The odd shading in the southern basin is most easily explained as one of those big lobate scarps crossing the floor, or possibly part of a multi-ring structure. That bright spot alluded to earlier - a fresh impact crater or one of those craters we saw in the first encounter with extremely bright deposits on the floor. The past (encounter 1) is the key to the present, at least to generate a first hypothesis.

As for 'skinakas' - the feature described from earth was a lot bigger than the darker spots outlined above. If there's a basin rim up there I can't see it.

Phil

I almost decided it was a chance alignment of craters, too -- but my eye keeps going back to the dark-albedo arcs to the north and south. Those seem to be independent of the craters in the area, and their arc shapes define a big circular feature. Now, it seems to me that a big circular feature like that would have to be either the degraded remnants of a huge shield volcano or the degraded remnants of a basin. Since we've seen a lot of the latter and no other indications of the former, I sort of get led down the garden path to Skinakas...

-the other Doug

It will be interesting to see if there are volcanoes at the opposite side of Caloris Basin. So far the southern side looks less cratered.

I know what you mean. I can't get over the feeling that there is something there. At the very least, we may be seeing the chance illusion that led to Skinakas in the first place. This may be one of those cases where more detail isn't going to help, and the coarse resolution pictures may show it best, provided there is an "it". If there is an old basin there, it may take laser altimetry from orbit to settle the issue.

Well, I may regret this, but I'm going to vote that there is something to Skinakas.

This one had occurred to me as well. Maybe that's what we ought to concentrate on trying to sort out.

I wonder if the illusion (if that's what it is) could be reproduced by taking some of tomorrow's images, and running them through a low pass filter to fuzz them out a bit?

My opinion is that Skinakas is nothing more than a region relatively free of ray craters, appearing a bit darker than its surroundings. You have to look at the original paper to see how tenuous the basin interpretation was. That sort of study can be done with these early images, there's no need to wait.

Check it out here - figure 9 is the image.

http://www.alpo-astronomy.org/mercury/Ksanfomality.pdf

Phil

Just over 8 hrs to closest approach, Messenger is now inside Mercury's hill-sphere. First wave of systems flyby mode activation is now just 2 hours away. Mercury is now "growing" noticeably as seen from Messenger ... JPL's solar system simulator seems to be holding up at present, so you can still watch the auto-refreshed images and timeline ticking by on my timeline simulator at http://www.dmuller.net/messenger

A new picture appeared.
http://messenger.jhuapl.edu/gallery/scienc...0131695690M.jpg

Very nice. Now high enough res to actually do some analysis, not just make guess as to what we are seeing (even if it is a lot of fun

The southern hemisphere basin looks like a double-ring basin with a dark-halo crater near the center of it. The very bright spot in the northern hemisphere looks like a small ray crater, but very fresh with a lot bright material surrounding it. I see no evidence to support a large, northern hemisphere basin

Arrgh. VP beat me to it!

Anyway here's my contrast enhanced view of the southern multi-ring basin, and two other smaller multi-ring craters up at the top of the image. The bright reflection of the outer ring of the southern ring basin is visible (and bright like you'd expect).
Click to view attachment



(And I'm gonna assume that's a hot pixel or cosmic ray hit just off Mercury's limb)

-Mike

[EDIT: The edge of the southern basin at the terminator is gonna look really dramatic as we get closer!]

Here's a rough attempt at generating an overhead view:

Click to view attachment

Close Approach has passed. Is there any news about the spacecraft's performance during this critical stage?

The spacecraft doesn't start downlinking for several hours yet.

Thanks.

I just figured the spacecraft would be monitored throughout the encounter, and we would have word by now that the spacecraft didn't safe or something similar.

They have an update

http://messenger.jhuapl.edu/news_room/details.php?id=110

Here's a relevant bit from it:

At a little after 4:40 a.m. EDT, MESSENGER skimmed 200 kilometers (124 miles) above the surface of Mercury . . .
Initial indications from the radio signals indicate that the spacecraft continues to operate nominally.
The first pictures from the flyby will be released around 10:00 a.m. on October 7, 2008.

--Greg

Gak! You know you're living online too long when... your brain automatically labels time values without a TZ as non-conformant

All the other times in the update are given in EST, so presumably that's 1500 UTC / 4pm BST.

This is a rough fit of the inbound coverage to Steve's map, to give an idea of the locations of features. I took IanR's image (above) and projected it to make the terminator a straight line, then overlaid it on Steve's map and fiddled with the scales until there was a reasonable match between features in the radar images and these new navigation images. There are about 10 or 12 matches between radar and messenger, so I think it's roughly correct. I emphasize roughly though, as the distortions to fit this to the map are very ad hoc.

Phil

Click to view attachment

... and here is the last image from the first encounter, processed to emphasize detail on the terminator. The big bite out of the terminator is the other bit of the rim of the 'new' southern basin.

Phil

Click to view attachment

Combination of Phil Stooke's image and my image of the Southern Basin:
Click to view attachment

(Dunno how accurate it is, but it was fun to try!)

-Mike

Just waiting for the latest images from Messenger to come in, so I thought I'd step outside my office and take a look at the 70-metre dish performing the downlink. Here's a nice view of Deep Space Station 43 currently bringing down the high priority data which should include the full-disk inbound and outbound images from yesterday's flyby.
Click to view attachment

Astro0

hey Astro0 ... there's no USB plug on that thing with a cable straight to your PC?

BTW sent you updated script just now

New image of Mercury.
Click to view attachment

That is amazing! It has the feel of this Mariner-10 image.

ooo..stripy!
link for description:
http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=214

It is indeed.!!!!!!

I've had a go at cropping off & enlargening the previously unseen terrain towards the hermean limb.
Click to view attachment

Andrew Brown.

A collage of 4 views of Mercury provided by MESSENGER:

The top two shots are January flyby WAC shots in calibrated RGB color (contrast-stretched as noted in previous threads), below are the two highest resolution shots yet released in pseudo-color based on top composites.



EDIT: Updated the inbound crescent with a higher resolution WAC shot just released.

Can we say that Skinakas doesn't exist? I don't see any basin.

From the longitude and latitude, the Skinakas Basin would've been the dark albedo circle just below yours.

http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=215
http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=217

Skinakas was a ray-free area of cratered terrain, not a basin. I think a good analogy here is with the old Soviet Mountains in Luna 3 images - low resolution albedo interpreted as topography, which is unwarranted. See the link to the original Skinakas paper in post #56 above.

Phil

It looks like Tycho's all over...

The first close-ups are also in, I can't wait to see the pictures of the Caloris Antipoidal point.

http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=215

The level of detail in pic 217 looks eerily like a model of the lunar surface.

Here's the oblique view reprojected.

Phil

Click to view attachment

So the feature on the right is the NW corner of what we've been calling the "southern basin" then?

-Mike

Here is Ugordan's montage with the Mariner 10 mosaics added.

Ted

Click to view attachment

Awesome, Ted!

Thanks. I will say that the color is a bit wacky. I tried to tweak the images to match Messenger color. Since the filters don't come anywhere near matching, there were limits to how well this could be done. It is interesting how that one new ray crater dominates so much of the planet.

Next image set:
http://messenger.jhuapl.edu/gallery/scienc...hp?gallery_id=2

From caption for this image:


[I can hear the UMSF processor chips revving up now....]

Was the processing loud?

Here's an updated version of my context map. The new WAC image doesn't quite overlap with the NAC from yesterday, but there is nice overlap with the WAC.

Click to view attachment

The large crater in the center of the mosaic is Boethius; the large one to the upper right is Polygnotus.

--Emily

In the "are we there yet" spirit, given that this flyby dropped the period of Messenger's orbit from 132 days to 116 days, Flyby #3 (almost a year away) will happen in just a bit more than three orbits. Remembering that the original orbit had exactly a one-year period, we sure have come a long way!

--Greg

Here's a reprojection of the smooth plains image. If this isn't a case of volcanic plains embaying the cratered terrain I'm a monkey's uncle.

Phil

Click to view attachment

... and another one of the northern limb. This kind of reprojection makes the limb images much easier to interpret.

Phil

Click to view attachment

Is it just me or does almost every other "fresher" crater in Doug's combined image here seem to have a scarp bisecting the crater?

-Mike

Wow - are those wrinkle ridges in that picture Phil? If so, does this indicate that this volcanic flow was more viscous than those we typically see on the Moon?

Mercury's starting to look a lot like one of Chesley Bonestell's Moon paintings...

I don't think you're wrong.

Hmm. Makes you kind of wonder if the crust of Mercury may have extensive deep magma reservoirs above the Hermian equivalent of the Mohorovicic Discontinuity; too deep to produce vulcanism, but enough to cause slumping & shifting after a major impact.

Well, we haven't actually seen a picture of you, so it's hard to be sure.

--Greg :-)

The Vivaldi release - showing that the same crater can be seen in both encounters with opposite lighting - and Juramike's post showing the big southern basin in a composite of two views - suggest that you can combine the views from these two encounters. It's possible but not perfect. Here is one hemisphere:

Click to view attachment

It works very well. Several craters along the terminator are visible in both views, and the combination of views looks roughly globe-like. The other side doesn't work so well:

Click to view attachment

It's not as symmetric as you might think. But it does give the idea. A proper Steve Albers-style reprojection would allow it to work properly. I'm only playing with Photoshop here.

Phil