Around the Moon in 28 Days: Lunar Observing for Beginners Course Notes Section 13 - Lunar Day 8 Section 14 - Lunar Day 9 Section 15 - Lunar Day 10 Section 16 - Lunar Day 11 Section 17 - Lunar Day 12 Section 18 - Lunar Day 13 Section 19 - Lunar Day 14 (Full Moon) Copyright © 2010 Mintaka Publishing Inc. Section 13 - Lunar Day 8 Let's begin tonight with a deeper look at the "Sea of Rains" - Mare Imbrium- landing place of Apollo 15. Stretching out 1123 kilometers over the Moon's northwest quadrant, Imbrium was formed around 3800 million years ago when a huge object impacted the lunar surface and created a gigantic basin. The basin itself is surrounded by three concentric rings of mountains. The most distant ring reaches a diameter of 1300 kilometers and involves the Montes Carpatus to the south, the Montes Apenninus southwest, and the Caucasus to the east. The central ring is formed by the Montes Alpes, and the innermost has long been lost except for a few low hills that still protrude after eons of lava flow. Figure 13-1: The major features of the Moon on Day 8. Around the Moon in 28 Days: Lunar Observing for Beginners Originally the impact basin was believed to be as much as 100 kilometers deep. So devastating was the impact event that created Mare Imbrium that a Moon-wide series of fault lines appeared as the massive strike shattered the lunar lithosphere. Imbrium is also home to a huge mascon, and images of the far side show areas opposite the basin where seismic waves traveled through the interior and shaped its landscape. The floor of the basin rebounded from the cataclysm and filled in to a depth of around 12 kilometers. Over time, lava flow and regolith added another five kilometers of material, yet evidence remains of the ejecta which was flung more than 800 kilometers away, carving long runnels through the landscape. Figure 13-2: The major features in and around Mare Imbrium There's no ducking lunar impacts and it's time to a look at the grandest crater-causing impact of all - Class I crater Tycho. Spanning 90 kilometers wide and descending 4206 meters below lunar surface, Tycho's massive walls are 21 kilometers thick. As one of the youngest craters, Tycho might not look like much tonight, but it is surely one of the most impressive of all features when the Moon reaches Full. Look around the perimeters of Tycho for six small craters Around the Moon in 28 Days: Lunar Observing for Beginners encircling it like an old analog telephone dial. To the southeast, another prominent feature calls attention to itself - Maginus. Power up and look closely at the more than 50 meteoritic impacts that have all but destroyed it. The very largest of the wall craters is on the southwest crest and is named Maginus C. On the outer north wall, look for less conspicuous Proctor. It, too, has been struck many times! Figure 13-3: A closeup of the crater Tycho (courtesy Damian Peach) If you're catching a very spectacular crater nearly central on the terminator and are ready to have a look, then let's wait no longer. While Copernicus is not the oldest, deepest, largest, or brightest crater on the Moon, it certainly is one of the most detailed. Visible in binoculars and spectacular when magnified in a powerful telescope, this youthful crater gives a highly etched appearance. Its location in a fairly smooth plain near the center of the Moon's disc, and its prominent "splash" ray system, all combine to make Copernicus visually stunning in all optics. Spanning 100 kilometers, with 23 kilometer thick walls, the "Mighty One" is most definitely an impact crater that left its impression down to 3840 meters below the surface. Geologist Gene Shoemaker cited many features of Copernicus which mirror our own terrestrial impact features. Many of these Copernican features could have been caused by a large meteoritic body - a Around the Moon in 28 Days: Lunar Observing for Beginners body about the size of Comet Halley's nucleus. No matter what optical aid you use, mid- placed Copernicus simply rocks! Figure 13-4: A closeup of the crater Copernicus (courtesy Damian Peach) Around the Moon in 28 Days: Lunar Observing for Beginners Chapter 14 - Lunar Day 9 Tonight let's have a look through binoculars or telescopes at another tremendous impact region located to the lunar west of Plato. Sinus Iridum is one of the most fascinating and calming areas on the Moon. At around 241 kilometers in diameter and ringed by the Jura Mountains, it's known by the peaceful name of the “Bay of Rainbows”. But it was formed by a cataclysm. Astronomers speculate a minor planet around 200 kilometers across impacted our forming Moon at a glancing angle, and the result of this crash caused "waves" of material to wash up to a "shoreline," forming this delightful C-shaped lunar feature. Looking at Sinus Iridum is much like looking at an Earthly bay. The smooth inner sands show soft waves called "rilles," broken only by a few small impact craters. The picture is completed by Promontoriums Heraclides and LaPlace, which tower above the surface, at 1800 meters and 3000 meters respectively, and appear as distant "lighthouses" set on either tip of Sinus Iridum's opening. Figure 14-1: The major features of the Moon on Day 9. Around the Moon in 28 Days: Lunar Observing for Beginners Figure 14-2: Sinus Iridum Region (courtesy of Peter Lloyd) Mare Insularum, the "Sea Of Islands", will be partially revealed tonight. While only a small section of this reasonably young mare is now visible southwest of Copernicus, the lighting will be just right to spot its many-hued lava flows. To the northeast is a lunar challenge: Sinus Aestuum - the “Bay of Billows”. This mare-like region has an approximate diameter of 290 kilometers, and its total area is about the size of the state of New Hampshire. Containing almost no features, this area is low albedo (it provides very little surface reflectivity). Can you see any of Copernicus' splash rays beginning to appear across it yet? Can you see two larger craters to the southwest? The northernmost is Wilhelm, but set your sights toward the southern - Longomontanus. Named for Danish astronomer and assistant to Tycho Brahe, Christian S. Longomontanus, this splendid mountain-walled plain measures about 150 kilometers in diameter and shows a broken border on its north and an off-center mountain peak. Notice how its smooth sands have eroded its edges over time. Just outside its eastern wall, look for the remains of a much older crater destroyed when Longomontanus Around the Moon in 28 Days: Lunar Observing for Beginners formed. This splendid binocular and small telescope trophy is often overlooked in favor of its grander neighbors. Figure 14-3: Mare Insularum / Sinus Aestuum – Clementine (image courtesy of NASA) Figure 14-4: Crater Longomontanus (courtesy of Damian Peach) Around the Moon in 28 Days: Lunar Observing for Beginners Chapter 15 - Lunar Day 10 Tonight we'll begin in the lunar north with Sinus Roris - "The Bay of Dew". As an extension of the vast Oceanus Procellarum it covers about 202 kilometers, though many lunar maps aren't quite true to Sinus Roris' dimensions. The borders aren't well defined because we are viewing it on a curve. However, we do know the eastern edges join Mare Frigoris. Sinus Roris is far lighter in color than other features of its type, the result of ejecta from many nearby impacts. It also holds a fanciful place in history, as seen in this excerpt from the science fiction story "Man on the Moon" by the greatest rocket scientist at all, Wernher van Braun: “There's one section of the moon that meets all our requirements, and unless something better turns up on closer inspection, that's where we'll land. It's an area called Sinus Roris, or "Dewy Bay," on the northern branch of a plain known as Oceanus Procellarum, or "Stormy Ocean" (so called by early astronomers who thought the moon's plains were great seas). Dr. Fred L. Whipple, chairman of Harvard University's astronomy department, says Sinus Roris is ideal for our purpose - about 1000 kilometers from the lunar north pole, where the daytime temperature averages a reasonably pleasant 40 degrees and the terrain is flat enough to land on, yet irregular enough to hide in." Figure 15-1: Man in the Moon (courtesy of the Astronomical League) Around the Moon in 28 Days: Lunar Observing for Beginners Figure 15-2: The major features of the Moon on Day 10. As you stand here on Earth and look for Sinus Roris, don't forget to use your imagination as well. Tonight is a great time to blur your science eyes just a little bit and see if you can spot the combination of light a dark areas which make the lunar globe look like a face... and behold the "Man In the Moon" (see above)! Now, let's take a look at where real men have been to the Moon. It's time to investigate Mare Cognitum - "The Sea That Has Become Known." Look for Mare Cognitum south of crater Copernicus. Just to its east is the shallow Fra Mauro, the landing area for Apollo 14. Let's talk about why its exploration was so important. Named for the 80 kilometer diameter Fra Mauro crater, these highland hills might be ejecta from the formation of Mare Imbrium. Debris may have been blasted up from depth of 160 kilometers, so studying the area would give us insight to the physical and chemical nature below the lunar crust.