Earth and Moon Full Earth from Apollo 17
Earth Data http://www.charlesgilchrist.com/SGEO/Square/Earth.jpg Surface Gravity if Earth = 1 Sidereal: 23 hr. 56 min. 4.1 sec. Length of Year (revolution around the sun)
Mean Distance from the sun
Earth as a Planet http://www.nasa.gov/centers/glenn/images/content/84036main_solrwalk.jpg
Recognition : It was not until the time of Copernicus (the 1500’s) that it was understood that the earth is another planet.
What Makes the Earth Unique? Name : Earth is the only planet whose English name does not derive from Greek/Roman mythology. Name derives from Old English and Germanic.
In Roman mythology, the goddess of earth was Tellus (Greek: Gaia).
Water Liquid Water : Oceans like ours, that cover about ¾ of the globe, exist nowhere else in the solar system
Liquid water may lie beneath the surface on other, icier bodies (such as Jupiter’s moons), and rivers and lakes may once have existed on Mars.
Goldilocks Planet Location : Not too close to the sun like hot Mercury or too far from the sun like cold Mars http://www.bbc.co.uk/radio4/science/media/goldilocks.jpg
Our distance allows liquid water to exist on the surface and provides a comfortable environment
Atmosphere Atmosphere : Consisting mostly of Nitrogen (78%) and oxygen (21%).
Earth’s oxygen atmosphere was likely created by plants early in earth history
Plate Tectonics Continental Drift : The continents may have once been connected together in a single landmass named Pangaea. Plate Tectonics : The earth’s outer crust is broken into about a dozen plates These plates move slowly, growing in some areas and sinking back into the earth
Edges of plates feature earthquakes, volcanoes, and mountains
Continental Drift The continents shift and move slowly over time. At one point, the continents are believed to have been together, in the form of a supercontinent called Pangaea. This supercontinent then separated into smaller continental plates. Some plates separated further, creating mid-oceanic ridges, while others collided, creating large mountain ranges.
Eventually the familiar continents of today emerged.
The Earth’s Major Tectonic Plates The boundaries of Earth’s tectonic plates show different motions Sliding past one another Separating Colliding
Magnetic Field Earth’s magnetic field is strong The field protects life from excess solar radiation
Interaction between the earth’s magnetic field, atmosphere, and solar radiation (solar wind) create the northern lights
Earth is surrounded by a magnetic field believed to be produced by convection in its molten iron core. The magnetic field produced is similar to that of a bar magnet. The axis of the Earth’s magnetic field differs from the axis of rotation by 11 °, placing the north magnetic pole in a different location than the geographic (true) North Pole.
The Earth’s Magnetic Field Protects us from the Solar Wind
Near the magnetic poles, these particles sometimes leak into our atmosphere, causing the gases to glow. This is known as the aurora or northern lights.
Earth’s Moon Earth’s Moon : Of the four inner planets, earth alone features a large satellite The moon likely formed early in earth history when our planet was struck by a Mars-sized object
This impact ejected material to form the moon
Life Life : Earth is the only place in the universe where life is known to exist. Life may have existed once on Mars (this is still unproven) Organic molecules (e.g., amino acids) exist in comets and meteorites
It is likely that the components of life came from space, perhaps from meteorites or comets
Moon Data http://www.vegaattractions.com/astrology/symbols.html www.solarviews.com/cap/ moon /v moon 1.htm Surface Gravity if Earth = 1 Mean Distance from Earth 238,900 miles
Length of “Year” (revolution around the earth)
Perspective Earth to Moon : About 250,000 miles
Roughly the distance between New York City and Los Angeles.
Discovery The moon is the second brightest object in the sky after the sun.
The moon is actually made of dark material, its albedo is 11%
Lunar phases result from the moon’s revolution around the earth
Animation: The Moon’s Rotation
Animation 6.5: The Moon’s Rotation
Motions Synchronous: The moon rotates on its axis and revolves around the earth in 29.5 days Perigee, farthest from earth Due to its synchronous rotation and revolution, the moon always presents the same face towards the earth
The back side of the moon was first imaged by a Russian robotic space mission in 1959 (Luna 3)
Perigee and Apogee Apogee and perigee cause the moon to be slightly larger or smaller throughout the year
Libration The moon appears to “rock” and “nod” due to its elliptical orbit and tilt compared to earth
As a result, 56% of the moon’s surface is visible from earth
Libration Simulation Libration: Apparent “rocking” http://antwrp.gsfc.nasa.gov/apod/image/0709/lunation_ajc.gif
Perigee & Apogee: Larger and smaller appearance
20 Full Moons
Lunar Terrain Lunar Terrain : Two types, mare and highlands Mare : Dark, younger (less cratered), consists of immense lava flows (lunar seas) Highlands, upper half of image, maria below
Highlands : Bright, old (heavily cratered), moon’s original crust
Harvest Moon Rising http://www.stargazing.net/david/moon/moonrise20050917.html
Identify highlands, maria
Lunar Seas The maria make up the shape of the “man in the moon” or the “rabbit in the moon.” Apollo 11 landed at Mare Tranquilitatis, the “Sea of Tranquility”
Originally immense impact basins, later filled with molten lava
Lunar Maria (Seas) Sea of Clouds Mare Nubium Sea of Moisture Mare Humorum Known Sea Mare Cognitum Sea of Isles Mare Insularum Ocean of Storms Oceanus Procellarum Sea of Rains Mare Imbrium Sea of Cold Mare Frigoris Sea of Vapors Mare Vaporum Sea of Nectar Mare Nectaris Sea of Tranquility Mare Tranquilitatis Sea of Serenity Mare Serenitatis Sea of Fertility Mare Fecunditatis Sea of Crises Mare Crisium Meaning Name
Craters Most result of meteorite impacts Up to 100 miles in diameter Can exhibit central mountains and bright streaks of ejecta
Galileo was the first scientist to observe lunar craters with a telescope (1609)
Galileo’s Moon Paintings, Sketch http://www.mhhe.com/physsci/astronomy/fix/student/images/09f18.jpg
Mountains Often surround edge of mare These mountains are the edges of immense impact basins that later filled with lava Named after prominent mountain ranges on earth
For example, there are lunar Appenines and Alps
Lunar Features Terminator : The line separating lunar day and night
Craters are visible due to long shadows
Lunar Nomenclature Lunar Names : Named for famous figures in the history of science such as Tycho, Copernicus, and Ptolemaeus (Ptolemy)
Features on Venus are named for women
Sinus Iridum Named http://www.webcam-astrophotography.com/moon/sinus-iridum.html
Far Side Back of the moon, never visible from earth Same side of moon always faces earth
Mostly highlands, mystery
Lunar Exploration Moon the only extraterrestrial body ever to have been visited by humans. Apollo 8, in Dec 1968, first men to orbit First landing on the moon was July 20, 1969 (Apollo 11), the last was in December 1972 (Apollo 17).
12 men walked on the moon (6 missions)
Apollo: Men on the Moon Astronauts: Frank Borman, James Lovell, William Anders First to leave earth’s gravity, orbit moon and return Astronauts: Neil Armstrong, Buzz Aldrin, Michael Collins (Command Module) Location: Mare Tranquilitatus First men on moon, fulfilled Kennedy’s dream Astronauts: Charles Conrad, Alan Bean, Richard Gordon (CM) Location: Oceanus Procellarum
First pinpoint landing, returned pieces of Surveyor III
Apollo Missions Astronauts: Alan Shepard, Edgar Mitchell, Stuart Roosa (CM) Location: Fra Mauro Crater Landed in location planned for Apollo 13, Shepard hit two golf balls on the moon, returned 42.9 kg of moon rocks Astronauts: David Scott, James Irwin, Alfred Worden (CM) Location: Hadley Rille in the lunar Apennines
First use of LRV, Lunar Roving Vehicle
Apollo Missions, Cont. Astronauts: John Young, Charlie Duke, Thomas Mattingly (CM) Location: Descartes Crater Astronauts spent 71 hours on the moon, explored for 20 hours, collected 95 kg of moon rocks using LRV Astronauts: Eugene Cernan, Harrison Schmidt, Ronald Evans (CM)
First geologist (Schmidt) on the moon, last man on the moon (Cernan)
Moon Rocks Three types returned by astronauts: Anorthosite-light colored, moon’s original crust (Genesis Rock)
Breccia-fused debris from many impacts
Meteorites from the Moon MacAlpine Hills 88105 is a lunar meteorite found in Antarctica in 1989 Meteorites from Mars have also been identified
List: http:// meteorites.wustl.edu/lunar/moon_meteorites_list_alpha.htm
How the Moon Formed Formation of the Moon : There are four major theories : Co-Accretion : The earth and moon formed individually and at the same time from the solar nebula Fission : The moon split off from the earth Capture : The moon formed elsewhere and was later captured by the earth
Impact : The earth collided with a Mars-sized body (not the planet Mars!) and the moon formed from the ejected material. This theory is now widely accepted.
The similarity in materials making up the Earth and Moon suggest that the Moon may have been created from Earth material ejected after a collision with a large planetesimal. EARTH MOON This computer simulation shows how the Moon could have been formed in a collision between the Earth and a large planetesimal.
Animation : Formation of the Moon