Category: Vallis or valley

Raised, Tilted and polygonal

Aristarchus Plateau

The Aristarchus Plateau
By Frank McCabe

The Aristarchus Plateau
  
  The 3.6 billion year old Aristarchus plateau is a raised, tilted polygonal block
of crust in the ocean of storms with a collection of interesting features that can
be seen with telescopes of all sizes. Crater Aristarchus left of center is a large
(41 km.) 3.2 km. deep crater that is bright, young (500 million years old) and
sits near the SE edge of the plateau.  Lunar Prospector spacecraft back in 1998-99
detected radon gas being released from this region. The Space Telescope Science
Institute along with Northwestern University and others conducted an ultraviolet
and visible light analysis using the Hubble telescope to detect the presence of
titanium oxide near crater Aristarchus. This could be a potential source of oxygen
on the lunar surface and also a source of titanium metal.
   I remember well my disappointment when Apollo 18, 19 and 20 were cancelled in
1970. Apollo 18 was scheduled to land on the Aristarchus plateau near Schroter
valley. Schroter valley is an old Imbrium (3.5 billion years old) volcanic
feature that begins at the famous cobra head 25 km. north of ancient crater
Herodotus. This feature meanders north then west then southwest for more than 150
km. The bend is nearly 170 degrees. It is also large enough to be seen in a 2
inch telescope under conditions of good seeing.
  The region surrounding the beginning of Schroter valley was carefully imaged March
3rd and April 27th in 1994 by Clementine spacecraft because of reported color
changes. Clementine confirmed these changes were real. This region of the moon
shows color visible to some observers. It is described as reddish or yellowish by
those that can see this color.
  Don’t think of the moon as an annoyance that spoils galaxy hunting as some deep
sky enthusiasts sometimes do, but embrace it as the beautiful satellite it is,
awaiting observation and exploration.  
  
  
  Sketch:
  Graphite pencil, pen and ink sketch on copy paper 8.5”x11”
  Date: 1-2-2007 1:50 to 3:45 UT
  Temperature: -1.2 °C (30° F)
  Calm, seeing good for this part of Illinois
  Antoniadi mostly IV briefly III
  13.1 inch f / 5.9 Dobsonian 6mm ortho ocular 327X
  Colongitude: 66.8°
  Lunation: 12.5 days
  Illumination: 97%
  

Of Blocky Origins

Vallis Rheita
 

The Region of Vallis Rheita
  
  Very early Sunday morning the moon was approaching the meridian about 35° above
the southeastern horizon when I decided to take a closer telescopic look and
select a sketching target. Prominently on display near the sunset terminator was
the famous 330 kilometer long Vallis Rheita. This valley formed as a by-product of
the secondary blocks thrown from the mare Nectarius basin forming event that
occurred 3.92 billion years ago. Apollo 16 astronauts John Young and Charles Duke
collected rock samples that included ejecta from the Nectarius event which
permitted the dating. A multitude of monstrous blocks heaved out from the initial
impact to the south created this less than regular catena. The valley lines up
nicely with the west central region of the Sea of Nectar accounting for this
hypothesis.
  Adjacent to the northern end of Vallis Rheita and slightly younger in age is
crater Rheita, a 70 kilometer gouge with a low central peak and a fairly sharp
crest. Across the deep valley from Rheita to the southwest is 88 kilometer crater
Metius with its 4 kilometer high walls and small crater Rheita B east of a pair of
low ridges on the crater floor. This highland region of the moon is very old and
battered. It was showing some of its best features in the setting sun.
  
  
  Sketching:

For this sketch I used: black Strathmore 400 Artagain paper, 8”x 10”, white and
black Conte’pastel pencils and a blending stump. Brightness was slightly decreased
(-5) and contrast increased (+5) after scanning using Microsoft Office Picture
Manager.

Telescope: 10 inch f/5.7 Dobsonian and 6mm eyepiece 241x
Date: 2-24-2008 0:10-1:00 UT
Temperature: -8°C (19°F)
clear, calm
Seeing:   Antoniadi III
Co longitude: 123.2°
Lunation: 17 days
Illumination: 90.1 %
Phase:   323.3°

Frank McCabe