Kitt Peak Nightly Observing Program
Splendors of the Universe on YOUR Night!
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Aristarchus and Herodotus
Aristarchus is not a particularly large crater, but it manages to stand out as an extremely bright crater. Near the northwestern limb of the Moon, Aristarchus is more reflective than the darker Oceanus Procellarum surrounding it. Nearby crater Herodotus is similar in size, but different in appearance. Herodotus is shallower and darker.
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.
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 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.
This is the largest sinuous rille on the Moon. It is about 3 km wide at its western end, and widens up to 6 km toward the eastern end, where you will find the Cobra Head. The Cobra Head is a steep volcanic depression near the top of a mountaid at the end of the snake-like sinuous rille. Shcröter’s Valley may have been a major source of the lava that formed the Oceanus Procellarum.Schröter’s Valley is part of the Aristarchus Plateau, and is foundto the immediate northwest of the small, but very bright crater Aristarchus.
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Nightly Observing Program. Most of the above images were taken as
the Overnight Telescope Observing Program. For more information on this unique experience please visit Overnight Telescope Observing Program.
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