Difference between revisions of "September 22, 2020"

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=A Highly Featured Hole in the Ground=
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=Young And Old=
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Originally published April 4, 2011
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Originally published March 18, 2011
 
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<em>image by [mailto:jupiter182002@yahoo.ca Maximilian Teodorescu], Dumitrana, Romania</em><br />
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<em>left image from [http://www.esa.int/esaMI/Mars_Express/SEMTK5VTLKG_1.html#subhead4 ESA Mars Express]; right image from [http://lroc.sese.asu.edu/news/index.php?/archives/341-Nearside-Spectacular!.html#extended LRO nearside mosaic] (NASA/GSFC/Arizona State University)</em><br />
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<br />
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The European Space Agency has just released another superb image from the Mars Express orbiter.
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It shows a very familiar looking crater three or four times as long as it is wide. Every lunar observer will
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recognize the similarity to Schiller, although the ESA press release doesn't include such a mention.
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Gerhard Neukum, my colleague and a long time lunar expert, wrote the ESA caption, including the com-
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ment that it was <em>probably caused by the impact of a train of projectiles.</em> That is one possibility, but the 78
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km long martian crater is young enough to preserve its ejecta blanket, which only extends to the sides of
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the elongated structure. That is a diagnostic sign of an oblique impact. The Moon's 180 km long Schiller
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looks almost identical in outline but its floor has been filled in, and part of it does have a linear central
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peak, another diagnostic sign of oblique impact. Lavas erupted into the Schiller-Zucchius Basin covered
 +
Schiller's ejecta, but I am sure it too only extended to the sides. It was noted 25 years ago that there are
 +
quite a few elongated craters on Mars, and Pete Schultz of Brown University suggested that a population
 +
of previous moons crashed to the surface of Mars, causing oblique impacts and elongated craters; Phobos
 +
and Deimos are elongated craters waiting to happen. The Moon has only one Schiller, it probably formed
 +
from a one-off (large) oblique impact event.
 
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Looking like a mighty turreted fortress, the central peak complex of Petavius almost steals the show from its massive rim-to-peak trench. Petavius has so many unusual features that it is hard to account for them all. Here is a list: (1) the [[August_14,_2006|rim]], (4) the slight dome and [[March_21,_2006|pyroclastic deposits]], (5) roughly radial and concentric [[December_12,_2006|rilles]], (6) the ghostly hint of a ring of hills like a transition to a central peak basin, and (7) the apparent doming of the central area of the crater. Most of these features can be explained by the the idea that Petavius is a floor-fractured crater. The standard model is that the impact breccia under a large crater near a mare gets invaded by a mass of rising magma that lifts the crater floor. That causes (7) and (5), and some magma leaks to the surface leading to (4). Since Petavius is large it is at the early end of the transition to basins (6). The remaining three features seem unrelated to the others. But (1) and (2) clearly are related; is the wider rim (3) an older crater, mostly covered by Petavius? I don't really think so....<br />
 
 
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<em>[mailto:tychocrater@yahoo.com Chuck Wood]</em><br />
 
<em>[mailto:tychocrater@yahoo.com Chuck Wood]</em><br />
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<br />
 
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<strong>Technical Details</strong><br />
 
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October 25, 2010, 01:34 U.T. 12&quot; Newtonian @F/25, DFK 21 AF 04.AS, 2500/6000.<br />
 
 
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<br />
 
<strong>Related Links</strong><br />
 
<strong>Related Links</strong><br />
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Rükl plate [https://the-moon.us/wiki/R%C3%BCkl_59 59]<br />
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Rükl plate [https://the-moon.us/wiki/R%C3%BCkl_71 71]<br />
 
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<p><b>Yesterday's LPOD:</b> [[September 21, 2020|Invisible Triumph]] </p>
 
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<p><b>Tomorrow's LPOD:</b> [[September 23, 2020|Observing with a Mission]] </p>
 
 
<hr />
 
<hr />
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<p><b>Yesterday's LPOD:</b> [[September 21, 2020|What is Hidden Below the Surface?]] </p>
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<p><b>Tomorrow's LPOD:</b> [[September 23, 2020|Twins Separated Before Birth]] </p>
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Latest revision as of 02:12, 22 September 2020

Young And Old

Originally published March 18, 2011 LPOD-Mar18-11.jpg
left image from ESA Mars Express; right image from LRO nearside mosaic (NASA/GSFC/Arizona State University)

The European Space Agency has just released another superb image from the Mars Express orbiter. It shows a very familiar looking crater three or four times as long as it is wide. Every lunar observer will recognize the similarity to Schiller, although the ESA press release doesn't include such a mention. Gerhard Neukum, my colleague and a long time lunar expert, wrote the ESA caption, including the com- ment that it was probably caused by the impact of a train of projectiles. That is one possibility, but the 78 km long martian crater is young enough to preserve its ejecta blanket, which only extends to the sides of the elongated structure. That is a diagnostic sign of an oblique impact. The Moon's 180 km long Schiller looks almost identical in outline but its floor has been filled in, and part of it does have a linear central peak, another diagnostic sign of oblique impact. Lavas erupted into the Schiller-Zucchius Basin covered Schiller's ejecta, but I am sure it too only extended to the sides. It was noted 25 years ago that there are quite a few elongated craters on Mars, and Pete Schultz of Brown University suggested that a population of previous moons crashed to the surface of Mars, causing oblique impacts and elongated craters; Phobos and Deimos are elongated craters waiting to happen. The Moon has only one Schiller, it probably formed from a one-off (large) oblique impact event.

Chuck Wood

Related Links
Rükl plate 71

Yesterday's LPOD: What is Hidden Below the Surface?

Tomorrow's LPOD: Twins Separated Before Birth

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