Each time you look up to the sky and see a star you are looking at a sun in another galaxy. If you were on another planet looking back at our solar system, you would see our sun as a star.It’s believed that every sun has planets orbiting it.
Our Milky Way galaxy has more planets than it has stars. In our solar system we have eight planets: Mercury, Venus, Earth, and Mars are the inner rocky planets.
Jupiter and Saturn are the outer gas giants. Uranus and Neptune are the outer ice giants. In recent years, astronomers have designed a new class called the “dwarf planets.”
These are smaller worlds, not quite big enough to be considered a standard planet, and include Pluto. Mercury is the first planet, and closest to the sun.
- View on Maps: google.com/maps/space/mercury
- Moons: None
- Distance from Sun: 35.98 million mi
- Radius: 1,516 mi
- Diameter: 4,879 km
- Orbital period: 88 days
- Mass: 3.285 × 10^23 kg (0.055 M⊕)
- Surface Temperature: -173 to 427°C
- Number of Moons: None
- First Record: 14th century BCE by Assyrian astronomers
How did Mercury get its name:
It’s thought that many civilizations recognized the planet Mercury as far back as 5,000 years. It was named about the Roman messenger god that was known for moving fast, because the planet orbited the sun more quickly than other planets. For many years it was believed that Earth was the center of our solar system with both the sun and other planets orbiting Earth.
The Greek philosopher, Heraclitus was the first to indicate that the Sun was the center, with both Mercury and Venus orbiting it instead of Earth.
Planets are created when gravity pulls dust and swirling gas together. Mercury was formed around 4.5 billion years ago and became the small planet that is closest to our sun. It’s considered to be a “terrestrial planet” because Mercury has a central core, a rock mantle, and a solid crust.
Structure and Surface:
After Earth, Mercury is the second densest planet in our solar system. Mercury’s core is metallic with a radius of around 1,289 mi/2,074 km, which is about 85% of the planet’s entire radius.
Scientists believe that they have found evidence that shows that part of the metallic core is molten or liquid. The outer shell or mantle and crust is around 250 mi/400 km thick.
When you stare at the surface of Mercury, you can’t help but realize that it resembles that of our moon. The surface is covered with a lot of craters that that were caused by collisions with comets and meteoroids.
We have named a lot of these craters for famous people, including authors, musicians, and artists. Two of the craters are named for Dr. Seuss, famous author of children’s books and Alvin Ailey, a pioneer in dance.
The crater Caloris Basin is the result of an asteroid around 60 mi wide hitting Mercury; large enough to fit the state of Texas. It’s almost 960 miles wide and scientists believe that the impact could be compared to 1 trillion 1-megeton bombs going off.
It’s thought that an impact of this magnitude may have been the cause of Mercury’s odd spin.
Mercury’s surface is covered with what are called “lobe-shaped” cliffs. These can reach up to a mile high and run hundreds of miles throughout Mercury. The cliffs were created billions of years ago as Mercury went through a cooling process.
A majority of the surface of Mercury would look like a kind of greyish-brown color to the human eye. There are bright streaks that are called “crater rays,” caused when a comet or asteroid hits the surface.
The intense energy that is released upon impact not only digs a huge hole in the ground while crushing a large amount of rock at the impact point.
When some of the crushed rock and material is thrown away from the impact crater it falls to the surface so that it creates a kind of “ray” effect.
The crushed rock particles are a lot more reflective than the bigger pieces, so that these rays appear to be brighter. Over time, solar-wind particles and dust in the environment will cause the rays to darken a bit.
The planet Mercury is the closest to the sun and zips around its orbit very quickly. It has a very thin atmosphere, but not enough to reflect the sun’s intense heat.
The lack of a significant atmosphere also doesn’t protect it from the impacts of the many space objects. The surface of Mercury shows evidence of impacts, with craters of all sizes.
Since there isn’t any weather or seasons, scientists can observe the craters and try to learn about the history of Mercury.
Mercury isn’t just extremely hot, it is also extremely cold. The high 840 degree temperatures are reached during the day but during the night, the surface temperature drops to -290 degrees F (- 180 degrees C).
It’s thought that Mercury may have water ice deep inside the craters at its south and north poles, but only within those areas that are in a constant shadow.
The permanent shadow would be cold enough to keep water ice, even when the rest of the planet is intensely hot.
Atmosphere. Magnetosphere, and Moon Status:
While some planets do have an atmosphere, Mercury doesn’t have one. Instead it has a thin “exosphere” which consists of atoms that are created with meteoroids hit the surface and the solar wind catches them and blasts them upwards.
The exosphere of Mercury is made up of mostly oxygen, sodium, hydrogen, helium, and potassium.
Mercury’s magnetic field is relative to the equator of the planet. While it has just 1% of the strength of our Earth’s magnetosphere, it does interact with the solar wind magnetic field so that it can create really intense magnetic tornadoes.
These storms funnel the hot solar wind plasma down to the planet’s surface. Once the ions hit the surface, they imbalance the atoms that are neutrally charged and quickly send them back into the sky.
Mercury doesn’t have a moon or rings.
Could Life Exist on Mercury?
The solar radiation and temperatures on Mercury are not conducive to life as we know it. The planet has too many extremes for organisms to be able to adapt to.
Mercury is not only the planet that is the smallest in our solar system, it’s also the planet that is closest to the sun. When you look at Mercury’s size you will see that it’s only a little bit larger than the Earth’s moon.
If you were standing on Mercury’s surface, the sun would look three times as large as it does when you see it from Earth, and the sunlight would be seven times brighter.
You would think that being the closest to the sun, Mercury would be the hottest planet in our solar system, however, that’s not the case. Due to the dense atmosphere, Venus holds the title of being the hottest planet in our solar system.
Due to Mercury’s odd elliptical orbit and slow speed of rotation, both sunrise and sunset would appear strange to us. If we watched the sunrise, it would appear to rise, set and then rise up again.
The same thing happens during sunset. It’s difficult to look directly at Mercury from Earth because it’s so close to the sun. However, 13 times every century, an event called a “transit” occurs where we can watch as Mercury passes across the face of the sun.
Space Missions to Mercury:
1974-1975 Mariner 10: The spacecraft orbited Mercury three times and mapped around half of the surface of Mercury. During the Mariner 10 mission it discovered evidence that Mercury has a magnetic field.
Comparisons have shown that the magnetic field is only around 1% of Earth’s, but it’s highly active, being responsible for the solar wind tornados on the surface of Mercury.
The images that Mariner took covered around 45% of the surface of Mercury and prompted interest to launch later missions.
2004 Messenger Probe: The probe orbited Mercury for four years, sending an incredible amount of data back to Earth before it crashed into the surface.
2018 BepiColombo: The ESA (European Space Agency) launched BepiColombo as part of their first mission for the exploration of Mercury.
Even with the intense heat and temperature fluctuations, there are still locations on Mercury that are permanently shaded from the Sun’s heat. In 2012, NASA’s spacecraft MESSENGER found water ice in the craters around the north pole of Mercury.
There may be other areas that have water ice, however, the orbit of MESSENGER didn’t include probing the southern pole. It’s believed that meteorites or comets may be responsible for delivering ice to these locations or water vapor may have been outgassed from the interior of the planet and then out to the poles.
- 1631: Galileo Galilei and Thomas Harriot had invented a new telescope that gave them the ability to observe Mercury.
- 1965: Astronomers use radar to discover that the previous theory of the same side of Mercury constantly facing the sun was incorrect. The radar proved that Mercury rotates three times for every two orbits.
- 1974-1975: The Mariner 10 mission sent images back to Earth of around 43% of the surface of Mercury as it accomplished three flybys.
- 1991: Scientist made use of Earth-based radar to discover that Mecury’s shadow areas in their craters within the polar-regions showed signs of permanently locked ice.
- 2008-2009: The MESSENGER probe accomplishes three flybys of Mercury.
- 2011: The MESSENGER probe orbits around Mercury, sending an incredible array of images and compositional data about the planet.
- 2015: The MESSENGER probe was sent to Mercury to crash into the surface. Scientists made sure that all of the propellant was expended prior to the crash as the mission was ended.
- 2018: The BepiColombo mission was launched by the European Space Agency.
Facts about Mercury:
- Mercury may be the closest planet to the sun but it experiences temperature changes that are the most extreme of any planet in the solar system, including dropping to -275 F/-170 C.
- Mercury is only slightly larger than the Earth’s moon.
- Mercury travels around the sun more quickly than any of the other planets in the solar system.
- One Mercury year is equal to only 88 Earth days.
- The core at Mercury’s center is mostly made up of iron and takes up about 75% of the planet’s radius.
- Mercury does have a very thin atmosphere called an exosphere.
- Mercury seems to have a stream of particles that appear to expand out from the surface giving it a look like it has “tails.”
While many of our planets have played a part in legend and stories, Mercury seems to have been a focus of our collective imaginations.
There are a lot of science fiction writers that have used the smallest planet in our solar system for inspiration for their novels.
The list of authors include: Isaac Asimov, C.S. Lewis, Ray Bradbury, H.P. Lovecraft, and Arthur C. Clarke. TV and movie writers also seemed to be enthralled with the little planet as part of their scripts.
The animated television show “Invader Zim,” has Mercury being changed into a giant ship prototype spaceship by an extinct group of Martians.
In film called “Sunshine”, released in 2007, a spacecraft called the “Icarus II” orbits around Mercury to meet up with the Icarus I.
Even the comic strip “Calvin and Hobbes” has mention of Mercury. In one of the series Calvin and his friend Susie give a class presentation about Mercury, and Calvin fills the presentation with very questionable information such as: “The planet Mercury was named after a Roman god with winged feet,” says Calvin.
“Mercury was the god of flowers and bouquets, which is why today he is a registered trademark of FTD florists. Why they named a planet after this guy, I can’t imagine.”