Moon Course Section 20-26 V1.0
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Around the Moon in 28 Days: Lunar Observing for Beginners Course Notes Section 20 - Lunar Day 15 Section 21 - Lunar Day 16 Section 22 - Lunar Day 17 Section 23 - Lunar Day 18 Section 24 - Lunar Day 19 Section 25 - Lunar Day 20 Section 26 - Lunar Day 21 (Last Quarter) Copyright © 2010 Mintaka Publishing Inc. Section 20 - Lunar Day 15 Tonight we'll begin a limb-to-limb lunar history adventure by learning about the Soviet probe, Lunik 9. In 1966, the unmanned lunar traveler became the first to achieve a soft landing on the Moon’s surface and successfully transmit photographs back to Earth. The lander weighed in at 99 kg, and had four outward opening antenna petals. Within five minutes of touchdown on January 31, the antennae sprang to life and the on-board television cameras began broadcasting the first panoramic images of the surface of another world – thus proving a lander would not simply sink into the lunar dust. Last contact with the spacecraft occurred just before midnight on February 6, 1966. If you'd like to see where Lunik 9’s remains stand, turn your binoculars or telescopes towards the western lunar limb for Oceanus Procellarum. On its western edge, you can easily identify the dark oval of crater Grimaldi. About one Grimaldi- length northward and on the western shore of Procellarum is where you will find Lunik 9’s resting place. Figure 20-1: The major features of the eastern part of the Moon on Day 15 Around the Moon in 28 Days: Lunar Observing for Beginners Figure 20-2: Image from the Luna 9 lander in February, 1966 in the Oceanus Procellarum Now let's go for the opposite limb to check out the eastern edge of Mare Crisium in a different relief. The bright point on the shoreline is Promontorium Agarum with shallow crater Condorcet to its east. Look along the shore of the mare for a southern mountain known as Mons Usov just west of Condorcet. At its northern edge that Luna 24 landed. This mission was the last of the Soviet Luna spacecraft and the third to successfully retrieve and return. It carried back 170 grams of lunar samples to the Earth on August 22 1976. For over thirty years, Luna 24 held the distinction of being the final spacecraft from any country to have landed on the Moon, only to have that record broken by Chandrayaan-1 in 2008. However, the record still holds for "soft landings"! Luna 24 also had the distinction as the last spacecraft to retrieve extra-terrestrial samples until Stardust returned in 2006. Just south of Lunik 24's final resting place is the silent Luna 23, which touched down on November 6, 1974. While it was intended to take deep core samples and return to Earth, the mission partially failed. However, it still successfully transmitted back three days of data. Directly to its west are the remains of Luna 15. It wasn't quite so lucky, though... it smashed into the surface on July 21, 1969, just a day after Armstrong and Aldrin walked on the Moon’s surface Unfortunate? Hardly. It began the revolutionary age of creating good relations between the Soviet Space Agency and NASA, since each agency had to share flight plans! Around the Moon in 28 Days: Lunar Observing for Beginners Figure 20-3: A rendering of Luna (or Lunik) 24 (courtesy of NASA) Are you ready to see a crater that few ever get to see? Then look along the edge of the east limb and slightly south of central to identify crater Humboldt. Seen on the curve, this roughly 200 km wide crater holds a wealth of geographical details. Its flat, cracked floor has central peaks and a small mountain range, as well as radial rille structure. If libration and steady skies are in your favor, power up and look for dark pyroclastic areas and a concentric inner crater. Look for long, shallow Legendre and Phillips on Humboldt's west wall. It's not often you'll have a chance to study this crater, and your best bet is during the early part of the waning phase. Figure 20-4: Humboldt crater (courtesy of Damian Peach) Around the Moon in 28 Days: Lunar Observing for Beginners Section 21 - Lunar Day 16 As the Moon begins to wane, we see features in a much different light, since the shadows are cast on the other side! Tonight our mission is to return to Mare Crisium and power up with the telescope to discover some of the outstanding details that can be seen. Use the map below to help you discover these wonderful features: Figure 21-1: Map of the Mare Crisium Region (image courtesy of Roger Warner, annotations courtesy of Tammy Plotner) (1) Bernoulli, (2) Geminus, (3) Burckhardt, (4) Cleomides, (5) Debes, (6) Tralles, (7) Lacus Bonitatis, (8) Macrobius, (9) Tisserand, (10) Fredholm, (11) Proclus, (12) Palus Somni, (13) Swift and Pierce, (14) Picard, (15) Sinus Concordiae, (16) Taruntius, (17) Lick, (18) Shapely, (19) Firmicus, (20) Promontorium Agarum. Around the Moon in 28 Days: Lunar Observing for Beginners For a telescopic challenge, continue south to identify Petavius on the southern terminator. Just beyond its east wall, look for a ridge that extends from north to south separated by darkness from Petavius. This is Palitzsch, a very strange, gorge-like formation that looks as if it was caused by a meteor plowing through the Moon's surface. Palitzsch's true nature wasn't known until 1954 when the incomparable Sir Patrick Moore resolved it as a "crater chain" using the 25" Newall refractor at Cambridge University Observatory. While you’re admiring Petavius and its branching rima, keep in mind this 80-kilometer long crack is a buckle in the lava flow across the crater floor! Figure 21-2: Petavius Region (courtesy of Peter Lloyd). Around the Moon in 28 Days: Lunar Observing for Beginners Section 22 - Lunar Day 17 Tonight Mare Crisium slowly disappears into the shadows. Just northwest of its shore is the “lunar challenge” crater, Macrobius. Spanning 64 kilometers in diameter, this Class I impact crater drops below the surface to a depth of nearly 3600 meters - about the same as many of our Earthly mines. Its central peak rises back up, and at 1100 meters may be visible as a small speck inside the crater's interior. Power up and look at how steep its crater slopes are. Can you spot the smaller impact crater Macrobius O to the southeast and conjoining crater Tisserand to the east? Check out how the sunlight highlights the walls. In this particular light you can see how high and terraced they really are! Figure 22-1: The major features of the Moon on Day 17 Around the Moon in 28 Days: Lunar Observing for Beginners Figure 22-2: Macrobius Crater (courtesy of Damian Peach) For another great challenge, look where Mare Fecunditatis and Mare Tranquillitatis meet for the conspicuous crater Taruntius. Formed in the Copernician era and perhaps only about a billion years old, this 58 kilometer wide ring is really eroded – especially considered how young it is compared to other craters. Figure 22-3: Taruntius crater (courtesy of Damian Peach) Around the Moon in 28 Days: Lunar Observing for Beginners One of the reasons for looking during the waning phase is because you'll stand a better chance at spotting some of the many "ghost rings" which accompany Taruntius and the unusual amounts of lava floodings to the southwest. If the lighting is right, apply high magnification in a telescope and you'll notice its floor is fractured from an upheaval and the northwest rim has been broken up by Cameron crater. Did you notice a slightly darker area around Cameron? Good for you for being observant! Chances are this is a deposit of volcanic ash from a small vent. Can you spot the other just south of the central peak? Now let's have some quiet time as we view an area highlighted by sunset - the Caucasus Mountains. Easily spotted in both binoculars and small telescopes, this range towers some 5182 meters above the surrounding plains - making its peaks as high as Mount Ararat. As the shadows throw the rugged terrain into bold relief, take the time to enjoy watching nightly as the terminator moves along the lunar surface. As time passes you can follow the mountain's shadows shortening and details emerging. It's a very peaceful experience. Figure 22-4: The Caucasus Mountains (courtesy of Greg Konkel) Around the Moon in 28 Days: Lunar Observing for Beginners Section 23 - Lunar Day 18 Tonight the Moon gives a wonderful opportunity to revisit ancient landmark crater Posidonius and learn some more history. Start by identifying crater Charconac to Posidonius' southeast. It is far older than Posidonius itself and its steep northwest slopes are nearly obliterated by the larger crater's presence. Charonac is just one of those features we don't usually study - although we should. At an estimated 4 billion years old, it sprang to life in the pre-Imbrian period, and one look at its distressed floor tells of a violent life. Look for craterlet Chacornac A and Rimae Chacornac inside of its 50 kilometer diameter expanse! Figure 23-1: The major features of the Moon on Day 18 Around the Moon in 28 Days: Lunar Observing for Beginners Figure 23-2: The craters Posidonius and Charconac (Cacornac) and region. If you continue southward from Posidonius and Charconac along the edge of Mare Serenitatis, you'll catch partially open crater Le Monnier.