Ch. 28-Minor Bodies of Solar System

1. Ch. 28-Minor Bodies of Solar System • Objectives • Kinds of lunar surface features • Layers of the moon • Stages by which the moon formed • Shape of moon’s orbit around Earth • Why eclipses occur • Appearance of phases of moon • Characteristics of moons of Mars • How volcanoes were discovered on Lo • Characteristics of each Galilean moon • Characteristics of rings of Saturn w/ rings of other outer planets • Physical characteristics of asteroids and comets • Compare meteoroids, meteorites, and meteors • Explain relationship between the Oort cloud and comets

2. Lunar Surface Features • Define satellite • Body that orbits larger body • 6 planets w/ moons • What was Sputnik? • 1st artificial satellite launched into space • Explorer 1-U.S. launched satellite in 1958 • 1969-1972-6 spacecraft to moon • Gravity is 1/6 of Earths • No significant atmosphere to absorb and transport heat

3. Lunar Surface • Anorthosites-lighter areas that are rough highlands composed of rock • Maria-darker areas that are smooth and reflect less light • Mare-large dark area of basalt on the moon • Craters-bowl shaped depressions, formed when debris struck moon • Rays-bright streaks of younger craters • Rilles-long, deep channels that run through maria, left over lava channels from formation of maria • Ridges-long, narrow elevations of rock, rise out of surface and cris-cross the maria • Regoith covers most of lunar surface-dust and smaller fragments

4. Lunar rocks-similar to rocks on Earth • Different proportions of elements • Igneous that are composed of oxygen and silicon • Highland rocks-rich in calcium and aluminum • Maria rocks-fine grained basalts-large amounts of titanium, magnesium, and iron • Rocks do not contain water

5. Layers of Moon • Interior Moon-density about 3/5ths of Earth • Moonquakes occur in mantle at depth 10 times deeper than depth of Earthquakes • Moon’s Crust • Near side is side that always faces Earth • Far side’s crust is thicker cause of gravity, mountainous and few small maria • Mantle and core • Rock rich in silica, magnesium and iron • Mantle makes up half of radius • Small iron core, rotation not uniform indicates core neither completely solid nor completely liquid, no overall magnetic field

6. Moon’s Formation • Giant Impact Hypothesis-large object collided w/ Earth about 4 billion yrs ago • Collision ejected chucks of Earth’s mantle into orbit around Earth • Debris clumped together to form moon • Differentiation led to densest materials toward center forming small core • Meteorite bombardment-left over debris from formation of solar system struck surface and produced craters and regolith • Lava flows on moon-impacts on moon’s surface formed deep basins, lava flowed out of cracks to form maria, no evidence of large active volcanoes, or plate tectonics

7. Sec 2-Movements of Moon • Rotates once every 27.3 days standing on N. Pole. 29.5 Earth days long on lunar surface, How? • Mass of moon=1/80th of Earths • Orbits around Earth in an ellipse-5% more elongated than circle • Distance between moon and Earth varies • Perigee-closest to Earth • Apogee-farthest from Earth

8. Moonrises or sets app. 50 min later each night, Why? • Both of Earth’s rotation and moon’s revolution • Each completes one rotation each day, moon also moves on its orbit around Earth • Takes 1/29th of Earth’s rotation or 50 min for horizon to catch up to moon • Lunar Rotation-Very slow and completes a rotation only once during each orbit around Earth-27.3 days • Always see same side of moon because rotation and revolution of moon always takes same amount of time

9. Eclipses • Event in which the shadow of one celestial body falls on another • Umbra-inner, cone shaped part of shadow, sunlight is completely blocked • Penumbra-outer part of shadow, sunlight is only partially blocked • Solar eclipses-passing of moon between Earth and sun, shadow of moon falls on Earth • Total solar eclipse-sun’s light completely blocked by moon • Lasts more than 7 min at any one location • Not visible in U.S. until 2017, happens somewhere on Earth about every 18 months

10. Lunar eclipses-Earth is positioned between moon and sun, Earth’s shadow crosses lighted half of moon • May last for an hr, sunlight bent around Earth, moon appears to have reddish color • 7 eclipses may occur during calendar yr • Moon crosses plane of Earth’s orbit only twice in each revolution around Earth • Visible everywhere on dark side of Earth • Total solar eclipse-seen in small path of moon’s shadow as it moves across Earth’s lighted surface

11. Phases of Moon • Phases-varying shapes, lighted by reflected sunlight of moon, caused by changing positions of Earth, sun, moon • New moon phase-moon directly between sun and Earth, rays strike far side and near side of moon is dark, not visible • Waxing-size of lighted part of moon is increasing

12. Waxing phases of moon • Waxing crescent-sliver of moon’s lighted side illuminated • Semicircle-1/4 of orbit after new moon phase, ½ is lighted • Waxing gibbous-lighted part is larger than semicircle, still increasing in size • Full moon-Earth is between sun and moon

13. Waning phases of moon • Waning gibbous-lighted part still larger than semicircle • ¾ phase-lighted part of near side becomes semicircle • Waning crescent-only sliver of near side visible • New moon to new moon=29.3, moon revolves around Earth=27.3 days. 2.2 days is due to orbiting of Earth moon system around sun • Tidal bulges-bulges in Earth’s oceans-moon’s gravitational pull on Earth decreases w/ distance from moon

14. Sec 3-Satellites of Outer Planets • 1610 Galileo discovered 4 moons orbiting Jupiter, observed rings of Saturn • All planets but Mercury and Venus have moons, gas giants have rings • Moons of Mars • Phobos and Deimos-revolve around Mars quickly, irregularly shaped chunks of rock, captured asteroids, dark surface w/ craters • What does the large number of craters on Mars’s moon indicate?

15. Moons of Jupiter • Most have diameter of less than 200 km, Galilean moons are the largest • Lo-1st extraterrestrial body w/ active volcanoes, lava much hotter than Earth’s-more magnesium and iron, giant iron core w/ possible magnetic field • Europa-size of Earth’s moon, less dense. 100 km of crust of ice covering core, believed ocean of liquid water may exist under blanket of ice • Ganymede-largest moon in solar system, larger than Mercury, small mass that is composed mostly of ice mixed w/ rock, crater filled and long ridges w/ valleys • Callisto-similar to Ganymede in size, density, and composition, rougher surface, one of most densely cratered moons in solar system

16. Moons of Saturn • At least 47 moons, small icy bodies w/ many craters • Titan-largest moon, thick atmosphere-nitrogen. Probe showed signs of flowing liquid-methane • Other moons-icy moons that resemble Jupiter’s, irregular shapes • Janus-smaller moons thought to be captured by Saturn’s gravity

17. Moons of Uranus and Neptune • Uranus’s 4 largest moons • Oberon, Titania, Umbriel, Ariel-1800’s • Miranda-1948, more moons have been discovered-at least 2 dozen small moons • Neptune-at least 13 moons • Triton-icy moon, unusual cuz revolves around Neptune in a backward or retrograde orbit, thin atmosphere

18. Pluto’s Moons • At least 3 moons • Charon-largest moon, half size of Pluto • Both orbit common balance pt • Hydra and Nix moons-much smaller, discovered in 2005 by Hubble Space Telescope

19. Rings of Gas Giants • Rings of Saturn discovered 300 yrs ago • Each ring circling Saturn is divided into hundreds of small ringlets, composed of billions of pieces of rock and ice • Range in size of small particles to chunks of small houses • Ring system of Saturn is very thin • Rings are remains of large comet like body that entered Saturn’s system, ripped apart by tidal forces

20. Jupiter’s rings-discovered in 1979 by Voyager 1 • Single thin ring-microscopic particles given off by Io or other moons • Uranus-dozen thin rings • Neptune-relatively small number of rings, clumpy rather than thin and uniform

21. Sec 4-Asteroids, Comets, Meteoroids • Asteroids-fragments of rock that orbit the sun • How may asteroids? • 5000 • Ceres-largest known asteroid, 1000 km diameter, became round cuz of gravity, considered dwarf planet • Most asteroids located between Mars and Jupiter=asteroid belt • Composition of asteroids-similar to inner planets, made mostly of carbon materials, dark color • Also made of silicate minerals, look like Earth’s rocks • Rarest asteroids are composed of iron and nickel, shiny metallic appearance • Meteor Crater-small asteroid that struck Arizona 40,000 yrs ago

22. Comets • Define • Small bodies of ice, rock, and cosmic dust that follow highly elliptical orbits around sun • Halley’s comet-passes Earth every 76 yrs • Passed in ’86, returns in 2061 • Commet Hale Bopp-1997, visible every 5-10 yrs • Composition of comet • Core or nucleus=rock, metals, and ice • Coma-spherical cloud of gas and dust, surrounds nucleus, bright appearance. • Head of comet=core and coma • Tails of comets=sunlight causes comet’s ice to change to gas

23. Oort cloud-where most comets originate, spherical cloud of dust and ice that lies beyond Neptune’s orbit • Surrounds solar system, may reach halfway to nearest star, leftover from formation of solar system • Kuiper Belt-region of solar system that starts beyond the orbit of Neptune, contains dwarf planets made mostly of ice • Short period comets-take less than 200 yrs to complete one orbit around sun • Kuiper Belt, Halley’s comet period=76 yrs

24. The trip M’s • Meteoroids-relatively small, rocky body that travels through space, diameter less than 1 mm, pieces of matter that become detached from passing comets • Meteors-bright streak of light that results when meteoroid burns up in Earth’s atmosphere-burning stars • How do they form? • Fireball-meteoroids vaporize very quickly in a brilliant flash of light, may hear loud noise • Meteor shower=large # of small meteoroids enter Earth’s atmosphere in short period of time • Occur at same time each yr, Why?

25. Meteorites-any part of meteoroid that is left when meteoroid hits Earth cuz they are relatively large and do not burn up in atmosphere • Small w/ mass of less than kg • Large ones strike surface like large bomb, leave large craters • Stony, iron, or stony iron • Stony meteorites-similar in composition to rocks on Earth, carbon bearing compounds similar to living organisms • Iron-easier to find cuz they have distinctive metallic appearance, makes them easy to distinguish from common Earth rocks • Stony-iron- contain iron and stone, very rare. Believed to come from collisions between asteroids • Rare ones originate on moon or Mars, collisions w/ moon can eject rocks then fall to Earth, found in Antarctica