Unit 8 Chapter 28 Minor Bodies of the

Unit 8 Chapter 28 Minor Bodies of the Solar System

Section 1 Earth’s Moon • In 1957 the Soviets launched “Sputnik” which was the first satellite into space. • In 1958 the US launched our first satellite into space. • In 1959 the Soviets launched a probe called “Luna” which was the first manmade object to encounter the moon.

Exploring the Moon • In 1969 the Apollo Astronauts walked on the moon. • In 1972 the final Apollo mission brought back to Earth about 400 kg of moon rocks. • Interesting facts: • The moon is 386, 000 km away • Moon’s diameter is 3476 km (approx ¼ Earths) • Moon’s mass is approx 1/8 of Earths • Moon’s density 3. 3 km 3 : Earth’s density 5. 5 km 3 • Gravity is 1/6 of the Earth’s • Ex. 150 lb. Man weighs = 25 lbs. • 200 lb. Equipment = 33 lbs. • 350 lbs. = 58 lbs. • The temperature range is from 134 o in the day to -17 o at night

Lunar Surface • Luna – name for baby moon • Lunar – name for features on the moon • Lava flowed on the surface due to the strength of these impacts. The cooled lava formed flat dark surfaces (called lunar Maria). • When we first started to study the moon, we thought the dark areas were filled with water. That is why the scientists named them “Maria”. It is the Latin word for seas. The dark areas are actually filled with hardened lava. • Mascons areas of greater gravity. Scientists believe it is that way because of the type of lava that was released.

Craters, Rilles and Ridges The moon looks like a giant golf ball with all of the impact crates on it. Craters were formed when meteors hit the surface. They varied in size which caused some shattered rock and dust to splash out of the craters like “rays”. • The impacts were thought to be caused by meteoroids, comets or other debris colliding with the surface creating craters or depressions. Rille: A rille is a trench in the Maria which is formed when new lava came up and flowed away. Highland: The highland is the lighter colored rocks that reflect the sunlight.

Regolith is the layer of dust and rock on the lunar surface. Lunar Rocks The rocks on the moon are similar to those on Earth except they have different proportions of the elements involved. They also have less of certain common elements which are thought to be boiled off because of the lack of atmosphere.

The Interior of the Moon • The density of the moon is about 3/5 th of Earth’s. • The moon has moonquakes (like earthquakes) which allowed scientists to create a model of the interior of the moon. It has layers of solid rock with different densities, no pure liquid layer. The Moon’s Crust • One side of the moon always faces the Earth. • Nearside – the side that faces us • Farside – the side that does not The Moon’s mantle and core • The moon’s mantle is made of silica, magnesium and iron. It is approximately half the distance of the radius. • Iron core is approximately 700 km thick • It has almost no magnetic field.

The Formation of the Moon Rocks taken from the moon by the Apollo Astronauts provided us with incite into the history of the moon’s formation. The Giant Impact Theory • The giant impact theory states that more than 4 billion years ago a giant Asteroid (the size of Mars) hit the molten Earth. The collision ejected a chunk that later clumped together and hardened into the moon. Differentiation of the Lunar Interior • The denser surface material moved toward the center of the moon because of the rotation of the moon. The other materials that were dense but not as dense settled in the layer in between the core and crust. • The lighter materials stayed on top. Meteorite Bombardment • In the beginning the moon was bombarded frequently. After time the impacting slowed down. The craters we see were the original features, so Scientists use that information to learn about the early solar system. Lava Flows on the Moon • After the impacts stopped, lava started to flow out of the cracks and fissures. Where the lava came from Scientists are still trying to figure it out. However, they feel that the flows ended about 3. 1 billion years ago.

Section 2 Movement of the Moon The moon revolves around the Earth from west to east, once every 271/3 days but it appears to travel from east to west in the sky. Why? The Moon’s Elliptical Orbit • The moon’s orbit is not in the same plane as the Earth. The angle is about 5 o, which is why we have eclipses. • Perigee – near the earth • Apogee – far from the earth • The moon and the sun appear to be about the same size – why • • Moon Rise and Moon Set If the moon’s orbit is 271/3 days, how come it takes 291/2 days from one full moon to the next? Because the Earth revolves around the sun as the moon revolves around the Earth. Each moonrise or moonset is 50 minutes later each day because of the Earth’s revolution. This is also the reason that we see the moon in the daylight some times. When the moon is between the Earth and Sun, you see it mostly in the daytime, but when it is opposite the sun, you see it at night. Lunar Rotation • The moon rotates (turns on axis) in the exact same time it revolves (moves around earth). This means that the same side of the moon is always facing us.

Eclipses An Eclipse will occur when one celestial body passes through the shadow of another. The Moon and the Earth cast a shadow that has 2 different parts Umbra - total shadow – small cone Penumbra – partial shadow

Solar Eclipses Total Solar Eclipses • occurs when moons umbra shadow reaches to earth. • the moon blocks out sunlight • can only happen when the moon is closest (perigee) in orbit to the earth • Only in the new moon phase Partial Solar Eclipses • The moons penumbra shadow reaches the earth. Happens around the umbra shadow or when the moon is farthest (apogee) in orbit around the earth • At least one solar eclipse occurs every 18 months. A given area experiences a total solar eclipse only once every three to four centuries. They only last for about 7 ½ minutes anyway. The next one for us in North America will occur in 2017.

Effects of Solar Eclipses Diamond ring Effect: During a total solar eclipse, people on the ground are in the moon's umbra. In the areas on Earth's surface under the umbra, the sky becomes as dark as it does at twilight. During this period of darkness, the sunlight that is not eclipsed by the moon shows the normally invisible outer layers of the sun's atmosphere. Annular Eclipse During an annular eclipse, the sun is never completely blocked out. Instead, a thin ring of sunlight is visible around the outer edge of the moon. The brightness of this thin ring of ordinary sunlight prevents observers from seeing the outer layers of the sun’s atmosphere that are visible during a total solar eclipse. An annular eclipse will be visible from the American Southwest on May 20, 2012.

Lunar Eclipses Happens only when there are full moons. The earth’s shadow blocks out the sunlight and the moon doesn’t’ reflect back the sunlight. A lunar eclipse lasts for several hours. Even during a total lunar eclipse, sunlight is bent around Earth through our atmosphere. Mainly red light reaches the moon, so the totally eclipsed moon appears to have a reddish color Frequency of Solar and Lunar Eclipses As many as seven eclipses may occur during a calendar year. Four may be lunar, and three may be solar or vice versa. However, total eclipses of the sun and the moon occur infrequently. Solar and lunar eclipses do not occur during every lunar orbit. This is because the orbit of the moon is not in the same plane as the orbit of Earth around the sun. The moon crosses the plane of Earth’s orbit only twice in each revolution around Earth. A solar eclipse will occur only if this crossing occurs when the moon is between Earth and the sun. If this crossing occurs when Earth is between the moon and the sun, a lunar eclipse will occur. Lunar eclipses are visible everywhere from the dark side of Earth. A total solar eclipse, however, can be seen only by observers in the small path of the moon’s shadow as it moves across Earth’s lighted surface. A partial solar eclipse can be seen for thousands of kilometers on either side of the path of the umbra.

Phases of the Moon: l They are the daily changes in the moons appearance l It is when sunlight is reflected off the moon’s surface l Occur because the moon revolves around the earth l 1/2 of the moon is always lit by the sun (except for lunar eclipses) l We see different portions of the lit half of the moon (but only the same side of the moon) Earth Shine is when sunlight is reflected off of the moon.

Waxing Phases of the Moon Waxing phase - the lit half is becoming bigger this happens during the first two weeks Crescent – a slight sliver is illuminated on the right side Quarter – when half of what is visible is illuminated on the right side Gibbous - more than half of the right side of the moon is bright and the other part is dark Waning Phases of the Moon Waning phase - the lit half is becoming smaller, this happens during the second two weeks Crescent – a slight sliver is illuminated on the left side Quarter – when the left half of the moon is visible is illuminated Gibbous – the left side of the moon is bright and the other part is dark

Time from New Moon to New Moon Phases listed: Day 1 – New Moon Day 3 ¾ – Waxing Crescent Day 7 ½ – 1 st Quarter Day 11 ½ - Waxing Gibbous Day 14 ½ - Full Moon Day 18 ½ - Waning Gibbous Day 22 ½ - Last Quarter Day 26 - Waning Crescent Day 29 ½ - New Moon

u New Moon u Waxing Crescent u First Quarter u Waxing Gibbous u Full Moon u Waning Gibbous u Third Quarter (last quarter) u Waning Crescent

Section 3 Satellites of the Other Planets Until the 1600’s everyone thought that we were the only ones with a moon. In 1610 Galileo discovered 4 moons orbiting Jupiter and he also saw the rings of Saturn. Moons of Mars • Mars has two moons Phobos and Deimos Moons of Jupiter • Jupiter has 67 moons. • The largest 4 are called Galilean Moons because he discovered them • Io, Europa, Ganymede, Callisto Moons of Saturn • Saturn has 63 Moons • The largest one is called Titan Moons of Uranus and Neptune • • Uranus has 27 Moons Neptune has 13 Moons Pluto’s Moons • Pluto has 3 moons. • Charon is half the size of Pluto • Hydra and Nix were discovered in 2005

Rings of Gas Giants • Saturn's spectacular set of rings, shown was discovered more than 300 years ago. Each of the rings circling Saturn is divided into hundreds of small ringlets. The ringlets are composed of billions of pieces of rock and ice. These pieces range in size from particles the size of dust to chunks the size of a house. Each piece follows its own orbit around Saturn. The ring system of Saturn is very thin. • The other gas giants have rings as well. These rings are relatively narrow. Jupiter’s were not discovered until the Voyager 1 spacecraft flew by Jupiter in 1979. Jupiter has a single, thin ring made of microscopic particles that may have been given off by Io or one of Jupiter's other moons. The particles may also be debris from collisions of comets or meteorites with Jupiter's moons. Uranus also has a dozen thin rings. Neptune's relatively small numbers of rings are clumpy rather than thin and uniform.

Section 4 Asteroids, Comets and Meteoroids There is a lot of space junk out there! Asteroids • An asteroid is a small planet like bodies made entirely of rock with irregular shapes. Most orbit in a belt between Mars and Jupiter, called the asteroid belt. They revolve in the same direction as the planets. The 2 largest Ceres (about 1000 km is also considered a dwarf planet) & Pallas are spherical (diameters about 11, 000 km). • In 1908 a small asteroid exploded with the force of a 10 -megaton detonation over Tunguska, Siberia. Composition of Asteroids • There are 3 categories of asteroids • Carbon – dark ones • Silica – light ones • Iron-Nickel – the rarest ones are shiny

Near-Earth Asteroids More than a thousand asteroids have orbits that sometimes bring them very close to Earth. These asteroids have wide, elliptical orbits that bring them near Earth's orbit. Barringer Meteorite Crater, also known simply as Meteor Crater, in Arizona, has a diameter of more than 1 km which scientists believe came from an asteroid that had a diameter of less than 50 m. Dozens of such craters have resulted from past impacts on Earth, but most craters have eroded or have been covered by sediment. We now have set up a few detection agencies to help detect them before its too late.

Comets are small bodies of ice, rock, and cosmic dust that follow highly elliptical orbits around the sun. The most famous is Halley's Comet, which passes by Earth every 76 years. It last passed Earth in 1986 and will return in 2061. Every 5 to 10 years, another very bright comet will be visible from Earth. Comet Hale-Bopp was particularly spectacular as it passed Earth in 1997, as was comet Mc. Naught in 2007.

Composition of Comets The composition of a comet is mainly water, carbon dioxide, methane and ammonia. When close to the sun the comet reflects light and solar winds push off particles of the comet to form a tail. The tail always points away from the sun. The head is made of mainly ice and rock material. The Kuiper Belt is found beyond Neptune. It is where Pluto lives and where we are currently finding more and more dwarf planets, comets and other space “junk”. The Oort Cloud The Oort cloud is a spherical cloud of dust and ice that lies far beyond Neptune’s orbit and that contains the nuclei of billions of comets. The total mass of the Oort cloud is estimated to be between 10 and 40 Earth masses. It surrounds the solar system and may reach as far as halfway to the nearest star. Scientists think that the matter in the Oort cloud was left over from the formation of the solar system Short-Period Comets A short period comet takes less than 200 years to complete one orbit. Halley’s Comet is one of them, it takes 76 years.

Meteoroids Most meteoroids are less than 1 mm in diameter. They are usually chunks of rock which are moving through space. Meteors • • A Fireball will occur when a meteor burns up and becomes a brilliant flash of light in the sky. Rock that passes through our atmosphere. We see a light as it passes through the atmosphere. As the particles move through the atmosphere, friction creates enough heat to make the rock glow and melt. Meteor shower A shower will occur when earth passes through a tail of a comet. The shower is named for the Constellation from which they appear to migrate from. They will occur at the same time each year. Meteorites It is the rock that remains after a meteoroid hits the earth. Three types: • Stony – common 94% of them • Iron – 5% of them • Stony Iron – 1% of them