The Moon
What is the Moon? A natural satellite One of more than 96 moons in our Solar System The only moon of the planet Earth
Location, location, location! About 384,000 km (240,000 miles) from Earth 3,468 km (2,155 miles) in diameter (about ¼ the size of Earth)
Origin of the Moon Giant Impact Theory 4.6 byr ago -- Moon formed, possibly due to collision of Earth and a large, Mars-sized object. If Earth was already differentiated, most material expelled would be mantle material, not iron core. What would this explain? Lower Density of the moon compared to Earth.
Giant Impact Theory Rock at impact heated, losing volatile elements Some debris falls back to Earth, some forms Moon. Earth and Moon each pulled back into spherical shape by gravity.
4.6-4.0 byr ago Era of Accretion ( heavy bombardment ) Moon differentiates, denser material moves inward. Lunar History Lighter material moves to surface, forms crust ~60 km thick (Lunar Highlands) Heavy cratering
Lunar History ~ 4-3 byr ago Heavy bombardment ends Interior melts due to radioactive decay. Basalts fill in low areas (large impact basins) to form maria. Light cratering
Lunar History ~ 3 byr ago -- Moon cools, light cratering continues. ~ 3 byr ago - Present -- dead Moon Light cratering continues. No evidence for geologic activity
Cut to the Core 3 major divisions of the Lunar interior Crust - average thickness of about 70 kilometers Mantle Core - radius is between 300 and 425 kilometers
Interior Structure Mass ~ 1/80 of Earth s mass Size ~ 1/4 of Earth Density: 3300 kg/m 3 (compared to Earth s 3800 kg/m 3 ) Made mainly of rock Interior mainly solid Why? Moon is smaller cools more rapidly No global magnetic field Little metal or metal is not molten.
Moon is differentiated Outer Crust Mantle Interior Structure Possible iron rich core Known from moonquakes Caused by tidal forces from the Earth
The Moon s Surface No atmosphere No liquid water Extreme temperatures Daytime = 130 C (265 F) Nighttime = -190 C (- 310 F) 1/6 Earth s gravity
Surface Features on the Moon Two types of Surfaces Highlands More heavily cratered surface is older. Lighter colored. Predominantly anorthosites Maria ( Seas ) Less heavily cratered surface is younger. Darker colored Basalts Predominantly found on near side of the Moon
Surface of the Moon No atmosphere Temperature too high to hold onto gases Gravity too weak to hold even the heaviest gasses Frozen water detected in craters at poles Detected by Clementine and Lunar Prospector Missions (radar imaging) Sun does not reach bottoms of craters at poles Water not evaporated or lost to space Most promising site for a Lunar Base
Lunar Features - Highlands Mountains up to 7500 m (25,000 ft) tall Rilles (trenchlike valleys)
Lunar Highlands Geology Image width = 250 km
Lunar Features - Craters Up to 2500 km (1,553 miles) across Most formed by meteorite impact on the Moon Some formed by volcanic action inside the Moon
Craters on the Moon Craters due to bombardment by debris in space. Impact creates shock wave with circular crater Material is pushed away from crater forming ejecta blanket The rock beneath the crater is shattered, some is melted by impact
Lunar Features - Maria Originally thought to be seas by early astronomers Darkest parts of lunar landscape Filled by lava after crash of huge meteorites on lunar surface 3-4 billion years ago Mostly basalt rock
Far Side of the Moon First seen by Luna 3 Russian space probe in 1959 Surface features different from near side More craters Very few maria Thicker crust
Moon -- Part of Far Side
Movements of the Moon Phases the moon goes through a complete set of phases every 27.33 days The moon rises in the east and sets in the west The moon rises and sets 50 minutes later each day Rotation Moon turns on its axis once every 27 days Revolution the moon orbits the Earth once every 27 days Same side of Moon always faces Earth
It s Just a Phase Moonlight is reflected sunlight Half the moon s surface is always reflecting light From Earth we see different amounts of the Moon s lit surface The amount seen is called a phase
Waxing and Waning New moon Waxing Crescent moon First Quarter moon Waxing Gibbous moon Full moon moon orbit`s earth Waning Gibbous moon SUN Third Quarter moon crescent Waning Crescent moon New moon earth last (third)quarter waning Moon gibbous moon new moon full moon crescent gibbous moon waxing Moon first quarter
How do we know the phase of the moon just by looking at it?
Your Job On a half sheet of paper that will be collected at the end of the period: Devise a method of explaining to someone how to identify and remember the current phase of the moon just by looking at it one time. In other words, you walk outside one morning/day/night and see the moon. Explain how you would automatically know the phase.
Things we know: The phase of the moon is based on how much of the illuminated portion we see. It is determined by the angle made by the Earth, sun, and moon. The moon orbits the Earth once every 28 days. It orbits counter-clockwise if viewed from above Earth s north pole. The moon always rises in the east and sets in the west, one time every day. The moon rises and sets 50 minutes later every day.
FOUR MAIN SHAPES FULL CRESCENT QUARTER GIBBOUS
SUN crescent moon orbit`s earth last (third)quarter waning Moon gibbous moon earth new moon full moon crescent gibbous moon waxing Moon first quarter
In which phase would we see a solar eclipse? In which phase would we see a lunar eclipse?
Why do we not see a solar eclipse during every new moon? Why do we not see a lunar eclipse during every full moon?
Lunar Eclipses Moon moves into Earth s shadow this shadow darkens the Moon Umbra Penumbra About 2-3 per year Last up to 4 hours
This is an animation showing a total lunar eclipse from start To finish.
Plane of earth s orbit Earth Moon Moon Plane of lunar orbit
Eclipses occur only when the Sun and Moon are both on the line of nodes
Lunar Eclipses The Earth moves between the Sun and the Moon, blocking th Sun s light, and causing the moon to glow red.
Lunar eclipses can be either total, partial, or penumbral, depending on the alignment of the Sun, Earth, and Moon
Umbra The dark inner portion of the shadow cone. Penumbra the lighter outer portion of the shadow.
Types of Lunar Eclipses Total Lunar Eclipse when the Moon passes completely into the Umbra, or total shadow of the Earth. Partial Lunar Eclipse Occur when the Moon does not fully move into the Umbra. Penumbral Lunar Eclipse When the moon passes only through the penumbra, or partial shadow. They are barely visible.
Moon moves between Earth and Sun Moon casts a shadow on part of the Earth Total eclipses rare only once every 360 years from one location! Solar Eclipses
Types of Solar Eclipses Total Solar Eclipse can only occur if you are at the exact spot within the moon s umbra (which isn t very big). Partial Solar Eclipse Visible is you are in the penumbra of the shadow. Only some of the moon will be shadowed. Annular Eclipse occurs when the moon is farthest from the Earth in its orbit. This makes the moon look smaller, so during the eclipse you see an outer ring of light from the Sun.
Solar eclipses can be either total, partial, or annular, depending on the alignment of the Sun, Earth, and Moon
Total Solar Eclipse can only occur if you are at the exact spot within the moon s umbra (which isn t very big).
Solar Eclipse
This animation shows that the moon creates a small shadow which Only allows certain areas of the earth to see a total solar eclipse.
Partial Solar Eclipse Visible if you are in the penumbra of the shadow. Only some of the moon will be shadowed.
Annular Eclipse occurs when the moon is farthest from the Earth in its orbit. This makes the moon look smaller, so during the eclipse you see an outer ring of light from the Sun.
Paths of Future Solar Eclipses
Name this phase! Full Moon What time does this phase rise and set?
Craters Name these features. Maria Name these feature
Does this image show us the near side or far side of the moon? Far Side How can you tell?
Is this line the limb or terminator? Limb Terminator Is this line the limb or terminator?
Name this phase! First Quarter
Name this phase! Waxing Crescent
Does this image show the near side or the far side of the moon? Near Side
Name this phase! Waning Gibbous
Name this phase! Third Quarter
From what direction does the moon rise? The East
Name this phase! Waxing Gibbous
Name this phase! Waning Crescent
What might be happening in this image? Lunar Eclipse
Is this line the limb or the terminator? Limb
Name this phase! Look closely! Waxing Gibbous
True or False: The Far Side and the Dark Side of the moon are the same thing. False!
Name this phase! Full Moon
Name this phase! New Moon
Does the moon rise or set in the west? It sets in the west.
Name this phase! Waning Gibbous
Name this phase! Waning Crescent
Name this phase! Waning Gibbous
The Tides Tides caused by pull of Moon s gravity on Earth High tide Side facing Moon and side away from Moon Every 12 hours, 25 ½ minutes Low tide On sides of Earth
Tidal Forces Gravity of Moon pulls on Earth Force on near side stronger than far side
Tidal Forces The result is to pull object apart. Difference in forces on far and near side = tidal force Causes bulge in water on Earth. Earth also slightly distorted
Tides are generated by: 1.Gravitational pull of the moon and sun 2.Centripetal force of the rotating Earth
Tides are generated by: the gravitational pull of the moon and sun - moon has 2x greater gravitational pull than the sun - sun is 10 million x more massive than the moon and is 390 times farther away
Centripetal force
GRAVITATIONAL FORCE CENTRIPETAL GRAVITATIONAL & CENTRIPETAL
Description of tides High water: a water level maximum ("high tide") Low water: a water level minimum ("low tide") Tidal range: the difference between high and low tide Spring Tide: full moon and new moon (14.77 days) Neap Tide: 1 st quarter and 3 rd quarter (14.77 days) High tide Intertidal zone Low tide
The monthly tidal cycle (29½ days) About every 7 days, Earth alternates between: Spring tide Alignment of Earth-Moon-Sun system (syzygy) Lunar and solar bulges constructively interfere Large tidal range Neap tide Earth-Moon-Sun system at right angles (quadrature) Lunar and solar bulges destructively interfere Small tidal range
Earth-Moon-Sun positions and the monthly tidal cycle Spring Tide Highest high tide and lowest low tide Neap Tide Moderate tidal range
The Bay of Fundy: Site of the world s largest tidal range
Bay of Fundy Alma at High Tide Alma at Low Tide
Tidal bore = a true tidal wave Wall of water that moves upriver Caused by an incoming high tide Occurs in some low-lying rivers Can be large enough to surf or raft