* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Formation of Planets III
Impact event wikipedia , lookup
Astronomical unit wikipedia , lookup
Theoretical astronomy wikipedia , lookup
Outer space wikipedia , lookup
Nebular hypothesis wikipedia , lookup
Definition of planet wikipedia , lookup
IAU definition of planet wikipedia , lookup
Solar System wikipedia , lookup
Geocentric model wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Astrobiology wikipedia , lookup
Planetary habitability wikipedia , lookup
Comparative planetary science wikipedia , lookup
Formation of Planets III Integrated Science We have looked at general characteristics of the 4 inner and outer planets. We found that the 4 inner planets have less ________ but a higher ____________. This is because the solid material that inner planets formed from did not include _____________ which are lighter but very abundant, whereas temperature conditions during the formation of the outer planets were much ____________ so the abundant ices were solid and became part of the planets. Today we will examine the composition of the 4 inner planets in more detail. The densities of most rocks at the Earth’s surface are between _______ and ______ g/cm3. However, if we look at the overall density of the earth, the value is approximately ______ g/cm3. There must be some density change beneath the earth’s surface. Smaller objects in space can give us some information. An asteroid is a rocky object in space, varying in size from several meters up to about ______ km. An asteroid group is a collection of asteroids moving in a similar orbit. Most asteroids are found in a belt between _____________ and _______________, although some are outside of this region, including some near-Earth asteroids. A ____________ is a space rock that hits the earth’s atmosphere, sometimes called a ____________. Most of these vaporize, but some reach the earth’s surface. Those reaching the surface are called _______________. Most meteorites are from parts blasted from asteroids that have collided with one another. Meteorites are the oldest objects known and some are thought to be pieces of the solar nebula that avoided incorporation into a planet, so they give us information about the original material from which planets were formed. Evidence for this is that some meteorites, _______________ meteorites, contain spheres called _____________ of millimeter size that are thought to have formed from liquid material in the solar nebula that solidified. A magnified view of a chondrule is shown below. Because the chondrules were once liquid, they formed around the melting temperature of rock and metal, about 11000C. Material between the chondrules in meteorites was often formed under different conditions. One type is called a _______________ chondrite, which has a high carbon concentration between the chondrules. The portion with the high carbon concentration could have formed only under temperature conditions less than _________. Carbonaceous chondrites have a composition of nonvolatile elements (elements other than those which vaporize at low temperatures) that is identical to the nonvolatile composition of the sun as determined by spectral analysis. Therefore, these provide information to us about the elements that formed the _________ 4 planets. The relative metallic abundance in chondrites is shown in the table below. These abundances, then, give us some idea of the proportion of metals for the inner planet’s compositions. These metals all combine with oxygen in forming minerals, so oxygen is an important element. Looking at the mineral composition of the chondrites provides some indication about the high density of the inner planets. Some iron is combined with silicon to form silicate minerals that are oxides (remember that silicate minerals have SiO4 as their basic building blocks, other iron is combined with sulfur to form iron sulfides, and other iron is by itself. Iron has a density of _______ g/cm3 while the others have a density of about _______ g/cm3. Combinations of these can help explain the density values for the inner planets. There are meteorites that do not have chondrites are called ________________. Some of these have a composition similar to volcanic rocks at the earth’s surface. Others are primarily of solid __________ with some nickel mixed in. These are probably from asteroids that were broken apart. If an asteroid has a liquid iron silicate and iron mixture, the __________________ will float to the top and the ________ will sink. We can therefore explain the reason for the lower density of rocks at a planet’s surface compared to the density of the entire planet. The sulfides and silicates with the metals have a lighter density and are near the surface. The metals by themselves are more dense and form the center or ___________. The figure below summarizes the formation of the solar system: There are two questions that remain to be answered. The first deals with angular _______________. The sun contains 99.9% of the solar system’s mass, yet, in looking at its slow spin speed, it has only 2% of the angular momentum. The second question is that hydrogen and helium gas by themselves made up the majority of the material away from the sun, yet, because they were a gas, they would never become part of a planet (which only gathered ___________ material). Today, however, most space between planets has no elements, it is empty. What happened to this gas? A possible solution has been found from observations of the early stages in life cycles of newly forming stars. Before the fusion of hydrogens to form helium begins, the star emits a large wind, called a ________________, named after the star where it was first observed. This wind would push out all the gas from the solar system and also cause the spin of the sun to slow down. We can now look at a list of the elements in the original nebular cloud and see how they relate to Earth. The first is _____________. Most hydrogen was either as a gas or liquid in the region of the inner planets, so for the most part it was not part of the formation of our planet. Helium also was a gas, and should not have been present. There is only a small amount of helium on earth today, most coming from the _________________ decay of uranium and thorium. Lithium, beryllium, and boron were not produced in significant amounts in stars, so there abundance is minor. Carbon and nitrogen mostly joined with hydrogen to form CH4, NH3, and CO, which were gases, so they did not form the Earth. Oxygen readily combines with ______________, so it is abundant on the Earth. Fluorine combined with hydrogen, and HF was a gas, so was not part of the Earth’s formation. Also, Neon is a noble gas, so was not involved in the Earth’s formation. Of the 10 first elements, then, 6 formed __________, so were not involved in the earth’s formation, and 3 were not abundant in the solar nebula, so are present only in minor amounts. Only _____________ is abundant. The next 5 elements are all _____________ and join with ____________. Sodium is rather volatile, so is not very abundant. __________, ____________, ____________, and _____________ were in solid form, so were part of the Earth’s formation. ____________ and ___________ are produced in greater abundance that the other two elements in stars, so they are important. ________ and _______ are very abundant in the Earth. Next is Sulfur. A significant amount of this was captured by ________, so it is present in a significant amount on Earth. Most Chlorine and Argon were lost as gases. Next are potassium, K, and calcium, Ca. Potassium is largely volatile, so was lost. Calcium combined with oxygen, so is relatively abundant. Of the second set of 10 elements, then, 5 (_____, _____, _____, _____, and _____) were largely captured, 3 were partially captured (_____, _____, and _____), and two were lost (_____ and _____). None of the elements between calcium and iron were largely produced in stars, so they are not very abundant. Remembering that ___________ was the last element to be produced in the regular cycle in stars, it is available in abundance, close to magnesium and silicon. After iron, the abundance drops off significantly, with only ______ fairly abundant. One question that still remains, though, is to explain the presence of carbon and hydrogen on the Earth today. Although we are not sure, it is thought that shortly after the Earth formed there were many ___________ (the equivalent of asteroids, but composed primarily of ices) that struck the earth. These would provide the Earth a source of some of the more volatile elements.