A donut on the Moon
In this case the donut is a crater dubbed Bell E Crater, with a second concentric rim in its interior. The photo to the right, reduced to post here, was taken by Lunar Reconnaissance Orbiter (LRO) as part of its high resolution survey of the entire Moon. As noted at the first link:
Craters not only vary in shape but also in complexity. There are simple craters and complex craters with ring structures and mountains at the center. Somewhere in between is Bell E, a small crater located within the larger Bell crater. These donut-shaped formations are commonly known as concentric craters. Many questions remain on the origin of donut craters. While there have been several ideas about their origin, including double impacts, the currently favored hypotheses involve volcanic processes and compositional variations.
The article outlines four hypotheses for explaining this crater’s formation, a perfectly aligned double impact, ripples at impact into thick warm lava, layers of different densities, and later volcanic activity. None do a good job of explaining all of the concentric craters found on the Moon, and thus suggest that these craters might have formed from some combination of more than one theory.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
In this case the donut is a crater dubbed Bell E Crater, with a second concentric rim in its interior. The photo to the right, reduced to post here, was taken by Lunar Reconnaissance Orbiter (LRO) as part of its high resolution survey of the entire Moon. As noted at the first link:
Craters not only vary in shape but also in complexity. There are simple craters and complex craters with ring structures and mountains at the center. Somewhere in between is Bell E, a small crater located within the larger Bell crater. These donut-shaped formations are commonly known as concentric craters. Many questions remain on the origin of donut craters. While there have been several ideas about their origin, including double impacts, the currently favored hypotheses involve volcanic processes and compositional variations.
The article outlines four hypotheses for explaining this crater’s formation, a perfectly aligned double impact, ripples at impact into thick warm lava, layers of different densities, and later volcanic activity. None do a good job of explaining all of the concentric craters found on the Moon, and thus suggest that these craters might have formed from some combination of more than one theory.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
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