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Slide1: 

Chapter 23: Planets and their Moons Artists concept of Saturn sized planet orbiting a distant star (detected by astronomers). Fig. 23-CO, p.548

The Solar System: 

The Solar System Formed about 4.6 billion years ago from diffuse cloud of dust and gas (exploding stars) rotating in space (under gravity). Cloud composed of about 92% hydrogen, 7.8% helium (all other elements only 0.2% of Solar System). Sun formed under gravity, hydrogen fused some converted to helium; fusion is source of Sun’s energy). Remaining matter formed disc-shaped rotating nebula that coalesced into planets. Early atmospheres (H and He) boiled off or blown away by solar winds. Rock and metal left, terrestrial planets formed (solid rock with metallic cores). Planets in outer reaches of Solar System remained cool; they are larger and called Jovian planets. Retained H and He.

The planets: 

The planets *Terrestrial planets: *Jovian planets: Mercury Jupiter Venus Saturn Earth Uranus Mars Neptune and…….Pluto See pages 550-551 in text

Slide4: 

Table 23-1, p.552

Mercury: a planet the size of the Moon : 

Mercury: a planet the size of the Moon Radius is 2,400 km. Closest to Sun. Orbits Sun in 88 Earth days; rotates 3 days in 2 years (176 days Mercury time) Temp ranges from 427 degrees C (melt lead) to -175 degrees C (freeze methane). No atmosphere; meteorite impact craters; interior has cooled. Has magnetic field (why?); ice at poles; no tilt in axis. Fig. 23-1, p.553

Questions: 

Questions Describe implications of Mercury’s lack of both an atmosphere and hot interior. Describe implications of greenhouse gases and a cool interior on Venus. Describe implications of the Moon’s size relative to Earth; how does this account for geologic features found on Earth and on our Moon? Describe implications of Mars’ distance from the Sun (relative to Earth).

Venus: the Greenhouse Planet: 

Venus: the Greenhouse Planet *Closely resembles Earth in size, density and distance from Sun *Atmosphere is 90 times denser than Earth (1000 meters beneath the sea); 97% C02 *Why is the surface hotter than Mercury? *Few craters; landforms appear 300-500 million years old (catastrophic event?); today volcanic activity may have ceased; 60% of surface is flat, with mountain chains and canyons; Maat Mons (larger than Everest); *Blob Tectonics? Surface too hot and/or lithosphere too thick? Fig. 23-2, p.553

Slide8: 

The volcano Maat Mons on Venus, Lava flows in foreground. Image from Magellan Spacecraft. Fig. 23-3, p.554

Map of Venus Lowland in blue; highlands in yellow and red-brown.: 

Map of Venus Lowland in blue; highlands in yellow and red-brown. Fig. 23-4, p.554

The Moon: 

The Moon 1600s Galileo named the plains maria (for seas) because he thought they were oceans. Heavily cratered. Fig. 23-5, p.555

Slide11: 

*Shows cratered surface of the moon. *In some places there are craters within craters. Fig. 23-6, p.555

Slide12: 

Six Apollo missions answered many scientific questions about the origin, structure and history of the Moon. Fig. 23-7, p.556

Slide13: 

How did the Moon form? Most current hypothesis is that a large object, possibly larger than Mars, collided with Earth shortly after our planet formed. This vaporized silica-rich rocks, creating a cloud around the Earth that coalesced to form the Moon Fig. 23-8, p.557

Slide14: 

This slide shows how the impact could have created vaporized rock that orbited the Earth and coalesced into the Moon about 4.5 billion years ago, similar to the solar nebula that created the planets. Fig. 23-8a, p.557

Slide15: 

After the Moon formed, it was bombarded by meteorites that cratered the surface. This along with gravitational coalescence probably accounts for early melting of the Moon, which formed igneous rocks (e.g., basalt) found at the surface. Eventually the surface cooled; some of the oldest rocks (of the highlands) are 4.4 billion years old. Fig. 23-8b, p.557

Slide16: 

Between 4.2 and 3.9 billion years ago swarms of meteorites bombarded the Moon again, and this, along with radioactive decay heating the interior of the Moon, resulted in magma erupting onto the surface and filling meteorite craters (and forming the maria that we see today). The Moon is much smaller than the Earth, so it cooled and has remained geologically inactive for the past 3.1 billion years. Fig. 23-8c, p.557

Mars: A search for Lost Water: 

Mars: A search for Lost Water Cratered and mountainous regions shown on the surface of Mars. Lava flows cover the plains. Which surface is oldest and why? Fig. 23-9, p.558

Slide18: 

Olympus Mons, located on the Tharsis bulge which is the biggest plain, is the largest volcano on Mars and in our Solar System (nearly 3 times higher than Mount Everest). Blob tectonics (similar to Venus) could account for its massive size…how? Fig. 23-10, p.558

Slide19: 

More evidence for blob tectonics are tremendous parallel cracks split in the crust adjacent to the Tharsis bulge. There is no folding or offsetting of the cracks. Therefore, scientists suggest that a rising mantle plume formed the Tharsis bulge and its volcanoes (the cracks are from stretching during uplift of the crust). Fig. 23-11, p.559

Martian Atmosphere: 

Martian Atmosphere Today the atmosphere is frigid and dry. Surface temperatures average -60 degrees C (-76 degrees F) at the equator (ice doesn’t melt), and -120 degrees C at the poles (frozen CO2). The atmosphere is very thin compared to Earth. Evidence shows the climate on Mars was once much warmer and water flowed across the surface. When did water exist and why is it gone?

Valles Marineris: 

Valles Marineris A giant canyon was eroded by flowing water and is many times larger than the Grand Canyon. Also find eroded crater walls, alluvial fans and extinct stream and lake beds. Fig. 23-12, p.560

Slide22: 

See “Focus on Extraterrestrial Life”, pages 560-561. This meteorite from Mars may harbor signs of early life on Mars. p.560

Slide23: 

This is a microscopic view of the meteorite and it might show fossils of early life? p.561

Jupiter: A star that failed: 

Jupiter: A star that failed The largest planet in our Solar System (71,000 km or 45,000 miles radius). Composed mainly of H and He with ammonia, H2O and methane (confirmed by Galileo probe, 1995). Similar to our Sun, but not massive enough to generate fusion temps (so not a star). Fig. 23-14, p.563

Slide25: 

Surface: vast sea of cold liquid hydrogen and helium (12,000 km deep) Below this, temps rise to 30,000 degrees C under great pressure where hydrogen atoms are packed tightly allowing electrons to flow and conduct electricity (liquid metallic hydrogen); this generates a magnetic field 10> than Earth’s magnetic field. Beneath this, the core is 10-20 times as massive as Earth (probably composed of metals and rock surrounded by lighter elements such as carbon, nitrogen and oxygen). Fig. 23-13, p.562

Slide26: 

Io (left); Europa (right); Voyager spacecraft image. Great Red Spot shown along with turbulent cloud system. Fig. 23-15, p.563

Moons of Jupiter : 

Moons of Jupiter By 2003, 60 moons were known. Most are small. The four discovered by Galileo are largest and most widely studied. Io: innermost moon, about size of Earth’s Moon. Active volcanically. Gas and rock erupt to a height of 200 km. Galileo probe showed 100 volcanoes erupting simultaneously. Gravitational pull of Jupiter and other moons causes great rock distortion and frictional heating. The surface is smooth (no craters) from lava (see slide). Europa: similar to Earth. Interior composed of rock, much of surface covered by water, but water is frozen into ice crust. Galileo probe showed fractured, jumbled, chaotic terrain like Arctic ice on Earth (see slides). Ganymede and Callisto: see next slides on Ganymede; Callisto may have a subterranean ocean; its surface is heavily cratered (what does this imply?).

Slide28: 

Volcanic explosion on Io (Voyager I image). Eruption on horizon is ejecting material to an altitude of about 200 km. Fig. 23-16, p.564

Slide29: 

The jumbled terrain of Europa resembles Arctic ice break up during spring. Scientists estimate the ice is a few km thick, and is floating on subsurface water. Fig. 23-17, p.564

Slide30: 

Smooth, circular region (center; left) formed when subsurface water rose to the surface of froze, covering older wrinkles and cracks in the crust of Europa. Water may be warmed by tidal effects. Could there be life at the subterranean oceans? Fig. 23-18, p.564

Slide31: 

Ganymede has a magnetic field, possibly from a convecting metallic core surrounded by a silicate mantle and covered by water/ice. The surface is so cold it is brittle and acts like rock. Fig. 23-19, p.565

Slide32: 

The surface of Ganymede is pockmarked by dense concentrations of impact craters (white spots) younger regions of fewer impact craters. Fig. 23-20, p.565

Slide33: 

A close up of young terrain on Ganymede shows numerous grooves (> 1 km wide). These grooves may have formed by recent tectonic activity? Fig. 23-21, p.565

Slide34: 

Saturn The Ringed Giant *2nd largest planet. *Lowest density of all planets (it would float on water). *Composed primarily of H and He, with a small core of rock/metal and atmosphere similar to Jupiter (dense clouds; great storms). Titan is largest of 31 moons that are known to orbit Saturn today. It is larger than Mercury, has an atmosphere (only moon known to have one probably because of its size and cold temperature) composed of nitrogen, methane and other gases. Temps avg. -180 degrees C, atmospheric pressure is 1.5 times greater than Earth’s surface. At these conditions, methane on Titan could act like water on Earth. Fig. 23-22, p.566

Titan: 

Titan The Cassini-Huygens spacecraft was launched during 1997 to study Saturn and its moons. The Huygens probe (sent to study Saturn’s largest moon: Titan) separated from the spacecraft (which arrived at Saturn during July, 2004) and landed on Titan’s surface during January of 2005. Why study Titan?

Assignment (don’t do unless specifically assigned): 

Assignment (don’t do unless specifically assigned) You are presenting a paper at a scientific seminar on Titan (Saturn’s largest moon). Some scientists believe “Titan more closely resembles the early Earth than Earth itself does today”. Your presentation must cover the latest findings from scientific research on Titan, and then address the statement above: from scientific data, discoveries, observations, etc., regarding Titan do you believe the above statement is accurate? Why or why not? Do you believe life (as we know it) could evolve on Titan? Why or why not? Your report must be a minimum of one page typewritten (single-spaced). http://www.esa.int/SPECIALS/Cassini-Huygens/index.html (could start here).

Slide37: 

Rings of Saturn *Six major rings with smaller ringlets *Thickness from 10-25 meters, but extremely wide (425,000 km from inner to outer edge). *Composed of dust, rock and ice; larger particles at inner rings, clay size at outer rings. *May be fragments of a moon that never coalesced, or remnants of a moon that formed and was ripped apart by Saturn’s gravitational field. Fig. 23-23, p.566

Slide38: 

Voyager I and II planetary spacecraft provided valuable data on Jupiter, Saturn, Uranus and Neptune. Fig. 23-24, p.567

Uranus and Neptune: 

Uranus and Neptune So distant, not known until the 1980s. Voyager II to Neptune after 12 years and 7.1 billion miles. Both planets: thick atmospheres of H and He; molecular H below this and interiors are methane, ammonia and water, with rock/metal cores. Both have magnetic fields tilted at 50-60 degrees from spin axis! Great storms rage on these planets (1,100 km/hr rip through Neptune’s atmosphere, clouds rise and fall; the Great Dark Spot is found on Neptune). Methane may decompose to C and H (from great pressure), and C may crystallize into diamond (releasing great energy). Uranus has rings and 22 moons; Neptune has rings and 11 moons. Triton (largest moon) is about 75 % rock and 25% ice with craters, mountains and plains (filled with ice or frozen methane). Fig. 23-25, p.568

Slide40: 

Data shows Pluto is the smallest planet in the Solar System (smaller than Earth’s Moon). It’s diameter and mass suggest it is made of rock and ice. Temp is about -220 degrees C, and surface may be frozen methane. Atmosphere is thin, composed of carbon monoxide, nitrogen and methane. Pluto and Charon (Pluto’s Moon) may be escaped moons from Neptune. Fig. 23-26ab, p.568

Slide41: 

Never visited by spacecraft, so how do we know Pluto’s properties? During 1978 Charon was discovered; by measuring Charon’s orbit, can calculate relative masses of each. From diameter and mass calculations, Pluto’s density is less that granite and greater than ice (so mixture of rock and ice). Infrared and spectral measurements provide temp and composition data. Fig. 23-26c, p.568

Asteroids, Comets and Meteoroids: 

Asteroids, Comets and Meteoroids Asteroids: wide ring between Mars and Jupiter. Orbits not permanent like planets, but planets may deflect their orbits. Can crash into planets, possibly reason for mass extinctions on Earth.

Comets: 

Comets Glowing objects traveling in elongated, elliptical orbit around the Sun. They are cold, from outer reaches of Solar System, composed of water-ice mixed with frozen crystals of methane, ammonia, C02 and other stuff…it forms a “tail” from melting as comets approach the Sun. They consist of a solid, dense nucleus, brighter outer sheath (coma) and long tail (some have been 104 million km long). Halley’s comet had a coma radius of 4500 km when it passed Earth during 1986.

Slide44: 

Comet Hale-Bopp was the brightest comet see from Earth in decades. It was brightest in March and April of 1997. Fig. 23-27, p.569

Meteoroids: 

Meteoroids Fragment of comet or asteroid that orbits the inner Solar System. Some can fall the Earth, friction with atmosphere produces fiery streak across the sky (most are about the size of a sand grain!). Larger ones reach the Earth. Most are stony (90% silica, 10% Fe and Ni, similar to mass ratio of rock to metal in the Earth’s mantle and core). May reflect primordial composition of the Solar system. Some have chondrules which contain organic molecules. Some are more metallic. We obtain knowledge of the Earth’s mantle and core from meteorites.

Slide46: 

Fig. 23-28, p.570

Slide47: 

Meteorite, believed to be a fragment of the asteroid Vesta. Ceres is the largest asteroid with a diameter of 930 km. Fig. 23-29, p.570

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