![]() However, another 2016 study suggested Mercury's volcano eruptions likely ended about 3.5 billion years ago. Indeed, a 2016 study of cliffs on Mercury's surface suggested the planet may still rumble with earthquakes, or "Mercuryquakes." In addition, in the past, Mercury's surface was constantly reshaped by volcanic activity. "The young age of the small scarps means that Mercury joins Earth as a tectonically active planet with new faults likely forming today as Mercury's interior continues to cool and the planet contracts," Tom Watters, Smithsonian senior scientist at the National Air and Space Museum in Washington, D.C., said in a NASA statement. The process crumpled the surface, creating lobe-shaped scarps or cliffs, some hundreds of miles long and soaring up to a mile high, as well as Mercury's "Great Valley," which at about 620 miles long, 250 miles wide and two miles deep (1,000 by 400 by 3.2 km) is larger than Arizona's famous Grand Canyon and deeper than the Great Rift Valley in East Africa. As the core cools, it solidifies, reducing the planet's volume and causing it to shrink. The tiny planet is made up of a single continental plate over a cooling iron core. By comparison: 0.459 times that of EarthĪs if Mercury isn't small enough, it not only shrank in its past but is continuing to shrink today, according to a 2016 report. By comparison: 0.313 times that of EarthĪphelion (farthest distance from sun): 43,380,000 miles (69,820,000 km). By comparison: 0.38 Earth's distance from the sun 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.Īverage distance from the sun: 35,983,095 miles (57,909,175 km). The southern pole may also contain icy pockets, but MESSENGER's orbit did not allow scientists to probe the area. Mercury surface characteristicsĪs close to the sun as Mercury is, in 2012, NASA's MESSENGER spacecraft discovered water ice in the craters around its north pole in 2017, where regions may be permanently shaded from the heat of the sun. Another large impact may have helped create the planet's odd spin, according to research in 2011. ![]() Known as the Caloris Basin, this crater could hold the entire state of Texas. About 4 billion years ago, an asteroid roughly 60 miles (100 km) wide struck Mercury with an impact equal to 1 trillion 1-megaton bombs, creating a vast impact crater roughly 960 miles (1,550 km) wide. Since it has no significant atmosphere to stop impacts, the planet is pockmarked with craters. Mercury is the smallest planet in the solar system - it is only slightly larger than Earth's moon. However, since this world doesn't have much of a real atmosphere to entrap any heat, at night temperatures can plummet to minus 275 degrees Fahrenheit (minus degrees 170 Celsius), a temperature swing of more than 1,100 degrees Fahrenheit (600 degrees Celsius), the greatest in the solar system. How hot is Mercury?īecause the planet is so close to the sun, Mercury's surface temperature can reach a scorching 840 degrees Fahrenheit (450 degrees Celsius). ![]() Greek astronomers knew, however, that the two names referred to the same body, and Heraclitus, around 500 B.C., correctly thought that both Mercury and Venus orbited the sun, not Earth. Mercury was also given separate names for its appearance as both a morning star and an evening star.
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