MadSci Network: Astronomy

Re: Are there any lunar survey comparisions of modern lunar feature changes?

Date: Fri Apr 29 17:20:29 2005
Posted By: Chris Peterson, Faculty, Denver Museum of Nature and Science
Area of science: Astronomy
ID: 1113758232.As

I'm not aware of any detailed comparative surveys like this. But you could conduct one yourself! There have been a number of photographic surveys of the Moon made over the years. Until the 1960s, these were all produced by Earth-based telescopes. The best such images can just resolve features about 1000 meters across. During 1966 and 1967 higher resolution images were returned from the five Lunar Orbiter spacecraft (this was in preparation for the Apollo landings). The best LO data has a resolution of about 65 meters. This would be the best data to use for your "before" images (but keep in mind that many images are of lower resolution, and there is not complete coverage of the lunar surface). You can access the images at

The Clementine mission in 1994 mapped much of the lunar surface at high resolution. These would be the best data to use for your "after" images. The dataset is available at .

No before/after feature changes resulting from impacts have ever been documented photographically. Light flashes have been observed (both visually and photographically) on the surface of the Moon during meteor showers and are presumed to be the result of small impacts. These events have all required the use of a telescope to see or record, and have not produced features at a scale we can image. There is an interesting historical mystery from 1178, when Gervase of Canterbury described a visual lunar phenomenon that could have been a large impact. Several craters have been proposed as the result of this event, but recent analysis has largely discredited the possibility that what Gervase witnessed was an asteroid strike.

More recently (in 1953), a photograph of a possible impact was made by Dr Leon Stewart. While no high resolution images of the Moon existed at that time to use for comparison, Clementine images have recently been studied and a 1.5km crater found at the location seen in the photograph. The spectral data show that the crater must be very new, and energy calculations predict the size. It is fairly well accepted that this crater did result from the event witnessed by Dr Stewart. This is the only confirmed association between a lunar feature and a witnessed impact. You can read more about it here.

The phenomenon you witnessed may be explainable by something other than an impact. The main argument against an impact is that one large enough to be visible to the naked eye would be expected to send a substantial shower of debris towards the Earth, resulting in an impressive meteor storm that would not go unnoticed. Still, I would urge you to pursue this further with the data linked above. This is an interesting piece of your family's history, and worth investigation.

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