Astronomy Exam 2

Earth Impact on The Moon

- Earth and the Moon have evolved together. - Because Earth is so much more massive than the Moon, the lunar tidal bulge is considerably larger, and the synchronization process correspondingly faster. - the tidal interaction between the Earth and the Moon causes Moon's synchronous orbit, the same side of the moon always faces our planet

Jupiter's Moons

- Jupiter has 63 Moons - 16 of Jupiter's family of 63 moons can be divided into at least 3 smaller groupings: 1. 8 outer moons which orbit in two groups of four that are traveling in opposite directions, which have eccentric orbits, dark surfaces, and which are probably captured asteroids 2. 4 inner moons which orbit very close to Jupiter and which are probably fragmented moonlets. 3. 4 large satellites orbiting in nearly circular orbits which are known as the Galilean moons in honor of their discoverer. -The smallest of these 4 large moons is 5,000 times more massive than is the largest of the remaining Jovian moons.

Mercury's View in The Sky

- Mercury appears lower in the sky at dawn or dusk than Venus. - it is easiest to see when the Sun is below the horizon. - of all the planets visible to the naked eye Mercury is the hardest for people on Earth to see. - because it is so close to the Sun in the sky, it can be seen low on the horizon just before sunrise in the east or just after sunset in the west.

Moon-Like

- Mercury appears similar to our Moon, both are covered with many impact craters. -Mercury's craters are less prominent; the planet's surface gravity is twice that of the Moon so loose material will not stack as steeply. - Mercury lacks the larger maria seen on the Moon because Mercury cooled more slowly than did the Moon, meteorites were able to penetrate its crust over a longer period, which allowed lava to flow out over a longer period and to obliterate the older craters. - this resulted in the plains that can be seen between craters.

Mercury Phases

- Mercury exhibits phases as does Venus - however, features are hard to discern from Earth because Mercury is small, and when it is near the horizon its like much pass through many layers of the atmosphere.

Buried Glaciers at Mars

- Nearly pure ice "glaciers" covered by rock are common at mid- latitudes on Mars - Previous spacecraft images indicated glacier-like features next to steep slopes and filling some craters, but could not see through the overlying rock to confirm there presence. -the layer of rock protects the ice from evaporating in Mars' cold dry climate -Debris-covered glaciers at mid-latitudes on Mars may contain enough ice to cover the entire planet in 20 cm of water -These ice reservoirs are covered by only a few meters of material - easily accessible for future human and scientific exploration -Buried ice may record the history of Mars' climate, as ice cores from Earth's glaciers do

Saturn's Moons: Titan

- Second largest moon in the solar system -Titan provides a veritable laboratory to study organic chemistry -Many analogues to Earth's early atmosphere - provides an environment to study prebiotic processes that may have characterized early Earth -Only moon with a substantial atmosphere -Its dense atmosphere is thought to be a colder version of Earth's early atmosphere. -Ultraviolet-absorbing haze, ultraviolet/ optical haze layer, main haze layer, aerosol haze, methane clouds - Troposphere, stratosphere, condensation of organics - Titan has an atmosphere composed of nitrogen. - Its atmosphere contains about 10 times more gas than Earth's atmosphere and because of Titan's weaker gravitational pull, extends 10 times farther into space farther than does our own. - propylene on Titan - Titan has a low mass and low surface gravity - The upper atmosphere is thick with smoggy haze, and the surface may be covered with hydrocarbon sediment that has settled from clouds. -Titan's 94K surface temperature, which is considerably lower than that of Jupiter's moons, making it easier for the moon to retain an atmosphere. - The model indicates that Titan has a rocky core surrounded by a thick layer of liquid water a few tens of kilometers below the surface. - Methane is irreversibly lost to organics over a period considerably shorter than the lifetime of Titan's atmosphere. - since its atmosphere is primarily composed of methane- ammonia, this could have a major impact on Titan atmospheric stability. - Methane cycle -The Cassini spacecraft recently recorded a flash of sunlight off a region of the northern hemisphere -The reflection comes from a dark, smooth region suspected to be a large lake or sea -Infrared and radar observations previously revealed hundreds of likely lakes near the north pole, and a few lakes near the south pole -The lakes are filled with ethane, and probably methane -Above is a false color Cassini image showing the amount of radar signal reflected from a region of Titan's northern hemisphere. Dark regions are likely lakes. -Methane and ethane should be exchanged between the atmosphere and lakes through evaporation and precipitation (similar to water on Earth) -These processes can help maintain the high atmospheric methane abundance and contribute to observed seasonal variations in the lakes Core: 1. Surface 2. Near Surface Ice 3. Liquid water 4. High Pressure Ice 5. Silicate core -Large ions in the upper atmosphere maybe a source of haze

Condensation Theory

- begins with a large cloud of interstellar dust and gas- called a nebula- that is a light-year or so across. - now suppose that due to some external influence, such as a collision with another interstellar cloud or perhaps the explosion of a nearby star, the nebula starts to contract under the influence of its own gravity. - as it contracts, it becomes denser and hotter. - the conservation of angular momentum demands that our hypothetical nebula must spin faster as it contracts. - the increase in rotation speed causes the nebula's shape to change, eventually forming a disk. -the nebula collapses most rapidly along the rotation axis. -protoplanets-accumulations of matter that would eventually evolve into the planets we know today- formed in the disk and became planets, while the central protosun became the sun. - particles of interstellar dust helped cool the solar nebula and acted as condensation nuclei- microscopic platforms in which other atoms can attach, forming larger and larger balls of matter-that begin the planet-building process. - small clumps grew by accretion- the gradual growth of small objects by collision and sticking, sticking together and growing into moon-sized planetesimals- objects the size of small moons, having gravitational fields strong enough to affect their neighbors- whose gravitational field accelerated the accretion. - as planetesimals collided and merged, a few planet-sized objects remained. -this formed the terrestrial planets

Solar Wind

- is the continuous flow of nuclei and electrons from the Sun. -it is also the outermost part of the solar atmosphere. -near the Earth the solar wind travels at speeds of 400-1000km. -is an invisible stream of matter and radiation escaping from the Sun.

Saturn's Moons: Iapetus

- is the third-largest natural satellite of Saturn - inner edge of Phoebe ring and farthest large moon from Saturn -Saturn's moon Iapetus has a dark leading side, while trailing face of Saturn's moon Iapetus is ~10 times brighter than its leading face -For 300 years, astronomers debated whether the cause was internal (e.g. eruption of dark material on one face) or external (e.g. debris from a nearby impact) -The discovery of a giant ring around Saturn and close-up Cassini images confirm an external cause: dust particles coat one side and drive ice to the other by sublimation -Impactors strike one of several distant dark Saturn moons (such as Phoebe), supplying a ring of dark particles that orbit Saturn 'backwards', like Phoebe -Sunlight pushes the ~10 micron particles inward over thousands of years -Particles collide with Iapetus and other inner moons, making their leading face slightly darker -The darkened ice absorbs more sunlight, warms up, and sublimes, recondensing as bright frost on the trailing side and poles

Galilean Moons: Io

- it is the innermost galilean satellite and it is almost perfectly circular. -Io is surrounded by a halo of sodium atoms. -Oxygen, potassium, chlorine also observed to be escaping from Io -Sulfur and other gases emanating from volcanoes quickly freeze - SO2 snow -Io's density is about 3.5 gm/cm3, indicating that is it composed mostly of rock; high density - Orange- yellow mottled surface. -Yellowish color is caused by sulfur which covers the surface. -Sulfur chemistry plays an important role in the chemistry on IO's surface and tenuous atmosphere. -Io, the Galilean moon closest to Jupiter, has active volcanic geysers that spew hot sulfur onto the surface. -SO2 and hot sulfur released from volcanoes rapidly resurface Io -surface is always changing- it lacks impact craters - Io's heat is produced by tidal forces caused by its eccentric orbit around Jupiter. - Io's interior is believed to be differentiated, with and iron or iron-sulfide core. - Io's source of energy is external- Jupiter's gravity.

Scarps

- more scarps- long cliffs in a line- are found on Mercury than on the Moon. - most are believed to have formed from the shrinking of Mercury's crust as it cooled.

Asteroids

- objects inside the orbit of Jupiter - most can be found between orbit of Mars and Jupiter, in the asteroid belt, 2.2 to 3.3 AU. -The asteroids revolve around the Sun in a counterclockwise direction like the planets. -Most asteroids orbit in or near the plane of the ecliptic. -Asteroids are not evenly distributed across the asteroid belt. -Asteroids are known as minor planets -At certain distances, for example, 2.5 and 3.28 AU, gaps appear which are related, respectively, to 1/3 and 1/2 of Jupiter's orbital period.

Van Allen Belts

- the Van Allen belts are two doughnut-shaped regions composed of charged particles (protons and electrons) emitted by the Sun and captured by the magnetic field of the Earth. -the are located in the earth's magnetosphere

Interior Density of the Earth

- the average density—the ratio of its mass to its volume—of the Earth is 5.52 g/cm3. - the average density is what tells us that Earth is primarily a rocky and metallic object.

Formation of Jovian Worlds: Conventional Scenario

- the four largest protoplanets in the outer solar system grew rapidly and became massive enough to enter a third phase of planetary development- their strong gravitational fields swept up large amounts of gas directly from the solar nebula. - there was a lot more raw material available for planet building in the outer solar system, so protoplanets grew much fast there.

Formation of Jovian Worlds: Second Scenario

- the giant planets formed through instabilities in the cool outer regions of the solar nebula, mimicking on small scales the collapse of the initial interstellar cloud. - in this view, the jovian protoplanets formed directly and very rapidly, skipping the initial accretion stage and perhaps taking less than a thousand years to acquire much of their mass. - the first protoplanets had gravitational fields strong enough the scoop up dust from the solar nebula, allowing them to grow into the giants we see today. - Instabilities in the cool gas of the outer solar nebula

Formation of the Moon: Large Impact Hypothesis

- the large impact theory, proposed in the 1970s, holds that the Moon formed as the result of a glancing impact between a large Mars-sized object and the Earth. -this theory can explain the relative compositions of the Earth and Moon, the orbit of the Moon, and the rotation rate of the Earth. -this theory has also been successfully modeled on a supercomputer.

Largest Meteoroid or Meteorite

- the largest meteoroids are large enough that they are able to pass through the Earth's atmosphere without being completely evaporated. - it is estimated that only 1 in 1 million meteoroids that hit the atmosphere survives to reach the surface. - these are called a meteorite. - some meteorites which have landed on the Earth have come from the Moon and from Mars. - are usually not associated with comets -meteorites are meteors that have reached Earth

Olympus Mons

- the largest volcano is Olympus Mons, who height of 24 km is twice that of Earth's largest mountain. - Mars can "grow" larger volcanoes than Earth because it lacks tectonic plates. - formed over a hot spot of lava, a volcano can grow to enormous size if it does not move off of the hot spot. - Earth's crustal motion will move a volcano before it can become as large as Olympus Mons.

Synchronous Orbit

- the rotation period of a body is precisely equal to its orbital period around another body. - the moon is in a synchronous orbit and so it presents the same face toward the earth at all times.

Angular Momentum

- the tendency of an object to keep rotating; proportional to the mass, radius, and rotation speed of the body. - when the radius decreases, the rotation rate must increase in order to keep the total angular moment unchanged. - the planets have more total angular momentum than does the sun, even though the sun has most of the mass

Melting Pot Temperature

- when the local temperature is lower than the melting-point temperature,the rock is solid. - when the local temperature is above the melting-point temperature, the rock is molten. - the alternation of the two curves is why the interior of the Earth goes from being solid to liquid and back again with increasing distance beneath the surface.

Gullies

-'Gullies' are channels carved when material moves downhill. -They are seen in a variety of locations on Mars, including crater walls, cliffs, and dunes -Proposed formation mechanisms: water seeping from the subsurface, melting ice or snow, water frost, carbon dioxide (CO2) frost, and dry flows - but there's no direct evidence for any of these -Scientists must use indirect evidence: melting water would form gullies at the warmest times and locations, but subliming or condensing CO2 would form gullies at the coldest times and places.

Neptune's Moons

-13 moons are now known. -its largest moon is triton

Neap Tide

-A neap tide is the smallest difference between high and low tide in a single day. Such tides occur when the solar tide most nearly cancels the lunar tide (i.e., when the solar tides are located 90° away from the lunar tides). -Neap tides occur when the Moon is located either 90 degrees ahead of or 90 degrees behind the Sun, occurring at 1st or 3rd quarter phase.

Spring Tide

-A spring tide is the greatest difference between high and low tide during a given day. Such tides occur about twice a month when the lunar and solar tides correspond. -Spring tides occur when the Sun, Moon, and Earth are all located in a line (i.e. at syzygy), occurring at new or full Moon.

Pluto's Discovery

-An analysis of the orbital data of Uranus indicated that 98% of its orbital variation could be accounted for by the presence of Neptune; the remaining unexplained 2% variation led to the search for Planet X. -In 1905 Percival Lowell initiated what would become a successful search for Planet X. Unfortunately, Lowell died in 1916 before Pluto was discovered. -Clyde Tombaugh finally discovered Pluto at the Lowell Observatory in 1930. -Tombaugh used a blink comparator to compare two photos of the sky taken a few days apart. A moving object such as a planet will appear to jump from one spot to another as the observer quickly changes views from the first photograph to the second. -Pluto was discovered 6° from where Lowell had predicted it would be found. -Pluto's mass, however, is too small to cause the irregularities that had been seen in Uranus's orbit. -Later it was shown that these irregularities were not caused by another planet but were variations due to the limited accuracy of the available data. -In conclusion, we now know that Pluto's discovery was an accident, although without Lowell's predictions, the search would not have been pursued so vigorously

Jovian Hot Spots

-Areas in Jupiter's atmosphere relatively free of clouds -Heat can escape from deeper areas in the atmosphere without much absorption -Thought to be areas of downdrafts or possibly associated with planetary scale waves.

Kirkwood's Gaps

-Asteroids are not evenly distributed across the asteroid belt. -At certain distances, for example, 2.5 and 3.28 AU, gaps appear which are related, respectively, to 1/3 and 1/2 of Jupiter's orbital period. -These gaps, also called Kirkwood's Gaps, are due to synchronous tugs from Jupiter on the asteroids which used to be located there. -There are gaps that also appear corresponding to 2/5 and 3/5 of Jupiter's orbital period, which are additional examples Kirkwood's Gaps.

A Former Moon of Neptune?

-Because Pluto is small and has an eccentric orbit, some theorize that it a former moon of Neptune that was somehow ejected. -The discovery of Charon made it seem less likely that Pluto was once Neptune's moon. However, Charon's density of 1.2-1.3 g/cm3—or less than Pluto's density—points to its possible capture by Pluto, so it could have been captured after Pluto left Neptune. -We really do not know how Pluto originated.

Galilean Moons: Callisto

-Callisto, the outermost Galilean moon, shows more cratering, has the least active surface, & experiences little tidal heating. -Callisto has the largest known impact crater—Valhalla— in the solar system.

Pluto's Moon: Charon

-Charon's orbit is tilted at 61° to Pluto's orbit around the Sun. -Charon orbits Pluto every 6.4 days, the same as Pluto's rotation. -Charon's diameter is about 1,200 km. -Pluto's mass is about 12 times Charon's, but only 1/5 of our Moon's. -In 2005, Pluto was recently discovered to have two additional moons, so its total in now three.

What is the Fate of Comets?

-Comets eventually "die" -through gradual evaporation of their nuclei -through evaporation of all their volatile materials, leaving chunks of rock -by falling into the Sun

Mars's Surface Features

-Dark markings were observed as early as 1660, and Mars's rotation rate was determined from their motion. -Changes in the dark areas on Mars led to speculation that there is vegetation on the planet that changes color in response to seasonal growth; but in fact they are spring winds stripping lighter- colored dust grains from the dark under-lying surface. - Mars shows evidence of two water polar caps. which are mostly carbon dioxide - We see seasons on Mars as we do on Earth, but each Martian season is almost six months. - Seasonal shifts in temperature in the southern hemisphere is greater than in the northern hemisphere - Mar's surface was seen to be populated with craters, large volcanoes, and canyons - northern hemisphere is made up of largely rolling volcanic planes. - southern hemisphere is made up of highlands

Jupiter's Density

-Density (r) = Mass (M) / Volume (V) -Jupiter's density is 1.3 gm/cm3, or only 1/4 the mean density of the Earth. -Its low density means that Jupiter is composed of a higher percentage of light elements such as hydrogen and helium than are the terrestrial planets

Earth's Crust Composition

-Earth's crust is composed of a variety of rocks that can be further broken down into minerals -minerals are solid chemical compounds that occur naturally, and that can be separated mechanically for other minerals that make up a rock -composition is determined by chemical processing that occurred in the primordial solar nebula and in the past/present Earth's interior

Saturn's Moons: Enceladus

-Enceladus is surprisingly active for such a small body - likely a consequence of tidal heating -If Enceladus has an ocean, then it contains all of the 'ingredients' known to be important for life: liquid water, molecular building blocks, and energy -The plumes seen above Enceladus' edge over its south polar region are believed to be geysers erupting. -NASA's Cassini spacecraft has observed plumes of material escaping from Saturn's small icy moon, Enceladus -The plume is mostly water vapor, with tiny ice particles and other gaseous molecules mixed in (e.g. CO2, CH4, C2H6) -The plume supplies ice particles to one of Saturn's rings -Some ice particles contain salt, which may indicate they originate in an ocean deep below the icy crust -Plumes may be material escaping through surface cracks from an internal salty ocean or lake -Alternatively, ice along cracks may sublime or melt, followed by escape of water vapor and icy particles -Many scientists find the salty ocean model most convincing, but others favor combinations of alternative explanations -maybe a source of water and oxygen in Saturn's system

Galilean Moons: Europa

-Europa's surface is ice; its moderate density indicates a rocky world covered by an ocean of frozen and possibly also liquid water. -Europa also experiences some tidal heating. -Europa is now the subject of great interest due to the possibility of life in its ocean, since its ice flows show evidence of motion. -Galileo probe suggests that Europa has induced magnetic field reversing every 5 1/2 hours.

Uranus's Moons

-Five moons were known before the Voyager 2 mission; now 22 more (for a total of 27) are known. All are low-density, icy worlds. -The innermost, Miranda, is perhaps the strangest looking object in the solar system. - It appears as if it were torn apart by a great collision and then re-assembled. Two of Uranus's moons are so-called shepherd moons.

Galilean Moons: Ganymede

-Ganymede—larger than Mercury —is the largest moon in the solar system. -Ganymede exhibits a less active, darker surface than Io or Europa - more craters -Grooved terrain may have been caused by plate tectonics -There is some evidence that Ganymede generates its own magnetic field as well

Where Do Comets Come From?

-However, most comets approach us from far beyond the orbits of the planets -comets come from Oort Cloud (10,000 and 100,000 AU from the Sun)

Mars's Channels

-In 1887 Giovanni Schiaparelli's drawing of channels or canali on Mars was misinterpreted by the public to mean canals dug by a race of intelligent beings. -Percival Lowell, who opened his observatory in Flagstaff, AZ, in 1894, reported he saw many canals. Other astronomers could not confirm his findings. -The Mariner spacecraft of the late '60s and early '70s returned images that ended the speculation about canals. - Mar's surface is populated with craters, large volcanoes, and canyons

Pluto's Reclassification as a Dwarf Planet

-In 2006, Pluto was reclassified as a dwarf planet. -One of many Kuiper Belt objects. -Discovery of more than 1300 trans-Neptunian objects - Discovery of Eris provided KBO larger than Pluto -KBO objects similar to Pluto in composition -Definition of planet changed to: "A body that orbits the Sun, is massive enough for its gravity to make it round, and has cleared its neighborhood of smaller objects around its orbit" -These objects above now considered "plutoids" -Eris is a large icy object orbiting in the outer solar system. It was originally thought likely to be larger and more massive than Pluto. -A recent measurement of the size of Eris using a more accurate method shows that it is approximately the same size as Pluto -The recent measurements took advantage of a stellar occultation - an event where -Eris passed between Earth and a distant star. - Eris therefore casts a 'shadow' in starlight on Earth. -Observers at different locations on Earth were in shadow (saw the star disappear behind Eris) for different periods of time, allowing scientists to figure out the size of the dwarf planet -The improved measurements of Eris' size allow scientists to infer its reflectivity (very bright) and density (larger than Pluto's). -Knowledge of these properties enable us to infer much about what Eris is like inside and on the surface. -Classification of solar system objects is not as important as understanding them. The new observations of Eris provide better constraints for those seeking to understand how it formed and evolved.

Jupiter's Excess Energy Output

-Jupiter emits more energy (about twice as much) than it receives from the Sun. -Jupiter would have to be 100 times more massive to support nuclear fusion, so it cannot act like a miniature star. -It is thought that Jupiter's excess energy is left over from its formation; because of its great size, Jupiter is also cooling very slowly and it may also be contracting.

Jupiter's Differential Rotation

-Jupiter exhibits differential rotation—the rotation of an object in which different parts have different periods of rotation. -The differential rotation of Jupiter's cloud bands leads to swirling at the boundaries. -On Jupiter cloud bands near the equator rotate slightly faster (9h50m) than bands near the poles (9h56m).

The Great Red Spot

-Jupiter has a large red oval in its atmosphere known as the Great Red Spot. -The German Samuel Schwabe first noted the same spot we see today in 1831. -The Great Red Spot is 40,000 km long and 15,000 km across, or larger than the 13,000-km diameter Earth. -The red spot is a high-pressure storm system that rotates counterclockwise with a period of 6 days.

Jupiter's Mass and Diameter

-Jupiter is 318 times more massive than the Earth. -Jupiter has more than twice the mass of the other planets, their moons, and the asteroids. -Jupiter's diameter is 11 times that of the Earth, hence its volume is 1,300 times Earth's. -Jupiter's equatorial diameter is 6% greater than its polar diameter.

Jupiter's Location

-Jupiter is 5.2 AU from the Sun and takes 12 years to complete one orbit of the Sun.

Jupiter's Spin

-Jupiter spins on its axis very quickly, once every 9h50m. -Jovian planets have much greater rotation rates than do terrestrial planets.

Jupiter's Structure and Magnetic Field

-Jupiter's core, if it exists, is relatively small, contributing only 1% of the planet's mass. -Jupiter's magnetic field is quite strong— nearly 20,000 times stronger than Earth's. -Jupiter's magnetic field is generated by its large mass of liquid metal hydrogen and by its rapid rotation rate. -Jupiter's magnetic field deflects the solar wind around the planet as well as trapping charged particles of the wind in belts. -Jupiter's magnetosphere—the volume of space in which the motion of charged particles is controlled by the magnetic field of the planet rather than by the solar wind —extends 15 million km from Jupiter and envelopes most of its satellites.

Light and Dark Areas

-Light areas (the zones) are high-pressure regions of rising gas -dark areas (the belts) are low-pressure regions of falling gas. - the zones and belts vary in both latitude and intensity during the year, but the general patter is always present. - these variations appear to be the result of convection motion in the planets atmosphere. - The zones lie above upward-moving convection current, while the belts are the downward part of the cycle, where material is generally sinking.

Mercury's Magnetic Field

-Mariner 10 did detect a magnetic field on Mercury, but it is only about 1% as strong as is the Earth's. -Mercury's magnetic field suggests that part of its metallic core must be molten in order for the dynamo effect to operate. -Recent measurements of heat loss indicate that its core is not molten, but this question is still open. -On the other hand, in spite of the relatively large and possibly molten iron core, the field is very weak. -This must be due to the relatively slow rotation rate (59 Earth days) of Mercury.

Mars's Moons

-Mars has two small moons: Phobos and Deimos; both are shaped like potatoes, very dark surfaces. - they both appear to be captured asteroids and orbit very close to the martian surface.

Mars's Visibility

-Mars is the only planet with surface features that can be seen from Earth. -Mars's surface visibility varies greatly, depending on its distance from Earth and the presence (or absence) of dust storms.

Mars's Orbit

-Mars orbits the Sun at an average of 1.524 AU (about 228 million km). -Mars's orbit is more eccentric than Earth's, so Mars's distance from the Sun varies from 210 million km to 250 million km. -Mars takes 1.88 Earth years to complete its orbit around the Sun.

Mars's Atmosphere

-Mars's atmosphere is extremely thin, with a surface pressure about 1/200 of Earth's. -Mars has the thinnest of the atmospheres of the three terrestrial planets. - Near the Martian equator, noontime soil temperatures can reach as high as 20°C (68°F). -At night the temperature drops to <140°C (<220°F). -Mars' thin atmosphere just cannot retain infrared radiation (heat). - Mars' escape velocity is 5 km/s, less than 1/2 of Earth's. -Though Mars is colder than Earth, its lower escape velocity and lack of ozone layer has allowed water vapor (which is broken up by UV radiation) as well as methane and ammonia to escape. -As the water vapor was broken up by UV, the hydrogen escaped and the oxygen reacted with the iron-rich crust to form rust—giving Mars its characteristic red color.

Mercury's Orbital Period

-Mercury circles the Sun in 88 days, moving at 48 km/s along its orbit. - except for Pluto, Mercury has the most eccentric orbit, varying between 47 and 71 million km distance from the Sun.

Mercury's Atmosphere

-Mercury does not exhibit much of an atmosphere, but does have an exosphere as a result of interaction between solar particles and its surface - its exosphere- the outermost region of planet's atmosphere- is escape region - this is due to the high temperature and low gravity. - the exosphere contains a variable collection of H, He, O, Na, Ca, K, H2) molecules and ions. - there are large variations in temperature.

Craters: Moon

-Most craters on the Moon are the result of impacts by meteorites—an interplanetary chunk of matter that has struck a planet or moon. -The moon has no atmosphere to protect it from meteorite impacts; craters therefore remain intact and visible for billions of years (unlike earth) -Giant impacts near the end of the cratering formed the maria as heated lava escaped from the lunar interior. -After the cratering ended, the Moon's interior became hot for a second time due to radioactive decay and molten lava flowed. These flows ended about 3.1 billion years ago. -The Moon has probably remained relatively unchanged since then. -Micrometeorites (tiny meteorites) still hit the Moon, but only one small, new crater has been possibly been observed to form on the lunar surface since we have been studying it. - tiny meteorites that do not create craters on the Moon after hitting it.

Comet Halley

-Most famous comet is Comet Halley, which appears every 75-76 years, documented since 3rd century B.C. -Last appeared in 1986. -The comet travels between the orbits of Mercury & Venus at its closest point to the Sun, extending out near the orbit of Pluto at its furthest from the Sun in a retrograde orbit. -Large inclination, rising 17° above the ecliptic. -The nucleus of Comet Halley is made up of a mixture of ice and dust surrounded by an ice mantle and covered with a dark crust. -Material is ejected as comet is heated by Sun.

Neptune's Composition

-Neptune's composition matches that of Uranus. -Neptune's color is much bluer than is Uranus.

What is the Cause of Jupiter's Colors?

-None of the gases in the atmosphere can account for Jupiter's coloration. - Scientists think that a complex chemical processes occurring in Jupiter's turbulent atmosphere are responsible for these colors, although the details are not fully understood. - The trace elements sulfur and phosphorus may play important roles in influencing the cloud colors- particularly the reds, browns, and yellows. -The energy that powers the reactions comes in many forms: the planet's own internal heat, solar ultraviolet radiation, aurorae in the planet's magnetosphere, and lightning discharges within the white clouds.

Buried Carbonates on Mars

-Observations from the center of one Martian crater show carbonate rocks (containing CO3), which have been detected only in restricted areas elsewhere on Mars -The most likely explanation implies the carbonates formed in an ancient body of water in contact with Mars' carbon dioxide (CO2) atmosphere

Neptune's Magnetic Field

-On average, Neptune's magnetic field rotates more rapidly than its atmosphere. -Neptune's magnetic field rotates with a period of 16h3m, which is taken as the planet's basic rotation rate.

Doppler Method

-One method of identifying planets around other stars is using the Doppler Method. -Stars exhibiting a discernable wobble can be evidence of an unseen companion— such as a large planet or group of planets. -Since 1995, this Doppler method has found evidence of more than 370 planets orbiting stars such as 51 Pegasi, 70 Virginis, and 47 Ursae Majoris.

Transit Method

-Other planets can be identified using the transit method -As the planet passes between the star and Earth, light is reduced. -The periodic nature of this attenuation produces a positive identification. -Combining with doppler data allows a determination of size and mass, yielding density. -Only very few exoplanets can be discovered this way because orbit must be almost exactly edge-on.

Why does Titan have a nitrogen dioxide atmosphere?

-Reducing atmospheres typically have nitrogen in the form of ammonia (NH3) -How did Titan come to have so much nitrogen gas (N2)? -bombardment by icy planetesimals -shock-induced conversion from NH3 to N2 -photolytic conversion in presence of CH4, H2O

Saturn's Moons

-Saturn has 62 moons - most of them appear to be captured asteroids -Most inner moons have low density - similar to water ice -Primary moons of Saturn are Titan & Enceladus

Saturn's Tilt

-Saturn is tilted 27° with respect to its orbital plane, so over time its rings appear in different orientations when viewed from Earth.

Saturn's Orbit

-Saturn orbits the Sun at 9.5 AU; its distance from the Earth varies from 8.5 AU to 10.5 AU. -Saturn has an orbital period of 29.5 years.

Saturn's Radiation of Energy

-Saturn radiates more heat than it absorbs -at the temperature and high pressures found in Jupiter's interior, liquid helium dissolves in liquid hydrogen. -In Saturn, where the internal temperature is lower, the helium doesn't dissolve so easily and tends to form droplets instead. - Saturn probably started out with a fairly uniform mix of hydrogen and helium, but the helium tended to condense of the surrounding hydrogen, much as water vapor condenses out of Earth's atmosphere to form a mist. - The amount of helium condensation was greatest in the planet's outer cool layers, where the mist turned to rain. - A light shower of liquid helium has been falling through Saturn's atmosphere ever since. - This helium precipitation is responsible for depleting the outer layers of their helium content. - As the helium sinks toward the center, the planet's gravitational field compresses it and heats it up. - The energy thus released is the source of Saturn's internal heating.

Saturn's Atmosphere

-Saturn's cloud tops have a temperature of 95 K. -Saturn's clouds are less colorful than Jupiter's because the colder temperatures at Saturn's distance from the Sun inhibit some of the photochemical reactions that give Jupiter's atmosphere its varied colors, and a layer of methane haze above the cloud tops on Saturn further blurs out the possible color differences. -Vortex motion of Saturn cyclones at the South Pole. - Hexagonal features at Saturn's North Pole -Saturn has atmospheric features similar to Jupiter's, but Saturn's winds reach speeds 3 to 4 times faster

Saturn's Magnetic Field

-Saturn's magnetic field is only 5% as strong as Jupiter's because Saturn's liquid metallic hydrogen layer is much thinner than is the same layer at Jupiter. -This means there are fewer charged particles moving around in Saturn's interior. - Core Layers: 1. Molecular Hydrogen/ Liquid Hydrogen 2. Liquid Metallic Hydrogen 3. Ice 4. Rocky core

Periods of Comets

-Short period comets (< 200 years) - Long period comets (> 200 years) - Long-period comets sometimes become short-period comets through the combined gravitational influence of Jupiter or Saturn and the Sun.

Pluto's Atmosphere

-Stellar occultations indicate that Pluto has a methane atmosphere. -At aphelion it is probably too cold for the methane to remain gaseous. -Since Pluto's atmosphere was only discovered shortly before Pluto reached its perihelion point in 1989, that atmosphere may only be temporary. -This is one reason why there was such urgency to launch NASA's Pluto Express mission on a trajectory which will get it there faster than lower-energy trajectory.

Venus: Surface Composition

-Surface composition is similar to Earth's, suggesting that high density must be due to differentiated metallic core. - the surface is shrouded by heavy clouds - Sharp-edged rockes on its surface indicates calm winds. - 2/3 covered with rolling hills, has about 1,000 craters that are larger than a few km in diameter. - it has more craters than the Earth, but fewer than Moon - no craters older than 800 million years old - past evidence of volcanic and tectonic activity: mountains, large lava flows, volcanoes. -highlands occupy less than 10 percent , with lower-lying areas making up the rest. -although there is some indirect evidence of possible recent volcanic and tectonic activity, such as landslides observed by Magellan, Venus may lack tectonic plates because its crust may be too thin to be strong enough to remain in large pieces.

Phoebe Ring

-The "Phoebe ring" is the largest and most distant from its parent body -This ring along with other moons help to "paint" the surface of Iapetus

Craters: Earth

-The Earth has few impact craters which are still visible because the atmosphere keeps all but the largest particles from reaching the surface. -Over time, erosion and tectonic plate movement have erased all but a relative few of the largest craters.

Lithosphere

-The Earth's crust and the outer 40 miles of its mantle comprise the lithosphere, which is broken into about 12 tectonic plates.

Jupiter's Composition

-The Galileo probe showed that Jupiter is about 90% hydrogen, 10% helium, small amounts of water (H2O), methane (CH3), and ammonia (NH3) - Mainly hydrogen -Jupiter's composition is closer to that of the Sun and other stars than it is to Earth. -Jupiter's highest clouds are composed of ammonia crystals, have a temperature of 120 K, and have a pressure at the top of the clouds of 70% of the pressure found at the Earth's surface. -A lower, warmer (220 K) cloud layer is visible through gaps in the upper layer. -Models of Jupiter's atmosphere predict that at a depth of 60-80 km, the temperature is Earth-like & the pressure is 10 times Earth's surface. -Colors seen in Jupiter's upper atmosphere are likely due to photochemical reactions induced by sunlight and/or lightning in its atmosphere.

Roche Limit

-The Roche limit is the minimum radius at which a satellite (held together by gravitational forces) may orbit without being broken apart by tidal forces. -Saturn's rings are inside Saturn's Roche limit, so no moons can form from the particles. -All ring particles would form a small moon about the mass of Janus.

1. Crust

-The crust is the thin (<100 km) outermost layer of the Earth. -It is rocky and has a density ranging between 2.5 and 3 g/cm3

High Tides

-The differential gravitational pull of the Moon on the various parts of the Earth results in two high tides located on opposite sides of the Earth. -On the side of the Earth that is nearest to the Moon, the water and the rock feel a greater force and they both flow to the area underneath the Moon, causing a high tide in the both the ocean and in the Earth there. -High tide on the opposite side of the Earth occurs because center of the Earth feels a greater force toward the Moon than either the water or the rock on the far side - main body of the Earth is pulled away from the water and rock on far side, resulting in another high tide. This high tide is located exactly opposite the first one. -This tide occurs not as the Earth rotates on its axis, the Moon also revolves around the Earth. Because the Moon is not stationary, the Earth must turn for about its axis for an additional 50 minutes each day before a spot on the Earth's surface returns to the same position with respect to the Moon. This is what causes the high tides and the rising and setting of the Moon to occur about 50 minutes later each day. -The Earth's rotational motion tends to drag the tides along with it, so that a high tide is not located directly underneath the Moon, but is instead located slightly farther to the east of the line from the Earth to the Moon.

Jupiter's Atmospheric Layers

-The gaseous atmosphere on Jupiter is a few thousand miles thick. -As one goes deeper into Jupiter's atmosphere, the gaseous hydrogen turns into liquid molecular hydrogen. -At 15,000 km below the clouds, it is theorized that the pressure and temperature create a state of liquid metallic hydrogen. -water ice -ammonium hydrosulfide ice -ammonia ice -ionosphere -haze layer -stratosphere

4. Inner Core

-The inner core is the centermost portion. - It ranges in density up to 13 g/cm3 and is mainly composed of solid iron and nickel.

2. Mantle

-The mantle is the thick (2,900 km), solid layer between the crust and the Earth's core. -The density of the mantle is 3-9 g/cm3. -The crust sits on top of the mantle.

The Nature of Meteorites Found on Earth

-The most prominent impact crater on Earth is Meteor Crater near Winslow, Arizona. -Other large circular features have been more eroded than this crater but are also thought to have been created by meteorite impacts. -The meteorite that formed Meteor Crater is estimated to have had a total mass of 300 million tons and to have been about 45 m across. -It struck about 25,000 years ago at a speed of about 25,000 mph. -Tunguska event was a blast likely equal to the power of 10-15 megatons of TNT, knocking down 80 million trees over a 2000 km2 area.

Theories of Ring Formation

-The origin of Saturn's rings is not well understood but is thought to be the result of a close-orbiting, icy moon that was shattered by a collision with a passing asteroid. -Tidal forces are greater on a moon in orbit close to a planet than they are on a moon in an orbit farther out. -Alternatively, the rings could have been formed when a comet or an asteroid passed too close to Saturn and it was pulled apart by the tidal force of the planet acting on that comet or asteroid. -Finally, the rings might also be due to material which was too close to the planet to ever form a moon in the first place.

3. Outer Core

-The outer core is the next part of the Earth. -It is composed of liquid metals. -It is about 1800 km (1100 miles) in thickness.

Saturn's Rings

-The rings were discovered in 1655 by Christian Huygens. -Later Cassini discovered the famous gap between two groups of the rings. -Saturn's rings are very thin, in some cases less than 100 meters across. -The rings are not solid sheets but are made up of small particles of water ice or rock coated with ice. -Each ring particle revolves around Saturn according to Kepler's laws. -Ground-based images showed 3 rings which were named (outer to inner) A, B, C. -Actually, we now know from spacecraft images that there are more than 1000 rings -The largest division between some of the rings is known as Cassini's division. -This space is caused largely by the gravity of Mimas acting synchronously on the orbital path of nearby ring particles. -Other ring features are explained by the presence of small shepherd moons ( small moons that orbit near the edges or between rings) - Saturns rings change throughout orbit from the perspective of the Earth

Mercury: Core

-The surface rocks look similar to Earth's. -Mercury must have a relatively large iron core, perhaps 65%-75% of its total mass. -Astronomers speculate that early in the history of the solar system a collision with a large asteroid blasted away most of Mercury's rocky mantle. -large planetary density

Parts of Comets: Tail

-The tail of a comet is the gas and/or dust that is swept away from a comet's head. -All comets have a straight gas, or ionic, tail; some comets also have a curved dust tail. -Comets tail is most pronounced when the comet is closest to the Sun. -A comet's tail always points away from the Sun. -After passing the Sun, a comet's tail actually leads the head. -Comet tails are typically 107 to 108 km long and may be as much as 1 AU long.

Neptune's Moons: Triton

-Triton, Neptune's largest moon, is the only major moon to revolve around a planet in a clockwise (retrograde) direction with an inclination of 20°. -This orbital direction is unstable and Triton will crash onto Neptune in the future -Triton has a light-colored surface composed of water ice with some nitrogen and methane frost. - Its surface appears young, with few craters but with active geyser-type nitrogen volcanoes observed, probably supplying thin atmosphere. -Triton's surface resembles a cantaloupe's. -Triton has a density of 1.76 g/cm3, Tsurf = 37 K. -Triton's active volcanism is probably due to internal heating from tidal forces caused by Neptune's gravity

Neptune's Weather

-Unlike the nearly featureless Uranus, Neptune exhibits weather patterns in its atmosphere. -Great Dark Spot on Neptune, similar in appearance to Jupiter's Great Red Spot. -In 1994, astronomers using the Hubble Space Telescope could find no trace of Neptune's dark spot, which seems to have disappeared. -Neptune's winds—driven by the internal heat—reach speeds of 700 mph. -Wispy white clouds seen on Neptune are thought to be crystals of methane. -Neptune exhibits the most extreme differential rotation of the planets:12 hours at the equator and 18 hours at the poles.

Uranus's Temperature and Cloud Bands

-Uranus has a fairly uniform temperature over its surface: -200°C. -Uranus has cloud bands that rotate differentially—16 hours at the equator and 28 hours at the poles.

Uranus's Rings

-Uranus has a system of 10 thin rings that contain very little material. -These rings were first discovered using ground-based stellar occultation studies. -Their existence was later confirmed by Voyager 2. -Uranus's rings only reflect 5% of the sunlight that hits them so they cannot be seen from Earth. (Saturn's rings reflect 80% of incident sunlight.)

Uranus's Atmosphere

-Uranus's atmosphere is similar to Jupiter and Saturn: mostly hydrogen and helium with some methane. -Uranus does not have thick cloud layers, so the methane in its atmosphere, which absorbs red light, makes the planet appear blueish-green. -Less methane than Neptune - less blue. -Uranus, like Jupiter and Saturn, is 3/4 hydrogen and the remainder helium with some methane.

Uranus's Diameter

-Uranus's diameter is difficult to determine from Earth because its angular size is very small and it can't be seen clearly -An improved determination of Uranus's diameter was made in 1977 during an occultation of a star by the planet.

Uranus's Equatorial Plane

-Uranus's equatorial plane is tilted nearly 90 degrees to its plane of revolution. -Its obliquity is 98 degrees. -This means that its north pole is located below the ecliptic plane. -One of Uranus' poles is currently facing the Sun. In 42 years its other pole will be facing the Sun instead. -This in turn means that Uranus is rotating in the backward, or retrograde, direction.

Uranus's Magnetic Field

-Uranus's magnetic field is comparable to Saturn's. -The magnetic field's axis is tilted 60° with respect to its rotation axis. -No other planet has such a large angle between the two axes (though Neptune's at 46° is close).

Uranus

-Uranus, though barely visible to the naked eye, was unknown by the ancients. -Plotted on star charts as early as 1690, Uranus's slow orbital motion caused it to go unnoticed until Sir William Herschel discovered it in 1781.

Venus's Rotational Period

-Venus has a retrograde motion, meaning it rotates clockwise. - this could be a result of a large collision during the formation or number of collisions during accretion. -its rotational period is 243 sidereal days.

The Atmosphere of Venus

-Venus's atmosphere is composed of 96% carbon dioxide (CO2), 3.5% nitrogen (N2), and small amounts of water (H2O), sulfuric acid (H2SO4), and hydrochloric acid (HCl). - Venus's atmosphere is primarily carbon dioxide. -The upper atmosphere is very windy; wind speeds reach 350 km/hr (225 mi/hr). 4-5 day circulation at cloud tops (60x rotation of surface) -As one descends to Venus's surface, the wind speed decreases to almost zero. -Mechanism for this superrotation is not well understood -The atmospheric pressure on Venus's surface is about 90 times that found at the Earth's surface - equivalent 1 km underwater on Earth. -Surface temperature of Venus has been measured at about 460°C (860°F). -Venus's clouds form a layer between altitudes of 50 and 70 km down to 30 km.

Run-Away Greenhouse Effect on Venus

-Venus's higher surface temperature (due to its formation somewhat closer to the Sun) created a run-away greenhouse effect. -Being closer to the Sun, our planet would warm up. -More water would evaporate from the oceans, leading to an increase in atmospheric water vapor. - Because of the ability of both the oceans and surface rocks to hold carbon dioxide diminishes with increasing temperature, more carbon dioxide would enter the atmosphere. -The additional greenhouse heating would warm our planet still further increase in atmospheric greenhouse gases, and so on. - This runaway greenhouse effect would eventually lead to the complete evaporation of the oceans, restoring all the original greenhouse gases to the atmosphere. -Finally an equilibrium was reached between the infrared radiation reflected back from the clouds and that reemitted into space.

Jupiter's Rings

-Voyager I discovered a thin ring around Jupiter. -That ring is close to Jupiter, being located only about 1.8 planetary radii away. -More recently two other rings have been detected, so that Jupiter now has a total of three rings. -The rings are now known to be replenished from the small moonlets located near them

Tectonic Activity on Mars

-While gigantic size of Olympus Mons suggests absence of tectonic plates on Mars, recent measurements of its surface magnetic field indicate a striped pattern similar to that of the earth's magnetic field near the Mid-Atlantic Ridge. -Since these stripes in the geomagnetic field are due to tectonic activity, these recent Martian observations suggest possible tectonic activity there as well. -Mars may lack tectonic plates because it cooled quickly, leaving its crust too thick and strong to be broken into pieces.

Comets

-While only faint, fuzzy patches of light when far away, some grow an spectacular tail when approaching the Sun. -Comets typically have very eccentric orbits, which makes them visible for only a short period of time. -No visible light of their own

Meteor

-a meteor is the phenomenon of a streak in the sky which results when a dust-grain sized or a pebble-sized meteoroid is heated up by its passage through the Earth's atmosphere. -the heated material heats up the atmosphere until a trail of glowing material can be seen from the ground, the brightest of which are called fireballs. -meteors are what meteoroids entering Earth's atmosphere are called

Ozone Layer

-about 50 km above the surface is the ozone layer, which is an efficient absorber of UV radiation from the Sun. -this absorption of solar UV light causes the temperature to peak at the height of the ozone layer. -it is the ozone layer that has protected life on Earth for billions of years, by absorbing potentially dangerous high-frequency radiation, it acts as a planetary umbrella. -the release of chlorofluorocarbons during the 20th century has reduced the amount of ozone (through molecular interactions) available to protect us- ozone hole.

Stratosphere

-above the troposphere, extending up to an altitude of 40-50 km, lies the stratosphere. - the Ozone layer is located within the stratosphere.

A Successful Theory Must Be Able to Explain:

-all the planets revolve around the Sun in the same direction, and all planetary orbits are nearly circular (except for Mercury and Pluto). -all of the planets lie in nearly the same plane of revolution: eastward -most of the planets rotate in the same direction as they orbit the Sun counterclockwise, except for Venus, Uranus, and Pluto, which rotate in the retrograde, or clockwise, direction. -the majority of planetary satellites revolve around their parent planet in the same direction as the planets revolve around the Sun. -there is a pattern of spacing of the planets as one moves out from the Sun with each planet being about twice as from the Sun as the previous one - Titius-Bode's Law. -similarities of chemical composition exist among the planets, but there are also differences. -the outer planets contain more volatile elements and are less dense than the inner. -all of the planets and moons that have a solid surface show evidence of craters. -all of the Jovian planets have ring systems. -the asteroids, comets, and meteoroids populate the system along with the planets, and each category of objects has its own pattern of motion and location. -the planets have more total angular momentum than does the Sun, even though the Sun has most of the mass. -recent evidence indicates that planetary systems in various stages of development may exist around other stars.

Solar System Debris

-asteroids and comets provide a way to peer into the origins of the solar system -most of the other objects in the solar system can be classified as debris— an accumulation of rock fragments. -solar system debris comes in a number of forms, including asteroids, meteoroids, comets, and dust.

Evolution Throughout Orbit

-during most of the comets orbit, far from the sun, only its frozen nucleus exits. -but if a comet comes within a few astronomical units of the sun, its icy surface becomes too warm to remain stable. - Part of it becomes gaseous and expands into space forming a diffuse coma (halo) of dust and evaporated gas around the nucleus. -the comes gets larger and brighter as the comet nears the sun.

Greenhouse effect

-eventually our planet should radiate as much energy back as it receives from the Sun, without any complications. - there is a complication, however. - long-wavelength infrared radiation is partially blocked by Earth's atmosphere, mainly because of carbon dioxide and water vapor, both of which absorb very efficiently in the infrared portion of the spectrum. -even though these two gases account only for a tiny fraction of our atmosphere, they manage to absorb a large fraction of all the infrared radiation emitted from the surface. -consequently only some of that radiation escapes back into space. -the rest is radiated back to the surface, causing the temperature to rise. -the name comes about because a similar process operates in a greenhouse- the sunlight passes relatively unhindered through glass panes, but much of the infrared radiation reemitted by the planets is blocked by the glass and cannot get out. -consequently the interior of the greenhouse heats up.

Mercury's Temperatures

-high temperatures on Mercury can reach 450°C (842°F), or well above the melting point of lead (330°C or 626°F). -on the night-side of Mercury, temperatures can fall to -150°C (-250°F). - it is a lot hotter than Earth on the side facing the Sun because it s a lot closer to the Sun, plus it does not have an permanent atmosphere.

Outgassing: Earth's Atmosphere

-in outgassing vents and volcanoes allowed heated gases to escape from the rock of the mantle and crust (i.e. from Earth's interior). -the most important gas which was outgassed was water vapor, or steam, since this water vapor went into the early atmosphere where it eventually condensed into liquid form and rained down to become the oceans. -the second-most important gas to outgas was CO2 which combined with the surface rocks to form carbonate minerals. -the third-most important gas to outgas during this epoch was nitrogen. -a fourth significant gas to outgas was argon. Argon was important because it is a product of certain radioactive decays and hence its relative abundance has helped us to date the Earth.

Irons

-iron meteorites that are made up of 80%-90% iron (with some nickel).

Ida

-is a S-type asteroid that has a moon of its own, called Dactyl. -Galileo probe visited S-type asteroids Gaspra and Ida

Meteoroid

-is any piece of interplanetary matter that is smaller than an asteroid. - chunk of interplanetary debris prior to encountering Earth's atmosphere.

Tidal Bulge

-is elongation of earth caused by the difference between the gravitational force on the side nearest the Moon and the force on the side farthest from the Moon. - the long axis of the tidal bulge points toward the Moon. - More generally, the deformation of the any body produced by the tidal effect of a nearby gravitating object.

Occultation

-is the passing of one astronomical object in front of another. -the light from the distant object is dimmed when the closer object passes in front.

Meteor Shower

-is the phenomenon of a large group of meteors seeming to come from a particular area of the celestial sphere. - is an event during which many meteors can be seen each hour, caused by the yearly passage of the Earth through the debris spread along the orbit of a comet.

Plate Tectonics

-is the study of the motions of the Earth's plates across the underlying mantle. -the tectonic plates extend inward by about 50 to 100 km (i.e. 30 to 60 mi).

Uranus's Core

-its core is made up of molecular hydrogen, ice, and rock; it does not have metallic hydrogen -Pressures are not great enough for metallic hydrogen on Uranus/Neptune -"Slush" likely makes up deep interior -Density suggests larger core

Volcanic Features on Venus

-many areas of Venus have volcanic features. - lava domes formed when lava oozed out of the surface, formed the dome, then withdrew, leaving the crust the crack and subside. - lava domes such as these are found in several locations on Venus. - the most common volcanoes on the planet are the type known as shield volcanoes. -those on Earth are associated with lava welling up through a "hot spot" in the crust. -they are built up over long periods of time by successive eruptions and lava flows. - a characteristic of a shield volcano is the formation or a caldera, at the summit when the underlying lava withdraws and the surface collapses. - the larges volcanic structures on Venus are huge, roughly circular regions know as coronae. -Coronae are unique to Venus. - they appear to be the result of upwelling motions in the mantle that caused the surface to bulge outward, but never developed into full-fledged convection as on Earth. - Coronae generally have both volcanoes both in and around them, and their rims usually show evidence of extensive lava flows in the plains below. - there is indirect evidence that suggests that volcanism continues on Venus.

Venus: Magnetic Field

-no magnetic field has been detected for Venus - slow rotation - though it should have one that is detectable. -could be the result of reversing of magnetic field

Continental Drift: Alfred Wegener

-over millions of years, these moving plates— often crashing into one another—have caused the continents to "drift," mountains to be uplifted, ocean trenches to be formed, and earthquakes to occur. -also, chains of volcanoes are found to lie above the subduction zones as in the Western U.S.

Mercury's Rotation Period

-radar observations show that Mercury rotates once very 58.65 Earth days, which is precisely 2/3 of its orbital period. This is another example of spin-orbit coupling. -Mercury's unusual coupled rotation period and revolution period are probably due to the unbalanced nature of its mass. -it is suggested that the object that created the Caloris Basin was very dense, and its presence under Mercury's surface has caused the planet to be lopsided, which ultimately led to the coupling of its periods of rotation and revolution.

Mercury: High Albedo

-recent radar observations show a high albedo for Mercury's polar regions, suggesting the presence of ice. - yet ice should have evaporated over the ages. -how ice could remain for so long remains a mystery.

Stones

-stony meteorites that can contain flakes of iron and nickel.

Magnetic Field

-the Earth's magnetic field is now thought to originate in its liquid outer core. -earth's magnetic poles are not located at its poles of rotation. -rather, the magnetic axis is tipped by about 13 degrees. -also, the location of the magnetic poles changes with time. -the magnetic field lines, which indicate the strength and direction of the field at any point in space, run from south to north.

Moon's Magnetic Field

-the Moon's weak magnetic field—10-4 times that of Earth's magnetic field— suggests the presence of such a small iron core, although this has not been confirmed.

Aurorae

-the aurorae result from disturbances in the Earth's magnetic field which cause some of the particles to follow the magnetic field lines down into the atmosphere, where their collisions with atoms cause the air to glow in patterns of different colors.

Formation of the Moon: Capture Theory

-the capture theory, proposed early in the 20th century, holds that the Moon was originally solar system debris that was captured by the Earth's gravitational field. -dynamically, a third object is required for capture, and the chance of this happening with the Moon and Earth is remote at best.

Coma

-the coma is the part of a comet's head made up of a diffuse cloud of gas and dust. -solar wind causes coma to turn into a tail pointing away from the sun

Lunar Crust

-the crust of the Moon ranges in depth from 60-100 km. -it is thinner on the side facing the Earth than it is on the lunar far side.

Earth's Atmosphere

-the density of the Earth's atmosphere decreases with increasing height. -the Earth's atmosphere consists of about 80% nitrogen (N2), 20% oxygen (O2), with minor amounts of water vapor (H2O), carbon dioxide (CO2), argon (Ar), and trace amounts of ozone (O3). -we do not think that the early atmosphere contained any free oxygen, rather we now believe that our current oxygen was created later by plant life using photosynthesis. -has four layers: troposphere, stratosphere, mesosphere, and ionosphere. -the temperature of the Earth's atmosphere generally decreases with increasing height, but in the so-called inversion layers the temperature temporarily increases with increasing height.

Dynamo Effect

-the dynamo effect is the model that explains the Earth's and other planets' magnetic fields as being due to electric currents flowing within molten iron cores.

Differences Between Earth and Venus

-the earth has large quantities of H2O. - on earth most of the carbon dioxide is sequestered as carbonate rock. - on Venus most of the carbon dioxide is in the atmosphere. - on earth sulfur resides in oceans - on Venus there are large quantities of sulfur dioxide - on earth chlorine is in the for of sodium chloride in oceans. - on Venus larges amount of hydrogen chloride.

Formation of the Moon: Fission Hypothesis

-the fission hypothesis proposed that Earth in its early fluid stages rotated so rapidly, that it expelled a large piece of its mass into space, making up a proto-Moon. - the large basin of the Pacific Ocean was proposed to be the place from which the Moon was ejected. -we know today that the age of the oceanic crust is much younger than the age of the Moon. -furthermore, models cannot reproduce this event, accounting for the right combination of properties to produce this result. -the present angular momentum cannot be accounted for.

Radioactive Decay

-the interior of much of the Earth was heated over a period of about 900 million years by the radioactive decay of uranium and other elements. -this source of heat resulted in an interval of extensive volcanic activity. -such volcanic activity was the origin of the Earth's atmosphere through the process of outgassing.

Lunar Maria

-the maria (singular mare) are any of the lowlands of the Moon or Mars that resemble a sea when viewed from Earth. -the lunar maria were named this way by Galileo, who thought they were oceans. -giant impacts near the end of the cratering formed the maria as heated lava escaped from the lunar interior. - lunar maria are darker in color - found mostly on the side facing Earth

Lunar Atmosphere

-the moon's surface gravity is too low for it to have retained a substantial atmosphere. -any massive early atmosphere would have long since evaporated into space. -the solar wind does knock off small numbers of sodium atoms from the lunar surface, but these form only a very low density, temporary atmosphere. -without a permanent atmosphere, the lunar temperatures range from 130 degrees C to -170 degrees C- wide variations in surface temperature. - for all practical purposes, there is none. - the Moon's escape speed is only 2.4 km/s compared with 11.2 km/s for Earth. - simply put, the Moon has a lot less pulling power- any atmosphere it might once have had is gone forever.

Lunar Highlands

-the mountains on the Moon are the result of extensive cratering over eons (i.e., they are not the result of tectonic activity there). - lunar highlands are light in color

Nucleus

-the nucleus of a comet is the solid chunk of a comet, located in the head. -the nucleus of a comet is at most a few kilometers in diameter and is essentially a dirty snowball made up of water ice, frozen carbon dioxide, and small solid grains.

Smallest Meteoroids or Micro-meteorites

-the smallest meteoroids are slowed down at the top of the Earth's atmosphere and are not evaporated during their passage. -these tiny particles are referred to as micro-meteorites and they land on the Earth's surface constantly. - are mainly the rocky remains of broken-up comets. -each time a comet passes near the sun, some fragments dislodge from the main body. - the fragments initially travel in a tightly knit group of dust or pebble-sized object called a meteoroid swarm, moving in nearly the same orbit as the parent comet. - over the course of time, the swarm gradually disperses along the orbit, so that eventually the micrometeoroids, as these small meteoroids are known, to become more or less smoothly spread around the parents comet's orbit.

Ionosphere

-the temperature of the Earth's atmosphere generally decreases with increasing height, but in the so-called inversion layers the temperature temporarily increases with increasing height. -one such inversion layer is in the ionosphere where the upper atmosphere is being ionized by solar UV radiation.

Troposphere

-the troposphere is the lowest level of the Earth's atmosphere, containing 75% of its total mass. It is about 11 km (7 mi) in thickness and is the layer in which our weather occurs. -because the troposphere receives most if its heat as infrared radiation from the ground, the temperature of the troposphere drops with increasing height above the surface.

Convection: Troposphere

-the troposphere is the region where convection occurs. -convection is the constant upwelling of warm air and the concurrent downward flow of cooler air to take its place. -part of the Earth's surface is heated by the Sun. -the air immediately above the warmed surface is heated, expands a little, and becomes less dense. -as a result, it becomes buoyant and starts to rise. -at higher altitudes the opposite effect occurs: the air gradually cools, grows denser, and sinks back to the ground. -the cool air at the surface rushes in to replace the hot, buoyant air that has risen. - in this way, a circulation pattern is established. - these convection cells of rising and falling air contribute to atmospheric heating and are responsible for surface winds and all the weather we experience. -above the troposphere the atmosphere is stable and calm.

Escape Velocity

-theory has shown that a planet will retain a particular gas for billions of years if its escape velocity is about 10x the average speed of that gas -because of their size (and mass) the Jovian planets have retained almost all of their gases.

Low Tides

-there are two low tides each day

Tidal Bulge and Tidal Friction Interaction

-tidal bulge raised in Earth by the Moon does not point directly at the Moon. -instead, because of the effects of friction, the bulge points slightly ahead of the Moon, in the direction of Earth's rotation.

Tidal Friction

-tidal friction is the torque which results from the tidal pull of the Moon on the rotating Earth. -this torque has slowed the Earth's rate of rotation over billions of years. -while this torque is called tidal friction, it is not a true frictional force.

Tides

-tides are a result of the gravitational influence of the Moon and the Sun on the Earth. -the Sun's gravitational attraction also causes tides on the Earth, though the effect of the Sun is small than that of the Moon

Meteoroid Facts

-unlike most asteroids, meteoroids may orbit the Sun in any orientation. -it is thought that many small meteoroids are debris from asteroid collisions. -many other meteors come from material evaporated from a comet's nucleus -most of the major meteor showers are associated with comets. -some showers change in intensity from year to year because the swarm of particles that cause the shower clump together in one region of the comet's orbit.

Inversion Layers

-where the temperature increases with increasing height in the atmosphere. - Example: Ionosphere

Sea Floor Spreading

-where the warm magna that is rising within the mantle reaches the Earth's surface, it must stop flowing vertically and must begin to flow horizontally. -this horizontal motion of the ocean floors is called sea-floor spreading. -because of this spreading Africa and South America have been separating for 150 million years and the oldest sea floor rocks are those near both continents.

Magnetosphere

-while the Earth's magnetic field is thought to originate in its molten outer core, it also extends into space. -the region of interplanetary space surrounding the Earth in which the geomagnetic field dominates the interplanetary magnetic field (which in turn originates in the solar corona) is called the earth's magnetosphere.

Saturn's Density

.69g/cm^3; less dense then earth and has the lowest density of all the Jovian planets

Venus: Solar Day

117 earth days long

Curved Tail

A curved tail is caused by dust in the coma being pushed away by solar radiation pressure.

Rift Zone

A rift zone is a place where tectonic plates are being pushed apart, normally by molten material being forced up out of the mantle.

Three Types of Asteroids

C-type (carbonaceous, dark), S-type (rocky), M-type (metallic)

Martian Climate and Volcanism

Carbonates require liquid water and CO2 to form. The observations reveal the end of a multi-stage process: 1.Carbonates form at the surface in the presence of liquid water, possibly in a denser ancient atmosphere 2.The atmosphere changed and/or liquid surface water disappeared - surface carbonates stopped forming 3.Subsequent volcanic activity buried the carbonates, altering them 4.Impacts exposed the carbonates in some places, including tell-tale signatures of their alteration

Meteorites Are Classified into 3 Categories

Irons, Stones, Stony Irons

Venus's Orbit

Its orbit is almost circular with a sidereal orbital period of 225 days

Jupiter's Oblateness

Jupiter is very oblate, which is caused by its rapid rate of rotation.

Saturn's Rotation Rate

Like Jupiter, Saturn's cloud belts rotate differently; Saturn's rotation rate is 10h39m

Mars's Tilt

Mars's equator is tilted by 25.2° with respect to its orbital plane, close to Earth's 23.4°(i.e., their obliquities are almost identical).

Mars's Rotational Period

Mars's sidereal rotational period is 24h37m; its day is 24h40m long, very similar to that of Earth.

Elongation

Maximum elongation is 28 degrees, the larger the elongation, the easier it is to see and higher it appear in the sky.

Order of Planets

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

Oblateness

Mercury is spherical (zero oblateness)

Neptune's Orbital Period

Neptune has an orbital period of 165 years.

Neptune's Rings

Neptune has thin rings

Neptune's Diameter

Neptune is similar to Uranus, slightly smaller at 49,500 km in diameter.

Internal Heat

Neptune radiates more internal heat than Uranus, although the cause is unknown.

Neptune's Tilt

Neptune's axis is tilted by about 29° to its orbit; so it is similar in obliquity to Saturn.

Neptune's Density

Neptune's greater density (1.6 vs. 1.2 gm/cm3 for Uranus) is probably due to a somewhat larger rocky core.

Neptune's Temperature

Neptune's temperature is remarkably uniform at 55 K at cloud tops.

Pluto's Size

Pluto's atmosphere limits an accurate determination of its size, which is probably between 2,362 km and 2,412 km.

Pluto's Density

Pluto's density is between 1.8 and 2.1gm/cm3.

P-waves

Primary waves are pressure waves, they alternately expand and compress the medium through which they move, that travel through both liquid and solids at 5-6km/s

Saturn's Mass

Saturn is 95 earth masses; 5.685 X 10^26kg

Saturn's Oblateness

Saturn is even more oblate (0.102) than Jupiter, with its equatorial diameter 10% greater than its polar diameter.

S-waves

Secondary waves are shear waves, they travel in a side to side motion, they cannot travel through liquid and they travel at 3-4km/s

Moonquakes

Sensors on the Moon have detected very weak natural moonquakes, which occur only when micrometeorites bombard the Moon or when the Moon is at perigee.

Venus: Tilt

Spin axis tilt of 177 degrees and because the angle is greater than 90 degrees we know that Venus has a retrograde motion.

Moon's Density

The Moon's average density is 3.36 g/cm^3, or about 62 percent of the Earth's density.

Moon's Surface

The Moon's surface can be divided into maria and mountainous, cratered regions.

Basalt

The Moon's surface is covered with two different types of the mineral basalt

Parts of Comets: Head

The head of a comet consists of its coma and nucleus

Convection

The plates are thought to be moved by the phenomenon of convection, in which warm magma rises, moves horizontally, and then falls back inward at the subduction zones.

Straight Tail

The straight tail consists of charged gas molecules or ions - photoelectric effect.

Seasonal Changes

There are also some seasonal changes on the planet

Sizes of Meteoroids

There are three different sizes of meteoroids which produce different objects as they pass through the atmosphere.

Trojan Asteroids

There are two groups of asteroids which are located at Jupiter's distance from the Sun but which are either 60o in front of or behind Jupiter's location at the vertices of equilateral triangles

Density Increases Inwardly

This pattern in which the density increases inwardly is due to the process of chemical differentiation, which was caused by the sinking of denser materials toward the center of the early Earth when the Earth was completely molten.

Surface Features

Unlike terrestrial planets, surface features have little effect on Jupiter's upper atmosphere, allowing weather patterns to last for long periods.

Uranus's Orbital Period

Uranus orbital period is 84 years.

Valles Marineris

Valles Marineris is an enormous canyon on Mars that stretches nearly 4,000 km, 7 km deep and up to 600 km wide, compared to our Grand Canyon at 450 km long, 1.6 km deep, and up to 29 km wide.

Subduction Zone

Where a denser sea floor plate is sliding into the edge of a less-dense continental plate, the material in the sea floor plate dips into the Earth and slides beneath the continental plate. Such a location on the Earth is called a subduction zone.

Nebula

a large cloud of interstellar dust and gas

Jupiter's Influence on Asteroids

astronomers speculate that Jupiter's gravity kept collection of rocks from coalescing into another planet

Ceres

at 1,000 km (600 mi) in diameter, is the largest asteroid and makes up 30% of the mass of all asteroids.

Astronomic method/ Doppler method

detects Extra-Solar planets by observing if stars exhibit 'wobbles,' which might indicate evidence of a large planet or planet grouping.

Excited Charged Particles

emit photons when de-excited

"Apollo" Asteroids

have orbits that cross Earth's orbit at some point, and the risk of collision is higher than other bodies

Mercury: Carolis Basin

is a large "bulls-eye" impact crater.

Volatile Element

is an element that exists in a gaseous state at a relatively low temperature

Nonvolatile Element

is an element that is gaseous only at high temperatures and condenses to a liquid or solid when temperatures decrease.

Earths Structure

is made up of four parts. 1. Crust 2. Mantle 3. The outer core 4. The inner core

Albedo

is the fraction of incident sunlight that an object reflects.

Differentiation

is the variation in the density and composition of a body, such as Earth, with low-density material on the surface and higher-density material in the core.

Albedo

it is a measure of the reflectivity of an object.

Mars's Oblateness

it is the most oblate of all terrestrial planets.

Mercury's Size

it is the smallest planet

Saturn's Albedo

saturn is less reflective then earth

Seismology

studies the make up of the Earth by analyzing travel times of two types of waves generated by earthquakes

Eddies

swirling air

Mesosphere

the mesosphere is located 50-80 km below the surface.

Radioactive Dating Techniques

we know from radioactive dating techniques that the Moon was formed about 4.6 billion years ago.

Stony Irons

—meteorites that are half stone and half iron.