The space environment – dust impacts and solar-wind particles – causes the rays to darken with time. Fine particles of crushed rock are more reflective than large pieces, so the rays look brighter. Some of this crushed material is thrown far from the crater and then falls to the surface, forming the 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. The bright streaks are called "crater rays." They are formed when an asteroid or comet strikes the surface. Most of Mercury's surface would appear greyish-brown to the human eye. They rose as the planet's interior cooled and contracted over the billions of years since Mercury formed. While there are large areas of smooth terrain, there are also cliffs, some hundreds of miles long and soaring up to a mile high. Very large impact basins, including Caloris (960 miles or 1,550 kilometers in diameter) and Rachmaninoff (190 miles, or 306 kilometers in diameter), were created by asteroid impacts on the planet's surface early in the solar system's history. Craters and features on Mercury are named after famous deceased artists, musicians, or authors, including children's author Dr. Mercury's surface resembles that of Earth's Moon, scarred by many impact craters resulting from collisions with meteoroids and comets. Mercury's outer shell, comparable to Earth's outer shell (called the mantle and crust), is only about 400 kilometers (250 miles) thick. There is evidence that it is partly molten or liquid. It has a large metallic core with a radius of about 1,289 miles (2,074 kilometers), about 85 percent of the planet's radius. Mercury is the second densest planet, after Earth. Like its fellow terrestrial planets, Mercury has a central core, a rocky mantle, and a solid crust. Mercury formed about 4.5 billion years ago when gravity pulled swirling gas and dust together to form this small planet nearest the Sun. That means it spins nearly perfectly upright and so does not experience seasons as many other planets do. Mercury's axis of rotation is tilted just 2 degrees with respect to the plane of its orbit around the Sun.
#FACE OF MARS BUTT OF MERCURY FULL#
One Mercury solar day (one full day-night cycle) equals 176 Earth days – just over two years on Mercury. The same thing happens in reverse at sunset for other parts of the surface. The morning Sun appears to rise briefly, set, and rise again from some parts of the planet's surface. But when Mercury is moving fastest in its elliptical orbit around the Sun (and it is closest to the Sun), each rotation is not accompanied by sunrise and sunset like it is on most other planets. Mercury spins slowly on its axis and completes one rotation every 59 Earth days.
It speeds around the Sun every 88 days, traveling through space at nearly 29 miles (47 kilometers) per second, faster than any other planet. Mercury's highly eccentric, egg-shaped orbit takes the planet as close as 29 million miles (47 million kilometers) and as far as 43 million miles (70 million kilometers) from the Sun. Credit: NASA Visualization Technology Applications and Development (VTAD) From this distance, it takes sunlight 3.2 minutes to travel from the Sun to Mercury.Ī 3D model of Mercury, the innermost planet. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. If Earth were the size of a nickel, Mercury would be about as big as a blueberry.įrom an average distance of 36 million miles (58 million kilometers), Mercury is 0.4 astronomical units away from the Sun. With a radius of 1,516 miles (2,440 kilometers), Mercury is a little more than 1/3 the width of Earth. The temperatures and solar radiation that characterize this planet are most likely too extreme for organisms to adapt to. Mercury's environment is not conducive to life as we know it. Mercury is appropriately named for the swiftest of the ancient Roman gods. But Mercury is the fastest planet, zipping around the Sun every 88 Earth days. Without an atmosphere to retain that heat at night, temperatures can dip as low as -290☏ (-180☌).ĭespite its proximity to the Sun, Mercury is not the hottest planet in our solar system – that title belongs to nearby Venus, thanks to its dense atmosphere. Because the planet is so close to the Sun, day temperatures can reach highs of 800☏ (430☌). Mercury's surface temperatures are both extremely hot and cold. From the surface of Mercury, the Sun would appear more than three times as large as it does when viewed from Earth, and the sunlight would be as much as seven times brighter. 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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