor are they prevented when they are on a collision course with the planet.
Because of Mercury’s distance from the Sun, Its geology and its atmosphere, Mercury is only the second hottest planet, second to Venus, reaching temperatures of 430 C in the sun and -180 C in the shade. These temperatures vary depending on the planet’s location in its orbit and rotation. Mercury has no moons. Because of the Close orbit to the Sun, the Sun’s strong gravitational force would pull the moon out of orbit. On the same logic – Mercury doesn’t have any rings either. Mercury’s Magnetic field is offset relative to the planet’s equator and only has 1% of Earth’s magnetic strength at the surface. Solar winds interact with the Magnetosphere creating intense magnetic tornados that funnel down to the surface. |
False colour Images
False Colour Images, Similar to mineral moon images, are used to enhance the view of chemical, mineralogical and physical differences between the geology on the planet.
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Photography and Viewing
Photographing Mercury is tricky because it’s so close to the sun. The best times are usually when it is in the transition of the sun (moving in front of the sun from our perspective) and taking photos when photographing the sun. (different topic, please follow advice on photographing the sun – do not look directly at the sun with or without a scope. Permanent eye damage will occur)
Other methods are at sunset and sunrise. The safer way is at sunset but either way, the planet is very close to the surface and caution is needed when viewing or photographing Mercury (This literally can’t be stressed enough). The same methods can be used as other planets with non-cooled cameras which have a high frame rate and video the planet.
Photographing Mercury is tricky because it’s so close to the sun. The best times are usually when it is in the transition of the sun (moving in front of the sun from our perspective) and taking photos when photographing the sun. (different topic, please follow advice on photographing the sun – do not look directly at the sun with or without a scope. Permanent eye damage will occur)
Other methods are at sunset and sunrise. The safer way is at sunset but either way, the planet is very close to the surface and caution is needed when viewing or photographing Mercury (This literally can’t be stressed enough). The same methods can be used as other planets with non-cooled cameras which have a high frame rate and video the planet.
Space craft visiting Mercury
Mariner 10 passed by Mercury in 1974 and 1975, and MESSENGER, launched in 2004, orbited the planet more than 4,000 times over four years before running out of fuel and crashing on the planet's surface on April 30, 2015. Mercury will be visited by the BepiColombo spacecraft in 2025.