Imagine that astronauts have landed on Mercury - in some distant future. How they would experience a day on this planet? It would be a very long workday from an Earth perspective! This is because Mercury's rotation around its axis lasts 59 days, and it takes 88 days to move around its orbit around the Sun.
This is not by chance - it is an effect of the Sun's gravitational field on Mercury. It is a similar phenomenon that the Earth's Moon always has the same "face"; the Moon always turns the same side towards the Earth. In fact, such a day on Mercury is twice as long as a Mercurian "year"! On average, Earth days elapse between one sunrise and the next on Mercury - this is therefore the length of the Mercurian day. Since Mercury revolves around the Sun in an elliptical orbit and rotates around its own axis comparatively slowly, the Sun appears to move in a strange way in the sky above that astronaut on Mercury's surface.
At some moment, he or she would watch the Sun come to a complete halt. Then the Sun would appear to move backwards for some time before returning to its original position, performing a loop in the sky. Length of Day and Year on Mercury.
Each sidereal day on Mercury last This means that it takes Now look at the figures above. While this might lead some to conclude that a single day on Mercury is about 58 Earth days — thus making the length of a day and year correspond to the same ratio — this would be inaccurate.
Due to its rapid orbital velocity and slow sidereal rotation, a Solar Day on Mercury the time it takes for the Sun to return to the same place in the sky is actually days. In that respect, the ratio of days to years on Mercury is actually The only places that are exempt to this day and night cycle are the polar regions. The cratered northern polar region, for example, exists in a state of perpetual shadow.
Temperatures in these craters are also cool enough that significant concentrations of water ice can exist in stable form.
Just another oddity for a planet that likes to keep things really hot, really cold, and is really eccentric. Listen here, Episode Mercury. There is evidence that it is partly molten or liquid. Mercury's outer shell, comparable to Earth's outer shell called the mantle and crust , is only about kilometers miles thick.
Mercury's surface resembles that of Earth's Moon, scarred by many impact craters resulting from collisions with meteoroids and comets. Craters and features on Mercury are named after famous deceased artists, musicians, or authors, including children's author Dr. Seuss and dance pioneer Alvin Ailey. Very large impact basins, including Caloris miles or 1, kilometers in diameter and Rachmaninoff miles, or kilometers in diameter , were created by asteroid impacts on the planet's surface early in the solar system's history.
While there are large areas of smooth terrain, there are also cliffs, some hundreds of miles long and soaring up to a mile high. They rose as the planet's interior cooled and contracted over the billions of years since Mercury formed. Most of Mercury's surface would appear greyish-brown to the human eye. The bright streaks are called "crater rays. The tremendous amount of energy that is released in such an impact digs a big hole in the ground, and also crushes a huge amount of rock under the point of impact.
Some of this crushed material is thrown far from the crater and then falls to the surface, forming the rays. Fine particles of crushed rock are more reflective than large pieces, so the rays look brighter. The space environment — dust impacts and solar-wind particles — causes the rays to darken with time.
Temperatures on Mercury are extreme. During the day, temperatures on the surface can reach degrees Fahrenheit degrees Celsius.
Because the planet has no atmosphere to retain that heat, nighttime temperatures on the surface can drop to minus degrees Fahrenheit minus degrees Celsius. Mercury may have water ice at its north and south poles inside deep craters, but only in regions in permanent shadows. In those shadows, it could be cold enough to preserve water ice despite the high temperatures on sunlit parts of the planet. Instead of an atmosphere, Mercury possesses a thin exosphere made up of atoms blasted off the surface by the solar wind and striking meteoroids.
Mercury's exosphere is composed mostly of oxygen, sodium, hydrogen, helium, and potassium. Mercury's magnetic field is offset relative to the planet's equator. When the ions strike the surface, they knock off neutrally charged atoms and send them on a loop high into the sky.
Mercury Poster. Introduction The smallest planet in our solar system and nearest to the Sun, Mercury is only slightly larger than Earth's Moon.
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