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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.
From the press release: From the moment he is handed a possibility of making the first alien contact, Saunders Maxwell decides he will do it, even if doing so takes him through hell and back.
Unfortunately, that is exactly where that journey takes him.
The vision that Zimmerman paints of vibrant human colonies on the Moon, Mars, the asteroids, and beyond, indomitably fighting the harsh lifeless environment of space to build new societies, captures perfectly the emerging space race we see today.
He also captures in Pioneer the heart of the human spirit, willing to push forward no matter the odds, no matter the cost. It is that spirit that will make the exploration of the heavens possible, forever, into the never-ending future.
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