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All about Mercury | Physical characteristics | Orbit and Rotation | Mercury missions

As most of us know our Earth is part of a superordinate planetary system. In detail this consists of eight different planets which orbit around a fixed star our sun at a finely tuned regularity. The corresponding celestial bodies however are as diverse as they are astonishing. Saturn amazes people with its gigantic ring system and its countless moons. Mars also known as the red planet has always been accompanied by fantastic myths and legends. And Mercury

Mercury

Some years ago NASA came up with the first real images of the celestial body. The images that were subsequently published showed us the planet in all its detailed beauty and complexity. Images of this kind help us humans to better understand the universe around us. But what actually distinguishes mercury? what mercury missions have been carried out by the international space agencies to date? and what level of knowledge do we currently have about our galactic neighbor?

All about Mercury | Physical characteristics | Orbit and Rotation | Mercury missions
Outgoing Hemisphere. Image credit – NASA

In this blog I would like to explore all about Mercury. Mercury smaller, faster, closer of all eight recognized planets that make up our solar system. Is the closest to our fixed star. Hermes or Mercury is also listed as the first planet in our solar system. The relatively small spatial distance between mercury and the sun averages about 58 million kilometers.

For comparison the Earth is located on average about 149.6 million kilometers away from our central fixed star. This small distance also ensures that Mercury is the fastest celestial body in our planetary system. While our blue home planet is known to take 365 days to completely orbit the sun. Mercury manages this feat in just 88 days.

Mercury is not only the fastest, closest and smallest of planets in our solar system. With a diameter of 142870 kilometers Jupiter represents the upper end of the flagpole, at the same time Mercury diameter in kilometres is 4880. In the case of our earth the corresponding value is 12742 kilometers. Mercury is also out of the ordinary in terms of its surface temperatures. During the day the thermometer on the planet reaches values of up to more than 430 degrees celsius.

However once the sun has set the surface of mercury is bitterly cold and then the values drop to as low as -170 degrees celsius. Thus mercury has the largest temperature fluctuations of all the planets in our solar system. The first planet in our solar system was given its name by the ancient romans. In roman mythology the deity mercuriusplayed the role of messenger of the gods and thus represented the counterpart to the greek armies.

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Physical characteristics

The closest planet to the Sun, but also thatit’s this giant rock floating in space.

Mercury Composition

Mercury consists of approximately 70% metallic and 30% silicate materials. It’s actually more metallic than rocky. Because of this, Mercury’s density is the second highest in the solar system at 5.427 grams per centimetre cubed. Only slightly less than the planet with the greatest density – that of Earth at 5.515 grams per centimetre cubed.

If Mercury happened to be the same size as Earth, that would mean it would have pretty the same gravitational pull as its surface. But being the size that it is, its surfacegravity is only 3.7 metres per second squared.

What colour is Mercury?

Mercury also possesses a particularly thin atmosphere that’s made from hydrogen, helium, oxygen, sodium, calcium, potassium and other elements. This atmosphere is so tenuous that astronomers ask it as an exosphere, one which neither absorbs nor reflects light. So once we check out Mercury, no matter whether it’s from the surface or space, we get a transparent view of its surface. And what we’ve seen may be a mercury color dark gray, rocky planet.

Comparison of size with that of Ganymede and Titan against Mercury.

Ganymede is the solar system’s biggest moon and also the biggest moon of Jupiter, while Titan is Saturn’s biggest moon. And the second biggest moon in the solar system.These two giant moons are bigger than Mercury butt their masses are far less.If you look closely at Mercury’s surface, you’ll see its appearance is similar to that of our Moon.

It shows extensive mare like plains and heavycratering indicating that it has been geologically inactive for billions of years. But it obviously was geologically active at one point. Because one of the distinctive features of Mercury’s surface is the presence of many narrow ridges extending out to several hundred kilometres in length.

It’s believed that these were formed as Mercury’score and mantle cooled and contracted over time when the crust had already solidified. And one among the foremost distinctive things you’ll notice about Mercury is that this huge crater on its surface called Caloris Basin. With a diameterof 1,550 kilometres. The impact that created Caloris Basin was so powerful it caused lava eruptions and left a concentric ring over two kilometres tallsurrounding the impact crater.

All about Mercury | Physical characteristics | Orbit and Rotation | Mercury missions
Source- NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Orbit and Rotation

Mercury has the most eccentric orbits of all the planets. With its distance from the Sun ranging from 46 million kilometres to 70 million kilometres. Mercury takes about 88 Earth days to completean orbit around the Sun. It also has a 3-2 spin orbit resonance of the planet’s rotation around its axis.

This means it spins three times around its axis for every two times that it orbits around the Sun. Although it takes about 59 Earth days for Mercury to rotate on its axis once, which is what we call a day, this 3:2 orbital resonance means if you were actually standing on Mercury, it might appear that at some point – from sunrise to sunrise, or what’s called a day is 2 Mercurian years.

Standing on Mercury, you would see the Sun rise relatively fast, and then as it approaches midday, it slows down and even starts going backwards before continuing on again to sunset. That took a whole year, which means a night-time on Mercury also takes a year.

The Sun starts going backwards in the sky because approximately four Earth days beforeperihelion, the speed in which Mercury travels along its orbit equals the speed in which it is rotating. At this point, the Sun’s apparent motion stays stationary.

At perihelion itself, Mercury’s orbital speed exceeds its rotational speed. So to a person actually standing on Mercury, the Sun appears to move backwards. Four days after perihelion, the sun’s normal motion resumes. This even clearer from a top-down perspective of Mercury. Twice a day on one of its poles, the Sun seems to pause and then continue on again.

Something else to note about Mercury’s orbitis that its inclined by 7 degrees to the plane of Earth’s orbit. As a result of this, we can only see Mercury transit in front of the Sun when it’s directly between us on Earth and the Sun itself. And because its orbit is inclined by seven degrees, this only happens about once every 7 Earth years.

The rotation of Mercury is that its axial tilt is almost zero, with the best measured value as low 0.027 degrees. This is even smaller than that of Jupiter which has been measured at 3.1 degrees.

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Mercury In Space Research

So far three missions have been carried out by the various space agencies. All of which were concerned with the exploration of the first planet in our solar system. Let’s have a look at the Mercury Space Program in detail.

Mercury Missions

• The Mariner 10 Mission

Already on November 3rd 1973, the unmanned space probe Mariner 10 set out to provide mankind with the first precise information about mercury in detail. This mission was characterized by its high complexity. To get close to Mercury, the probe had to perform a so-called swing by maneuver. In this method the missile was steered into the immediate vicinity of venus in order to reduce its own orbital energy. Thus the Mariner 10 passed Venus in February 1974 and finally reached the immediate vicinity of Mercury on March 29 of the same year.

At the same time the NASA flight vehicle was the first space probe ever to reach the area around the nearest celestial body in our planetary system. Before the probe was finally switched off on March 24th 1975 it collected many important data concerning Mercury. There were approximately 9000 images taken by the Mariner 10. During the mission about 45% of Mercury’s planetary surface could be captured by the camera. In retrospect however the results of the Mariner mission were classified as rather rough. Many questions about the nature and natural mechanisms of mercury remained unanswered.

Here are some of the Pictures Of Mercury captured by Mariener 10 mission

All about Mercury | Physical characteristics | Orbit and Rotation | Mercury missions
Mercury’s south pole Image credit – NASA
Large Mercurian Crater. Image credit – NASA
All about Mercury | Physical characteristics | Orbit and Rotation | Mercury missions
Earth and Moon as viewed by Mariener 10. Image credit – NASA
Kuiper Crater Image credit – NASA

• The Messenger Mission

Since the launch of the Mariner 10 on November 3rd 1973, over 30 years were to pass before NASA initiated a new exploration of the smallest planet in our solar system. The space probe used for this purpose was Christened Messenger. In detail this is an acronym consisting of the words Mercury surface, Space environment, Geochemistry and Ranging thus the name messenger alludes to the planet’s name origin which was borrowed from roman mythology.

Compared to the other representatives in our planetary system very little was known about Mercury in the run-up to the messenger mission. The natural position of the planet is a major obstacle for space research. Because of the small distance between Mercury and the Sun NASA’s probes have to withstand enormous heat and intense radiation. However observing Mercury from our Earth is also more difficult in practice than some would initially suspect. For this reason the successful execution of the messenger mission was the top priority of the renowned space agency.

In the course of the previous Mariner mission various measurements of the Mercury magnetic field had already been made. These rare data which are now more than 30 years old were to be supplemented and extended over a large area within the framework of the messenger program. The now far more advanced technology also enabled the scientists to study the planet much more thoroughly than the limited resources of the mariner 10 once allowed.

Equipped with the most modern equipment the messenger finally took off into space. On August 3rd 2004 from the cape canaveral spaceport in the U.S. state of Florida. New findings on the composition of Mercury after covering a distance of 8 billion kilometers the NASA space probe was the first man-made flying object to reach the direct orbit of Mercury in spring 2011. During the mission the Messenger was located between 215000 kilometers above the planet’s surface. The data collected during the flights caused pure astonishment among scientists.

The images taken by the space probe showed that unusually high concentrations of calcium and magnesium are found on the night side of the celestial body. In addition Mercury’s magnetic field is not as expected at the center of the body but in much more northern regions. During November 2012 the galactic drumbeat finally followed, Messenger found frozen water on Mercury that had accumulated at the planet’s North pole. In addition, further organic material was detected in several craters on the planet’s surface.

After the NASA space probe’s fuel was completely depleted the Messenger hit the surface of Mercury on April 30th, 2015. At a breathtaking speed of more than 14000 kilometers per hour leaving a crater about 16 meters wide.

Breathtaking pictures of the Mercury planetary surface

The photos of the Mercury surface taken during the Messenger mission are both beautiful and impressive. The spacecraft succeeded in capturing many areas of the celestial body that were previously completely unknown to mankind. For example some of the Messenger photos show the huge crater called Debussy which has a gigantic diameter of 80 kilometers. All in all the gray giant resembles our Earth Moon in its outer appearance. Never before have such detailed photos of the sunniest representative of our planetary system been taken.

All about Mercury | Physical characteristics | Orbit and Rotation | Mercury missions
Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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Present and future of the Mercury missions

The international space agencies are still trying to investigate our galactic neighbor more closely. Another space probe began its flight towards the smallest planet in our system after the Messenger mission was completed. While the two previous programs were carried by NASA. The last trip to Mercury so far started under the care of two other space agencies. The European Space Agency (ESA) co-operated with its Japanese colleagues from JAXA for this undertaking.

The spacecraft named BepiColombo and left Earth on October 10th 2018. During the mission both the history of the planet and it’s physical composition will be studied in detail. However several years pass before BepiColombo finally reaches Mercury’s orbit. Currently experts assume that the space probe will probably reach the distant planet in December 2025. We can remain curious about the groundbreaking results and breathtaking images that new mission will bring us.

All about Mercury | Physical characteristics | Orbit and Rotation | Mercury missions

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