MERCURY: The 1st Planet from the Sun and smallest in our solar system.

All the technology we have so far is based on materials available on our planet. At least for now. However at one point in time as technology continues to advance we might be able one day to exploit natural resources available in our Solar Sistem.

Except Earth there are 4 bodies outhere we can consider to investigate. The 1st one is The Moon and then our 3 sister planets a.k.a. Mercury, Venus and Mars.

For now we can only go (more or less) safe on one place outside Earth. We can go to the Moon. But in the comming years this status quo could very likely changed and Mars could be the 2nd neigbour we will visit. It’s still a long way to go until the tech will be safe enough for humans to go in such a voyage. However we do already have advanced enough technology that can allows us to remotely explore our Solar Sistem and untill today we have collected a huge amout of data about what’s going on outside Earth. As I had the chance and pleasure to study these things, I would like to share my knowledge on these topics. That being said let me introduce you our little rocky brother in the solar sistem: Meet MERCURY.

When was Mercury first discovered?

Like the “discovery” of most natural phenomena, it is challenging to pinpoint a single person who can get the credit for discovering Mercury. The main reason for this is that Mercury is one of the other 3 inner rocky planets that can be seen without using a telescope or binoculars. It is visible to the naked eye around sunrise and sunset and it was well known in ancient times. However, Mercury is a little “trickier” to find than other planets as it tends to not travel too far from the Sun (from our point of view on Earth). This makes it harder to spot in the sky and probably meant it was one of the latest planets to be found when compared to the other 4, like Venus, Mars, Jupiter or Saturn. That being said, we can be very confident that anyone, at any time, could have seen it simply by looking up into the night’s sky. For this reason, a better question might be to ask who were the first to record their observations of Mercury? 

From what we can ascertain today, the Sumerians might have been the first. They had records showing the planet’s existence around 3000 BCE. The ancient Babylonians (around 1000 BCE) called the planet Nabu the god of writing and learning. The ancient Greeks originally thought that Mercury was 2 planets, but in the 4th century BCE, they realized it was just one object. Fast forward a few millennia, the great Copernicus developed his Sun-centered solar system model, published in 1543, which clearly showed that Mercury was a planet. The first person known to observe the planet using a telescope directly was the late, great Gallileo. In the 17th century, In 1611 Gallileo makes the 1st obeservations of Mercury though a telescope. He guesses it is a planet but his telescope is not powerful enough to reveal that Mercury has phases, however with this he provided the first “proof,” so to speak, that Mercury was, indeed, another planet. He also confirmed that Venus must be orbiting the Sun, as it appeared and disappeared at regular occurrences on either side of the Sun. 

What’s fascinating about Mercury?

About 4 billion years ago, an enormous asteroid is also thought to have slammed into Mercury. Rather than destroying the planet, Mercury actually managed to survive the impact.The asteroid that hit Mercury is estimated to have been 99.5 km wide and created a vast crater now named the Caloris Basin which is 1,545 km across. That is enormous. To put that into perspective, the asteroid that is thought to have killed off the dinosaurs was about 10km wide. If this isn’t enough to make the planet special, then some other aspects of Mercury also make it strangely unique.

Mercury is the smallest of the 8 major planets in our Solar Sistem. It is the closest to the Sun and the richest in iron (Fe). With an average density of 5,4g/cm3 it is the second densest planet of the other 8 (the 1st being Earth with an average density of 5.5g/cm3). Mercury is only slightly larger than the Earth’s moon and has a diameter of about 4,879.4 km, slightly larger than the width of the United States.

Mercury might be smallest planet in our Solar System, but its certainly a fighter. Its surface has been churned up by meteoritic bombardment and is dark and dusty. With almost no atmosphere for protection, Mercury is continually exposed to the battering of even small meteorites. Impact craters of all sizes pit the planet’s surface.The surface is stable, with no moving plates, meaning that features such as impact craters remain undisturbed on the planet for billions of years.Its surface environment is extremelly harsh. There is hardly any shielding atmosphere, and for this reason you cannot find any weater phenomenon except for some, frankly, crazy fluctuations in temperature.

With regards to temperature, despite being closer to the Sun, Mercury is 2nd only to the planet Venus. The reason for this is that Venus has a dense atmosphere that helps it trap heat. In this regard, it is sort of the opposite of Mercury, which has little to no atmosphere that lets heat escape from its surface.The atmosphere of Mercury is in fact a thin exosphere of atoms blasted off the surface by the solar wind. Heat is also better distributed around Venus when compared to Mercury. This is because Venus has highly volatile “weather” that is able to move heat around the planet’s surface. Mercury, on the other hand, has areas of incredibly hot and incredibly cold.

The temperature on Mercury rises to a blistering +430°C during the day (hot enough to melt lead) then because there is only a thin atmosphere, heat escapes quick enough and therefore the temperature plummets to an air-freezing -180°C at night. No other planet experiences such a wide range of temperatures.The average temperature on Mercury is, however, around +170°C. Still, some places remain cold enough for water ice. Complex radar studies have shown water ice from comet residue appears to be present on the shady side of craters on Mercury’s North pole, for example. These extremes in temperature on Mercury probably rule out any organisms surviving there, but there may be “goldilocks” parts of the planet that possibly could support life. Also in the southern hemisphere around the south pole which is shielded from the Sun’s heat, there is a crater called Chao Meng-Fu where NASA’s Messanger spacecraft has found radar-bright patches that could be a mix of frozen water and organic materials. But is highly unlikely and accepted that the planet itself can support life.

The craters on Mercury’s hot, dark surface resemble the craters on our Moon. This suggest that it has lost rock from its outer layers. If so, one explanation might be that early in its history Mercury was struck by a planetesimal, one of the many protoplanets that whirled through the Solar System as it formed. The devastating impact caused by this planetesimal – which was probably about one-sixth the size of the planet itself – blasted away much of Mercury’s rocky exterior. At least this is the 1st theory supported by the data coming from the Messenger spacecraft launched in 2004.

Data about Mercury:

Another special feature of Mercury is its magnetic field. Mercury’s magnetic field is offset relative to its equator. Even though the strength of the planet’s magnetic field is only 1% that of Earth, it interacts with the solar wind to cause magnetic tornadoes, channeling the fast, hot solar wind plasma down to the surface. However, the planet does have other features. As the planet’s large core cools, the planet “shrinks,” creating cliffs hundreds of km long and up to 1,5 km high, as well as great valleys up to 1,000 km and 3.2 km deep. 


Mercury, like all 4 of the rocky siblings, was formed of molten rock. A few million years later, as the young planet began to cool, its crust solidified and its journey around the Sun transformed from being part of a swirling cloud into a clearly defined passage, an orbit. The path the infant Mercury travelled, however, was most probably far removed from the course it now holds.

The young Mercury was born not as the closest planet to the Sun but at a much greater distance, far beyond the orbit of Venus, beyond Earth perhaps even beyond Mars. This was a planet that came into being in the mildest region of the Solar System. It was far enough away from the Sun to allow volatile elements like Sulphur (S), Potassium (K) and Phosphorus (P) to be folded into its 1st rocks without being vaporized away by the heat of the Sun, but maybe near enough for its surface to be warmed, perhaps even just the right amount for liquid water to settle on its surface. This may well have been a planet big enough to hold an atmosphere, a watery world upon which all the ingredients of life could well have existed. Mercury, it seems, really did have its own moment in the sun, but these hopeful beginnings were not last. One possible theory is that Mercury didn’t form where it is today, but much closer to the other planets, maybe even outside Venus or Earth, or somewhere in between. Then because of interactions with Jupiter, Earth, Venus and so on, it got put into a chaotic path that pushed it farther into the Sun.

Today it’s hard to imagine the planets in any orbit other than the one they currently have in our night sky. They feel eternal, permanent, and so it’s natural to think of the Solar System as a piece of celestial clockwork, a mechanism running with perpetual and unchanging precision, marking out the passage of time. In time frames that we can comprehend – day, weeks, months and years – the motion and trajectory of the planets are just clockwork. We use these markers to plot out the 24 hours of a day, 365 days of a year and the lunar cycle is of course, intimatelly linked to our months. Beyond that, Newton’s laws of universal gravitation 1st described in 1967 allow us to this day to plot out the trajectories of all the heavenly bodies far into the future and back into the distant past. This predictability of motion is what allows us to plot great astronomical events, such as eclipses and transits far into the future. It’s why, for example, we can predict that on 14 September 2099 the Sun, Moon and Earth will be in precise alignment to create the final total solar eclipse of the 21st century across North America. But 100 years ahead or behind us is nothing more than a proverbial blink in terms of the life of the Solar Sysyem, and over longer durations the clockwork becomes a lot less reliable.

If there were only 1 planet orbiting 1 star – for example, if Mercury was the orphan child of the Solar System – we would be able to calculate precisely the gravitational forces between Mercury and the Sun, and to plot Mercury’s orbit around the Sun with essentially infinite precision. But add one more planet into our rather vacant imaginary solar system – let’s say we make it Jupiter – so there is now a gravitational force between all 3 objects – the Sun, Mercury and Jupiter – and it’s no longer possible to calculate exactly where they’re all going to be in the future or where they were at some point in the past.

Aptly named after the speedy messenger god of the Roman pantheon (Hermes in the ancient Greek one), the planet Mercury is the “speed freak” of our Solar System. Not only that, but Mercury, like all of our other planet neighbors, has a unique set of characteristics and circumstances that have dictated its history till the modern-day.

Mercury spins on its axis very slowly, with one rotation taking almost 59 Earth days. Yet because is closest to the Sun, it is also the fastest orbiting of all the planets completing its circuit of the Sun in just 88 Earth-days. It travels through space at speeds of around 47 km/s along its eliptical orbit, faster than any other planet (Earth is doing that at only 30km/s) . By the time the sunny side begins to turn away, the whole planet has been swept round to face the Sun from the opposite side. Mercury rotates 3 times in 2 orbits – in other words there are 3 Mecurian “days” in 2 Mecrurian “years”. This is what is known as a 3:2 spin orbital resonance. This spin-orbit coupling means that for an observer standing on Mercury there would be an interval of 176 Earth days between one sunrise and the next. Therefore solar days on Mercury are longer than years. In effect, you could be travelling over its surface at walking pace and keep the Sun at the same point in the sky as you strolled through eternal twilight. The reason for this is that Mercury and the Sun have a near tidal lock, slowing Mercury’s rotation. Despite the long Mercurial days, Mercury’s sky always looks black due to the incredibly thin atmosphere which is not thick enough to reflect light.

Mercury has the most eccentric orbit of all major planets; an egg-shaped orbit that ranges from 47 million kilometers (at perihelion) to 70 million kilometers (at aphelion) from the Sun. This is by far the most irregular of orbits of all the planets.The planet tilts on its axis by just about 2 degrees with respect to the plane of its orbit around the Sun and 7 degrees to the plane of Earth’s orbit. This means that it spins while almost completely upright, so does not have any seasons, and that’s why craters close to the poles never receive any sunlight being permanently cold. The axial tilt of Mercury is only 0.01° and for this reason unlike most other planets, Mercury also has a near-perfect circular spherical shape, the most nearly circular of all the planets besides Venus.

Because of the planet’s orbit, there are places on mercurian surface where a hypothetical observer would be able to see the (2 and a half times larger in the sky) Sun appear to rise and set twice during one Mercurian day. It rises, then arcs across the sky, stops, move back towards the rising horizon, stops again and finally restarts its journey towards the setting horizon. Most of Mercury’s anomalies can be explained by the orbital mechanics of its journey around the Sun, except, that is, for the odd elliptical orbit that takes it o such an oval-shaped, elongated course. This irregularity has puzzled astronomers for centuries and hints at an ancient planet that was very different from Mercury we see today.

Mercury’s perihelion advances by about 1.55° every century whici is 0.012° more than is expected given the gravitational influence of other planets. Hence its closest point to the Sun moves forward with each pass.

 Poor old Mercury orbits alone – Unlike most of the planets in our Solar System, Mercury doesn’t appear to have any natural satellites or moons. It also lacks rings. Venus, as it happens, also lacks rings or moons. I am not entirely sure why, but astronomers believe that these planets actually did have them once upon a time. However, the Sun’s intense gravity probably pulled them away because Mercury has a weak gravitational pull due to its size and distance from the Sun. 

Mercury might be the smallest of the planets in our Solar System, but it certainly punches above its weight for intrigue. A strange planet compared to what we’re used to here on Earth, it is certainly a place full of other wonders yet to be discovered. That’s it about Mercury for now.

To be continued…;-)

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