And a quick peek at the new image of the rayed crater near the limb, reprojected. Looks like another one with bright material inside it.

Phil

Click to view attachment

(I really should try to get a bit of work done...)

Just as Mercury has 'hot poles' does it also have, perhaps 'impact poles'; areas which (owing to Mercury's orbital and rotational properties) are likely to receive slightly more and/or slightly higher velocity impacts than other places?

No, it doesn't.

Phil

That question is ringing a bell. Wasn't there a new paper out recently saying that Mercury doesn't have impact poles, but Mars does preferentially have more impacts near the poles?

Today's two three image releases appear to be from NAC departure mosaic #3. Updated context map is attached.
Click to view attachment

Key:

Inbound:
blue squares = NAC approach mosaic

Outbound:
Yellow = WAC Departure mosaic #1
Blue = NAC Departure mosaic #1
Purple = NAC Departure mosaic #2
Blue-green = NAC Departure mosaic #3

--Emily

Why not? It is true that Mercury is not tidally locked, like the moon (which does have cratering asymmetry for that very reason*), but it does have that 3:2 spin-orbit resonance resulting in a notable insolation asymmetry. Maybe I should crunch some numbers and find out.


*

It's been done? I really should pay more attention!

Le Feuvre, M, and Wieczorek, M.A. Icarus 197 (2008) 291-306. "Non-uniform cratering of the terrestrial planets". doi: 10.1016/j.icarus.2008.04.011 (freely available here!)

From the article, the authors find about 10% increased cratering at Mercury's poles compared to the equator, and Mercury's cratering flux is about 1.9x that of our moon.

-Mike


[And Emily's right, this was in the September 2008 issue of Icarus]

Ah, but they only consider cratering rates as a function of latitude, not as a function of longitude.

A news item worth noting in passing. Thanks to the solar sailing technique, the targeting for this flyby was awfully good. In fact, they are claiming it was the most accurate targeting of any planetary flyby other than earth. It came in just a wee bit under 200 km.

MESSENGER News

Going back to the question about longitudinal variations in cratering, people have been looking for that for decades. I think there are some claims from modelling and some from crater counts, applied to bodies all over the solar system. I don't find any of them convincing. As for Earth focussing impacts on one side of the moon or the other - or, even worse, shading the nearside from impacts - even less convincing. Whatever slight variations there might be are either overwhelmed by saturation cratering or by various geological effects, or they fall into that class of observations which exist only in the statistics, but not in any meaningful way in reality. Show me a visible impact gradient and I'll back down!

Phil

And here's the new limb view reprojected. There's quite a bit of relief distortion.

Phil

Click to view attachment

The only body I can think of is Triton, where there is a difference in the distribution of craters between the trailing and leading hemisphere.

I'll say. That crater on the left looks like a cake pan.

volcanopele: "The only body I can think of is Triton, where there is a difference in the distribution of craters between the trailing and leading hemisphere."

We have very limited coverage of Triton, not many craters, and an unknown effect from regional variations in geology (Canteloup terrain vs the plains units elsewhere) - it's not a very robust analysis.

Phil

Oh well...


Some new pics are up now, including a Mariner 10/Messenger comparison at different phase angles

I have found the analysis to be relatively good, at least given the coverage we have. However, with Triton being in a retrograde orbit, the reason for the asymmetry may have nothing to do with the reason for the asymmetry on Mercury.

The limited coverage and poorly understood geology are the keys. If the crater retention age on canteloup terrain is different from that on the plains on the other side of the disk - or even if our ability to identify small craters varies between the two areas - the whole analysis is out the window.

Phil

Back to Mercury! Some new images released today, including a limb view which I have rectified here.

Phil

Click to view attachment

A new limb view, a new reprojection...

Phil

Click to view attachment

These work better with flatter worlds!

Following up on this placement, here is how a new test version of my map shows the Flyby 2 coverage. It's interesting how the previous radar coverage matches the Messenger images, such as in the multi-ringed crater near the upper left limb of the approach crescent image.

Click to view attachment

Steve

That looks great!

Can't wait to see final product!

A new image from flyby 2 on the Messenger website.

Here's the full resolution post Decepticon...

http://laps.noaa.gov/albers/sos/sos.html#MERCURY

Also shown here at slightly lower resolution as an attachment:

Click to view attachment

Steve

Here's Steve's new map in polar equidistant azimuthal projection. North:

Click to view attachment

and South:

Click to view attachment

Phil

Beautiful...and distinctly alien. This is not the Moon's bigger brother.

Phil's north polar projection nicely illustrates the rays emanating from that crater at a high northern latitude. Looks like in both polar regions we see (mostly from radar) some craters where ice is suspected.

I might be able to expand the usage of a Mariner 10 south polar region image in the map. However there are apparently other high resolution Mariner 10 images near the south pole that could be added. An example would be if I can find an image that looks similar to this link below without the labels (and projected from a spacecraft point of view).

http://upload.wikimedia.org/wikipedia/comm...alia_region.jpg

Here is one such image mosaic that may work even if it's a bit contrasty looking:

http://photojournal.jpl.nasa.gov/catalog/PIA03101

The Chao-Meng Fu (very close to the south pole) and Bernini craters region would be the most interesting.

http://en.wikipedia.org/wiki/Chao_Meng-Fu_(crater)

So perhaps with these and other images if anyone can point to any I can improve the south polar appearance.

Steve

Latest news from MESSENGER.

More of Mercury

The pictures, graphs, and accompaning caption stories from the new conference yesterday:

Science results from NASA conference

Edit - Some more stuff:

Diverse color

Close up color

Exospheric magnesium

Solar wind interaction

Exosphere comparison

The lack of a hemispherical dichotomy is interesting, though not surprising since they are likely to be the result of random events, the biggest survivable impacts. Particularly interesting to me, though not mentioned, is the small number of large basins. A few more might appear in the areas of high sun or near-limb imaging, or the small gaps still remaining, but it looks now as if Caloris is the only big basin. The Moon has quite a few roughly Caloris-sized basins (within a factor of 2 diameter, I mean) on a smaller surface.

Phil

It's proving to be interesting to navigate the Mariner South Polar mosaic (middle link two posts up) in a consistent way with the other imagery. The location of Bach from the Mariner 10 basemap (and USGS Gazeteer) at latitude -68.5 S appears to be inconsistent with the position of the south polar crater Chao-Meng Fu in the map from the top link. This map has Bach straddling the -70 S line. My next step is to try and match the Mariner SP mosaic with the -68.5 S location of Bach. I'll be curious to see if the South Pole with this solution remains inside Chao-Meng Fu. Perhaps the Wikipedia position of this crater (87.3 S, 132 W) may be a good reference point as well.

In Phil's polar projection one can see the circular feature in the underlying radar data that looks like it may in fact be Chao-Meng Fu. A cursory glance suggests that the location seems consistent with the narration above, and with the suggestion that the South Pole may lie barely outside the rim of this crater.

The south pole mosaic looks to be able to improve the resolution of my map south of around 55 S latitude, or maybe a bit further north.

Steve

I was doing a major house cleaning yesterday and came across my book "Atlas of Mercury" (NASA SP423) which I bought at the JPL bookstore on my only visit there on my Honeymoon in 1980. I have no use for it and it's in impeccable shape.

Anyone want it let me know. No charge. Preferences to Canadian residences to avoid cross border issues. I also have that huge Lunar Orbiter Photographic Atlas I no longer really need.

Wow, I have both of those, but they hold way to much nostalgic value for me to ever part with them.

This version of the map has slightly adjusted navigation of the Messenger images. It also has the Mariner 10 south polar mosaic included up to about 45S. Chao-Meng Fu fits nicely at the Wikipedia page location with the south pole lying just outside its rim. The similar looking crater on the radar data remains just on the other side of the south pole.

Click to view attachment

Full res version at http://laps.noaa.gov/albers/sos/sos.html#MERCURY

That's the latest,

Steve

http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=274

MESSENGER team publishes a new image - Raphael crater!

USGS announced some new crater names for Mercury and this interesting item:


I'm working on placing the new names on Steve's map, then on the flyby pic. At first glance, I think we are mostly talking about names on the inbound crescent, but that might be wrong. EDIT: I was wrong. They're mostly on the outbound view from flyby 1.

--Emily

And here's a map of the new names. --E

Raw images available.
http://pds-imaging.jpl.nasa.gov/data/messenger/msgrmds_1001/
Click to view attachment
I wish you a pleasant evening with beautiful pictures.

Thanks for the heads-up, Peter. This is sweet.
Here's the calibrated version of 4 MESSENGER single-frame-global-color views of Mercury so far:

Yes, Peter, thanks for the heads up! And awesome images, Gordan.

Hmm. Anybody have any idea what the difference between the three volumes is? There's one called MDIS, one called msgrmds_1001, and one called msgrmds_2001, and they all seem to contain the same files.

--Emily

Eye-popping work as usual, Gordan!

That is really an intriguing little world, isn't it? Still can't believe how different it looks from MESSENGER than it did from Mariner 10; what a difference 30+ years in technological progress makes!

Compare also with image seen here in Phil Stookes post (this thread, post#100) here (Oct 9, 2008).

The Southern Basin is the 700 km impact crater Rembrandt.

space.com article: http://www.space.com/scienceastronomy/0904...cury-globe.html
space.com picture in today's article:Click to view attachment

Very nice Gordan. I may try this in my map (e.g. the lower right one). Out of curiosity do you have any comment on the way your colors compare with the various versions of PIA11364?

http://photojournal.jpl.nasa.gov/catalog/PIA11364

Is there a question per chance of whether the color saturation gets increased when one does contrast stretching? I know we discussed the color of Mercury in some past posts - if I could find them.

Thanks,

Steve

Yes, I said it earlier in some of the other posts. The composites shown here were not gamma corrected for the computer screen, making them contrast-enhanced and the colors are too exaggerated. I personally prefer gamma-correct stuff, though it appears I'm in a minority here as that washes down albedo differences and color, making the images less pleasing to others (though making them closer to actual appearance).

I did produce two gamma corrected global views from flyby 1 and written a short image advisory in the description explaining the reasoning.

A few notes here: even our Moon appears brownish when calibrated this way, and in fact a lot of digital camera images taken from the International Space Station & Shuttle show it brownish while it appears perfectly gray to us down here. I don't know how to explain it, other than it's a psychological thing and automatic "white balancing" in the human eye. This also suggests if you actually stared at Mercury for a while, it'd start to appear gray as well. Unless you held a piece of white paper in front of you for comparison I guess. It is more coppery-brownish than the Moon, but not terribly so. Its albedo markings are also weaker than lunar ones.

Color is really subjective depending on viewing conditions and we could go on discussing it for ages, but it's OT here so I'll just stop my rant here.

Yes, maybe a thread on Mercury's color would be an idea to consider. Meanwhile I noticed this Earth-based image showing a conjunction with the Moon and Venus that almost shows a hint of brown color in Mercury (compared with Venus)?

http://www.possumobservatory.co.nz/moon_ve...-800asa-web.jpg

http://www.possumobservatory.co.nz/latest_...-continuing.htm

Steve

Flyby Visualization Tools update.
Mercury Flyby 2, Planned and Actual Images
http://messenger.jhuapl.edu/the_mission/visualization.html

Strictly speaking, I think we're expecting some tools for Flyby 3 now, since it's just a bit over one Mercury-year away.

--Greg

Has anybody out there assembled any of the outbound NAC mosaics from Flyby 2? I'm in need of a high-resolution version of the Mercury-looks-like-a-giant-watermelon view.

--Emily

I second that request.
I have a 8,145 by 9,305 px, 6.2 Mb global mosaic from the first flyby, and have been itching for one from the second flyby as well.

I know they exist. I asked politely to see if the mission would release one, but they said no and that I could go make my own from the data in the PDS. Public engagement fail.

--Emily

Huh. That was a puzzling response by them, esp. considering your stature in the planetary science community.