Difference between revisions of "June 14, 2006"

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<em>image by Apollo 10 from[http://www.apolloarchive.com/apollo_gallery.html  Apollo Image Gallery]</em></p>
 
<em>image by Apollo 10 from[http://www.apolloarchive.com/apollo_gallery.html  Apollo Image Gallery]</em></p>
 
<p>Moltke crater is probably best known as a guidepost to the Apollo 11 landing site. It is a fresh, 7 km wide [http://www.classzone.com/books/earth_science/terc/content/investigations/es2506/es2506page07.cfm simple crater] with steep bowl-shaped walls. This Apollo 10 image beautifully shows the ejecta deposits that surround it. On a higher Sun view the ejecta shows up as a bright patch; in this closeup it is seen as a thinning pile of bumpy hills (called hummocks by geologists) and beyond them tiny secondary impact craters. In fact, this area - like every area seen at extreme high resolution - is peppered with tiny craters. Some are clearly secondaries (the wormy chains in the foreground) and any none clump member crater is assumed to be a primary impact. But a study of a very young impact crater on Mars has led some researchers to believe that millions of secondary craters may be created by the formation of a moderate size primary crater. That would mean that most small (with diameters less than 2 km) craters on Mars and the Moon are secondaries. And thus estimates of surface ages based on counts of small craters would be unreliable. Most craters observed telescopically are larger than 2 km and are probably primaries, but when looking at a great space image like this it is possible that nearly all of the small craters are secondaries.</p>
 
<p>Moltke crater is probably best known as a guidepost to the Apollo 11 landing site. It is a fresh, 7 km wide [http://www.classzone.com/books/earth_science/terc/content/investigations/es2506/es2506page07.cfm simple crater] with steep bowl-shaped walls. This Apollo 10 image beautifully shows the ejecta deposits that surround it. On a higher Sun view the ejecta shows up as a bright patch; in this closeup it is seen as a thinning pile of bumpy hills (called hummocks by geologists) and beyond them tiny secondary impact craters. In fact, this area - like every area seen at extreme high resolution - is peppered with tiny craters. Some are clearly secondaries (the wormy chains in the foreground) and any none clump member crater is assumed to be a primary impact. But a study of a very young impact crater on Mars has led some researchers to believe that millions of secondary craters may be created by the formation of a moderate size primary crater. That would mean that most small (with diameters less than 2 km) craters on Mars and the Moon are secondaries. And thus estimates of surface ages based on counts of small craters would be unreliable. Most craters observed telescopically are larger than 2 km and are probably primaries, but when looking at a great space image like this it is possible that nearly all of the small craters are secondaries.</p>
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<i>You can support LPOD when you buy ANY book from Amazon thru [http://www.lpod.org/?page_id=102  LPOD!]</i></p>
 
<i>You can support LPOD when you buy ANY book from Amazon thru [http://www.lpod.org/?page_id=102  LPOD!]</i></p>
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===COMMENTS?===  
 
===COMMENTS?===  
 
Click on this icon [[image:PostIcon.jpg]] at the upper right to post a comment.
 
Click on this icon [[image:PostIcon.jpg]] at the upper right to post a comment.

Revision as of 18:39, 4 January 2015

Primaries or Secondaries?

AS10-29-4324.jpg
image by Apollo 10 fromApollo Image Gallery

Moltke crater is probably best known as a guidepost to the Apollo 11 landing site. It is a fresh, 7 km wide simple crater with steep bowl-shaped walls. This Apollo 10 image beautifully shows the ejecta deposits that surround it. On a higher Sun view the ejecta shows up as a bright patch; in this closeup it is seen as a thinning pile of bumpy hills (called hummocks by geologists) and beyond them tiny secondary impact craters. In fact, this area - like every area seen at extreme high resolution - is peppered with tiny craters. Some are clearly secondaries (the wormy chains in the foreground) and any none clump member crater is assumed to be a primary impact. But a study of a very young impact crater on Mars has led some researchers to believe that millions of secondary craters may be created by the formation of a moderate size primary crater. That would mean that most small (with diameters less than 2 km) craters on Mars and the Moon are secondaries. And thus estimates of surface ages based on counts of small craters would be unreliable. Most craters observed telescopically are larger than 2 km and are probably primaries, but when looking at a great space image like this it is possible that nearly all of the small craters are secondaries.

Chuck Wood

Technical Details:
AS10-29-4324
NOTE: I will be at a games + society meeting in Madison, Wisconsin the next few days - look for a new LPOD on Sunday.

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