UNIT IV our planetary neighborhood

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Dec 6, 2023

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UNIT IV: Our Planetary Neighborhood Outline and Study Guide Overview of the Solar System ● Inventory 1. List the four categories of solar system objects, and give examples from each category star, planet, dwarf planet, moon/satellite, comet, and asteroid 2. Cite the recently adopted criteria that define a “planet” and “dwarf planet” It must orbit a star (in our cosmic neighborhood, the Sun). It must be big enough to have enough gravity to force it into a spherical shape. It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun. A 'dwarf planet' is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite. ● Scale of the Solar System 1. Using a meaningful analogy (ex: travel times or a scale model), discuss the relative sizes and distances of objects in the solar system Travel times By car By nasa By light Ny 18 hrs 4 minutes 0.004 sec The moon 5 months A few days 1.3 sec mars 60 yrs 8 months 3 min Neptune 6,000 years 12 years 5 hrs Alpha centauri A veeery long time 50,000 yrs 4 years 2. Define the terms light second, light hour, light year A light second A light hour is the distance that light travels in one second. Since light travels at a constant speed, this distance is always the same. In terms of numerical values, it's roughly 299,792 kilometers (or about 186,282 miles). Light Hour: A light hour is the distance that light travels in one hour. To calculate this, you would multiply the speed of light by the number of seconds in an hour (3600 seconds). Therefore, a light hour is approximately 1,079,252,848.8 kilometers (or about 670,616,629 miles). Light Year: A light year is the distance that light travels in one year. Since a year consists of many seconds, the distance covered by light in a year is significantly larger. To calculate a light year, you would
multiply the speed of light by the number of seconds in a year (approximately 31.56 million seconds). This results in a distance of about 9.461 × 10^12 kilometers (or around 5.878 × 10^12 miles). ● Gross Characteristics of the Planets 1. Identify the two physical characteristics that define the Terrestrial and Jovian groups of planets. Terrestrial planets mercury Venus, earth, and mars; slow rotation, (small) and relatively solid. heavy, metallic elements. No ring systems, few satellites Jovian: Jupiter (liquid) Saturn, Uranus, Neptune (much larger) are not solid objects, gasses, and liquids. Large and fluid. Light elements, hydrogen, and helium. Fast rotation. Ring systems, many satellites 2. Summarize the secondary physical characteristics that distinguish Terrestrial planets from Jovian planets. ; small and relatively solid. heavy, metallic elements. 9much larger) are not solid objects, gasses, and liquids. Large and fluid. Light elements, hydrogen, and helium SIZE and STRUCTURE 3. Summarize the dynamical similarities among the major planets and their satellites Motions, all planets revolve in nearly the same place. All revolve and rotate around the sun in the same direction. (Counterclockwise) Venus rotates clockwise. Many planets and their satellites have orbits that are aligned in a relatively flat plane. This is a consequence of the way they form from a rotating disk of gas and dust. All rotate with their axis of rotation perpendicular to their orbital plane (except Uranus tipped over 90 degrees) ● Origin of the Solar System 1. Describe, in general terms, the major stages in the formation and evolution of the solar system First you need gravity. Gravitational contraction. The process begins with a giant molecular cloud composed of gas and dust. This cloud undergoes gravitational collapse, leading to the formation of a rotating disk known as the solar nebula. Most of the material in the nebula is hydrogen and helium, with trace amounts of other elements. In the center of the solar nebula, a concentration of material forms a protostar. As this protostar accumulates more mass, its gravitational forces increase, and it begins to heat up. ( this is where a star forms) (conservation of angular momentum) to form a rocky planet you have to have solid particles (accretion) snowballing effect. 50 million years to form a planet. Frost line- critical distance away from the sun, far enough you can have snowflakes form .so now iron, rock, and little specs of ice. The ice particles are more abundant than the rocky ones. Planetesimals will gently collide and get bigger to form protoplanets. The protoplanets heat up due to gravitational energy and radioactive decay. This leads to differentiation, where heavier elements
sink towards the core, and lighter elements rise to the surface. This process results in the formation of layered structures in the planets. The forming Sun, now a young star, begins emitting solar wind that clears remaining gas and dust from the solar system, leaving behind a more orderly arrangement of planets and smaller celestial bodies. 2. Explain how this model accounts for a) some of the dynamical regularities of the major planets The scarcity of volatiles and the competition for rocky material limited the size of these planets. Jovian planets formed in the colder outer regions of the protoplanetary disk, where volatile compounds like water, ammonia, and methane could exist in solid form. These planets likely formed a solid core of rock and metal first, and then, through the process of accretion and capturing of gases from the disk, they accumulated massive atmospheres predominantly composed of hydrogen and helium. b) the difference in size and composition of Terrestrial and Jovian planets the differences in size and composition between Terrestrial and Jovian planets are attributed to their distinct formation locations in the protoplanetary disk, influencing the availability of volatile materials and the types of elements that could condense in each region. Principles of Planetology ● Basic Concepts 1. What are the four basic materials that make up the solar system? What are their relative abundances? Hydrogen (H): Abundance: Hydrogen is the most abundant element in the solar system. It constitutes about 74% of the elemental mass in the Sun and approximately 92% of the atoms. Helium (He): Abundance: Helium is the second most abundant element in the solar system. It makes up about 24% of the Sun's elemental mass and roughly 7-8% of the atoms. Oxygen (O): Abundance: Oxygen is the third most abundant element in the solar system. It accounts for approximately 1% of the Sun's elemental mass and about 0.1% of the atoms. Carbon (C): Abundance: Carbon is the fourth most abundant element, constituting about 0.3% of the Sun's elemental mass and around 0.03% of the atoms. It's important to note that these abundances are given in terms of the elemental composition of the Sun. The Sun is primarily composed of hydrogen and helium, with trace amounts of heavier elements like oxygen, carbon, nitrogen, and others. The abundances of elements in other parts of
the solar system, such as planets, moons, and asteroids, can vary, but the overall pattern of hydrogen and helium dominance holds. 2. Define mean density. What can be inferred about an object based on its mean density? P= m/v P is the mean density M is the mass of the object V is the volume of the object This measure gives an indication of how much mass is packed into a given volume . In summary, mean density is a valuable metric for understanding the composition, structure, and likely evolutionary history of celestial objects. It plays a crucial role in characterizing planets, moons, asteroids, and other astronomical bodies. 3. Define albedo, and explain how it is related to a planet’s surface temperature. The albedo of a planet plays a crucial role in determining its surface temperature through the following mechanisms: Albedo is a measure of the reflectivity of a surface, describing the fraction of sunlight or solar radiation that is reflected back into space. It is expressed as a percentage, with 0% indicating a perfectly absorbing (black) surface, and 100% indicating a perfectly reflective (white) surface. The albedo of an object is influenced by the type of material it is made of and the angle and intensity of incoming sunlight. Earth: The Standard of Comparison ● Earth’s Interior 1. Explain how we can study the internal structure of the Earth Earthquakes and seismographs 2. Identify the Earth’s major internal structural layers and their composition Core, mantle, and crust are divisions based on composition. The crust makes up less than 1 percent of Earth by mass, consisting of oceanic crust and continental crust is often more felsic rock. The mantle is hot and represents about 68 percent of Earth's mass. Finally, the core is mostly iron metal. Inner core is solid, pressure keeps it solid. outer core is liquid 3. Explain why the interior of the Earth and other planets became differentiated Most geologists believe that the key differentiation process in the Earth was melting of much of the inner rock material after the Earth formed. The source of the heat was radioactive minerals trapped in the Earth as it formed. Key Factors Leading to Differentiation: Gravity: The force of gravity plays a crucial role in the settling of denser materials toward the center of the planet. Heat: High temperatures in the early stages of planetary formation lead to melting and differentiation. Material Properties: Differences in material properties, such as density and composition, influence how materials segregate during differentiation.
● Earth’s Surface 1. Describe the process of convection and its relevance to plate tectonics Convection is a process of heat transfer that occurs in fluids (liquids and gases) where warmer, less dense material rises, and cooler, denser material sinks. The rising and sinking of material in the mantle create forces that lead to the formation of new crust at mid-ocean ridges, the sinking of crust at subduction zones, and the lateral movement of plates at plate boundaries. This dynamic process is central to the theory of plate tectonics, explaining the motion and interaction of Earth's lithospheric plates. Convection currents transfer heat from one place to another by mass motion of a fluid such as water, air or molten rock. Lava lamp! 2. Describe the different ways in which the Earth's lithospheric plates interact They crash. They crush. They scrape. They crumple. They slide. They split. They melt. In incredibly-slow motion . The movement of the plates creates three types of tectonic boundaries: convergent, where plates move into one another; divergent, where plates move apart; and transform, where plates move sideways in relation to each other. Subduction zones are where Earth's tectonic plates dive back into the mantle, at rates of a few to several centimeters per year. An oceanic trench shows where the plate disappears, and a dipping zone of earthquakes show where the subducting plate is. Subduction zones are where Earth's deepest (~ 700 km) and strongest earthquakes (Magnitude ~ 9) occur. 3. Identify the primary type of geological activity which results from each type of plate interaction At a convergent plate boundary, one plate dives (“subducts”) beneath the other, resulting in a variety of earthquakes and a line of volcanoes on the overriding plate; Transform plate boundaries are where plates slide laterally past one another, producing shallow earthquakes but little or no volcanic activity . ● Earth’s Atmosphere 1. Identify the natural mechanisms that have altered the composition of the atmosphere over time These have been caused by many natural factors, including changes in the sun, emissions from volcanoes, variations in Earth's orbit and levels of carbon dioxide. 2. Explain how the greenhouse effect contributes to global warming Certain gases in the atmosphere absorb energy, slowing or preventing the loss of heat to space. Those gases are known as “greenhouse gases.” They act like a blanket, making the earth warmer than it would otherwise be. This process, commonly known as the “greenhouse effect,” is natural and necessary to support life. Infrared light cannot pass through glass. Water is the most common greenhouse gas in the atmosphere. Greenhouse heating comes from water. The water vapor keeps global temperature 30 celcius degrees warmer, keeps us from being frozen. ● Earth’s Magnetic Field
1. Discuss the origin of Earth’s magnetic field Earth's magnetic field is powered by the solidification of the planet's liquid iron core. The cooling and crystallization of the core stirs up the surrounding liquid iron, creating powerful electric currents that generate a magnetic field stretching far out into space. 2. Explain how the Aurora Borealis is produced When a solar storm comes toward us, some of the energy and small particles can travel down the magnetic field lines at the north and south poles into Earth's atmosphere. The Moon ● The Earth-Moon System 1. Explain what is meant by synchronous rotation, including the rotation of an object that always shows the same face to an object that it is orbiting because its rotation period and orbital period are equal. a) the most obvious consequence of the Moon’s synchronous rotation b) the physical mechanism that has caused the Moon to rotate synchronously synchronous tidal locking, All the solar system’s large moons are tidally locked with their planets. The bigger moons synchronize early in their existence, within hundreds of thousands of orbits. 2. Explain how ocean tides are produced, and why there are two high tides and two low tides each day Because the Earth rotates through two tidal “bulges” every lunar day, coastal areas experience two high and two low tides every 24 hours and 50 minutes. High tides occur 12 hours and 25 minutes apart. It takes six hours and 12.5 minutes for the water at the shore to go from high to low, or from low to high. 3. Describe the inevitable consequence of tidal interactions between the Earth and Moon ● The Moon’s Surface 1. Distinguish between maria & highlands Lunar highlands are heavily cratered and mountainous. Maria are large, dark, basaltic plains on Earth's Moon, formed by ancient asteroid impacts. 2. Explain the origin of the lunar maria Really big asteroid impacts as well as melting and eruption of basaltic lava onto the lunar surface between 3.8 to about 2.8 billion years ago 3. Describe the topographic difference between the lunar nearside and farside On the nearside, the Moon has a low topography and thin crust, whereas on the farside, the Moon has a high topography and thick crust.
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