Author: Fraser Cain

The symbols of the planets, Moon and Sun are used in both astronomy and astrology. The symbol for Pluto is made from a monograph of the first two letters in the word PLuto. It’s also from the initials of the astronomer Percival Lowell, who predicted that the planet would be found through its gravitational influence on Neptune and Uranus. Of course, Pluto is not a planet anymore.

Unlike all of the other planets in the Solar System, Mercury is just bare rock. It does have a tenuous atmosphere, but ground and space-based observations see just the gray rocky color of Mercury. This gray color comes from Mercury’s molten surface that cooled and hardened billions of years ago after the formation of the Solar System.

There are no active tectonic or erosion processes happening on the surface of Mercury; it has remained unchanged for billions of years, reshaped only by the occasional meteorite impact. In the past, some of the basins were filled in by magma that flowed out of the planet when it still had an active geologic cycle. Geologists are fairly certain that there are no active volcanoes on Mercury any more, but it’s possible that there could still be the occasional lava flow. Fresh lava flows would appear as a different color on the surface of Mercury. Perhaps when NASA’s MESSENGER spacecraft enters orbit around Mercury, we’ll get a better idea of its colors. Certainly we’ll know more about its surface geology.

The photograph attached to this article provides one of the best true-color images of Mercury that we have. If you could fly over Mercury in your spacecraft, this is essentially what you’d see. The planet Mercury color is a dark gray surface, broken up by craters large and small. The color of Mercury’s surface is just textures of gray, with the occasional lighter patch, such as the newly discovered formation of crater and trenches that planetary geologists have named “The Spider”.

Mercury’s coloring is very similar to the Earth’s moon. In fact, when you’re looking at images of both objects, it’s very difficult to tell the two objects apart. Unlike the Moon, however, Mercury lacks the darker areas, or “seas”, that were created on the Moon by lava flows. Mercury’s color doesn’t have the variety that even the Moon has.

If you got here not asking what color is Mercury the planet, but what color is Mercury (the element), it’s silver, and a liquid at room temperature.

We have written many stories about Mercury here on Universe Today. Here’s an article about a side of Mercury never before seen by spacecraft, and here’s a story about the color of Mercury captured by NASA’s MESSENGER spacecraft during a recent flyby.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Reference:
New Science Findings From Messenger’s Third Mercury Flyby
NASA Science: Surprises from Mercury
NASA Solar System Exploration

Ancient people have known about the planets for millennia. It was only in the last few hundred years that new planets have been discovered that required a telescope to see. The earliest people thought of the planets as divine beings, moving across the heavens in unpredictable ways. If you’re wondering about the discovery of Mercury, though, it’s been known since prehistoric times, so there’s no way to really know who made the original discovery of planet mercury.

The five original naked-eye planets were Mercury, Venus, Mars, Jupiter and Saturn, and they had a significant impact on mythology, cosmology, and ancient astronomy. Any caveman could have made the Mercury discovery.

Mercury itself has been mentioned as early as the 2nd millennium BC by the Sumerians, and recorded by the Babylonians – they called the planet Nabu. The ancient Greeks associated Mercury with the god Hermes, who was thought to carry the Sun across the sky in his chariot. Later the Greeks called the planet Apollo when it was visible in the morning sky, and then Hermes in the evening sky. The Romans named the planet after the Roman messenger god Mercury, who was the same mythological figure as the Greek god Hermes.

The first telescopic observations were made by Galileo in the 17th century with his crude telescope; unfortunately, his crude instrument wasn’t powerful enough to see that the planet had phases, like Venus.

Mercury can occasionally be seen to pass directly in front of the Sun, as seen by Earth. This is called a transit. The last transit of Mercury happened in 2004, and was broadcasted worldwide across the Internet. But the first Mercury transit was seen in 1737 by John Bevis at the Royal Greenwich Observatory.

Until the 1960s, Mercury was thought to be tidally locked to the Sun, always facing one side towards our star. There were skeptics, who noted that if Mercury always faced one side towards the Sun, it should have a hot and a cold side, but research data didn’t back that up. Astronomers thought that maybe an atmosphere around Mercury kept the temperatures more even.

In 1962, Soviet scientists bounced the first radar signals off Mercury’s surface, and then American astronomers calculated that Mercury does rotate. It actually takes 59 days to turn once, and not the 88 days it takes to complete an orbit.

The first spacecraft to see Mercury up close was Mariner 10 back in 1974. Unfortunately, it was only able to see one hemisphere of the planet in total over the course of 3 flybys. Many of the missing pieces were filled in by NASA’s MESSENGER spacecraft, which completed its first flyby in January, 2008.

Descubrimiento del planeta Mercurio

References:
NASA Cosmic Distance Scales
NASA Solar System Exploration: Mariner 10

We can’t just talk about Mercury. Sometimes you’ve just got to see it. Before NASA’s MESSENGER spacecraft, there weren’t a lot of Mercury pictures to choose from. But now the floodgates are open, MESSENGER is sending back more pics of Mercury with each flyby. So here are some of the best photos of Mercury taken so far. I also recommend you to read these amazing books for more information about the planet Mercury.

This first image of Mercury was actually taken by NASA’s Mariner 10 spacecraft, while the others were seen by MESSENGER. As you can see, the new images are so much better than the older ones.

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This is one of the first close-up images of Mercury captured by NASA’s MESSENGER spacecraft just before its January 14th, 2008 flyby. It’s a full color image of Mercury, captured by the spacecraft’s Wide Angle Camera (WAC) filters in the infrared, far red, and violet wavelengths (red, green, and blue filters for this image.)

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This image of Mercury was captured when the spacecraft was much closer to the planet. The prominent feature is crater Matisse, named after the French artist Henri Matisse. This same crater was imaged by Mariner 10, so this gives scientists a chance to see the difference.

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Here’s an image of Mercury’s north pole, captured by MESSENGER during its January 14, 2008 flyby. It’s interesting to note that the planet’s southern regions are much more heavily cratered than its northern regions, which are relatively smooth in comparison. If you read the interesting facts about Mercury, you would know that there could be craters at the planet’s north pole that harbor deposits of ice.

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This is a side of Mercury that had never been seen by spacecraft until NASA’s MESSENGER arrived to photograph it on January 14, 2008. Until now, astronomers had only made ground observations of this side of the planet. These images will help astronomers tune their methods and let them compare their ground observations to the close up images captured by spacecraft.

Here are some facts about Mercury.