As such, it circles the sun faster than all the other planets, which is why the Romans named it after their swift-footed messenger god. The Sumerians also knew of Mercury since at least 5, years ago. Mercury was also given separate names for its appearance as both a morning star and as an evening star.
Greek astronomers knew, however, that the two names referred to the same body, and Heraclitus, around B. In comparison, Mercury's outer shell is only to miles to km thick. The combination of its massive core and composition , which includes an abundance of volatile elements, has left scientists puzzled for years.
Because the planet is so close to the sun, Mercury's surface temperature can reach a scorching degrees Fahrenheit degrees Celsius. However, since this world doesn't have much of a real atmosphere to entrap any heat, at night temperatures can plummet to minus degrees Fahrenheit minus degrees Celsius , a temperature swing of more than 1, degrees Fahrenheit degrees Celsius , the greatest in the solar system.
Mercury is the smallest planet — it is only slightly larger than Earth's moon. Since it has no significant atmosphere to stop impacts, the planet is pockmarked with craters. About 4 billion years ago, an asteroid roughly 60 miles km wide struck Mercury with an impact equal to 1 trillion 1-megaton bombs, creating a vast impact crater roughly miles 1, km wide. Known as the Caloris Basin, this crater could hold the entire state of Texas.
Another large impact may have helped create the planet's odd spin , according to research in Comets or meteorites may have delivered ice there, or water vapor may have outgassed from the planet's interior and frozen out at the poles.
Average distance from the sun: 35,, miles 57,, km. By comparison: 0. Perihelion closest approach to sun : 28,, miles 46,, km. Aphelion farthest distance from sun : 43,, miles 69,, km. As if Mercury isn't small enough, it not only shrank in its past but is continuing to shrink today, according to a report.
Sidereal Rotation: The time for a body to complete one rotation on its axis relative to the fixed stars such as our Sun. Earth's sidereal rotation is 23 hours, 57 minutes. Length of Day: The average time for the Sun to move from the Noon position in the sky at a point on the equator back to the same position. Axis tilt: Imagining that a body's orbital plane is perfectly horizontal, the axis tilt is the amount of tilt of the body's equator relative to the body's orbital plane.
Earth is tilted an average of Please Contact Us. Please try another search. Multiple locations were found. Please select one of the following:. Location Help. News Headlines. Customize Your Weather. Privacy Policy. The Planet Mercury Weather. Current Hazards. Local Radar. Rivers and Lakes. Climate and Past Weather.
Weather Story. Weather Map. Follow us on Twitter. Follow us on Facebook. Follow us on YouTube. Disclaimer Information Quality Help Glossary. In a separate study, Burger and his colleagues found a pattern for calcium that repeated over Mercury's short orbit.
Killen and colleagues then worked to figure out what happened when Mercury plowed through the cloud of debris known as zodiacal dust that surrounds the sun. Most of the calcium could be explained by the cloud, but the team found that Comet Encke's short 3.
Apparently, comet streams can have a huge, but periodic, effect. With virtually no atmosphere, Mercury feels very little in terms of traditional weather.
It does feel the presence of solar weather, with the constant ebb and flow of the solar wind bombarding its surface. The lack of atmosphere also contributes to the planet's wild temperature extremes. On other planets, the atmosphere functions as a blanket, helping to redistribute heat somewhat.
But on Mercury, the thin atmosphere does nothing to stabilize the incoming solar rays—and because the distance to Mercury from the sun is so small, the day side of the planet feels the heat keenly, while the night side, turned from the sun, only registers the cold.
Mercury's lack of atmosphere means that it is not the hottest planet; Venus, with its runaway global warming, has that honor. The temperature of Mercury varies from day to night, but the planet only changes slight during its seasons. The planet stands essentially straight up and down in relation to its orbit, with no tilt to put one hemisphere closer than the other.
That allows the world closest to the sun to host ice within its polar craters. However, the planet does boast the most eccentric orbit of all the other planets Pluto's orbit is more eccentric, but alas, it is only a dwarf planet. As such, Mercury does experience some temperature variations over the course of its short year.
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