Triple impact on Moon
Cool image time! A new image release from Lunar Reconnaissance Orbiter (LRO) takes a look at the impact process that created the crater Messier and its neighbor crater Messier A. The photo to the right, cropped to post here, shows both craters.
Take a close look at Messier A. It is actually a double crater itself. From the release:
Messier A crater, located in Mare Fecunditatis, presents an interesting puzzle. The main crater is beautifully preserved, with a solidified pond of impact melt resting in its floor. But there is another impact crater beneath and just to the west of Messier A. This more subdued and degraded impact crater clearly formed first.
Did these three craters happen as separate events. According to the data, it appears no. Instead, they might have all been part of a single rain of asteroids, all occurring in seconds.
Messier crater is extremely elongated, which is an indication that it formed when an impactor struck the surface at a very shallow angle (less than 15° from the surface). Its high-reflectance rays stretch to the north and south, caused by ejecta that was emplaced asymmetrically, another sign of a low-angle impact. Messier crater’s presence suggests that each of these impact craters may be related, forming when an impactor broke up, and struck the surface as three pieces instead of just one.
…Another theory (the “decapitated” impactor scenario) suggests that the impactor could have actually split apart after hitting the surface at the Messier impact site, with a portion of the impactor continuing downrange to form Messier A crater.
Try to imagine the event that created these 9-mile-wide craters, especially the second scenario, where the asteroid zooms in at a low angle, hits the ground, its top half breaking off into two pieces that smash into the ground, bam-bam, just to the west.
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
Cool image time! A new image release from Lunar Reconnaissance Orbiter (LRO) takes a look at the impact process that created the crater Messier and its neighbor crater Messier A. The photo to the right, cropped to post here, shows both craters.
Take a close look at Messier A. It is actually a double crater itself. From the release:
Messier A crater, located in Mare Fecunditatis, presents an interesting puzzle. The main crater is beautifully preserved, with a solidified pond of impact melt resting in its floor. But there is another impact crater beneath and just to the west of Messier A. This more subdued and degraded impact crater clearly formed first.
Did these three craters happen as separate events. According to the data, it appears no. Instead, they might have all been part of a single rain of asteroids, all occurring in seconds.
Messier crater is extremely elongated, which is an indication that it formed when an impactor struck the surface at a very shallow angle (less than 15° from the surface). Its high-reflectance rays stretch to the north and south, caused by ejecta that was emplaced asymmetrically, another sign of a low-angle impact. Messier crater’s presence suggests that each of these impact craters may be related, forming when an impactor broke up, and struck the surface as three pieces instead of just one.
…Another theory (the “decapitated” impactor scenario) suggests that the impactor could have actually split apart after hitting the surface at the Messier impact site, with a portion of the impactor continuing downrange to form Messier A crater.
Try to imagine the event that created these 9-mile-wide craters, especially the second scenario, where the asteroid zooms in at a low angle, hits the ground, its top half breaking off into two pieces that smash into the ground, bam-bam, just to the west.
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
Excellent cool image Bob! How cool it would be to be a bystander ( at a safe distance!)
Carolina Bays!!
I was under the impression that all impact craters are round no matter the angle of impact. It has to do with the shock-wave rebounding off of the larger body blowing out material in a circle.
That said why is that one crater (b) oblong? Could it also be a simultaneous double impact of nearly identical objects?