Mercury is the littlest planet in the Solar System and the closest planet to the Sun. With a diameter of just over 3,000 miles, this little planet is only about 1/3 how big Earth and only about 40% bigger than Earth’s moon. On a scale where Earth is how big a baseball, Mercury could be about how big a golf ball.
Mercury features a very elongated orbit that takes the planet about 28.5 million miles from the Sun at its closest approach, known as PERIHELION, and as far away as 43 million miles at its farthest, known as APHELION. At perihelion, the Sun seems nearly 3 times larger and about eleven times brighter when viewed from the surface of Mercury than what we see from the surface of Earth (but the sky on Mercury could be black because Mercury does not have any air). Mercury is really close to the Sun that it’s usually obscured by it, making Mercury difficult to examine from the Earth even although the little planet is only about 48 to 50 million miles from the Earth at its closest approach.
Traveling at a speed of approximately 108,000 miles each hour, Mercury completes one orbit round the Sun in about 88 Earth-days. The Earth travels about 66,000 miles each hour, and completes one orbit round the Sun every 365 days. Mercury completes a lot more than four orbits of the Sun in a single Earth-year. In comparison to this short year, days and nights on Mercury are extremely long. Mercury turns slowly on its axis, taking about 59 Earth-days to perform just one rotation. Mercury only completes three rotations on its axis within the span of two orbits round the Sun. This means that three days on Mercury last two Mercurian-years.
Mercury was the name of the Roman messenger god who carried messages and performed errands for other gods. Mercury was also the god in charge of watching over trade, commerce, travelers and merchants. Mercury was often connected with peace and prosperity, and was also considered a god of the winds because of his speed. Because Mercury orbits the Sun faster than every other planet in the Solar System, ancient civilizations, including Mayans, Egyptians, Greeks and Romans, envisioned this speeding “star” as a messenger god in their religions and myths.
Mercury’s surface temperatures vary dramatically, from over 800 degrees Fahrenheit on the side facing the Sun to about minus 300 degrees Fahrenheit on the side facing away. This range in surface temperature between Mercury’s sunlit-side and dark-side is probably the most extreme for any planet in the Solar System. Mercury simultaneously broils and freezes… literally! A significant contributor to this cycle of extreme heat and cold is the truth that Mercury is too small to retain a substantial atmosphere. Mercury comes with an atmosphere, but it’s so thin – only about 1-trillionth the density of Earth’s atmosphere – that it’s practically non-existent. This thin atmosphere prevents Mercury from retaining and circulating heat round the planet. So as the small planet rotates, the side no more exposed to the Sun cools dramatically while the side facing the Sun roasts.
Mercury’s thin atmosphere contains traces of elements from the solar wind and gases that have been baked out from the planet’s crust and surface rocks. A planet retains its atmosphere using its gravitational pull. Mercury does not need sufficient mass to retain – by gravitational pull – a considerable atmosphere. Mercury’s surface gravity is only about 1/3 of the Earth’s. This means that a person who weighs 100 pounds on Earth would only weigh about 38 pounds on Mercury. Also, a planet as close to the Sun as Mercury is even less likely to retain a thick atmosphere than the usual more distant planet like Earth because it’s constantly being blasted by solar radiation. Charged particles emitted by the Sun are scorching the planet, and this atomic debris does manage to build up, however the intense heat coupled with Mercury’s weak gravity allows the gases to escape.
Mercury comprises about 70% iron and about 30% silicate material. It’s believed that most of Mercury’s iron is concentrated in its core. This core, the densest of some of the planets in the Solar System, accounts for about 75% of Mercury’s volume. This means that Mercury’s core is proportionally bigger than every other planet in the Solar System. This core may lead to creating paykwik kart weak – less than 1% as strong as Earth’s – but nonetheless detectable magnetic field. This magnetic field is a sign that Mercury’s core contains molten iron and isn’t completely solid. The fluid interior could – like Earth’s core – behave like a molten conductor. As Mercury spins on its axis, the molten iron in the core could generate the magnetic field that surrounds the little planet.