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

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

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

• 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

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

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

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

• 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

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

• 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

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

• 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

• 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

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?

• 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

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

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

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

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

• 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

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

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

• 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

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?

• 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