Exploring the Lunar Surface

Transcription

1 Exploring the Lunar Surface

2 Introduction When you look up at the Moon without optical aid, you may notice the variations in the texture of the lunar surface--some parts of the Moon are quite bright, while others look like random dark patches of various sizes and shapes. The dark patches are referred to as the lunar maria. The word mare is of Latin origin and is the singular form of the word maria meaning sea. Today, know that there is no liquid water on the Moon s surface, but hundreds of years ago when telescopes were first turned on the Moon by astronomers Thomas Harriot, Galileo Galilei, and others, they were unable to determine the composition of the moon and what lies on its surface. These dark, irregular patches appeared as seas and oceans. As a result, they were given names such as the Sea of Tranquility, the Sea of Crises, or the Sea of Rains. Instead of being oceans of liquid water, the lunar maria are low-lying regions on the Moon s surface that were inundated by lava flows after the period of time known as the Late Heavy Bombardment. The Late Heavy Bombardment was a time, about 4 billion years ago, when left-over planetesimals from the formation of the solar system s planets rained down on, not just our Moon, but all bodies large and small throughout the solar system. This heavy rain of infalling planetary remnants is responsible for the majority of the craters on the Moon. Following this period, the Moon s surface cooled and solidified. But, approximately 3.8 billion years ago, the radioactive decay of material in the Moon s mantle generated enough heat to remelt the Moon s crust allowing basaltic lava to reach the surface through weaker areas of crust. Once at the surface, the molten lava covered up much of lunar lowlands and erased the craters that were formed by impacts during the Late Heavy Bombardment. The basaltic lava was rich in iron and had a much darker coloration than the existing lunar surface material. When the lava cooled, its dark color Copyright 2018 Slooh LLC 1

3 remained against the bright regions of the Moon that were too high to be covered by the flowing lava. Because the maria show so few recent craters, we deduce that following this period that brought the formation of the mare, the rate of cratering on the Moon was drastically reduced and has remained very low since that time. In contrast, you ve also probably noticed that between many of the dark lunar maria are numerous, strikingly bright areas. These bright and heavily cratered regions are referred to as the lunar highlands. These areas were too high in elevation to become covered by flowing lava. The lunar highlands therefore represent the oldest parts of the Moon s surface, while the maria are considerably younger. To mark the locations of these features, astronomers use a method of selenographic coordinates, similar to the longitude and latitude human-designed coordinate system that describes specific locations on Earth (see figure, left). Longitude lines describe an east-west location, and run vertically around the globe from the north to the south pole. Latitude lines describe a north-south location, and run horizontally around the globe from the east to the west. Similarly, heliographic coordinates describe locations on the Sun. On the moon, coordinates are in units of degrees and describe the location north or south of the moon s equator (latitude) and the location east or west of the moon s prime meridian, or the middle of the moon s surface that faces us (longitude). The moon s prime meridian, because the moon is a sphere, is the closest point of the moon s surface to Earth. The prime meridian used to be determined by the location of the small crater Mösting A, but today is defined by laser precision. The line between the moon s night and day side, or where the moon is in shadow or illuminated by the Sun s bright light, is called the terminator line (see image, right). This line moves based on the phase of the moon. Copyright 2018 Slooh LLC 2

4 This coordinate method is an integral part of a very complex system that has allowed astronauts to land on the moon. Lunar landing sites are best chosen in areas with little to no surface features, which assures a flatter ground for the landing gear. Between the years of 1969 and 1972, six Apollo missions landed, successfully, on the moon. Take a walk in the space shoes of the Apollo astronauts and visit their landing sites (see image, below) with the Slooh telescopes. Copyright 2018 Slooh LLC 3

5 Procedure To select the appropriate Slooh telescope/camera system for this mission, you will want to consider what your field of view (FOV) and resolution requirements are. For example, if you want to take a relatively wide field image of the Moon, you would select an instrument that provides a wider FOV and will therefore show you the entire region of interest, especially if it is a large feature that covers a lot of area on the lunar surface. Then, once you have selected your lunar features, you will want to image your selected lunar features so that you can examine them closely and measure their size on the Moon s surface. For this, you will need a telescope with a longer focal length (FL), and as a result, a smaller FOV, to provide you more detailed images for a closer look to discern fine details within the various lunar features you have selected. For each of the six Apollo landing sites provide an image and show the landing site with a suitable marker. The table below provides the Apollo mission name and the lunar longitude and latitude of the landing site. The lunar landing site map included in the Introduction provides a visual of the locations on the Moon where the missions landed. Use this information to take your own images of the Moon using the Slooh telescopes and search for the six landing sites. Then annotate the image(s) with the corresponding spacecraft mission. Mission Latitude Longitude Apollo N latitude E longitude Apollo S latitude W longitude Apollo S latitude W longitude Apollo N latitude E longitude Apollo S latitude E longitude Apollo N latitude E longitude Copyright 2018 Slooh LLC 4

6 Questions 1. Notice, there is no Apollo 13 mission on this list. Why? Did something happen to this mission,or was NASA superstitious and avoided this number? 2. Identify a 7th lunar landing site, based on what appears to have been the best selections for the six Apollo missions. 3. Label the named lunar features that are closest to each of the six Apollo landing sites you have identified. Reporting Results Your lab write-up should include: I. Your name and title of the lab II. Statement of the objective III. A listing of all Slooh Missions you completed with dates and times of all missions. You must indicate if the mission was a piggyback mission or one you originated and include what equipment was utilized for each mission. IV. Weather conditions for each session V. Equipment used VI. All images of the moon used to identify each of the six Apollo landing sites VII. The annotated images that clearly show the six Apollo landing sites VIII. Answers to Questions Copyright 2018 Slooh LLC 5

7 References Longitude and Latitude on Earth Image 3. Apollo Lunar Landing Sites Image National Space Science Data Center, NASA's Goddard Space Flight Center Copyright 2018 Slooh LLC 6