That's an interesting one. You can see what look like several older boulder trails as well in the image.

Wonder if we'll get lucky & get some before & after shots of an event. This looks like something that happens relatively frequently!

We even get one seen close by by Apollo 17! Do we know when this one rolled down?

I seem to recall that the huge boulder at Taurus Littrow in that well-known Apollo 17 photo, was thought to be an ejecta block - so was 'flung' rather than rolled into position.

I'm not aware of any statement like that in the literature.

Phil

My earlier speculation on the movement of the Apollo 17 Morth Massif Split Rock and its descent trail was that it has moved as a result of incremental thermal creep, by preferential expansion in the downhill direction of least soil resistance, due to heating in the lunar day. The slope there seems to me not to be steep enough for such an enormous and unevenly shaped boudler to roll (when it was one piece before it split apart).

If this is correct, or at least plausible, we may have 3 methods of boulder transport which leave trails, in decreasing order of speed:

• ejecta bouncing across surfaces
• gravity tumbling/rolling/ sliding
• thermal creep over millennia.

"The slope there seems to me not to be steep enough "

Do you mean the slope at Station 6, where the rock is now? That's where it stopped rolling, not where it started, so we might expect it to be 'not steep enough' to roll.

Phil

I mean my general impression of the immediate part of the slope leading down to the boulder at Station 6, over which the rock rolled or slid, apparently gouging out a deep track or channel. The boulder track is evident as a sort of channel leading towards the boulder from the right side of this pan. The astronauts walked through this channel, as their footprints show.

Station 6 pan, Apollo 17

My admiitedly superficial impression is that the general slope angle is low for a gravity roll, but as you say, it ran out of energy and stopped here, perhaps for that reason. However, the depth of the track is very considerable, and I wonder if such a depth could really have been made by a boulder rolling over the surface - as opposed to my alternative thought that it was a partially embedded boulder moving downhill by creep over long periods of time.

Phil's crop of LRO, Station 6, Apollo 17

I can't find your orginal post of this picture, but the above is a re-post. Looking at it again, I think seeing the track from above does suggest the rolling of an irregular boulder rather than the uniform track width which the "ploughing boulder" might generate.

So I'm coming back to a rolling stone (!).... but still curious as to whether the ploughing boulder pehnomenon, caused by thermal expansion creep, might be seen elsewhere on the moon.

I was curious as to why I remembered reading that the boulder was assumed to have been thrown from a nearby crater, so checked in some of my books. Sure enough, in 'Planetary Geology' (1979 edition Guest, Butterworth, Murray, O'Donnell) the authors assert this most confidently. The fact that the boulder is in two pieces in situ perhaps made this seem the most likely explanation at the time. (i.e it split in two when it re-impacted)
However, having now seen the boulder and associated furrow from LRO, it's clearly rolled or bounced into position.

Jase

Well done for finding that significant reference!

Science is natural selection... the evolution of ideas.

Nice new bouncing boulder...

Very atypical picture, I can't recognize that this is a photo of the Moon. Looks rather like Mars image.
Frozen impact melt flows on the floor of Moore F, a farside highlands crater.

Oh, Lunar gullies. Dry or wet?

http://lroc.sese.asu.edu/news/index.php?/a...ius-Crater.html

It doesn't look like melt, it looks like slump fractures.

(actually, it also looks like a dirty glacier flowing over a rock bench, but we won't go there...!)

An interesting oblique view across the N rim of Cabeus crater:
http://wms.lroc.asu.edu/lroc_browse/view/M109937747

This isn't LROC... sorry! But check out a new radar image:

http://www.nasa.gov/mission_pages/Mini-RF/...e_20091110.html

Phil