Fifty Year Old Moon Mystery Explained

ekarjala writes "This article from NewScientist.com explains that a "flash" on the moon's surface that (captured by an amateur photographer 50 years ago) was probably the result of a 20 meter asteroid hitting the moon's surface."

Comments

where does the light come from?

[zogger]

--I am not any sort of expert on this so I have a question I don't see addressed in the article. I can understand a large kinetic hit, the crater and debris field. Where does the "light" come from? Inside an atmosphere like ours we have an "oxidiser" allowing some burning, if I am understanding this correctly, how we see meteorites after they enter (saw a bolide hit the ocean before, very spectacular). But on the moon in a vacuum, how does one rock hitting another create the light? Flint hitting steel creates a spark because a piece of the steel is burning, and it's burning because there's O2 present. On the moon I just don't get it. I'm sure there's an answer, I just don't know what it is, lacking any sort of decent chemistry. Thanks in advance for anyone who can explain this simply.

Re:where does the light come from?

[sczimme]

I would bet that the 'flash' was just a dust cloud, illuminated by and reflecting sunlight.

This is why: look where the incident occurred - right on the demarcation between light and dark. (It has a name, but I forget what it is.) Anyway, the area around the impact is dark due to the moon's position relative to the sun. The shadows fall at ground level, but the cloud from the impact presumably rose some distance above the moon's surface; I believe it went high enough that sunlight could strike it. Look at the craters along the [light-to-dark line] for other examples: the upper edges of some crater rims are in sunlight while the surrounding areas are dark. If the impact had occurred completely on the light side or completely on the dark side I don't think anyone would have noticed.

Other recorded lunar impacts

[Viadd]

In 1999 and 2001, I and other amateur astronomers recorded the flashes from Leonid Meteors hitting the Moon. These flashes were videorecorded and confirmed by multiple observers simultaneously.

The meteors in these cases were in probably in the 10 kg range, and the craters they produced were probably a few meters across (not large enough to see from the ground or any lunar orbiter we are likely to launch any time soon).