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October 26, 2007

BEFORE AND AFTER

Filed under: , — chuckwood @ 12:06 am

stadius_lpod.jpg
before image by François Emond, Hautes-Alpes, FRANCE.

Stadius should never have been named. There is hardly anything there but a hint of a past presence. Stadius formed on an earlier, lower surface and was later covered by lavas from Sinus Aestuum and/or Mare Insularum. Although only a few discontinuous pieces of its rim remain - the lavas really filled it to the brim - it is slightly larger than nearby Eratosthenes and originally must have looked similar, with a depth of 3 to 4 km. Now all of that hole is filled with lava. The area around Stadius was pounded by ejecta from the formation of Copernicus, and that association with the many little craterpits - which earlier selenographers didn’t seem to realize were from Copernicus - may have helped attract attention and ultimately a name. Indeed, Neison, Elger and Goodacre all commented on the pits, but never mentioned that they are related to Copernicus. The idea that these classic observers seemed to be struggling with was finally annuciated by Gilbert Fielder in his 1963 book, Lunar Geology. Fielder suggested that Stadius and other low rimmed features such as Wallace and Egede were really the youngest volcanic structures whose growth had not yet reached the great size of Copernicus and other older craters. Fielder recognized that the craterpits in radial lines from Copernicus were ejecta from that (volcanic) cone, but those in Stadius were volcanic pits themselves. Fielder, my friend, was wrong. I have swept away all the pits within Stadius to see how that part looked before Copernicus’ impact origin blasted the debris out that excavated the pits. That current view is at the bottom of the page.

Chuck Wood

Technical Details:
08/06/07; 03h45 UT, in Chorges (Hautes-Alpes, FRANCE). Dobsonian 16″ + FFC Barlow lens + webcam Vesta Pro (B & W, raw mode) + red filter.

Related Links:
Rükl plate 32
François’ website

Now you can support LPOD when you buy any book from Amazon thru LPOD!

stadius_060807_03h45TU.jpg

4 Comments »

  1. It’s interesting to note the difference between Stadius and Wargentin. Both craters are
    filled to the brim with lava. The lava that overwhelmed Stadius apparently came from outside the
    crater, while the lava that filled Wargentin came from the inside.

    Could Wargentin also be described as a ghost crater?

    –Bill

    Comment by Westwind — October 26, 2007 @ 8:48 am

  2. You gave me quite a shock when I first looked at the nearly craterless interior of Stadius. Then I
    read the caption and started feeling better that I had never noticed the lack of craterlets before!
    Here’s a real challenge: Sweep away the mare lavas to see what Stadius looked like before it was floodee.
    Do you suppose that someday, with the help of seismic data, that might be possible?
    Howard

    Comment by Howard E — October 26, 2007 @ 11:17 am

  3. Howard, check out
    http://www.lpod.org/?m=20070828
    I believe Lunar Deformation Forensic will be a popular past time. With new techniques borrowed from other fields of science, low priced yet powerful computers plus the right software; in addition radar-metic telemetry arriving from all the new Lunar probes: the amature with that extra range of seeing, will pretty much piece together a very accurate timeline of the moon, based on stratigraphy reveled by the eyes of light & radar. Maybe, as a bonus, fossilized craters under the Marii.[assumming they survived the initial wash process we see occurring at the beach when waves come in to demolish sandcastles away]

    Comment by Abadin — October 26, 2007 @ 7:12 pm

  4. Bill - Hmm - I’d never thought of Wargentin as a ghost, and in fact I slightly mis-used the word for Stadius. Typically ghost craters are ones that are marked by mare ridges - like Lambert R.

    Howard - sorry to frighten you! I don’t think we have to wait for seismic crews on the Moon to guess what Stadius looked like pre-inundation. It looked like Eratosthenes!

    Abadin - as you point our radar can look under some materials, but we can see many ghost craters already and, like Stadius, reconstruct in our minds what they were like.

    Chuck

    Comment by chuckwood — October 26, 2007 @ 7:20 pm

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