November 12, 2004

A Giant Messier

<nobr>A Giant Messier</nobr>

<img src="archive/2004/11/images/LPOD-2004-11-12.jpeg" border="0">

Image Credit: Tom Bash

A Giant Messier Schiller is bizarrely unique and has long been a topic of speculation and bewilderment. The problem with Schiller is obvious - craters are round, but Schiller definitely isn't. Because of its elongated shape, it was often claimed that Schiller could not be of impact origin and must be volcanic. But, volcanist were wrong again. And they were wrong for a good reason - who could have imaged that an impact event could produce something as non-circular as Schiller? The clue came from high speed-impact cratering experiments at NASA Ames Research Center in California in the 1970s. Vertical impact experiments by Don Gault and colleagues had recreated lunar crater shapes, central peaks and even ejecta deposits. But when the experimenters made oblique impacts they discovered dramatic changes in crater geometry. They were able to show that the crater pair Messier and Messier A were likely produced by a ricocheting impact at an angle of less than 5 degrees. Schiller appears to be another low angle impact of a much larger projectile, at a somewhat higher angle, that made a series of elliptical, overlapping and nearly simultaneous craters. In fact, the linear ridge seen at the northern end of Schiller also appears in the Ames experiments. This good photo also illustrates a later phase of Schiller's development. The lavas that rose up inside the crater created a floor that is not quite level. A previously unknown - at least to me - broad but low diagonal plateau exists on the floor of the broadest part of Schiller. Hmm. — Chuck Wood Technical Details: Oct 8, 2004. C9.25 + ToUcam web cam Related Links: Lunar Orbiter IV View Rukl Atlas of the Moon, Sheet 71 Tomorrow's LPOD: A 1689 Swedish Book on the Moon

Author & Editor: Charles A. Wood Technical Consultant: Anthony Ayiomamitis Contact Translator: " class="one Pablo Lonnie Pacheco Railey (Es) " class="one Christian Legrand (Fr) Contact Webmaster A service of: " class="one ObservingTheSky.Org Visit these other PODs: " class="one Astronomy | " class="one Mars | " class="one Earth

 

---

COMMENTS?

Click on this icon File:PostIcon.jpg at the upper right to post a comment.