Kitt Peak Nightly Observing Program
Splendors of the Universe on YOUR Night!
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Near the lunar south pole, in the rugged Southern Highlands, you can find the second largest crater on the Nearside of the Moon. Clavius looks very oblong, due to heavy foreshortening, but is a 230 km wide circular crater. It is heavily scarred by younger craters
Gassendi is a large, 110 km wide, easy to recognize crater on the northern rim of the Mare Humorum. Gassendi and smaller crater Gassendi A together form a sort of ring-with-gemstone shape, making it easy to pick out the pair amongst all the other craters in the SW quadrant of the Moon. The floor of Gassendi is not very deep, and heavily fractured. Its central peaks are easy to see.
Because of its very smooth, dark floor, Plato is a very distinct crater, seen just north of Mare Imbrium. Plato is 101 km across, and the peaks of the rim rise 2,000 meters above the floor.
Proclus is a very bright crater just west of Mare Crisium. Its bright rays radiate in mostly 3 directions. To its west is Palus Somni—the Marsh of Sleep.
Tycho is a prominent crater on the Moon—but it doesn’t stand out because of its size. At 85 km in diameter it is one of thousands of craters on the Moon its size and larger. Tycho stands out because of its rays. Crater rays are formed by ejecta—dust and debris ejected from the surface during and impact event, that spreads upwards and outwards, and eventually settles back down on the surface to leave behind radial spikes around newly formed craters. Prominent and extensive rays suggest that a crater is fresher, or more recently formed. Tycho may be as young as 108 million years old. That may sound old, but craters on the Moon can remain for billions of years.
Although we cannot see any of the materials left behind at the Apollo 11 landing site, we can still look at the spot on the Moon where the mission touched down and know, that humans first walked on the Moon in that location. There are a few images of the Apollo landing sites taken by NASA’s Lunar Reconnaissance Orbiter. Apollo 11 landed in Mare Tranquilitatis, also known as the Sea of Tranquility. The landing site is known as Tranquility Base.
Mare Crisium is distinctly seperated from all of the other maria on the near side of the Moon, making it easy to distinguish. This round feature on the Moon is nearing the eastern limb, and so, is severly foreshortened—meaning, we are not looking at it straigh on, but at an angle.
Mare Humorum is one of the smaller mare on the near side of the Moon. It is situated on the western hemisphere, south of Oceanus Procellarum. It is estimated to be about 3.9 billion years old, and is the site of one fo the Moon’s mascons. Mascons, short for mass concentrations) have slightly higher gravity than the are around them. Mare Humorum has some striking ridges and rilles. A prominant crater, Gassendi interupts the northern “coast” of Mare Humorum—its floor cracked with many rilles. Yet another, smaller crater interupts Gassendi’s northern rim—creating a memorable figure of a ring with gemstone.
The Mare Imbrium Impact Basin formed when a large object crashed into the Moon 3.9 billion years ago. subsurface lava rose to flood the giant crater, eventually solidifying into a younger, smoother terrain. Prominent features of Mare Imbrium include the crater Plato to the north, with a dark crater floor; Sinus Iridum (meaning Bay of Rainbows) to the northwest, with the Montes Jura mountain range forming a distinct C-shaped knob on the edge of the mare; and the 3 mountain ranges—Montes Alpes, Caucasus, and Apenninus—that mark the eastern edge of the mare.
Also known as a twilight zone, a terminator is where the shadow of night and the light of day come to meet on a planetary body. At the edge of where the Sun’s light reaches, the terminator is constantly moving as the Moon rotates. When observing the Moon, many features are best observed when they are near the terminator, where shadows are long and plentiful. The shadows provide higher contrast between surface features.
The mountain range Montes Alpes is one of the prominent mountain ranges along the eastern border of Mare Imbrium. The range is named for the Alps on Earth, and the peak Mons Blanc is named for the tallest peak in the Alps of Earth—though Mons Blanc is actually the 3rd tallest peak of the Lunar Alpes. The range culminates to the south in the Promontorium Agassiz. To the north, the range terminates just shy of dark-floored crater Plato.
On the eastern bank of the Mare Humorum lie a trio a satisfyingly concentric rilles.
Also known as the Straight Wall, Rupes Recta is actually a 100 km long incline along a fault. This kind of feature is known as a linear rille, or graben, and forms as the lunar crust is pulled apart. Though it looks like one continuous fault from Earth, Rupes Recta is actually a series of at least 5 segments, ranging from about 8 to about 50 km in length, each 1-3 km in width.
Your Telescope Operator and Guide. Thank you for joining me this evening! See you soon!!
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Nightly Observing Program. Most of the above images were taken as
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