Tuesday 8 July 2014

Copernicus and ejecta ring

Hi all,

A second sketch in less than a week!  An absolute flood compared to the previous 12 months!

I have sketched the crater Copernicus on other occasions.  I enjoy sketching this magnificent ray crater as it has so much to offer no matter the phase of the Moon.  Since my last Copernican sketch, I’ve come to find out more about this 95km diameter hole on the Moon.

The area around the crater Copernicus is fascinating, with so much lunar history on display – from amongst the oldest to the newest lunar formations.  From ‘ghost craters’ nearly totally lost in lava flows from long ago, to relatively recent, terrifying massive impacts whose devastating power is very much still visible.

Copernicus sits isolated surrounded by Seas and an Ocean.  These large areas of lava flows occurred a very long time ago.  The ghost crater is Stadius is nearly as large as Copernicus.  But all we see today is barely the barely visible rim of its crater, the result of an ancient impact with a very hot Moon that readily flooded the impact hole with lava.

A newer impact is the crater Erastothenes.  In structure it closely resembles Coperniucs with clear features of large impacts such as central peaks, terraced internal and external walls (the result of landslides of the steep walls).  But it is an older impact than Copernicus because the rays of ejecta material have been covered over by those of Copernicus.

The rock that created Copernicus was a massive one.  The impact through up an enormous amount much material.  Much was vaporized and pulverzied that blew way out from the impact zone, being deposited as the rays that we see today.  There are even ‘shadow zones’.  These formed when the cloud of polverised rock raced over a mountain range  and eddie currents were created depositing material behind the ledge.

Another great feature of Copernicus is another set of ejecta.  Rock was not only pulverised but also ejected out from the impact as huge bolders.  These rocks inturn created their own set of craterlets.  These craterlets surround Copernicus, even forming strings of impacts.  But these are not considered Chain Craters as they are the result of secondary impacts from a larger impact.  Chain Craters are a string of primary impacts.  In the sketch you will see one of the more prominent strings of secondary impacts.  These secondary impacts are not trivial ones either.  Some of these craterlets are over 5km in diameter which would have taken a substantially big rock to have been thrown out to make such a large crater.  Conditions on the night were not perfect.  If conditions were better a whole lot more of these secondary impacts would have been visible.

This night I also took a photo of myself at the eyepiece with all the gear I use while sketching.  The white box is a polystyrene box I use as a dew hutch to protect my materials from dew during the evening.  I also made a video of the sketch.  I’ll be looking at making a time lapse video of this as a 3hour video of the sketch is not gripping viewing…

Object:  Copernicus and surrounds
Telescope:  C8, 8” SCT
Gear:  8mm LVW, 250X
Date:  7th July 2014
Location:  Sydney, Australia
Media:  White and grey soft pastel, charcoal and white ink on A5 size black paper

Duration:  approx. 3hrs

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