Bad Astronomy

Tiny lunar volcanoes

The Moon is packed with all sorts of interesting features that only come to light – literally, in some cases – when very high-resolution imaging is done. For example, the lunar far side has a bunch of small volcanoes, some only a few hundred meters across, like this one:

[Click to enlunenate.]

The image is about 500 meters across, so this is a hill you could climb pretty easily, even though the low Sun angle implies the slope is greater than 13° (remember, the Moon has 1/6th the Earth’s gravity so that would be a pretty easy hike). Those boulders on the top are weird; they only appear to be on one side, and there doesn’t seem to be anything in that direction that would be a source of them. There are none on the plains around it, or at the bottom of a nearby crater, either. The source must be the volcano itself, I’d wager. Note the crater at the top of the mound, too - you might think that’s the volcanic vent, but in fact it’s not centered on the dome, indicating it’s a coincidental impact crater.


Because the Sun is coming from the side, some people might have a hard time seeing this as a dome. It’s a well-known illusion I’ve pointed out on this blog many times, but maybe this red/green 3D anaglyph by Nathanial Burton-Bradford will set you straight:

That one’s really cool; the opposite relief of the crater and volcano makes this one really fun to look at.

The Moon’s ancient volcanism is a pretty ripe field for study, since not a whole lot is known about it (gamma-ray mapping of this area shows it’s rich in the radioactive element thorium, for example – how about that?). I wonder if 3D images like the one above would help scientists understand this better?

Image credit: NASA/GSFC/Arizona State University

Related posts:

- Ash hole on the Moon
- A lunar illusion you’ll flip over
- Raising an impact in Africa
- Terra spots an impact on, um, Terra