by David Kingsley
Needing a break from the science, I spent an hour or so touring the first quarter moon from my backyard. Conditions were hazy, but seeing was actually very good. It was one of the first even clear nights after nearly two weeks of continuous rain at the beginning of the year and I was having a great time panning around the fabulous detail available on the moon. Although I have observed the moon a lot over the last several years, I was surprised to stumble on a very unusual feature located between Maurolycus and Maginus near the terminator. An unusual triple crater structure was so weird looking that I spent about 45 minutes sketching it and trying to work out a series of juxtaposition events that could generate a gigantic double trough between overlapping craters. When I went inside and looked it up in Rukl and on line, I found a bunch of other comments about the unusual appearance of this feature:
From Akkana on Hitchhikers guide to the moon:
DC:
Chart 73: Described in Rukl as a "ruined crater with central mountain range", Heraclitus is a strange rectangular structure stretching between two large craters (Licetus and Heraclitus D). It appears as though huge twin boulders had slid from one crater to the other, creating twin furrows, each wider than most normal craters. It's hard to imagine what natural process actually caused the strange appearance of this crater. It looks like a gigantic beetle
From Tom Trusock
Further south, my eye is drawn to the odd shape of the HERACLITUS complex. An old pair of twin elongated scrapes that connect LICETUS in the north to a grouping of smaller craters (sometimes listed as HERACLITUS D, among others) in the south. The major portion looks to be about 35 miles by 30 miles. Although listed as a single crater HERACLITUS has a clearly visible ridge that runs down the center and makes the crater certainly seem double. I've heard it described as "a ruined crater with a mountain range running down the center." Irregardless of weather it was a double or a single crater it is one of the more distinctive sights on the moon. If you haven't seen it already, you really owe it to yourself to take a look and speculate upon what forces caused this odd creature to come into existence.
Here is an image of the area giving some idea of the huge double furrow connecting other craters.
http://www.astroimaging.com/images/Stofler.jpg (triplet structure near bottom of image)
On this page, the double trough is colored in yellow http://www.astrosurf.com/cidadao/crater_heraclitus_01.jpg (lower righ)
While at the eyepiece, I thought I had worked out one possible sequence of events that could create the double furrow. With the low lighting on January 17th, the central ridge in the middle of the trough looked like it could have been formed by a huge landslide that tore away from the edge of a previous crater rim. There was even another larger crater squeezed right up against the double trough, a possible culprit for creating a massive landslide in the adjacent area.
The adjacent crater wasn't labeled on my initial Rukl chart, because the whole triple crater complex happens to occur at a border area between charts. But when I flipped through Rukl to identify the missing member of the trio, who should I find? It was my old friend Cuvier himself. One of the craters I had been sketching was named after the same French naturalist who had published the 175 year old pictures I had just been working all day for the Science figure. The same man who had first named the different fish species we have been catching, probing, and crossing for the last seven years, based on their dramatic skeletal differences in body armor. And a broad smile spread across my face as I realized the connections between all things, and sent off the last parts of the paper describing how the differences between Cuvier's old fish were actually created at the molecular level.
Post script: It turns out I am better at figuring out where different life forms come from than where interesting craters come from. When the whole lunar area became better illuminated over the next couple days, it was clear that the landslide appearance on January 17th was a complete artifact of low angle lighting near the terminator. With higher illumination, it was also clear that Cuvier was too worn and tired looking to have been a giant thwump that stimulated a landslide in an adjacent trough that looked sharper rimmed and more recent than Cuvier itself. Instead, the double-laned trough is probably the remains of a large elongated crater that has a linear mountain range down its middle, rather than an isolated single peak. (You can see a similar linear central range in the elongated crater Schiller, but they are rare on the moon because not many large craters are created by low angle impacts http://www.lpi.usra.edu/resources/lunar_orbiter/images/aimg/iv_155_h1.jpg).
Whatever generated the interesting structures, I agree with Tom Trusock's comment above that this really is "one of the most distinctive sights on the moon" And Tom's final comment is peculiarly appropriate to both the moon and the sticklebacks:
If you haven't seen it already, you really owe it to yourself to take a look and speculate upon what forces caused this odd creature to come into existence.
Posted on sf-bay-tac Mar 25, 2005 20:28:23 PT
Converted by report.pm 1.2 Apr 23, 2005 22:49:20 PT
