ASTR 1345 1st EditionExam # 4 Study Guide Lectures: 20 - 23Lecture 20 (November 13)Mercury, Venus, MarsWhat do we know about Mercury?Mercury is 20% the size of the Earth and has extreme variations in temperature. Mercury has noseasons and there are traces of an atmosphere. Mercury is filled with subtle blue and red areas, and wrinkle-like ridges are an indication that Mercury is shrinking. It has active volcanoes and a magnetic field.What is the Caloris Basin?Caloris Basin is found on Mercury and it is a crater of about 800 miles in diameter. It was probably formed by a major impact that occurred early on and shock waves from the impact produced a hilly landscape on the opposite side of the planet.What do we know about Venus?Venus is about the same size as Earth and has a runaway greenhouse effect caused by its dense toxic atmosphere which is hot enough to melt iron. Venus has no magnetic field and only the Moon outshines Venus because of its proximity. There are a lot of lava plains and the surface temperature is 750K at all times and latitudes.What do we know about Mars?Mars is half the size of Earth and contains the highest mountain and the deepest and longest valley. Because of its’ smaller size, the interior f Mars cooled faster than Earth’s, so surface activity has ceased. Mars’ sky is red due to fine iron oxide (rust). There are multiple indications that Mars once had water.Lecture 21 (November 18)Space Missions and JupiterWhat are Mars’ moons?Mars has 2 small moons named Phobos and Deimos discovered in 1877 by Asaph Hall. Phobos ispotato shaped and its period of 5 ½ hours means it orbits faster than Mars rotates, so it moves west to east across the sky. It is now believed that this moon is more like a pile of rubble. Deimos moves from east to west across the sky in about 3 Earth days.What happened with Voyager 1 and Voyager 2?Voyager 1 and 2 each reached Jupiter in 1979. Saturn gave Voyager 1 a gravitational slingshot out of the Solar System. Voyager 2 used Saturn’s gravity to propel it closer to Neptune (1986) and Uranus (1989). In 2008 after 31 years of travel both Voyagers crossed different parts of the solar system boundary, known as the termination shock, 90 AU from the Sun.What was the Galileo mission?Galileo made 3 passes through the inner solar system before reaching Jupiter in 1995. Galileo went through Jupiter’s moon system discovering large saltwater ocean under Europa’s icy crust.What was the Cassini mission?Cassini reached Saturn in 2004 later sending out a probe into the atmosphere of Titan, Saturn’s largest moon.What facts do we know about Jupiter?Jupiter’s AU is 5.2, sidereal period is 11.88 Earth years. Rotation period is just under 10 hrs, 5 min shorter at equator than at the poles. Tilt of rotation is 3 degrees, cloud-top temp. is 150K (-190 degrees F) It has 62 moons.What is Jupiter’s interior?The core of Jupiter is solid rock containing iron and silicon and gets about 25,000K because of high pressure. The mantle consists of hydrogen at pressures to make it a liquid metal. Excellent conductor of electricity, creating magnetic field at cloud level. What is in Jupiter’s atmosphere?Jupiter’s clouds take their red, white, brown and blue colors from sulfur, phosphorus, and other impurities in the atmosphere. Lowest layers of Jupiter’s atmosphere contain Hydrogen, Helium, methane, ammonia and water. Because of Jupiter’s fast rotation its clouds are in constant motion, confined to narrow jet streams. White ovals are higher and cooler and brown ovals are lower and warmer. Jupiter’s Great Red Spot is the size of 2 Earths and the largest storm in solar system.What is Jupiter’s aurora?Unlike auroras on Earth caused by solar wind, the main auroral ring on Jupiter is associated withJupiter’s magnetism and is constant in size.Lecture 22 (November 20)The Gas GiantsWhat are Jupiter’s 4 main moons?Jupiter has many moons but the 4 main ones are Io, Europa, Ganymede, and Calisto. Ganymede and Calisto are as large as Mercury.What is the importance of Io?Io is filled with craters and volcanoes. It lost its water through tidal heating caused by internal stresses produced as its distance from Jupiter changes during its orbit. This is the most volcanically active moon in the solar system and it produces a lot of mountains and geysers. Likeour own Moon, Io always shows the same face to Jupiter because it has the same rotation as Jupiter.What is the importance of Europa?25% of Europa’s mass could be water. This evidence comes from the surface ice flows and the moon’s reddish color due to salt deposits. It also has numerous surface cracks due to tidal flexing.What do we know about Saturn?Scientists believe there’s a hurricane on Saturn’s north pole that’s hexagon shaped and been there for many years. Saturn has visible rings, 60 moons, and a very low temp. It’s about 10AU and the mass is 100 times the mass of Earth. It has a low density, a 10hr day, and the tilt of its axis is about 27 degrees. It has a rocky core like all other gas giants and at its south pole a stormWhat is the importance of Saturn’s rings?Saturn’s rings are less than 100m thick, but stretch over a hundred thousand km. The rings extend to the Roche limit, which is when Saturn’s tidal forces overwhelm the tendency for particles to conglomerate. The F ring is the outermost ring, then A ring, B ring and C ring is closest to the planet.What is Saturn’s largest moon?Titan is Saturn’s largest moon and has a substantial atmosphere with 90% nitrogen, 10% argon, and the rest methane. The atmosphere could produce early primitive life forms. It’s very cold and the methane prevents the atmosphere from freezing.What do we know about Uranus?Uranus is 14.5 times the mass of the Earth, 20AU, and rotates at about 84 Earth years. The outerlayers are hydrogen, helium, and methane which absorbs red light and forms higher clouds giving the planet its blue colors. It has about 98 degree tilt and extreme seasons. Uranus has 5 moons, Miranda is one of them.What do we know about Neptune?Neptune has extreme high speed winds as fast as 2000km/h. It’s 30AU, 19hrs per day and extremely cold. It also appears blue because of methane in its atmosphere. Neptune has a total of 6 moons and Triton is Neptune’s largest moon.Lecture 23 (December 2)Meteoroids, Asteroids, and CometsDefine Meteoroids.Meteoroids are rocky and metallic space debris found orbiting the Sun. They are