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JRehling
Mercury and the Moon have surface histories written with the same alphabet, but in different languages. At a glance, they're just alike, but then a couple of seconds into looking at a Mercury image, I start to see things that violate expectations I didn't consciously know I had.

I'm thinking of Mercury as being intermediate in thermal evolution between the Moon and Mars. Much closer to the Moon in that regard, and with no weathering, but there's just been a lot more lava flowing around Mercury since the early heavy bombardment.
SpaceListener
QUOTE (Stu @ Jan 16 2008, 01:20 PM) *

That is a rather very good picture. The large, shadow-filled, double ringed crater to the upper right has another peculiar thing which are the rays of minicraters sprying outside and aslo I see a strange channels which connect two small craters at the lower left corner. Maybe this channel was formed by the falling action of a big rock soon after the big meteoro made the impact to Vivaldi crater.

Looking forward to see much more pictures specially in colored images. Hope it would be by february?
elakdawalla
Just for fun, the same area as seen by Mariner 10. Mosaic of two images, stretched vertically 200% to make the geometry look a bit more like the MESSENGER image. Click to enlarge.


--Emily
JRehling
[...]
ngunn
I've just realised why this view (the Vivaldi one) is somewhat disturbing to look at. It's because some of the craters aren't circular, and this messes up the normally unconscious process of 'reading' the perspective. For instance there is a smallish crater to the left of Vivaldi with a totally shadowed interior that looks almost like a circular black hole punched through the photograph. It just won't lie down on the surface of the planet when I look at it. In fact it must be considerably elongated along the line of sight to look circular in the image, but no matter how much I tell myself this it still looks . . . disturbing. I think this is going to be a characteristic of Mercury images in general. Looking forward to some 3D - THAT should make the surface behave properly!
dilo
Vivaldi's picture with corrected black (without the grey halo in the lower half of image), adjusted luminosity/contrast and sharpened:
Click to view attachment
Note the weak rim now visible inside the internal one...
tedstryk
Here is a comparison with a distant view and the new global view. There are a few features that are beyond the terminator in the Mariner-10 closeups. That large crater at the center of Caloris may well be a great drill down into Mercury.

I also attached the Mariner-10 image at a more reasonable side.

Click to view attachment

Click to view attachment
jsheff
QUOTE (JRehling @ Jan 16 2008, 03:38 PM) *
I think a really beautiful final image product will be an albedo map of Mercury laid on top of a shaded bump map so the albedo and terrain are both apparent simultaneously (the two seem never to co-occur in any real images of Mercury). An even more compelling ingredient for such a map might turn up when we see what kind of spectral variety exists.

Quite so. When you consider the history of Mars observation, we've had centuries of Earth-based mapping of albedo features. When up-close imaging became available, it turned out there was almost no correlation between albedo features and the geological ground truth. (Thaty's not to imply the albedo maps were useless, though!) It will be interesting to see if the same will hold for Mercury ...
- John Sheff
Cambridge, MA
peter59
I'm a little dissapointed. I don't know what is wrong, but first NAC image faintly looks like newspaper print. Please don't critic me too harshly, but it's my impression. WAC image is fantastic.
OWW
are you gonna tell me THIS looks like newspaper?

http://messenger.jhuapl.edu/gallery/scienc...0108826105M.png

WOW. WOW.
ugordan
Or this???

Check out what look like streams and streams of secondary craters! ohmy.gif
Sunspot
ohmy.gif Indeed
Astro0
OK, a big sorry for my posts yesterday. I was up for 20 hours yesterday and 18 hours the day before on the Messenger encounter and other stuff. As I was putting a few messages on UMSF, I must have been delirious with the data rate stuff.

To clarify, it is kilobits but per second (not per hour). I was told that the inital link data rate was 25-30kilobits per second and passed that on as 'per hour' - blink.gif - my bad.

During downlink of the actual data we get a top rate of 104,166kb/s.
Our coverage was from 0020-0720 UTC, so 7 hours of actual data downlink at nearly the top rate the entire pass.
There was a 5 minute period where we were unable to get clean data due to a brief but severe storm.

I hope that makes more sense. Glad I got some sleep last night.
Looks like there might be a few more late nights though browsing through all these great images coming online.

(sleepy) Astro0
ugordan
Here's context for that crater image (was rotated 180 deg and contrast-enhanced):



EDIT: Added both new images.

In the leftmost image in the above composite, notice how everywhere where the shadows are long, their edge is noticeably diffuse. No doubt a testament to the large angular size of the Sun there (3x as large as seen from Earth). I'm not sure you can see this in images of the Moon.
Phil Stooke
Thanks, ugordan! I think we can see from this that the images of the interior of Caloris at this resolution are going to be spectacular, high sun or not.

Phil
Juramike
QUOTE (OWW @ Jan 16 2008, 05:33 PM) *
are you gonna tell me THIS looks like newspaper?

http://messenger.jhuapl.edu/gallery/scienc...0108826105M.png

WOW. WOW.



Wow.

Any good explanation why there are pocket clusters of little craters surrounded by relatively smoothed over terrain in this image?
antipode
Any guesses about the total relief we are seeing here between crater rim and crater bottom? Pretty subdued? Maybe only a few Km???

P
JRehling
[...]
nprev
Never thought of that, JR...Mercury is already teaching us about general planetary processes, then, as promised! smile.gif
MarsIsImportant
This may be a little premature, but I'm going to ask it anyway...because of all the excitement. When will we have a rover on Mercury and where should we land it?

I know that the poles should have some moderate temperatures, so it might be possible.
JRehling
[...]
tasp
Can we expect a percentage of Hermian crater chains to be resultant from freshly solar disrupted comets ?
nprev
I dunno, Tasp; they'd have to be pretty small comets, IMHO. Maybe, if we find some that have no discernable relationship to larger craters, but doubt that they''d be tidally disrupted impactors; more likely thermal breakup.

A good-sized comet from the Oort Cloud's gonna have a tremendous relative velocity at impact (in fact, that's the horse I'd bet on for Caloris). Additionally, most comets don't seem to calve until well after perihelion, and usually they're beyond the orbit of Mercury by then.

Hmm. Almost makes me wish that Mercury was rotationally locked to the Sun 1:1 instead of 3:2. The differential crater densities between the two sides might have been most instructive.
dvandorn
Tasp raises a good point, though, Nick. Mercury's orbit sees more objects cross its path than any other planetary orbit in the system. First, it's the smallest piece of real estate in the system occupied by a planetary orbit, and second, ever since we've seen several comets *per year* glide directly into the Sun, we know that there are a lot of bodies infalling through its orbit.

A lot of those bodies will be the result of fragmentation of larger comets, so a lot of the Hermean impactors would expected to be relatively small (less than a km in widest dimension, most fist-sized or smaller) and travelling at very high speeds relative to Mercury.

From that, I would expect the impact flux to be higher (at this point in time) on Mercury than on any other Solar System body.

I'd also point out, to those who were contemplating the possibility of cometary or asteroidal debris finding its way into a Mercury orbit, that with the largest flux of potential impactors, Mercury would also see the largest flux of near-misses. And that while it can be difficult for a fly-by object to achieve an orbit if you consider it as a two-body problem, the proximity of the Sun makes any such trajectory a three-body problem, which opens up all sorts of otherwise unlikely-sounding possibilities for orbital insertions.

-the other Doug
nprev
QUOTE (dvandorn @ Jan 16 2008, 07:11 PM) *
Tasp raises a good point, though, Nick.


Oh, no doubt about it! smile.gif That's why I was wishing for orbital/rotational 1:1 synchronicity; would be fascinating to compare the density of inbounds on the dark side vs. outbounds on the light side, since the latter would presumably be mostly from comets rounding the Sun. As is, it's gonna be a normal distribution, though.
JRehling
[...]
elakdawalla
QUOTE (MarsIsImportant @ Jan 16 2008, 05:29 PM) *
This may be a little premature, but I'm going to ask it anyway...because of all the excitement. When will we have a rover on Mercury and where should we land it?

I dunno about rovers, but Alan Stern mentioned to me that one of the mission scenarios proposed under the what-if-you-could-have-a-nuke-powered-Discovery-mission call for proposals was a Mercury dark side lander.

--Emily
MarsIsImportant
It's interesting that you mentioned the Stirling generator in that article. I heard about it in this article concerning a possible Venus Rover. http://space.newscientist.com/article/dn12...line-news_rss20 I thought it might be possible for Mercury too.

Any who, I didn't mean to take things off topic. I mentioned a desire for a Mercury Rover because...well, look at those images we have seen of Mercury over the past few days! I cannot help but want a closer look.
Gladstoner
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edstrick
General observation on high resolution imagery of Mercury.

Mercury has been ***CHEWED*** on. The bulk of the surface is "functionally" older than lunar mare terrains, regardless of absolute dates. Most of the surface is like lunar highlands or impact basins and craters (Apollo 15, 16 and 17, Surveyor 7) and basin-ejecta-plains (like Apollo 14's Frau Mauro site). What lava plains there are, are hard to tell from welded basin ejecta blankets (Cayley Plains @ Apollo 14). Many existing lava plains may have basin ejecta blankets on top. Very-high to Ultra-high resolution imagery, and there was a little very high resolution data from Mariner 10 (the closest in approach and flyaway frames), will mostly show sharp features in recent craters and their ejecta secondary terrains, and "tree-bark" textures on rounded and quite blurry highland terrains.

Look at that new image near the terminator from the flyout sequence. Aside from fresher primary impacts and secondaries, ALL the terrain is rather rounded at the resolution of the image. At 10 times more resolution, there simply won't be much more data, just blurrier, softer terrains with sharp features of recently imposed disturbances on it. This is not like Mars, where crucially important processes primarily occur at sub-meter to meters scale, forming essentially important geologic features that can not be understood at all at hundred meter scales. Yes, high resolution will be important, will help, but don't expect the sort of "my-ghod" reactions you get from Mars or Europa or Io or (will get) from Titan. At least not nearly as many of them on as grandiose a scale.
kenny
QUOTE (edstrick @ Jan 17 2008, 07:15 AM) *
General observation on high resolution imagery of Mercury.

and basin-ejecta-plains (like Apollo 14's Frau Mauro site). What lava plains there are, are hard to tell from welded basin ejecta blankets (Cayley Plains @ Apollo 14).


Cayley Plains were at the Apollo 16 site, Descartes.
edstrick
Correct. But more interpreted-as "volcanic" plains that turned out to be anything but.
Doc
Observation notes

1) There appears to be lots of 'string of pearls' craters on Mercury (in the new close-up images). Some of them look curiosly like collapsed lava tubes? Does the number of such craters imply to the probablity that falling debris are often torn into 'strings' due to the proximity to the Sun.

2) The craters with bright materials can mostly be found in volcanic plains. Just like on the moon. Why? (difference in composition between volcanic plains and highlands?).
remcook
From Emily's blog:

QUOTE
So what do I see in this image? There's lots of craters, of course, but if you look closely at the craters you can see that there's a lot of differences among them. In particular, my eye is immediately drawn to the fact that the craters at the left side of the image mostly have very flat floors, but among them are a few craters that have fairly pristine bowl shapes and central peaks. When craters first form, they all have bowl shapes, or bowls with central peaks, or peak rings. Craters do not form with smooth, flat floors. So something must have happened -- some geologic activity -- to flatten the floors of all those flat craters; most likely they got filled in by some volcanic eruptions. Those volcanic eruptions had to happen before the central-peak craters, which never got filled in by lava. So already there is a geologic history to tell about this tiny area of Mercury, coming out of this one image.


As a complete layman, I wonder: if it's filled in by some lava flow from a volcano, wouldn't you see something at the edges of the crater instead of a nice uninterrupted ring? Or a volcano? These seem much smaller scales than on the moon where I assume a similar thing happed at the Mares. I wonder if it isn't just that below a thin crust the rock is rather soft or 'liquid' (over geological timescales) and that the floor just equilibriated like a lake before cooling down, whereas the ring around it is more rigid, since it is cold crustal material. Please teach me about crater formation smile.gif

edit - or is what I'm talking about a 'welded basin ejecta blankets'??
Doc
Someone in this forum talked about apparent cinder cones in Mariner 10 images.
So far I've seen lots of craters but no cinder cones.......I don't suppose there should be one when you take in to consideration that Mercurian lava is iron-rich. Cinder cones are formed from silic lava.
Oersted
http://messenger.jhuapl.edu/gallery/scienc...827082M_web.png

To me the big crater in the lower right side, with a string of minor craters on either side, make me think that this is what Shoemaker-Levy would have looked like, if it had hit a solid surface. Am I completely off on that assumption?
ngunn
QUOTE (Oersted @ Jan 17 2008, 12:42 PM) *
To me the big crater in the lower right side, with a string of minor craters on either side, make me think that this is what Shoemaker-Levy would have looked like, if it had hit a solid surface. Am I completely off on that assumption?


Sounds about right to me, except that mayby the big crater may be newer than the string. I think Im seeing varying amounts of ray material inside some string craters.
Phil Stooke
I'm sure ngunn is right about that - the bright crater is younger and its ejecta covers the crater chain.

This chain of craters is most probably a normal secondary crater chain rather than a disrupted object crater chain. And statistically, secondary chains are much more likely to occur. On the Moon we have thousands of secondary chains and maybe 2 or 3 possible disrupted object chains.

Phil
MarsIsImportant
I would like to get a much closer look at some of these crater features. Many are clearly impact origin; but others seem to be collapsed lava tubes. The bright ones with the bright material rays may be caldera. In fact, some of the collapsed lava tube features appear to originate from those bright craters that I think might be caldera.

The point I'm making is that I'm not sure. We need a closer look. And I'd like to know what the surface material is made of.
SpaceListener
QUOTE (Phil Stooke @ Jan 17 2008, 08:45 AM) *
This chain of craters is most probably a normal secondary crater chain rather than a disrupted object crater chain. And statistically, secondary chains are much more likely to occur. On the Moon we have thousands of secondary chains and maybe 2 or 3 possible disrupted object chains.

How can the chain of craters form?
  1. A broken falling rocks into small debris before hitting the surface
  2. Ejected a line of rocks from impacted big crater
  3. A depression from a subterranean tube spreading from the main crater
  4. Whatever else you name it
ugordan
Get these while they're hot:

MESSENGER Views Mercury’s Horizon

MESSENGER Reveals Mercury’s Geological History

The second image and a previous one have a bit of overlap, but radically different resolution:

Juramike
QUOTE (ugordan @ Jan 17 2008, 10:57 AM) *


Looks like theres a collapsed area in the middle of the infilled crater in the center of the above image:

Click to view attachment

-Mike
Phil Stooke
"In fact, some of the collapsed lava tube features appear to originate from those bright craters that I think might be caldera."

No... this is exactly the kind of argument that was fought back and forth for decades about the Moon. Read Don Wilhelms' "To a Rocky Moon" to see how it turned out.

The bright fresh craters are impact craters. No calderas like those on Mars are to be expected here, and calderas don't look like this anyway - this is a fresh impact crater with some terracing in its walls, like Kepler. Check out Arsia Mons or Olympus Mons to see what calderas would be like. And what do we expect to see radiating away from fresh impact craters? - chains of secondaries, like those around Copernicus on the Moon.

No reliable identification of any volcanic feature has been made yet on Mercury - no flow fronts, no sinuous rille type lava valleys, no vents. There is a suspected but FAR from certain dome. Like many people I will be looking for volcanic features in these new images. But the features you identify are classic impact morphologies.

Mercury isn't Io, so we know the balance of features has to be at least 99% impact plus a few (if any) volcanic features, just like the Moon. The features you point out are actually very common on Mercury. If your features are volcanic, so is pretty much everything else. That's another line of argument that these are not volcanic.

But keep looking! The real thing might be out there.

Phil
elakdawalla
QUOTE (Juramike @ Jan 17 2008, 09:32 AM) *
Looks like theres a collapsed area in the middle of the infilled crater in the center of the above image:

I don't know aout that. The linear features in that crater are most likely either lava flow fronts or tectonic ridges. If lava flow fronts, it's just an area where the lava didn't go. If tectonic ridges (which is my favored explanation, considering how many of them appear to have disregard for changing topography, across crater rims for instance), it's true that area was being onlapped by the adjacent materials being shoved up and over it, but the tectonism isn't of a style that's driven by collapse (vertical tension); it's of a style driven by lateral compressional forces. Search on wrinkle ridges. They're common across the terrestrial planets, all over the Moon, Mars, Venus, and Mercury and are even to be found in a few places on Earth (such as the Yakima folds).

--Emily
Juramike
Even cooler. The cute little crater cluster abruptly cuts off at the edge of the collapsed area. (Here's a zoomed image showing cutoff point indicated by yellow arrows.)

1) Big crater forms
2) infills with lava and stuff
3) Cute crater cluster forms
4) Area inside crater collapses (slumps) and obliterates cute crater cluster members over collapsed area
5) A few more craters form

Click to view attachment

-Mike
Stu
Being totally honest here, I don't know why I find this crater - visible on one of the new images - so fascinating, I just do...

Click to view attachment

Maybe it's the smaller crater in the middle... lots of detail around it, and with its irregular rim it looks to my woefully untrained eye like either a few small objects hit there, or there's been some slumping after the craterlet was formed...

Just fascinating! smile.gif
scalbers
Greetings,

I've now incorporated the Messenger wide-angle outbound image in the Mercury map. On my website this has also been increased in size to a 4K image. Here is a link:

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

Click to view attachment

Note that in this fairly close in Messenger view the perspective with such a wide angle camera ends up with the poles being significantly beyond the horizon.

Steve
Stu
Looking at these images has made me ask again just why I find them so fascinating, and yet again I haven't been able to put it into words. But, in a wonderful coincidence, I took a book out of the library the other day which kind of did it for me. The book is "READING THE ROCKS" by Marcia Bjornerud, and, well, it's just a fantastic, passionate, personal window into the science of geology. This is just from the prologue...

"Like the place names on the highway map, which are a palimpest record of human interaction with the land, rocks and landscapes are Earth's unsystematic chronicle of its past - its unintentional autobiography. Autobiographies are unavoidably subjective accounts of past events, blurred by imperfect memory, limited by myopia, and edited for aesthetic, egotistical or legal reasons. To write an autobiography requires consciousness of self, and this by definition precludes the possibility of creating an objective and comprehensive chronicle. The one autobiography that has been recorded with no self-consciousness is Earth's own life story, written, very literally, in stone.

"Unfortunately, stone has an undeserved reputation for being uncommunicative. The expressions stone deaf, stone cold, stony silence, and, simply, stoned, reveal much about the relationship most people have to the rocks beneath their feet. But to a geologist, stones are richly illustrated texts, telling gothic tales of scorching heat, violent tempests, endurance, cataclysm and reincarnation. Over more than 4 billion years, in beach sand, volcanic ash, granites and garnet schists, the planet has unintentionally kept a rich and idiosynchratic journal of its past."

Looks like Mercury has, too... smile.gif
Phil Stooke
Click to view attachment

Here's a rough reprojection of today's limb view. This area was on the outbound limb for Mariner 10, but seen much better here.

Phil
elakdawalla
Really cool, Phil. This makes it obvious that the area in the center of the image identified as "smooth plains" in the image caption is the very very flat floor of an ancient, infilled double-ring crater. Only about a third of its inner ring remains, but you can clearly see the circular expression of the outer ring.

--Emily
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