What Happens Outside Of Our Earth

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by jessicaj123
Last updated 5 years ago

Discipline:
Science
Subject:
Planets
Grade:
6

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What Happens Outside Of Our Earth

What happens outside of our Earth?

Our solar system is nearly 5 billion years old. It is made up of of 8 planets, a handful of so-called dwarf planets, and more than 170 moons, as well as dust, gas, and thousands of asteroids and comets, all orbiting around the sun.

Compared with the billions of other stars in the universe, the sun is unremarkable. But for Earth and the other planets that revolve around it, the sun is a powerful center of attention. It holds the solar system together; pours life-giving light, heat, and energy on Earth; and generates space weather.The sun is a big star. At about 864,000 miles (1.4 million kilometers) wide, it could hold 109 planet Earths across its surface. If the sun were a hollow ball, more than a million Earths could stuff inside it. But the sun isn't hollow. It's filled with scorching hot gases that account for more than 99.8 percent of the total mass in the solar system. How hot? The temperature is about 10,000 degrees Fahrenheit (5,500 degrees Celsius) on the surface and more than 28 million degrees Fahrenheit (15.5 million Celsius) at the core.

Mercury's orbit takes the small planet as close as 29 million miles (47 million kilometers) and as far as 43 million miles (70 million kilometers) from the sun. If one could stand on the scorching surface of Mercury when it is at its closest point to the sun, the sun would appear almost three times as large as it does when viewed from Earth.Temperatures on Mercury's surface can reach 800 degrees Fahrenheit (430 degrees Celsius). Because the planet has no atmosphere to retain that heat, nighttime temperatures on the surface can drop to -280 degrees Fahrenheit (-170 degrees Celsius).Because Mercury is so close to the sun, it is hard to directly observe from Earth except during twilight. Mercury makes an appearance indirectly, however, 13 times each century. Earth observers can watch Mercury pass across the face of the sun, an event called a transit. These rare transits fall within several days of May 8 and November 10.Scientists used to think that the same side of Mercury always faces the sun, but in 1965 astronomers discovered that the planet rotates three times during every two orbits. Mercury speeds around the sun every 88 days, traveling through space at nearly 31 miles (50 kilometers) per second faster than any other planet. The length of one Mercury day (sidereal rotation) is equal to 58.646 Earth days.No AtmosphereRather than an atmosphere, Mercury possesses a thin exosphere made up of atoms blasted off its surface by solar wind and striking micrometeoroids. Because of the planet's extreme surface temperature, the atoms quickly escape into space. With the thin exosphere, there has been no wind erosion of the surface and meteorites do not burn up due to friction as they do in other planetary atmospheres.Mercury's surface resembles that of Earth's moon, scarred by many impact craters resulting from collisions with meteoroids and comets. While there are areas of smooth terrain, there are also lobe-shaped scarps or cliffs, some hundreds of miles long and soaring up to a mile (1.6 kilometers) high, formed by early contraction of the crust. The Caloris Basin, one of the largest features on Mercury, is about 800 miles (1,300 kilometers) in diameter. It was the result of an asteroid impact on the planet's surface early in the solar system's history. Over the next half-billion years, Mercury shrank in radius about 0.6 to 1.2 miles (1 to 2 kilometers) as the planet cooled after its formation. The outer crust contracted and grew strong enough to prevent magma from reaching the surface, ending the period of geologic activity.Mercury is the second smallest planet in the solar system, larger only than previously measured planets, such as Pluto. Mercury is the second densest planet after Earth, with a large iron core having a radius of 1,100 to 1,200 miles (1,800 to 1,900 kilometers), about 75 percent of the planet's radius. Mercury's outer shell, comparable to Earth's outer shell (called the mantle), is only 300 to 400 miles (500 to 600 kilometers) thick. Mercury's magnetic field is thought to be a miniature version of Earth's, but scientists are uncertain of the strength of the field.Missions to MercuryOnly one spacecraft has ever visited Mercury: Mariner 10, which imaged about 45 percent of the surface. In 1991, astronomers using radar observations showed that Mercury may have water ice at its north and south poles inside deep craters that are perpetually cold. Falling comets or meteorites might have brought ice to these regions of Mercury.

Venus and Earth are similar in size, mass, density, composition, and distance from the sun. There, however, is where the similarities end.Venus is covered by a thick, rapidly spinning atmosphere, creating a scorched world with temperatures hot enough to melt lead and a surface pressure 90 times that of Earth. Because of its proximity to Earth and the way its clouds reflect sunlight, Venus appears to be the brightest planet in the sky.Like Mercury, Venus can be seen periodically passing across the face of the sun. These transits occur in pairs, with more than a century separating each pair. Since the telescope was invented, transits have been observed in 1631, 1639; 1761, 1769; and 1874, 1882. On June 8, 2004, astronomers worldwide saw the tiny dot of Venus crawl across the sun; the second in this pair of early 21st-century transits was on June 6 2012Toxic AtmosphereVenus's atmosphere consists mainly of carbon dioxide, with clouds of sulfuric acid droplets. Only trace amounts of water have been detected in the atmosphere. The thick atmosphere traps the sun's heat, resulting in surface temperatures over 880 degrees Fahrenheit (470 degrees Celsius). Probes that have landed on Venus have not survived more than a few hours before being destroyed by the incredibly high temperatures.The Venusian year (orbital period) is about 225 Earth days long, while the planet's rotation period is 243 Earth days, making a Venus day about 117 Earth days long. Venus rotates retrograde (east to west) compared with Earth's prograde (west to east) rotation. Seen from Venus, the sun would rise in the west and set in the east. As Venus moves forward in its solar orbit while slowly rotating "backwards" on its axis, the cloud-level atmosphere zips around the planet in the opposite direction from the rotation every four Earth days, driven by constant hurricane-force winds. How this atmospheric "super rotation" forms and is maintained continues to be a topic of scientific investigation.About 90 percent of the surface of Venus appears to be recently solidified basalt lava; it is thought that the planet was completely resurfaced by volcanic activity 300 million to 500 million years ago.Sulfur compounds, possibly attributable to volcanic activity, are abundant in Venus's clouds. The corrosive chemistry and dense, moving atmosphere cause significant surface weathering and erosion. Radar images of the surface show wind streaks and sand dunes. Craters smaller than 0.9 to 1.2 miles (1.5 to 2 kilometers) across do not exist on Venus, because small meteors burn up in the dense atmosphere before they can reach the surface.Geological FeaturesMore than a thousand volcanoes or volcanic centers larger than 12 miles (20 kilometers) in diameter dot the surface of Venus. Volcanic flows have produced long, sinuous channels extending for hundreds of kilometers.Venus has two large highland areas: Ishtar Terra, about the size of Australia, in the north polar region, and Aphrodite Terra, about the size of South America, straddling the equator and extending for almost 6,000 miles (10,000 kilometers). Maxwell Montes, the highest mountain on Venus and comparable to Mount Everest on Earth, is at the eastern edge of Ishtar Terra.Venus has an iron core about 1,200 miles (3,000 kilometers) in radius. Venus has no global magnetic field; though its core iron content is similar to that of Earth, Venus rotates too slowly to generate the type of magnetic field that Earth has.

Earth, our home planet, is the only planet in our solar system known to harbor life. All of the things we need to survive are provided under a thin layer of atmosphere that separates us from the uninhabitable void of space. Earth is made up of complex, interactive systems that are often unpredictable. Air, water, land, and life—including humans—combine forces to create a constantly changing world that we are striving to understand.Viewing Earth from the unique perspective of space provides the opportunity to see Earth as a whole. Scientists around the world have discovered many things about our planet by working together and sharing their findings.Some facts are well known. For instance, Earth is the third planet from the sun and the fifth largest in the solar system. Earth's diameter is just a few hundred kilometers larger than that of Venus. The four seasons are a result of Earth's axis of rotation being tilted more than 23 degrees.Oceans at least 2.5 miles (4 kilometers) deep cover nearly 70 percent of Earth's surface. Fresh water exists in the liquid phase only within a narrow temperature span (32 to 212 degrees Fahrenheit/ 0 to 100 degrees Celsius). This temperature span is especially narrow when contrasted with the full range of temperatures found within the solar system. The presence and distribution of water vapor in the atmosphere is responsible for much of Earth's weather.Protective AtmosphereNear the surface, an ocean of air that consists of 78 percent nitrogen, 21 percent oxygen, and 1 percent other ingredients envelops us. This atmosphere affects Earth's long-term climate and short-term local weather; shields us from nearly all harmful radiation coming from the sun; and protects us from meteors as well. Satellites have revealed that the upper atmosphere actually swells by day and contracts by night due to solar activity.Our planet's rapid spin and molten nickel-iron core give rise to a magnetic field, which the solar wind distorts into a teardrop shape. The solar wind is a stream of charged particles continuously ejected from the sun. The magnetic field does not fade off into space, but has definite boundaries. When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles. These air molecules then begin to glow and are known as the aurorae, or the Northern and Southern Lights.

Though too small to earn the distinction of planet, asteroids and comets strike huge fear in the human mind. And for good reason: at some point in the future, one of the chunky rocks or icy mud balls will slam into Earth and alter the course of history. Such an impact 65 million years ago is widely believed to have killed off the dinosaurs.Asteroids and comets are considered remnants from the giant cloud of gas and dust that condensed to create the sun, planets, and moons some 4.5 billion years ago. Today, most asteroids orbit the sun in a tightly packed belt located between Mars and Jupiter. Comets are relegated to either a cloud or belt on the solar system fringe. Gravitational tugs, orbital collisions, and interstellar jostles occasionally perturb an asteroid or comet onto a wayward path.The distinction between asteroids and comets is fuzzy—comets tend to have more chemical compounds that vaporize when heated, such as water, and more elliptical (egg-shaped) orbits than asteroids do. And when observed through a telescope, comets appear fuzzier.Asteroid BeltAsteroids are essentially chunks of rock that measure in size from a few feet to several miles in diameter. (Small asteroids are called meteoroids.) The largest asteroid, Ceres, is about 590 miles (950 kilometers) wide. Like most asteroids, it lies in the asteroid belt between Mars and Jupiter. Many astronomers believe the belt is primordial material that never glommed into a planet because of Jupiter's gravitational pull. Other astronomers say the belt is a planet that was broken apart during a collision.Comets are balls of rock and ice that grow tails as they approach the sun in the course of their highly elliptical orbits. As comets heat up, gas and dust are expelled and trail behind them. The sun illuminates this trail, causing it to glow. The glowing trails are visible in the night sky.While there are perhaps trillions of comets ringing the outer fringes of the solar system, bright comets appear in Earth's visible night sky about once per decade. Short-period comets such as Halley's were perturbed from the so-called Kuiper belt out beyond the orbit of Neptune and pass through the inner solar system once or twice in a human lifetime. Long-period comets come from the Oort Cloud, which rings the outer reaches of the solar system, and pass near the sun once every hundreds or thousands of years.Occasional collisions and gravitational tugs send asteroids and comets careering toward the sun on highly elliptical orbits, some close enough to Earth to pose a risk of impact. Astronomers are constantly on the lookout for bodies on such a catastrophic trajectory. Most asteroids, fortunately, are too small to cause any damage. Instead they burn up in the atmosphere and appear to us as a shooting star.

The skies above Earth are teeming with manmade objects large and small. The U.S. Space Surveillance Network uses radar to track more than 13,000 such items that are larger than four inches (ten centimeters). This celestial clutter includes everything from the International Space Station (ISS) and the Hubble Space Telescope to defunct satellites, rocket stages, or nuts and bolts left behind by astronauts. And there are millions of smaller, harder-to-track objects such as flecks of paint and bits of plastic.SatellitesFor half a century, humans have been putting satellites into orbit around Earth to serve a variety of functions. The Soviets launched the first, Sputnik 1, in October of 1957 just to prove they could. Four months later, the U.S. responded with Explorer 1.Since then, some 2,500 satellites have been sent aloft. These include Hubble and the ISS, the Russian Mir space station, the 27-satellite Global Positioning System, as well as hundreds of others that provide communications, broadcast television and radio signals, and help scientists predict weather, among many other purposes.These man-made objects circle Earth in orbits that range from as near as 150 miles (240 kilometers) to 22,500 miles (36,200 kilometers) away. Satellites in low-Earth orbit, or LEO, stay within 500 miles (800 kilometers) and travel extremely fast—17,000 miles an hour (27,400 kilometers an hour) or more—to keep from being drawn back into Earth's atmosphere. Most satellites around Earth are found in the LEO range.Other objects are sent much farther into space and placed in what is called geosynchronous orbit. This allows the satellite to match the Earth's rotation and "hover" over the same spot at all times. Weather and television satellites are generally in this category.Space JunkOrbital debris, the technical term for nonfunctional and human-made space junk, includes not only whole, abandoned satellites, but also pieces of broken satellites, deployed rocket bodies, human waste, and other random objects, like the glove lost by astronaut Ed White during his historic 1965 spacewalk. The oldest known piece of orbital debris is the 1958 Vanguard 1 research satellite, which ceased all functions in 1964. One of the newest is a refrigerator-size ammonia reservoir released into its own orbit in July 2007, following a NASA decision that no other disposal options were feasible.Like satellites, LEO debris whizzes around the planet at 17,000 miles an hour (27,400 kilometers an hour) or more. The orbits of these objects differ in direction, orbital plane, and speed, however—meaning collisions are inevitable. At such speeds, termed hypervelocity, even a miniscule piece of junk presents a serious hazard for satellites, spacecraft, and spacewalking astronauts.Gravitational pull will ensure that anything we've ever put in orbit will eventually make its way back to Earth. And though thus far no one has ever been killed by reentering space debris, NASA estimates on average one piece returns to Earth each day.NASA and other national space agencies have identified orbital debris as a serious problem and are currently devising plans to mitigate existing space junk and curb future debris.

Jessica - Mai Maxwell


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