Homework 9 The Moon and Mercury

Science 105 Homework #9 Moon and Mercury Define the following 1. Spring tide – The highest high tides of the lunar month. These occur on the full and new moons when the forces of the sun and moon add together. 2. Neap tide – The lowest tides of the lunar month. These occur on the first and third quarter moons when the forces of the sun and moon oppose each other. 3. Roche’s Limit – When we have one smaller body orbiting a larger body there exists a distance from the central body within which the tidal forces exerted on the smaller body are strong enough to disrupt (destroy) it. The distance for this depends upon the mass of the central body (the one being orbited) and the mass of the individual body that is orbiting the central body. 4. Maria – Smooth dark planes of basaltic material which were mistaken for seas. 5. Crater – Circular depressions caused by meteorite impacts. 6. Basin – Large impact crater flooded with basaltic material surrounded by concentric rings of faulted cliffs. 7. Scarp – Huge curved cliffs that formed as Mercury cooled. The planet shrank on the interior and the crust had to fall down onto the cooled interior. Since the cooling was not uniform the crust broke and part of it sank down forming these huge faulted cliffs. 8. Spin Orbit Coupling – The ratio of the rotation rate of a body to its orbital period. Answer the following questions. All questions must be answered in full sentences or full credit will not be given. Any question that has math associated with it you must show all work on your answers or full credit will not be given (just giving a number as an answer does not tell me that you know where the number came from). Note: A full sentence completely repeats or restates the question within the answer. 9. How can you determine the relative ages of the Moon’s maria and highlands? - You can determine the relative ages of the Moon’s maria and highlands through the method of Crater Counting: The Moon's surface is covered with craters from various impacts over millions of years. Differentiation Between Maria and Highlands: Maria are large, dark, flat plains on the Moon's surface formed by ancient volcanic activity. Highlands are the elevated areas, often heavily cratered, and composed of lighter-colored rocks. Baseline

Age: Scientists use samples returned from the Apollo missions to establish a baseline age for certain lunar regions. Radiometric dating of these samples provides absolute ages. Secondary Cratering: Some craters on the Moon are caused by secondary impacts, where debris ejected from a larger impact site creates smaller craters nearby. Superposition: In cases where craters overlap, the principle of superposition can be applied. If one crater overlies another, the overlying crater is younger. This helps in understanding the sequence of crater formation events. 10. How can you determine that the crater Copernicus is a young crater? - The crater Copernicus on the Moon is considered a young crater due to several reasons, including its well-preserved features, its relatively low number of superimposed craters, and the presence of rays extending from the crater. Sharpness of Features: Young craters have sharper, well-defined features because they have had less time to erode. Copernicus has a distinct, sharp rim and a deep central peak, indicating that it has not undergone significant erosion since its formation. Rays: Copernicus has bright rays extending outward from its center. These rays are composed of ejecta material thrown out during the impact event. Low Number of Superimposed Craters: Young craters have fewer superimposed craters inside them. When a new impact occurs, it erases smaller craters within its boundaries. Lunar Maria Interaction: Copernicus is located on the lunar mare called Oceanus Procellarum. Lunar maria are vast plains formed by ancient volcanic activity. Radiometric Dating: While direct radiometric dating of the Moon's surface features is challenging due to the lack of atmosphere and weathering, samples collected from nearby impact sites, like those from the Apollo missions, can provide age constraints. 11. What evidence can you cite that Mercury has a molten core? - Mercury's molten core is inferred from several lines of evidence, including its magnetic field, the planet's high density, and observations of its surface features. Here's a breakdown of the evidence supporting the presence of a molten core in Mercury: Magnetic Field: Mercury has a global magnetic field, which was confirmed by measurements taken during NASA's Mariner 10 mission in the 1970s and further studied by the MESSENGER mission (2004-2015). A planetary magnetic field is generally generated by the movement of molten metal in the planet's core. High Density: Mercury is unusually dense for its size. Its average density is comparable to Earth's, even though it is much smaller. This high density suggests that Mercury has a large, iron-rich core. Surface Features: Mercury's surface exhibits various geological features, including large impact basins, ridges, and scarps. Some of these features, like the "lobate scarps," are believed to be the result of the planet's interior cooling and contracting. Thermal Evolution Models: Scientists have developed models of Mercury's thermal evolution based on its size, composition, and observed surface features. These models suggest that the planet's core is at least partially molten. The presence of a molten core is essential to explain the observed magnetic field and the geological features on the surface.

14. Why are moon rocks much older than Earth rocks, even though both worlds formed at nearly the same time? - Moon rocks are indeed older than most Earth rocks, and this is due to the difference in their geological histories and the processes that shaped each celestial body after their formation. Here's why Moon rocks are generally older than Earth rocks: Lack of Active Geological Processes: The Moon is geologically inactive compared to Earth. Earth is tectonically active, with processes like plate tectonics, erosion, and weathering constantly reshaping its surface. Impact Bombardment: In the early solar system, both the Earth and the Moon were bombarded by a large number of asteroids and comets. However, Earth's active geological processes, such as erosion and plate tectonics, have erased most of the evidence of these ancient impacts. Differentiation and Mantle Solidification: The Moon's surface rocks are primarily basaltic, indicating that the Moon's crust was once molten and has since solidified. Limited Geological Reset: Earth has experienced multiple geological events, including the formation of supercontinents, massive volcanic activity, and extensive erosion, which have reset the geological clock in various regions. In summary, the lack of active geological processes, extensive impact cratering, rapid differentiation and solidification, and limited geological resets on the Moon have allowed its rocks to remain relatively unchanged over billions of years, making them older on average than most Earth rocks. 15. Explain why Mercury does not have an atmosphere. - Mercury, the closest planet to the Sun, has a very thin and tenuous atmosphere. However, it is often considered to be effectively lacking an atmosphere due to its incredibly low density and pressure. There are several reasons why Mercury's atmosphere is so sparse: Low Gravity: Mercury is a small planet with low gravity. Its gravitational pull is much weaker than that of Earth. Consequently, Mercury cannot hold onto an atmosphere as effectively as larger planets. High Temperatures: Being the closest planet to the Sun, Mercury experiences extremely high temperatures on its surface. Solar Wind Stripping: Mercury is bombarded by the solar wind, a continuous stream of charged particles emanating from the Sun. Lack of Volcanic Activity: Volcanic activity can release gases from a planet's interior, contributing to the formation and maintenance of an atmosphere. Unlike Earth, which has active volcanoes, Mercury's volcanic activity has significantly decreased over time. Limited Atmosphere Production: Mercury's small size and limited geological activity mean that there are fewer processes producing gases that could contribute to an atmosphere. In summary, Mercury does not have a substantial atmosphere due to its low gravity, high temperatures, constant bombardment by solar wind, limited volcanic activity, and a lack of processes that produce and retain gases. These factors combined have resulted in the planet having a very thin and tenuous atmosphere. 16. Compare the surfaces of the moon and Mercury. Explain how they are the same and how they are different. - The Moon and Mercury are both airless, rocky bodies in our solar system, and they share some similarities in their surface features while also exhibiting distinct differences. Here's a comparison of the surfaces of the Moon and Mercury, highlighting both their similarities and differences: (Similarities) - Cratered Surfaces: Both

the Moon and Mercury are heavily cratered worlds, indicating a history of intense bombardment by asteroids and comets. Impact craters of various sizes cover their surfaces, creating a rugged terrain. Regolith: Both bodies have a layer of loose, fragmented material called regolith, which is formed by the continuous impact of meteoroids. The regolith covers the solid bedrock and gives the surfaces a powdery appearance. Scarps and Ridges: Both the Moon and Mercury have scarps (cliffs) and ridges on their surfaces. These features are the result of geological processes, such as cooling and contraction, that cause the crust to crack and form these distinctive landforms. (Differences) - Volcanic Activity: While both the Moon and Mercury have evidence of past volcanic activity, volcanic features are more prominent on Mercury. Large expanses of smooth plains, known as volcanic plains or "smooth plains," cover significant portions of Mercury's surface, indicating extensive volcanic activity in the past. The Moon also has volcanic plains but to a lesser extent. Maria: The Moon has large, dark, flat plains called maria (singular: mare), which are primarily composed of basaltic lava flows. These maria were formed by ancient volcanic activity and are more prevalent on the Moon than on Mercury. Mercury's smooth plains, while similar in appearance, are more widespread. Temperature Extremes: Mercury experiences extreme temperature variations due to its lack of atmosphere. Surface temperatures on Mercury can reach up to 430 degrees Celsius (800 degrees Fahrenheit) during the day and drop to -180 degrees Celsius (-290 degrees Fahrenheit) at night. The Moon also has significant temperature variations, but its daytime temperatures are not as extreme as those on Mercury due to its longer rotation period. Extra Credit 1. Calculate the escape velocity of the moon, using its mass and diameter from chapter 12. - Escape Velocity = √ 2 x Gravitationalconstant x Mass of the Moon / Radius of the Moon - The gravitational constant (G G ) is approximately 6.674 × 10 − 11 m 3 /kg ⋅ s 2 - The mass of the Moon is approximately 7.34 × 10 22 kg. - The radius of the Moon is approximately 1,737,100 meters. - Plugging in these values, we can calculate the escape velocity: - Escape Velocity = √ 2 x 6.674 x 10 − 11 m 3 divideby kg ⋅ s 2 x 7.34 x 10 22 kg / 1,737,100 m - Escape Velocity = √ 9.78 x 10 12 / 1,737,100 - Escape Velocity = √ 5629.32 - Escape Velocity = 75.03 m/s - Therefore, the escape velocity of the Moon is approximately 75.03 meters per second75.03meters per second. 2. The smallest detail visible through an Earth-based telescope of the moon is about 1 arc second in diameter. What is the size of this on the moon in km? - Size (in km) = (Angular size in arc seconds × Distance to the object in km) x ❑ 180 x 3600