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Astronomy - Other Planets of the Solar System

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    Study Guide Astronomy – Other Planets of the Solar System 1. Mars Mars is a medium - sized rocky planet , often called the Red Planet because of its reddish surface. The color comes from iron - rich dust that covers much of the ground. Today, Mars is geologically quiet , meaning there are no active volcanoes. Scientists believe the last volcanic activity ended about 1.5 billion years ago .

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    Study Guide 1.1 Early History and Magne Ɵ c Clues Mars does not have a global magnetic field like Earth. However, spacecraft have discovered striped patterns of magnetism on its surface. These stripes have opposite magnetic directions and look very similar to the magnetic patterns found on Earth near mid - ocean ridges. These patterns tell scientists that long ago: • Mars likely had a molten iron core • The mantle was moving and convecting • Plate - tectonic - like activity may have occurred early in the planet’s history As Mars cooled, these processes stopped. 1.2 Extreme Surface Features Mars has the largest elevation differences of any rocky planet in the solar system. • In the northern hemisphere , there is a huge crater about 1,300 km wide , with a floor 10 km below the average surface level. • In contrast, Mars is home to Olympus Mons , the largest volcano in the solar system . Olympus Mons • Height: 25 km • Type: Shield volcano • Diameter: 600 km • About three times wider than the largest similar volcano on Earth (in Hawaii) Shield volcanoes form when thin lava flows easily , spreading out over large areas. 1.3 Northern vs. Southern Hemispheres Mars looks very different depending on where you are: • Northern Hemisphere o Covered mostly by smooth plains o Shaped by volcanic lava flows

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    Study Guide • Southern Hemisphere o Much older surface o Heavily cratered , showing billions of years of impacts This difference tells scientists that volcanic resurfacing mainly affected the north. 1.4 Weathering, Deserts, and Canyons Mars shows clear signs of weathering and erosion , even though liquid water is not present on the surface today. • Cratered regions show long - term erosion • Large desert areas are covered in sand dunes • Winds move dust around, causing seasonal changes in appearance Valles Marineris One of the most dramatic features on Mars is Valles Marineris , a massive canyon system: • Length: 4,000 km • Located near the equator • Includes many smaller side canyons Scientists think it formed when the Tharsis region bulged upward due to movement of molten material beneath the surface and then cracked apart. Unlike Earth’s rift valleys, this canyon was not formed by plate separation . 1.5 Evidence of Ancient Water Although liquid water does not exist on Mars today, many surface features suggest it once flowed there: • Teardrop - shaped islands • Dry river channels • Flood plains Any water remaining today is likely frozen underground , trapped as permafrost or frozen into rocks.

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    Study Guide 1.6 Ice Caps and Seasons Mars has polar ice caps that grow and shrink with the seasons. • Average temperature: 220 K ( − 60°F) • Seasonal variation: ±30 K The ice caps are made mostly of frozen carbon dioxide (dry ice) , with some water ice mixed in. Seasonal Ice Movement • In northern spring , carbon dioxide ice sublimates (turns directly from solid to gas) and moves south • In southern spring , the process reverses Dust left behind by sublimating ice forms layered, terraced patterns around the poles. 1.7 Thin but Ac Ɵ ve Atmosphere Mars has a very thin atmosphere , with surface pressure only about 1% of Earth’s . This is surprising because Mars has enough gravity to hold onto an atmosphere. Possible reasons for atmospheric loss include: • A massive meteor impact long ago • Erosion by the solar wind , especially after Mars lost its magnetic field Atmospheric Composition • 95% carbon dioxide • 3% nitrogen • 1.5% argon • Small, seasonal amounts of water vapor, oxygen, and helium Even though the atmosphere is thin, it can still produce: • Fast winds • Planet - wide dust storms , H igh clouds , especially in the morning At an altitude of 50 km , Mars’s atmosphere is actually denser than Earth’s atmosphere at the same height.

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    Study Guide 1.8 Interior Structure Inside, Mars has the familiar crust – mantle – core structure seen in rocky planets. Its low average density (about 3.9 g/cm³) suggests a small iron core . There is no evidence of current tectonic activity . 1.9 Moons of Mars Mars has two small, irregularly shaped moons : Phobos • Size: about 28 × 23 × 20 km • Orbits very close to Mars • Slowly spiraling inward • Expected to crash into Mars or break apart in about 100 million years Deimos • Size: about 16 × 12 × 10 km • Orbits farther away than Phobos Both moons: • Are heavily cratered • Always keep the same side facing Mars • Are likely captured asteroids , not moons that formed with the planet

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    Study Guide 2. Jupiter Jupiter is the largest planet in our solar system . It is so massive that it contains about two - thirds of all the planetary mass in the solar system (excluding the Sun). Because of its size and appearance, Jupiter is one of the easiest planets to spot in the night sky. 2.1 Appearance and Atmosphere Jupiter appears reddish - brown and is covered with dark belts and bright bands that wrap all the way around the planet. These are not solid surfaces . Instead, they are thick layers of clouds moving through Jupiter’s atmosphere. • The bright bands form when warm, light - colored gas rises from deep inside the planet. • As this gas reaches higher altitudes, ultraviolet (UV) light from the Sun causes chemical reactions. • These reactions create dark hydrocarbons , sometimes called photochemical smog . • Over time, the gas cools, becomes heavier, and sinks back down , creating a constant cycle of motion. 2.2 Fast Rota Ɵ on and Storms Jupiter spins extremely fast, completing one rotation in about 10 hours . This rapid spin causes two important effects: 1. Equatorial bulge – The planet is wider at the equator than at the poles.

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    Study Guide 2. Strong Coriolis effect – Moving gases are deflected east or west, shaping the clouds into long horizontal zones. This effect also causes powerful storms. The most famous one is the Great Red Spot : • It is a giant cyclonic storm that has lasted for at least 400 years . • It is about 35,000 km wide , large enough to fit Earth. • Its cloud tops rise 8 km higher than nearby clouds. • Winds inside the storm reach speeds of 500 km per hour . • The storm slowly drifts but never disappears. 2.3 Chemical Composi Ɵ on of the Atmosphere Jupiter’s outer atmosphere is made mostly of light gases: • Hydrogen – 60% • Helium – 36% • Neon – 2% • Water vapor – 0.9% • Small amounts of ammonia, methane, and argon The planet’s reddish color comes from: • Acetylene formation • Phosphorus compounds released from phosphine gas In the upper atmosphere, clouds form in distinct layers made of: • Ammonia • Water • Ammonium hydrosulfide

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    Study Guide 2.4 Exploring Jupiter’s Interior In 1995, the Galileo probe explored the outer few hundred kilometers of Jupiter’s atmosphere. Scientists also learned more when fragments of Comet Shoemaker – Levy 9 crashed into Jupiter in 1994. However, Jupiter’s deep interior cannot be directly observed . Scientists study it by using: • Jupiter’s mean density (about 1.3 g/cm³ ) • Known physical laws 2.5 Inside Jupiter: From Gas to Metal • The outer layers of Jupiter are made of gas. • Deeper inside, pressure becomes extremely high. • Under these conditions, hydrogen atoms break apart , and their electrons move freely. • This form of hydrogen behaves like a metal and is called metallic hydrogen . Because metallic hydrogen conducts electricity: • It creates strong electrical currents • These currents generate a powerful magnetic field • The magnetic field is tilted 10° from Jupiter’s rotation axis 2.6 Magne Ɵ c Field and Auroras Jupiter’s magnetic field is the strongest of any planet . Around the planet are huge radiation belts, much larger than Earth’s Van Allen belts. • Charged particles from the Sun get trapped in these belts. • When they follow magnetic field lines toward the poles, they create bright auroras in Jupiter’s atmosphere.

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    Study Guide 2.7 Core and Deep Interior Closer to Jupiter’s center: • Temperatures and pressures are even higher. • Scientists believe there may be icy materials and a solid rocky core . • The exact structure is still uncertain because small changes in assumptions can lead to different results. 2.8 Temperature and Energy Source The temperature of Jupiter’s upper atmosphere is about 125 K . This temperature is controlled by: • Absorbing energy from the Sun • Releasing heat as thermal radiation Jupiter also emits: • Radio waves , caused by lightning • Energy from interactions between its magnetic field and its moon Io Overall, Jupiter gives off about twice as much energy as it receives from the Sun . This means it must have an internal energy source . 2.9 Why Jupiter Produces Extra Energy The most likely explanation is gravitational contraction : • Jupiter is slowly shrinking as gravity pulls it inward. • It shrinks by about 3 centimeters per century . • This slow contraction releases energy as heat. Another way to think about it: • Jupiter is still losing heat left over from its formation. • As it cools, pressure decreases and the planet continues to shrink.

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    Study Guide This table summarizes important information such as: • Size and mass • Density and rotation speed • Distance from the Sun • Orbital period and tilt 3. Saturn 3.1 Meet Saturn Saturn is the second largest planet in our solar system. In many ways, it is similar to Jupiter, but there is one feature that makes Saturn instantly recognizable — its beautiful system of rings . These rings are made of thousands of thin, concentric bands that surround the planet and make it one of the most stunning sights in space.

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