ready steady science... cocoa craters
what you’ll need:
• Flour
• Cocoa powder
• Baking Tray
• Marbles
• Newspaper
what to do:
• Spread the newspaper out, and put the baking tray onto it. This activity is known as ‘protecting one’s carpet’ in scientific circles!
• Make a thick layer of flour in the baking tray. Smooth it out, and then cover this layer with a thinner layer of cocoa powder.
• Standby for action: drop marbles from different heights and observe the craters they make.
what's happening?
What does your tray of baking ingredients have in common with the Moon? The circular features you can see on the Moon's surface are impact craters just like what you’ve just done in the flour and cocoa. They were formed when impactors (ie incoming objects) smashed into the surface, and on the Moon, you can see layers upon layers of these craters have been created over the millennia. (Check out some images of the Moon’s surface at http://nssdc.gsfc.nasa.gov/photo_gallery/ )
The explosion and excavation of materials at each impacted site creates piles of rock (called ejecta) around the circular hole, as well as bright streaks of target material (called rays) which can be thrown great distances out of the crater.
Two basic ways in which craters are formed in nature are:
1) impact of a projectile on the surface
2) collapse of the top of a volcano creating a crater termed caldera.
By studying all types of craters on Earth and by creating impact craters in experimental laboratories, geologists concluded that the Moon's craters are "impact" in origin.
The factors affecting the appearance of impact craters and ejecta are the size and velocity of the impactor, and the geology of the target surface.
By recording the number, size, and extent of erosion of craters, lunar geologists can determine the ages of different surface units on the Moon and can piece together the geological history. This technique works because older surfaces are exposed to impacting meteorites for a longer period of time than are younger surfaces.
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