Hello everyone,
At long last I’ve managed a lunar sketch again! As things would have it, two nights and two
sketches!
I didn’t have things all my way. The first sketch was of Lacus Mortis, and it
was poetically killed off early…
One thing that I enjoy doing that is part of my sketching ‘process’
is looking up atlases and information about the area that I’ve sketched. Often when deciding upon a particular feature
to sketch, there has been something peculiar about that feature that has caught
my attention and imagination. And often
in my research, I come to have my suspicions justified with amazing
revelations. And sometimes, just
sometimes, the most amazing and unexpected details. Lacus Mortis proved to be one of these
exciting revelations, despite clouds rolling in to kill off the sketch session
early.
Lacus Mortis, the Lake of Death, is an ancient feature. It was created early in the Moon’s history
when the crust was very thin. A giant
asteroid crashed into the thin crust, and instead of forming a crater as we
know it, but the entire basin was flooded.
Lacus Mortis is not unique in this way.
All the Maria we see today all have this essentially round circumference
and completely flooded basin. What
distinguishes Lacus Mortis form other ‘seas’ is the fractures and faults that crisscross
it.
These fractures and faults all have a curious point of
convergence – the centrally located crater, Burg. Burg is also an ancient feature, though much
younger than providence of Lacus Mortis.
The floor of Burg is only partially flooded, giving a hint that the Moon
was cooler when Burg was formed that the crust was thicker.
Now, while sketching Burg, I noticed something strange about
the inside of its wester side. There
appeared to be another wall inside the western rim. It somewhat looked like the rim had somehow
detached, but the rim looked too intact to be damaged. But seeing was not good enough to allow for
more magnification or resolution of this curious feature.
When I looked up Lacus Mortis on Virtual Moon Atlas, the
anomaly that I had spotted became apparent.
This ‘detached wall is actually a gigantic set of volcanic domes!
There are a few clues to the origins of this anomalous internal
structure of Burg. You’ll notice that it
does not follow the concentric nature of the remnant terraces. Another distinguishing feature is this area
is made up of darker material than the surrounding material. And a third distinguishing feature we garner
from Earth based volcanic domes, like Mt St Helens’ multiple domes inside its
massive caldera.
Burg’s isolated location inside Lacus Mortis and lack of significant
later impact damage has meant that much of its original ejecta material ray
structures have been preserved. That
this ray system is no longer brilliantly while like Copernicus or Tyco is
evidence of the solar wind weathering that occurs on the lunar surface. A large impact on the Moon throws up material
that is from deeper layers under the surface, and its appearance is much
brighter. Though there is no atmosphere
or weather or water to cause erosion, weathering occurs as the radiation and
solar wind from the sun causes changes in the chemical composition of these
fresher material that has been thrown up, causing it to darken. The brilliant ray system of Copernicus and
Tyco will also eventually darken and lose its brilliance.
Lacus Mortis’ riles and fault lines are extensive and
massive. One particular fault line rival
Rupes Recta for the vertical height differential between the two sections. This particular fault line runs north-south
in the south-western quadrant. The shadow
that is cast westwards is so long, suggesting the massive height differential.
I so wanted to include the surround mountain ranges and
peripheral structures around Lacus Mortis, but clouds rolled in, somewhat appropriately
killing off the sketching session.
Object: Lacus Mortis
Scope: C8, 8” SCT
Gear: 8mm LVW, 250X
Date: 13th
April, 2016
Location: Sydney,
Australia
Media: White and grey
soft pastels, charcoal & white ink on A4 size black paper.
The following night I had a second chance for a sketch. Aristoteles beckoned this time.
Aristoteles is roughly of a similar age and many similar
features as Burg. It lies on the
tortured southern shore of Mare Frigoris.
Its floor is only partially flooded – there are smaller craters around
Aristoteles that are ghost craters – totally flooded with only the barest of
the original rim still showing. It has
also been spared damage from large subsequent impacts. Also like Burg, much of the remnant ray
system structures have been preserved, though now weathered and no longer
brilliantly white.
Aristoteles though share one feature with a much younger,
though just as massive impact that formed Copernicus. Surrounding Copernicus is an extensive system
of secondary impacts that were formed from the material that had been thrown
out from the original impact.
Aristoteles also shares an extensive collar of secondary impacts. Differentiating Aristoteles and Burg’s collars
apart of these secondary impacts is the very extensive within the ray system of
Burg. Many of these secondary impacts
are co-linear, radiating out from the centre of Burg, accentuating the
appearance & depth of the ray system. Aristoteles secondary impacts are much further
reaching, attesting to the much larger impact that formed Aristoteles.
One interesting feature around Aristoteles is the ancient,
flooded & highly damaged crater Mitchell, immediately on Aristoteles
eastern rim. My sketch shows that the
western rim of Mitchell has been obliterated by Aristoteles, and its eastern
rim is irregular. Photographs of
Mitchell show that its eastern rim has been filled in by material that had been
thrown out from the impact that created Aristoteles.
To the south of Aristoteles is the large crater Exudous.
Object: Aristoteles
& surrounds
Scope: C8, 8” SCT
Gear: 8mm LVW, 250X
Date: 14th
April, 2016
Location: Sydney,
Australia
Media: White &
grey soft pastel, charcoal and white ink on A5 size black paper
Beautiful work, and great narrative.
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