Astronomy Test 2 (Chpts. 6-9)

All the terrestrial worlds have layered interiors. We divide these layers by density into three major categories:

Core, mantle, crust

names of the Jovian planets

Jupiter, Saturn, Neptune, and Uranus

orbits and motions of the solar system

Patterns of motion among large bodies. The sun, planets, and large moons generally orbit and rotate in a very organized way. All planetary orbits are nearly circular and lie nearly in the same plane All planets orbit the Sun in the same direction: counterclockwise as viewed from high above Earth's north pole Most planets rotate in the same direction in which they orbit, with fairly small axis tilts. The sun also rotates in this direction

protosun

the gaseous cloud that underwent gravitational collapse to form the sun

some facts about Mercury

2/3 orbit resonance: neither the hottest nor the coldest planet. cratered surface- in some ways like the moon. appears to be a planet dominated by a metal-rich core. Significant shrinkage as the planet cooled, forming the scarps.

how many stages of evolution did the terrestrial planets have?

4

earth and the solar system are about how old

4 1/2 billion years old

definition of lithosphere

A planet's lithosphere is its outer layer of cool, rigid rock

The only ongoing geological change on the moon is?

a very slow "sandblasting" of the surface by micrometeorites, sand-size particles from space

stage three of terrestrial planet evolution

filling of the basins with lava (as in the mare regions of Luna)

stage four of terrestrial planet evolution

gradual surface evolution

lunar maria

the regions of the moon that look smooth from earth and actually are impact basins

earth's oceans

According to this theory, the ocean formed from the escape of water vapor and other gases from the molten rocks of the Earth to the atmosphere surrounding the cooling planet. After the Earth's surface had cooled to a temperature below the boiling point of water, rain began to fall—and continued to fall for centuries. As the water drained into the great hollows in the Earth's surface, the primeval ocean came into existence. The forces of gravity prevented the water from leaving the planet.

who predicted the location of Neptune and when?

Adams and Leverrier in 1846

features of mercury

Although there has been no more volcanism on mercury for billions of years, its surface still displays one odd form of geological activity: some crater floors appear to be releasing easily vaporized materials from the rock, causing the rock to crumble and make pits nicknamed "hollows" Mercury's most surprising feature is a set of tremendous cliffs that appear to be distributed all over the planet.

Mars's surface

Aside from the polar caps, the most striking feature is the dramatic difference in terrain around different parts of the planet. The differences in crater crowding tell us that the southern highlands are a much older surface than the northern plains, which must have had their early craters erased by other geological processes. Mars has clearly had active volcanism in the past, as it is dotted with towering volcanoes. Mars also has tectonic features, of which the most prominent is a long, deep system of valleys called Valles Marineris. Mars is not yet "geologically dead" like the moon or mercury. Strong evidence that Mars had flowing water in the distant past comes from both orbital and surface studies. Dried-up riverbeds and other geological features show that water flowed on Mars in the distant past.

more facts about asteroids

Asteroids are important because they remain much as they were when they first formed. Asteroids come in a wide variety of sizes and shapes. Vesta- the second largest asteroid by mass, might have once been volcanically active. The total mass of all asteroids is much less than the mass of any terrestrial planet. Small asteroid's gravity is too weak to form them into spheres. Primitive meteorites: meteorites that formed at the same time as the solar system itself, about 4.6 billion years ago. Primitive meteorites from the inner asteroid belt are usually stony, and those from the outer belt are usually carbon-rich. Processed meteorites: meteorites that apparently once were part of a larger object that "processed" the original material of the solar nebula into another form. Processed meteorites can be rocky if chipped from the surface or mantle, or metallic if blasted from the core. Most meteorites are pieces of asteroids, and they teach us much about the early history of our solar system. Jupiter's gravity, through the influence of orbital resonances, prevented asteroids from accreting into a planet and still shapes their orbits today. Asteroid belt is still undergoing changes everyday.

Viking mission of 1976 to Mars

By discovering many geological forms that are typically formed from large amounts of water, the images from the orbiters caused a revolution in our ideas about water on Mars. Huge river valleys were found in many areas. They showed that floods of water broke through dams, carved deep valleys, eroded grooves into bedrock, and travelled thousands of kilometers. Large areas in the southern hemisphere contained branched stream networks, suggesting that rain once fell. The flanks of some volcanoes are believed to have been exposed to rainfall because they resemble those caused on Hawaiian volcanoes. Many craters look as if the impactor fell into mud. When they were formed, ice in the soil may have melted, turned the ground into mud, then flowed across the surface. Normally, material from an impact goes up, then down. It does not flow across the surface, going around obstacles, as it does on some Martian craters.[7][8][9] Regions, called "Chaotic Terrain," seemed to have quickly lost great volumes of water, causing large channels to be formed. The amount of water involved was estimated to ten thousand times the flow of the Mississippi River.[10] Underground volcanism may have melted frozen ice; the water then flowed away and the ground collapsed to leave chaotic terrain.

Callisto

Callisto looks most like scientists would expect; a heavily cratered iceball. Could also be a subsurface ocean but nobody even has an idea how. Powdery substance that nobody knows how it got there.

comets

Comets are basically chunks of ice mixed with rocky dust and some more complex chemicals, and hence they are often described as "dirty snowballs." When a comet nears the Sun, its ices can vaporize into gas and carry off dust, creating a coma and long tails. Comets have two visible tails. Plasma tail: one of two tails seen when a comet passes near the Sun. It is composed of ionized gas blown away from the Sun by the solar wind. Dust tail: one of two tails seen when a comet passes near the Sun. It is composed of small solid particles pushed away from the Sun by the radiation pressure of sunlight. Comets lose their tails when they move away from the sun again Spectroscopy of this gas showed that the comet contains many complex organic molecules One of the most interesting results shows that the water ice that drives cometary activity near the Sun is hidden under a substantial crust of dusty material that is composed of rock and carbon-bearing molecules. Comets also eject sand- to pebble-size particles that are too big to be affected by either the solar wind or sunlight. These particles essentially form a third, invisible tail that follows the comet around its orbit. They are also the particles responsible for most meteors and meteor showers. Oort cloud: a huge, spherical region centered on the Sun, extending perhaps halfway to the nearest stars, in which trillions of comets orbit the sun with random inclinations, orbital directions, and eccentricities. Most comets travel in opposite direction of planets, small number travels in the same and those ones come from the Kuiper belt not the Oort cloud Kuiper belt comets orbit in the region in which they formed, just beyond Neptune's orbit. The more distant Oort cloud contains comets that once orbited among the jovian planets.

surface of the luna

Electrically charged lunar dust near shadowed craters can get lofted above the surface and jump over the shadowed region, bouncing back and forth between sunlit areas on opposite sides. This effect should be especially prominent during dusk and dawn, according to the team, as regions become partially illuminated while features like mountains and crater rims cast long shadows.

Europa

Europa's surface is made almost entirely of water ice, with very few impact craters and extensive cracks. Shows sign of geological activity which is caused by the same type of tidal heating Io has but it is weaker because it is farther from Jupiter. Europa may hide a deep ocean of liquid water between its rocky mantle and its icy crust. If it does exist it may have more than twice as much water as all of Earth's oceans combined.

division into Jovian and Terrestrial planets

Frost line: the boundary in the solar nebula beyond which ices could condense; only metals and rocks could condense within the frost line, which lay between the present-day orbits of Mars and Jupiter The frost line marked the key transition between the warm inner regions of the solar system where terrestrial planets formed and the cool outer regions where jovian planets formed. The total amount of solid material was far greater beyond the frost line than within it. The solid seeds contained only metal and rock in the inner solar system, but also included ices in the outer solar system The jovian planets began as large, icy planetesimals, which then captured hydrogen and helium gas from the solar nebula

Ganymede

Ganymede also has surface of water ice. Some regions are heavily cratered and some regions have very few craters. Might have a subsurface ocean of liquid water. Has some tidal heating but not enough to cause this. Perhaps ongoing radioactive decay supplies enough additional heat to make an ocean but scientists do not know for sure.

who accidentally discovered Uranus?

Herschel

Venus's young surface age

Its relatively few impact craters confirm that its surface is geologically young. In addition, the composition of venus's clouds suggests that volcanoes must still be active on geological time scales (erupting within the past 100 million years).

differences between the Jovian planets

Jupiter and saturn are made mostly of hydrogen and helium. While, uranus and neptune are much smaller and have much smaller proportions of hydrogen and helium.

Jupiter

Jupiter has a surprisingly high density Some extrasolar planets that are larger in mass than Jupiter are therefore smaller in size, because weight would actually compress the interior Jupiter's lack of a solid surface makes it tempting to think of the planet as "all atmosphere," but you could not fly through Jupiter's interior in the way airplanes fly through air. Jupiter has distinct layers; outer layer is gaseous=10%, next 10% in is liquid, and below that a liquid metallic, and then a sort of mix that is like a solid and liquid If you plunged below Jupiter's clouds, you'd never encounter a solid surface- just ever denser and hotter hydrogen/ helium compressed into bizarre liquid and metallic phases. Jupiter's magnetic field is by far the strongest, stronger than Earth's If we could see jupiter's magnetosphere, it would be larger than the full moon in our sky. The particles also create belts of intense radiation and contribute to auroras on Jupiter Jupiter's stripes represent alternating bands of rising and falling air, and their colors arise from the clouds that we see. Jupiter has very high east-west wind speeds- sometimes more than 400 kilometers per hour. Great Red Spot: a large, high-pressure storm on Jupiter. Perhaps Jupiter's biggest storms last for centuries simply because there's no solid surface effect to sap their energy.

name a few missions to our solar system

Mariner, Magellan, Viking, Voyager, Cassini, New Horizons, Galileo spacecraft, etc.

Mars's seasons

Mars bears many superficial similarities to Earth. Mars even has earth-like seasons as a result of having a similar axis tilt, though it is significantly closer to the sun during southern hemisphere summer, giving its southern hemisphere more extreme seasons.

names of the Terrestrial planets

Mercury, Venus, Earth, and Mars

origin of the solar system

Nebular theory: the detailed theory that describes how our solar system formed from a cloud of interstellar gas and dust Solar nebula: the piece of interstellar cloud from which our own solar system formed Gas that made up the solar nebula contained (by mass) about 98% hydrogen and helium and 2% all other elements combined Strong observational evidence supports this scenario. Spectroscopy shows that old stars have a smaller proportion of heavy elements than younger ones, just as we would expect if they were born at a time before many heavy elements had been manufactured The solar nebula probably began as a large and roughly spherical cloud of very cold, low-density gas. The collapse must have been triggered by a cataclysmic event, such as the impact of a shock wave from the explosion of a nearby star. Once the collapse started, gravity enabled it to continue. As the solar nebula shrank in size, three important processes altered its density, temperature, and shape: heating, spinning, and flattening The orderly motions of our solar system are a direct result of its birth in a spinning, flattened cloud of gas. The planets all orbit the sun in nearly the same plane because they formed in the flat disk. The direction in which the disk was spinning became the direction of the sun's rotation and the orbits of the planets. The fact that collisions in the disk tended to make orbits more circular explains why the planets in our solar system have nearly circular orbits. Observations of spinning disks of gas around other stars support the idea that our solar system formed in a similar disk; we have detected infrared radiation from many nebulae where star systems appear to be forming. Computer simulations successfully reproduce most of the general characteristics of motion in our solar system. Terrestrial planets formed in the warm, inner regions of the swirling disk, while jovian planets formed in the colder, outer regions Planet formation began around tiny "seeds" of solid metal, rock, or ice

Neptune

Neptune also has had a high pressure storm called the Great Dark Spot, did not last long as Jupiter's. is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune.[d] Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 astronomical units (4.50×109 km). Neptune's atmosphere is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, but it contains a higher proportion of "ices" such as water, ammonia, and methane. However, its interior, like that of Uranus, is primarily composed of ices and rock,[12] which is why Uranus and Neptune are normally considered "ice giants" to emphasise this distinction.[13] Traces of methane in the outermost regions in part account for the planet's blue appearance. Because of its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching 55 K (−218 °C). Temperatures at the planet's centre are approximately 5,400 K (5,100 °C).[16][17] Neptune has a faint and fragmented ring system (labelled "arcs"), which was discovered in 1982, then later confirmed by Voyager 2.[18]

earth's plate tectonics

Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere.

Pluto and it's moon Charon

Pluto orbits the sun once every 248 years, and its orbit is much more elliptical and inclined to the ecliptic plane than that of any of the eight planets. Pluto sometimes comes closer to the sun than neptune Pluto has five known moons. This suggest that Charon- as well as the smaller moons- formed as the result of a giant impact similar to the one thought to have formed our Moon. such an impact may also explain why Pluto rotates almost on its side. Observations of Charon's orbit allowed scientists to calculate Pluto's precise mass by applying Newton's version of Kepler's third law. Detailed analysis of brightness variations during these eclipses allowed the calculations of sizes, masses, and densities for both Pluto and Charon, confirming that both have comet-like compositions of ice and rock. The eclipse data even allowed astronomers to construct rough maps of Pluto's surface markings, and improved telescopic observations, including many with the Hubble Space Telescope, showed a varied surface suggestive of unknown forms of activity. Pluto is very cold with an average temperature of only 40 K, as we would expect at its great distance from the Sun. nevertheless, Earth-based observations showed that Pluto has a thin atmosphere of nitrogen, methane, and carbon monoxide formed by vaporization of surface ices. The mutual tidal forces acting between Pluto and Charon long ago made them rotate synchronously with each other, so Charon is visible from only one side of Pluto and always shows the same face to Pluto. The New Horizons mission revealed Pluto and Charon to have surprisingly high levels of geological activity. - it is likely that activity continues to this day Charon also has vast, smooth plains that are the hallmark of recent geological activity, as well as canyons comparable in length and depth to Earth's Grand Canyon. Scientists are still trying to understand the heat source that drives the geological activity of Pluto and Charon. Pluto- the atmosphere is visible looking back toward the sun because it contains enough haze to scatter sunlight forward. Pluto and other larger Kuiper belt objects are smaller, icier, and more distant than any of the planets. They can have moons, atmospheres, and possibly geological activity.

mercury compared to the moon

Recall that in addition to being larger than the moon, mercury also has a surprisingly large iron core. Mercury therefore gained and retained more internal heat than the moon, and this heat cause mercury's core to swell in size. Mercury is a good amount like the moon but has its key differences. In many places, mercury's craters are less crowded together than the craters in the most ancient regions of the moon, suggesting that molten lava covered up some of the craters that formed on mercury during the heavy bombardment. However, mercury does not appear to have any features formed by much later lava flows, like those of the lunar maria.

saturn

Saturn is considerably less dense than Uranus or Neptune. Saturn has the same basic layering as Jupiter, but its lower mass makes the weight of the overlying layers less than on Jupiter. As a result, we must look deeper into Saturn to find each level where pressure changes hydrogen from one phase to another. Uranus and Neptune have somewhat different layering because their internal pressures never become high enough to form liquid or metallic hydrogen, so they have only a thick layer of gaseous hydrogen surrounding their cores. Saturn has the same set of three cloud layers as jupiter, but saturn's lower temperatures mean these layer occur deeper in saturn's atmosphere. saturn's winds are even faster than Jupiter's.

atmospheres of the terrestrial planets depend in part on?

Temperature and mass of the planet, along with composition of the atmosphere

luna tides and synchronous rotation

The Moon has tidal bulges similar to those on Earth. It is thought that the Moon once rotated much faster than it does today. The friction created by the stretching and squeezing of the Moon caused the Moon's rate of rotation to slow down until its rotational period was the same as its orbital period. At this point there is no more tidal friction, the rate of rotation stabilizes and the Moon is locked in synchronous rotation with Earth.

Apollo missions and the lunar rocks

The chemical composition of the Moon, derived from studies of lunar rocks, is compatible with this theory of the origin of the Moon. We have learned that a crust formed on the Moon 4.4 billion years ago. This crust formation, the intense meteorite bombardment occurring afterward, and subsequent lava outpourings are recorded in the rocks. Radiation spewed out by the Sun since the formation of the Moon's crust, was trapped in the lunar soil as a permanent record of solar activity throughout this time.

why is the magnetic field important to earth?

The magnetic field is very important to life on earth because it creates a magnetosphere that acts like a protective bubble surrounding our planet, shielding earth's surface from the energetic charged particles of the solar wind.

Mars's atmosphere

The mars atmosphere is so thin that the atmospheric pressure is less than 1% of that on the surface of earth. The thin atmosphere also means a week greenhouse effect. Very cold temperatures. The lack of oxygen means that mars lacks an ozone layer, so much of the sun's damaging ultraviolet radiation passes unhindered to the surface.

big impact theory of the luna

The moon was formed ~4.5 billion years ago, about 30-50 million years after the origin of the Solar System, out of debris thrown into orbit by a massive collision between a smaller proto-Earth and another planetoid, about the size of Mars. The new data suggest that the moon may be made up of about 40 percent Theia- the object crashed into.

Triton (moon)

Triton is the largest natural satellite of the planet Neptune, and the first Neptunian moon to be discovered. It was discovered on October 10, 1846, by English astronomer William Lassell. It is the only large moon in the Solar System with a retrograde orbit, an orbit in the opposite direction to its planet's rotation. At 2,710 kilometres (1,680 mi) in diameter, it is the seventh-largest moon in the Solar System. Because of its retrograde orbit and composition similar to Pluto's, Triton is thought to have been a dwarf planet captured from the Kuiper belt. Triton has a surface of mostly frozen nitrogen, a mostly water-ice crust, an icy mantle and a substantial core of rock and metal. The core makes up two-thirds of its total mass. Triton has a mean density of 2.061 g/cm3 and is composed of approximately 15-35% water ice. Triton is one of the few moons in the Solar System known to be geologically active (the others being Jupiter's Io and Saturn's Enceladus). As a consequence, its surface is relatively young with few obvious impact craters, and a complex geological history revealed in intricate cryovolcanic and tectonic terrains. Part of its surface has geysers erupting sublimated nitrogen gas, contributing to a tenuous nitrogen atmosphere less than 1/70,000 the pressure of Earth's atmosphere at sea level.

uranus and neptune

Uranus and neptune are so cold that any cloud layers similar to those of jupiter and saturn would be buried to deep in their atmospheres for us to see. However, the cold temperatures allow some of their abundant methane gas to condense into clouds.

Venus's surface

Venus shows many geological features similar to earth's, including occasional impact craters, volcanoes, and evidence of surface contortions caused by tectonic forces. Venus also has some unique features, such as the large, circular coronae that were probably made by hot, rising plumes of mantle rock. These plumes probably also forced lava to the surface, explaining the volcanoes found near coronae.

differences of earth and Venus

Venus's lack of earth-like plate tectonics poses a scientific mystery, but may arise because Venus has a thicker and stronger lithosphere than earth. Earth has as much carbon dioxide as Venus, but it is mostly locked away in rock rather than in our atmosphere. In short, moving Earth to Venus's orbit would essentially turn our planet into another Venus.

Venus's runaway greenhouse effect

Venus's thick carbon dioxide atmosphere creates the extremely strong greenhouse effect that makes Venus so hot. a positive feedback cycle in which heating caused by the greenhouse effect cause more greenhouse gases to enter the atmosphere, which further enhances the greenhouse effect. Venus is too close to the Sun to have liquid water oceans. Without water to dissolve carbon dioxide gas, Venus was doomed to its runaway greenhouse effect.

earth's cratering

We have never witnessed a major impact on earth, but geologists have identified more than 150 impact craters. Evidence suggests that Earth's craters have been erased with time by geological activity such as volcanic eruptions and erosion.

Io

a moon that is by far the most volcanically active world in our solar system. It probably also has tectonic activity but those features have most likely been buried. Still quite hot inside which should not be possible. Tidal heating: a source of internal heating created by tidal friction. It is particularly important for satellites with eccentric orbits such as Io and Europa. Io is continuously being flexed in different directions. Orbital resonances among the Galilean moons make Io's orbit slightly elliptical, leading to tidal heating that explains Io's volcanic activity.

stage one of terrestrial planet evolution

accretion and crustal formation (aka differentiation)

stage two of terrestrial planet evolution

basin formation (cratering- just about everywhere we have been)

general characteristics of Jovian planets

compositions in the outer solar system: ice and rocky material, with H & He. strong magnetic fields and rapid rotation. atmospheres driven by internal heat. thick liquid interiors. Satellite systems and rings.

Uranus

had storms but they were more subdued. is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have different bulk chemical composition from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the gas giants. Uranus's atmosphere is similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, but it contains more "ices" such as water, ammonia, and methane, along with traces of other hydrocarbons.[12] It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (−224 °C; −371 °F), and has a complex, layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds.[12] The interior of Uranus is mainly composed of ices and rock. Like the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons. The Uranian system has a unique configuration among those of the planets because its axis of rotation is tilted sideways, nearly into the plane of its solar orbit. Its north and south poles, therefore, lie where most other planets have their equators.[16] In 1986, images from Voyager 2 showed Uranus as an almost featureless planet in visible light, without the cloud bands or storms associated with the other giant planets.[16] Observations from Earth have shown seasonal change and increased weather activity as Uranus approached its equinox in 2007. Wind speeds can reach 250 metres per second (900 km/h; 560 mph).

Heating (solar nebula)

increase temperature as it collapsed. Gravitational potential energy converted to kinetic energy of individual gas particles. Particles crashed into each other converting kinetic energy of inward fall to random motions of thermal energy. Sun formed in center, where temperatures and densities were highest

Miranda (moon)

is the smallest and innermost of Uranus's five round satellites. It was discovered by Gerard Kuiper on 16 February 1948 at McDonald Observatory, and named after Miranda from William Shakespeare's play The Tempest.[5] Like the other large moons of Uranus, Miranda orbits close to its planet's equatorial plane. Because Uranus orbits the Sun on its side, Miranda's orbit is perpendicular to the ecliptic and shares Uranus's extreme seasonal cycle. Like all of Uranus' moons, Miranda probably formed from an accretion disc that surrounded the planet shortly after its formation, and, like other large moons, it is likely differentiated, with an inner core of rock surrounded by a mantle of ice. Miranda has one of the most extreme and varied topographies of any object in the Solar System, including Verona Rupes, a 5- to 10-kilometer-high scarp, and chevron-shaped tectonic features called coronae. The origin and evolution of this varied geology, the most of any Uranian satellite, are still not fully understood, and multiple hypotheses exist regarding Miranda's evolution.

Venus's retrograde motion

it spins in the opposite direction from most other planets, including Earth, so that on Venus the sun rises in the west. Current theory holds that Venus initially spun in the same direction as most other planets and, in a way, still does: it simply flipped its axis 180 degrees at some point. In other words, it spins in the same direction it always has, just upside down, so that looking at it from other planets makes the spin seem backward. Scientists have argued that the sun's gravitational pull on the planet's very dense atmosphere could have caused strong atmospheric tides. Such tides, combined with friction between Venus's mantle and core, could have caused the flip in the first place.

Titan

largest moon of Saturn. It is the only moon known to have a dense atmosphere, and the only object in space other than Earth where clear evidence of stable bodies of surface liquid has been found.

general facts about Mars

last of the four inner planets of our solar system. Larger than mercury and moon but about half earth's size in diameter; its mass is about 10% that of Earth. Evidence that it must have had warm and wet periods in the past but it is now frozen. Air pressure is very low.

nature/ activity of terrestrial planet surfaces depends on?

mass (and amount of heat remaining within the planet- volcanism, tectonics, mountain-building) along with temperature (what materials are liquids and can flow on the surface?) sometimes cratering is about the only factor affecting/ changing the surface

meteorites

most meteorites come from the asteroid belt. they are stony, stony-iron, iron-nickel. cause cratering and impacts.

earth's atmosphere is composed primarily of what?

nitrogen

general facts about asteroids

rocky and metallic planetesimals mostly between mars and Jupiter. most meteorites come from the asteroid belt. several asteroids have orbits which cross the orbit of earth.

mantle

rocky material of moderate density- mostly minerals that contain silicon, oxygen, and other elements- form a thick mantle that surrounds the core.

Core

the highest-density material, consisting primarily of metals such as nickel and iron, resides in a central core.

crust

the lowest-density rock (which includes the familiar rocks of Earth's surface) forms a thin crust, essentially representing the world's outer skin.

Flattening (solar nebula)

the solar nebula flattened into a disk. This flattening is a natural consequence of collisions between particles in a spinning cloud

spinning (solar nebula)

the solar nebula rotated faster and faster as it shrank in radius. The rapid rotation helped ensure that not all the material in the solar nebula collapsed in the center