FACTS ABOUT MERCURY
Mercury is the littlest planet in our solar system and is positioned first from the sun. Its orbital period around the Sun of 87.97 days is the most brief of the other planets in the Solar System. It is named after the Roman god Mercury, the messenger of the Gods.
Like Venus, Mercury orbits the Sun inside Earth’s orbit as an inferior planet, and never surpasses 28° far from the Sun when seen from Earth. This closeness to the Sun implies the planet must be seen close to the western or eastern skyline amid the early night or early morning.
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Mercury is tidally locked with the Sun in a 3:2 turn orbit resonance, and rotates in a manner that is extraordinary in the Solar System. As observed in respect to the fixed stars, it turns on its axis precisely three times for each two revolutions it makes around the Sun. As observed from the Sun, in a frame of reference that rotates with the orbital motion, it seems to pivot just once every two Mercurian years. An onlooker on Mercury would along these lines see just a single day each two Mercurian years.
Mercury’s axis has the smallest tilt of any of the Solar System’s planets (about 1⁄30 degree). Its orbital eccentricity is the biggest of every planet in the Solar System; at perihelion, Mercury’s separation from the Sun is just around 66% of its separation at aphelion. Mercury’s surface shows up vigorously cratered and is comparable in appearance to the Moon’s, demonstrating that it has been topographically latent for billions of years.
Having no environment to hold heat, it has surface temperatures that fluctuate diurnally more than on some other planet in the Solar System, running from 100 K (−173 °C; −280 °F) around evening time to 700 K (427 °C; 800 °F) amid the day over the tropical regions. The polar-regions are always underneath 180 K (−93 °C; −136 °F). The planet has no known satellites.
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Two shuttle have visited Mercury: Mariner 10 flew by in 1974 and 1975; and MESSENGER, launched in 2004, orbited Mercury more than multiple times in four years before debilitating its fuel and colliding with the planet’s surface on April 30, 2015. The BepiColombo rocket is intended to touch base at Mercury in 2025.
The planet’s proximity to the Sun means the planet can only be seen near the western or eastern horizon during the early evening or early morning. At this time it may appear as a bright star-like object. Also mercury orbits so quickly that early civilizations believed that they were actually two stars one which appeared in the morning and the other which appeared in the evening.
Table of Contents
Temperature and atmosphere
The planet Mercury is very close to the sun therefore Mercury’s surface temperature can reach a scorching 840 degrees Fahrenheit. However at night temperatures can plummet to minus 275. The planet has highest temperature swing of more than 1,100 degrees F, the greatest in the solar system because it does not have any atmosphere to regulate temperature. Mercury is the second hottest planet. Mercury has a very thin atmosphere which is made up of atoms from surface of planets which have been blown away by solar winds.
As Mercury is so hot, atoms quickly escape into space and the atmosphere constantly gets replenished. Also due to Mercury’s proximity to the sun it is constantly bombarded by solar winds, which carries off most of what little atmosphere does accumulate. Thus mercurial atmosphere is so thin that it is virtually non-existent.
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In fact Mercury’s atmosphere is approximately 1015 less dense than the Earth’s atmosphere. Mercury does not experience any seasons because its axis has the smallest tilt as compared to other planets. Although the daylight temperature at the surface of Mercury is generally extremely high, observations strongly suggest that ice (frozen water) exists on Mercury.
The icy regions are estimated to contain more than a thousand kilograms of ice. Mercury is too small and hot for its gravity to retain any significant atmosphere over long periods of time, but it does have a tenuous surface bounded exosphere containing many gases like hydrogen, helium, oxygen, sodium, calcium, potassium and others.
Famous quote by Johann Wolfgang von Goethe,
“I had rather be Mercury, the smallest among seven planets, revolving round the sun, than the first among five moons revolving round Saturn.”
Size & appearance of the planet.
Mercury is slightly larger than our Moon – 15,329 kilometres around its equator. Mercury is about 2.6 times smaller than Earth. Mercury is one of the rocky planets. It has a solid surface that is covered with craters. Until 1974, the Mercurial surface remained, in large part, a mystery to scientists due to Mercury’s close proximity to the Sun.
Being so close to the Sun restricts Mercury’s visibility to just before dawn or right after dusk. At these times, unfortunately, the angle at which we see Mercury from the ground takes our line of sight through a significant amount of the Earth’s atmosphere, greatly obstructing our view.
Video by Michel van Biezen
However, during its three fly-bys of Mercury in 1974, the Mariner 10 spacecraft captured clear and stunning photographs of the planet’s surface. Amazingly, Mariner 10 photographed almost half of the planet’s surface during its mission! The results revealed that Mercury’s surface has three significant features.
The first feature is the huge number of impact craters that have accrued over billions of years. Caloris Basin is the largest of these with a diameter of 1,550 km. The second feature is the plains found between craters. These are smooth areas of the surface, hypothesized to have been created from ancient lava flows. The third feature is the cliffs (also known as scarps), which run anywhere from tens to thousands of kilometers in length and from one hundred meters to two kilometers in height.
The importance of these two features lies in what they imply. By the presence of ancient lava fields, it is clear that there was volcanic activity at one time. However, given the number and age of the craters, scientists have concluded that Mercury has been geologically inactive for a significant period.
The third of the surface features tells us something of great interest as well. Essentially, the scarps found on the surface are huge cliffs caused by the buckling of the planet’s crust. What is significant about the buckling on Mercury is what it implies. To understand the significance, we must use a comparison.
The buckling on Earth is due to the shifting of tectonic plates, whereas the buckling on Mercury is due to the shrinking of its core. The implication is that because Mercury’s core is shrinking so, too, is the planet as a whole. Recent estimates show that Mercury’s diameter has decreased in excess of 1.5 kilometers.
Orbit and rotation of Mercury.
The average orbital speed of Mercury is 170500 km/hour (47m/s). Mercury’s orbit is elongated, taking an almost oval- or egg-shaped course around the Sun. This means that its distance from the Sun varies throughout its circuit, between approximately 46 million and 70 million kilometres.
Mercury speeds around the Sun at nearly 47 kilometres per second – almost 60% faster than Earth’s orbiting speed.
Days on Mercury are very long because the planet rotates very slowly. One day-long spin lasts for 59Earth days. But because of its fast orbit, one Mercury year takes 88 Earth days.
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This means that two years on Mercury lasts for only three days. The planet’s sunrise would be unusual to us on Earth. Due to its elongated orbit and slow rotation, from some places on Mercury’s surface, the Sun appears to rise briefly before setting and rising again. At sunset, the reverse happens, with the Sun appearing to set twice. The planet spins almost vertically on its axis, so its poles are never fully sunlit. The lack of tilt also means that the planet does not experience yearly seasons like Earth.
Temperature conditions of the planet.
Mercury’s sun-facing side is scorched by temperatures of around 430°C, hot enough to melt lead. Without a substantial atmosphere to distribute heat away from the areas facing the Sun, the planet’s slow rotation makes for stark differences in temperature between its dark and light sides.
The side facing away cools to an approximate -180°C. But despite the intense heat the planet faces as it rotates, areas that are permanently shaded, such as some polar craters, may hold deposits of ice. Intense changes in temperature from day to night make it impossible for life as we know it to flourish on Mercury.
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Although it is the closest planet to the Sun, Mercury isn’t the hottest in the solar system. The dense atmosphere of Venus causes a greenhouse effect, resulting in higher temperatures.
Atmospheric conditions of the planet.
The Mercurial atmosphere is so thin that it is virtually non-existent. In fact, at approximately 1015 times less dense than the Earth’s atmosphere, Mercury’s is closer to a true vacuum than any man-made vacuum ever created. The explanation behind the lack of substantial atmosphere is twofold. Firstly, with a gravity only about 38% that of the Earth’s, Mercury is simply unable to retain much of an atmosphere.
Secondly, Mercury’s close proximity to the Sun causes it to be constantly bombarded by solar winds, which carries off most of what little atmosphere does accumulate.
However, as meagre as its atmosphere is, Mercury does have one. According to NASA, its chemical composition is thought to be as follows: 42% oxygen (O2), 29% sodium, 22% hydrogen (H2), 6% helium, .5% potassium, and possibly trace amounts of argon, carbon dioxide, water, nitrogen, xenon, krypton, neon, calcium (Ca, Ca+), and magnesium.
A notable result of such a sparse atmosphere is the extreme temperatures found on the planet’s surface. With a low temperature of approximately -180° C and high of approximately 430° C. Mercury has the largest range of surface temperatures found on any planet. The extreme highs present on the side facing the Sun are due to the insufficient atmosphere, for it is unable to absorb the solar radiation.
As for the extreme colds on the side facing away from the Sun, without a substantial atmsophere to trap solar radiation, all heat is lost to space.
Interior of the planet.
Broadly speaking, Mercury’s interior is composed of three distinct layers: a crust, mantle, and core. The planet’s crust is estimated to be between 100 and 300 kilometers in thickness. Mercury’s surface is part of the crust, so the presence of the previously mentioned scarps indicates that the crust is solid and brittle.
With a thickness of approximately 600 kilometers, Mercury’s mantle is relatively thin. Supposedly, its mantle has not always been this thin. Mercury used to have a much thicker mantle, but the leading theory explains that during formation of the Solar System, a large planetesimal collided with the planet, launching most of the mantle into space.
Mercury’s core has been the focus of much research. With an estimated diameter of 3,600 kilometers, the core gives the planet some interesting properties.
The most obvious of these properties is Mercury’s extreme density for its size. With a planetary diameter of 4,878 kilometers, Mercury is smaller than the Jovian moon Ganymede and the Saturnian moon Titan, whose diameters are 5,270 km and 5,152 km, respectively. However, with a mass of3.3 x 1023 kg, Mercury’s density of 5,540 kg/m3.
One debate that has recently be resolved regarding Mercury’s core is whether or not it is solid or liquid. By measuring how radio waves bounced off of the planet, scientists were able to determine that the core is, in fact, liquid. More specifically, the data gathered help to measure the amount of wobble in Mercury’s rotation. With a solid core the rotation would be rigid, whereas with a liquid core there are small amounts of variation in the rotation due to the liquid inside “sloshing” around.
Surface geology.
The surface of Mercury has numerous interesting features including a variety of crates, ridges and terrains ranging from heavily crated to nearly crater free. Craters are differently named after artists, musicians, painters, and authors who have made outstanding or fundamental contributions to their field.
Ridges, or dorsa, are named for scientists who have contributed to the study of Mercury. Depressions are named for works of architecture. Plains are named for Mercury in various languages. Valleys are named for radio telescope facilities. Craters appear in all states of degradation, from relatively fresh rayed craters to highly degraded crater remnants.
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There are many different types of craters like the new young crates on top of old craters, craters with peaks in the centre and craters with lines or rays of bright material pointing out from the central crater. Craters range from 10 m to 1300 km. Craters on Mercury range in diameter from small bowl-shaped cavities to multi-ringed impact basins hundreds of kilometers across.
If a crater is larger than 250km then it is known as Basin. Mercury’s core has high iron content than any other planet. Mercury’s surface is somewhat similar to that of Moon, showing extensive mare-like plains and heavy craters. The largest known crater is Caloris Basin, with a diameter of 1,550 km.
it is an interesting fact that one side of the planet is more heavily cratered than other. The tiny planet Mercury is made up of a single continental plate over a cooling iron core. As the core cools, it solidifies, reducing the planet’s volume and causing it to shrink.
The process crumpled the surface, creating lobe-shaped scarps or cliffs. Mercury was heavily bombarded by comets and asteroids during and shortly following its formation 4.6 billion years ago.
Compression features.
One unusual feature of Mercury’s surface is the numerous compression folds that crisscross the plains. The wrinkle ridges hat are scattered across the Mercury’s surface suggest that interior side of the planet cooled, it contracted causing squeezing and lifting of the surface. The scarps can reach lengths of 1000 km and heights of 3 km.
These compression features suggest that they are more recent than the craters and plains because they are present on the top side of the planet. Mapping of the features has suggested a total shrinkage of Mercury’s radius in the range of ~1 to 7 km. Small-scale thrust fault scarps have been found, tens of meters in height and with lengths in the range of a few km, that appear to be less than 50 million years old, indicating that compression of the interior and consequent surface geological activity continue to the present.
Some interesting facts about the planet Mercury.
- The planet has an equatorial circumference of 15,329 km and a radius of about 2,440 km approx.
- The average distance from the sun is 58 million kilometers.
- Surface temperature or the temperature on the planet ranges from about -180° C to 430° C.
- One Mercurian year is equal to 88 earth days.
- Average orbital speed of the planet Mercury is 170,500km/h (47km/s).
- The planet has no moons due and no rings due to low gravity.
- The planet is terrestrial judging by its surface properties.
- Mercury orbits so quickly around the Sun that early civilizations believed it was actually two different stars – one which appeared in the morning and another which appeared in the evening.
- Mercury is the smallest planet in the solar system with a diameter of 4,879 km and is one of five planets that is visible to the naked eye.
- After the Earth, Mercury is the second densest planet. Despite its small size, Mercury is very dense because it is composed mainly of heavy metals and rock – the main characteristic of terrestrial planets.
- Astronomers didn’t realize that Mercury was a planet until 1543 when Copernicus published his Sun-centered model of the Solar System – putting the Sun as the centre of the solar system rather than the previously believed centre, the Earth.
- The planet has just 38% of the gravity on Earth. This means that Mercury isn’t able to hold the atmosphere it has and it instead gets blown away by solar winds. However those same solar winds are also bringing in new gases, radioactive decay and dust from micrometeorites – replenishing the atmosphere.
- It was once believed that a planet called Vulcan existed between the orbit of Mercury and the Sun – however the proof of existence of such a planet was never found.
- The orbit of Mercury is an ellipse rather than circular. It has the most eccentric orbit in the solar system and the least circular of all of the planets, according to scientists and astronomers.
- Mercury is only the second hottest planet. Venus, though farther from the Sun than Mercury, actually experiences higher temperatures.
- This is because Mercury has no atmosphere to regulate temperature and results in the most extreme temperature change of all the planets – ranging from -170°C (-280°F) during the night to 430°C (800°F) during the day.
- Mercury does not experience any seasons. The axis of Mercury has the smallest tilt of all other planets, and this results in a lack of seasons on its surface.
- Mercury is the only planet which doesn’t rotate exactly once every year – instead rotating three times for every two orbits of the Sun. This is because it is nearly tidally locked to the Sun.
- The orbit of Mercury was important in proving Albert Einstein’s theory of General Relativity.
- Mercury has a large iron core that is around 40% of its volume (compared to a core volume of 17% for Earth) in its centre whose radius is 1800 to 1900 kilometers (1100 to 1180 miles). Scientists believe the core of Mercury is probably molten.
- The outer shell of Mercury is only 500 to 600 kilometers (310 to 375 miles) thick. Earth’s outer shell (the mantle and crust) is 2930 kilometers (1819 miles) thick.
- Mercury has a very thin atmosphere, which is made up of atoms from the surface of the planet that have been blown away by solar winds. As Mercury is so hot, these atoms quickly escape into space and so its atmosphere is constantly being replenished.
- Mercury has a weak magnetic field whose strength is about 1% of the magnetic field on Earth.
Only two spacecraft have ever visited Mercury. - The planet Mercury is gray rocky in color due to its tenuous surface.
- For every 2 orbits of the Sun, which takes around 88 Earth days, Mercury completes three rotations of its axis. It is gravitationally locked and this rotation is unique to the solar system.
- Mercury has a mean diameter of 4880km and a surface area of 7.48*107 km. It has a volume of 6.083*1010 km and a mass of 3.3011*1023 kg which is 5.5% of Earth’s mass.
- The surface gravity of Mercury is 3.7m/s2 which is just 38% of Earth’s gravity and due to this it is unable to hold atmosphere and gets blown away by solar winds.
- Mercury has a solid silicate crust, iron sulfide outer core layer, a deeper liquid core layer, and a solid inner core. Mercury is very dense because it is composed mainly of metals and rock.
- Mercury is one of the four terrestrial planets of our Solar System and is a rocky body like Earth.
- Despite the small size and slow rotation, Mercury has a significant, and apparently global, magnetic field. Mercury has a magnetic field of about 1% of Earth. Due to weak magnetic field Mercury has a slow rotational period.
- Mercury has no moons, rings or satellites due to low gravity and lack of atmosphere.
- The orbit of Mercury is the most eccentric and least circular in the solar system unlike other planets.
- Although the discovery date of Mercury is unknown but it is known since ancient times and the first mentions are believed to be around 3000 BC by Sumerians.
- Till now only two spacecrafts have ever visited to Mercury due to proximity to the Sun.
What remains intriguing about Mercury is how scant our knowledge has been regarding some of its key details until recently. For example, it was only in 1974 that the Mariner 10 spacecraft captured the first images providing any specific detail of the Mercurial surface. Within the last several years, unexpected discoveries regarding Mercury’s atmosphere and interior have challenged previously accepted theories.
While the passage unfolded several facts, figures and relevant data about the planet Mercury some questions still remain unanswered. We can only hope that in the coming years, we will be able to learn more about this incredible planet and that knowledge will help us navigate the universe better.
Related questions.
Due to the planet’s lack of atmosphere, what color is Mercury’s sky?
Despite its close proximity to the Sun, unlike planet Earth, Mercury has no real atmosphere to scatter the Sun’s rays, and so its sky appears black. Indeed the planet has the thinnest atmosphere of all of the planets that make up the Solar System, with most of the particles that make up its thin atmosphere stemming from the Sun.
What did robotic space probe, Mariner 10, reveal about Mercury?
NASA’s Mariner 10 was a robotic space probe that was launched on the 3rd of November, 1973, with the intention of taking certain measurements of both Mercury and Venus. Though it is widely known that it was the first mission to Mercury, the probe was also the first probe to visit two planets as part of one single mission. During one particular flyby, Mariner 10 detected that Mercury had a magnetic field, a fact that was previously unknown.
The Hubble Space Telescope has never been used to view the planet Mercury. Why not?
The Hubble Space Telescope is a space telescope that first entered orbit in 1990, and while it has observed some of the furthest away galaxies to ever be seen, it is unable to view Mercury, Venus or the Sun. The reason for this is that the rays of the Sun are so powerful that viewing it would likely cause irreparable damage to the Hubble Space Telescope. Moreover as Mercury and Venus are so close to the Sun, viewing either of these would have the same, catastrophic consequences, and so the Hubble Space Telescope is always pointed away from the Sun.
Mercury is known for its bizarre orbiting pattern, which is considered the most erratic of all the planets. How was Theory of Relativity used to understand it?
Mercury’s orbit of the Sun is relatively complex, as it traces a rosette pattern in space (similar to a spinning top). This seemingly bizarre pattern baffled astronomers for a long time, so much so that it took Albert Einstein’s General Theory of Relativity for astronomers and physicists to understand Mercury’s movements. Indeed Einstein’s theory correctly claimed that Mercury slowed down when it moved away from the Sun, only to speed up as it approached it. Moreover its complicated lurches resulted in an orbit that contradicted Newton’s Gravitational Theory.