Mercury: facts about the planet closest to the Sun

(ORDO NEWS) — Mercury is the smallest planet in our solar system. Known for its short years, long days, extreme temperatures and strange sunsets.

Mercury is the closest planet to the Sun. Thus, it revolves around the sun faster than all other planets, which is why the Romans named it after their fleet-footed messenger god.

Note that Mercury is the second densest planet after Earth, with a huge metallic core about 3,600 to 3,800 kilometers wide, or about 75% of the planet’s diameter.

By comparison, Mercury’s outer shell is only 500 to 600 km thick. The combination of its massive core and composition, which includes an abundance of volatile elements, has puzzled scientists for years.

Surface of Mercury

Because the planet is so close to the Sun, Mercury’s surface temperature can reach a scorching 450°C. However, since this world doesn’t have much of a real atmosphere to trap heat, temperatures can drop to minus 170°C at night, temperature fluctuations of over 600°C, the largest in the solar system.

Mercury doesn’t have a significant atmosphere to stop impacts, so the planet is cratered. About 4 billion years ago, an asteroid about 100 km wide hit Mercury with a force equal to 1 trillion 1-megaton bombs, creating a huge impact crater about 1550 km wide.

Known as the Caloris Basin, this crater could contain the entire state of Texas. According to 2011 research, another large impact may have helped create the planet’s odd rotation.

A study of rocks on the surface of Mercury in 2016 showed that the planet can still rumble with earthquakes. In addition, in the past, the surface of Mercury was constantly changing as a result of volcanic activity. However, another 2016 study found that Mercury’s volcanic eruptions likely ended around 3.5 billion years ago.

Mercury’s surface features can be broadly divided into two groups: one consists of older material that melted at higher pressures at the core-mantle interface, and the other of newer material that formed closer to Mercury’s surface.

Mercury’s magnetic field

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A completely unexpected discovery made by Mariner 10 was that Mercury has a magnetic field. Planets theoretically generate magnetic fields only if they rotate rapidly and have a molten core. But Mercury takes 59 days to rotate and is so small that its core should have cooled long ago.

MESSENGER observations have shown that the planet’s magnetic field is about three times stronger in the northern hemisphere than in the southern. It is assumed that the iron core of Mercury can turn from liquid to solid at the outer boundary of the core, and not at the inner one.

Although the magnetic field of Mercury is only 1% of the strength of the Earth, it is very active. The magnetic field in the solar wind – charged particles emanating from the sun – intermittently collide with Mercury’s field, creating powerful magnetic tornadoes that send the solar wind’s fast, hot plasma down to the planet’s surface.

Does Mercury have an atmosphere?

Instead of a dense atmosphere, Mercury has an ultrathin “exosphere” made up of atoms ejected from its surface by solar radiation, solar wind, and micrometeoroid impacts.

Mercury’s atmosphere is a surface exosphere, essentially a vacuum. According to NASA, it contains 42% oxygen, 29% sodium, 22% hydrogen, 6% helium, 0.5% potassium, with possible traces of argon, carbon dioxide, water, nitrogen, xenon, krypton and neon.

Orbit of Mercury

Mercury orbits the sun every 88 Earth days, traveling through space at nearly 180,000 km/h, faster than any other planet.

Its oval orbit is very elliptical, taking Mercury as close as 47 million km and as far as 70 million km from the Sun. If one could stand on Mercury when it is closest to the Sun, it would look three times as large as it does from Earth.

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Ironically, due to Mercury’s highly elliptical orbit and the 59 Earth days or so it takes to rotate on its axis, when on the planet’s scorching surface, the sun appears to briefly rise, set, and rise again before heading west across the sky. At sunset, the sun appears to set, rise briefly, and then set again.

Research
The first spacecraft to visit Mercury was Mariner 10, which imaged about 45% of the surface and detected its magnetic field.

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The NASA MESSENGER orbiter became the second spacecraft to visit Mercury. When it arrived in March 2011, it became the first spacecraft to orbit the planet. The mission came to an abrupt end on April 30, 2015, when a spacecraft, running out of fuel, deliberately crashed into the planet’s surface so scientists could observe the results.

In 2012, scientists discovered a group of meteorites in Morocco that they believe could have come from the planet Mercury. If so, this would make the rocky planet a member of a very select club with samples available on Earth; only the Moon, Mars, and the large asteroid Vesta have tested rocks in human laboratories.

In 2016, scientists released the world’s first global digital model of Mercury, which combined more than 10,000 MESSENGER images to take viewers through the wide open spaces of the tiny world.

In 2018, the new Mercury Explorer was launched, the BepiColombo mission jointly operated by the European and Japanese space agencies.

Currently, the mission passes through the inner part of the solar system. The science mission itself will begin in 2025 and will last for about one Earth year, or four Mercury years.

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