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| | =Primaries or Secondaries?= | | =Primaries or Secondaries?= |
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| | <div class="post" id="post-335"> | | <div class="post" id="post-335"> |
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| | <div class="storycontent"> | | <div class="storycontent"> |
| | <p>[[File:AS10-29-4324.jpg|AS10-29-4324.jpg]]<br /> | | <p>[[File:AS10-29-4324.jpg|AS10-29-4324.jpg]]<br /> |
| − | <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> |
| | <p>[mailto:tychocrater@yahoo.com Chuck Wood]</p> | | <p>[mailto:tychocrater@yahoo.com Chuck Wood]</p> |
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| | <p><b>Related Links:</b><br /> | | <p><b>Related Links:</b><br /> |
| | Rükl plate 46</p> | | Rükl plate 46</p> |
| − | <p><b>Yesterday's LPOD:</b> [[June 13, 2006|A Hot Day At Plato]] </p> | + | <p><b>Yesterday's LPOD:</b> [[June 13, 2006|A Hot Day at Plato]] </p> |
| | <p><b>Tomorrow's LPOD:</b> [[June 18, 2006|Oozing Ejecta]] </p> | | <p><b>Tomorrow's LPOD:</b> [[June 18, 2006|Oozing Ejecta]] </p> |
| − | <!-- Removed reference to store page --> | + | <!-- Removed reference to store page 2 --> |
| | </div> | | </div> |
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| − | ===COMMENTS?===
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