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Posted by: Mongo Aug 2 2007, 01:35 AM

A Side of Mercury Not Seen By Mariner 10
Gerald Cecil, Dmitry Rashkeev

http://xxx.lanl.gov/abs/0708.0146

More than 60,000 images of Mercury were taken at ~29 deg elevation during two sunrises, at 820 nm, and through a 1.35 m diameter off-axis aperture on the SOAR telescope. The sharpest resolve 0.2" (140 km) and cover 190-300 deg longitude -- a swath unseen by the Mariner 10 spacecraft -- at complementary phase angles to previous ground-based optical imagery. Our view is comparable to that of the Moon through weak binoculars. Evident are the large crater Mozart shadowed on the terminator, fresh rayed craters, and other albedo features keyed to topography and radar reflectivity, including the putative huge ``Basin S'' on the limb. Classical bright feature Liguria resolves across the northwest boundary of the Caloris basin into a bright splotch centered on a sharp, 20 km diameter radar crater, and is the brightest feature within a prominent darker ``cap'' (Hermean feature Solitudo Phoenicis) that covers much of the northern hemisphere between longitudes 80-250 deg. The cap may result from space weathering that darkens via a magnetically enhanced flux of the solar wind, or that reddens low latitudes via high solar insolation.

Bill

Posted by: As old as Voyager Aug 2 2007, 04:55 PM

Thanks for the post!

Mercury will be pretty much mapped at low resolution prior to the first MESSENGER flyby.

Posted by: Phil Stooke Aug 8 2007, 12:38 AM

Hmmm. that composite map of USGS relief and radar images looks VERY familiar...

Phil

Posted by: JRehling Aug 8 2007, 07:26 PM

To my eyeball, I'd say they actually lifted Phil's image and then made some additions where other coverage was available, but with an awful lot of the work being Phil's. It's an understatement to say that this should deserve credit, and there is none.

Unless they coincidentally produced a highly identical product (and it seems very unlikely to me), this is a case of serious dishonesty on the authors' part.

Posted by: Phil Stooke Aug 8 2007, 08:13 PM

It's mine, certainly. The way the poles were handled was unique and would be impossible to duplicate, just to take one point.

I don't care, actually. I do things and put them out there so they will be used by anyone who wants them. That's why I never attach names or copyright symbols to any of my stuff. (except the atlas!) A bit of attribution would be nice, though. Scott Horowitz was using my mosaic of Clementine HIRES images of the lunar south pole in one of his presentations in a similar unattributed way.

Phil

Posted by: stevesliva Aug 8 2007, 08:29 PM

It looked to me like all of the figures were attributed to other papers. Secondary source?

Posted by: Phil Stooke Aug 8 2007, 09:34 PM

No, not a secondary source. The reference in this new paper that appears to cite the map is actually to Harmon et al's paper, which was the source of the original radar images, not the composite map. There only was one source for the composite map, and it was my posting on UMSF.

Phil

Posted by: gcecil Aug 8 2007, 11:14 PM

Hello,

yes the base image is Prof. Stooke's composite, with John Harmon's radar data added to fill some holes. Lower panel ( b ) is new and puts our new Mercury images in the context of some previous work, as stated in the caption. For reasons I won't go into here but which Prof. Stooke will find in his email, the correct attribution to him was not made in the preprint posted at astro-ph. I'm attempting to add it to the paper galley proofs, hopefully that will be successful. I also plan to update the astroph version once I get off travel. Sources for material in the other figures are properly attributed if they are not from NASA archives.

If you have any questions on our Mercury imaging, I'm happy to respond (having just registered into this informative newsgroup.)

G. Cecil

Posted by: Phil Stooke Aug 8 2007, 11:23 PM

Thanks for this. Perhaps you could say something about the latitudinal extent of imaging which would be possible with your technique. Would the geometry permit global imaging at this resolution, over several orbits, or is it restricted to the longitudes already covered?

Phil Stooke

Posted by: gcecil Aug 8 2007, 11:41 PM

Well, the technique is just frame selection from stacks of short-exposure images, so far batting ~1 in 1000 to get down to ~0.2" resolution. I'm restricted to twilight observations for reasons mentioned in the paper, and from our site at 2700 m elevation in Chile (accessed remotely). This means only elongations that get to ~29 deg elevation, when we bang off 30,000 images. There aren't many of those opportunities left before the MESSENGER flybys, so I don't plan any follow ups. I have other astro programs to execute in the near term, but am working on an instrument for SOAR's adaptive optics system that could image planets in narrow spectral lines (and that I may use for Mercury sodium emission mapping before MESSENGER arrives in orbit). Although we work in twilight, it takes time to install the aperture mask for imaging that would otherwise go to important calibrations of other observing programs.

Leonid Ksanfomality sent me the other day a superb image from July 2006 with "Basin S" smack on the terminator, a bull's eye. Unfortunately, that feature (no question from his data that it is real) was on the bright limb in our data, so we couldn't say much about it in our paper. I imagine that he is working on a follow up of his expanded paper in last April Icarus. Perhaps he will be at the DPS meeting in Orlando.