Download Ch. 28-Minor Bodies of Solar System

Ch. 28-Minor Bodies of Solar
System
• Objectives
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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
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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 oceansmoon’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 atmospherenitrogen. 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 atmosphereburning 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