Messenger presentation will be shown live from the AGU conference (Monday Dec 15 0800-1000 PST):

http://www.agu.org/meetings/fm08/

Several new images released, probably in connection with AGU conference.
http://messenger.jhuapl.edu/gallery/scienc...hp?gallery_id=2

Ha! Vindicated!

One of the images recently released is a high-res version of the Southern basin we discussed in the Mercury Flyby 2 thread:

Recent MESSENGER release: http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=279
Image discussed on UMSF: Mercury Flyby 2 thread, post #69

Yes, discussed first right here at UMSF. I think this basin was called Manet in the talks.

Also some nice color imagery of Raditladi with an enhanced blue ring of mountains. Clark Chapman had a good discussion about its age (possibly about 1 billion years).

The newly released NAC mosaic might be nice to use in my map if I can figure out how to best splice it in. I'm so used to the spacecraft perspective images that I have to think twice about how to add in an already remapped image.

There have been regular image releases from MESSENGER - here's the latest in case people have forgotten about the innermost planet.

Phil

http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=292

Btw, MESSENGER was recently hunting for Vulcanoids

Regarding targets of opportunity such as possible Vulcanoids, Mariner 10 attempted some images of comet Kohoutek (sp), but I don't recall how far from the sun the comet was at the time of the observation.

I think they tried searching for Vulcanoids in SOHO LASCO images some time ago...presumably nothing was found.

This interesting article seems to prove that Vucanoids are unlikely to exist to this day

Messenger JHUAPL site seems to be down.... ?

It's up for me. Nothing new since February 9. Still 208 days to the last flyby and 743 days to MOI.

We're not there yet. :-)

--Greg

It appears that, while largely depleted, they suggest that 300-900 bodies with diameters exceeding 1 km are likely to remain. My own thought is is that, no matter what theory predicts, it is still worth looking -- at the very least you might validate the theory, or learn something interesting by invalidating it. Plus there's plenty of migration of asteroids out of the main belt in both directions, so you'd want to look closely at any detected objects to ascertain just where it originated.

Yes, the Messenger site is now back up, but it was down for a bit (the New Horizons JHUAPL site was also down at the same time).

Vulcanoids -- yes, the Vokrouhlicky article implies that there could still be a remnant population, but I think the erosive effect of high-energy collisions would bring the number down.

What is the limiting magnitude and field of view of the wide-angle camera? They are expecting to be able to find a 15KM object, but given what assumptions?

NASA TO HOLD BRIEFING TO DISCUSS NEW FINDINGS ABOUT PLANET MERCURY

WASHINGTON -- NASA will host a media teleconference on Thursday, April 30, at 2 p.m. EDT to discuss new data and findings revealed by the Mercury Surface, Space Environment, Geochemistry, and Ranging spacecraft known as MESSENGER.

I wouldn't be at all surprised if some major new findings with respect to the role of volcanism on Mercury's surface and perhaps some new insights into the planet's interior will form the highlight of this press briefing. Should be interesting.

I cannot wait for the main orbital mission. Given the relatively new findings concerning the magnetosphere and the exosphere of Mercury, the dynamics associated with the terminator should be interesting.

If heavy metals are being vaporized into the atmosphere, are they condensing out near the terminator? How active is this process? Over billions of years, could this create significant changes in surface texture? I'm sure there is little similarity to any other processes occurring on other planets in our solar system. The big questions are: how important is it actually on Mercury; and whether it had greater significance in the distant past?

Ten orbits down (almost); five more (and change) to go. Luckily the next five orbits will just be 105 days each. And at least we get another taste in just 29 days.

Coming up on 2000 days since launch !!

http://messenger.jhuapl.edu/

Right at the same time NH is 2000 days away from Pluto. These "fire and ice" parallels amuse me to no end!

--Greg

MESSENGER mission has been extended another year
http://twitter.com/#!/MESSENGER2011/st...369226310955008

EDIT: More about the mission extension here: http://messenger.jhuapl.edu/news_room/details.php?id=188

Great news!
I suppose the extension is until March 2013 now, since 3/2012 was the original timeframe?
If there is ~40kg of fuel remaining on board; what is the longest possible observation timeframe?

side note: Astronomy magazine features Mercury in its December issue.

Ina on steroids!

Phil



http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=693

An amazing perspective of Mercury from Messenger !!!!
http://messenger.jhuapl.edu/gallery/scienc...Limb_mosaic.png
Best regards,
Marc.

The last two daily images have been nice hemispheric views. I hope we'll get all four (or even six) orthogonal views.

Phil

The "Caloris" hemisphere :
http://messenger.jhuapl.edu/gallery/scienc...ortho_0_180.png
Just great
Marc.

So little 'herma incognita' left... (pardon my Latin):

http://messenger.jhuapl.edu/gallery/scienc..._ortho_90_0.png
If that big crater is any indication, there should be serious diminishing returns when it comes to the permanently shadowed areas....

Not sure I understand the point about the diminishing returns. Where would we expect to find the permanently shadowed areas if not in the permanent shadows? One question I have looking at that map is whether the hole in the middle is bounded on all sides by the limits of photographic coverage, or whether it is partially bounded by topographic shadows. It's a funny shape with partly straight boundaries, partly curved boundaries, and some irregular boundaries.

Photo coverage limits almost exclusively.

One thing we've learned from the Moon is that the hydrogen is not located just in true 100% permanent shadow. Occasionally illuminated areas also show some hydrogen and some shadows have none. An LPSC presentation a year or two ago suggested that a small amount of heating was useful to help the ice diffuse downwards into the regolith. And radar shows us very clearly where the ice is on Mercury. It's odd that ground-based radar is less useful for revealing ice on the Moon.

Phil

Well what I meant was, since Mercury has practically no axial tilt, and thus no seasons, there are long shadows covering almost everything (compared with the Moon and its tilted axis and orbit, where only the deepest craters are in permanent darkness). So filling in these last sections is pretty slow, even over many Hermean years.

I see what you mean. Don't worry too much about that, there's lots of redundant coverage at the poles as every orbit crosses them and polar illumination is a big topic of interest. Also, light reflected off nearby peaks and crater walls will faintly illuminate some areas.

Phil Stooke

Here are some videos of AGU conference presentations on MESSENGER.

First an overview talk by Sean Solomon: http://vimeo.com/33387373

Next is an entire session that includes a very well delivered presentation on volcanism by Jim Head that I saw in person (last talk): http://vimeo.com/33391425

Final Mercury session here (including some magnetosphere discussion): http://vimeo.com/33391931

Great! the Jim Head talk and many other excellent talks are in this presentation:

http://vimeo.com/33391425

(Head is right at the end)

See especially the talk by Blewett on hollows, the altimetry papers ... in fact they are all good.

Phil

Some great new pics in the MESSENGER picture of the day set recently! The volcanic vent on the SW edge of Caloris, hollows in a crater floor, and Pantheon Fossae in Caloris.

Phil


http://messenger.jhuapl.edu/

Those hollows are awesome. They are even on the central peak, not just around it.

They are so reminiscent of the cometary surfaces we've scene that I often wonder if they are caused by sublimation of light elements.

Or the martian Swiss cheese terrain. Some of the small hollows away from the peak could be from asteroids punching through a protective crust.

No - asteroids make craters. Hollows are very different. An internal process is more likely - volcanic or loss of volatiles, though the details are not understood yet. And there are a few on the Moon as well. In fact I think the lunar ones, which we will be able to look at close up or even sample one day, will be the key to understanding them.

Phil

Hmm. You made me think, Phil.

Mercury is ostensibly the most 'lunar' of the inner planets in many ways (mostly in appearance), but compositionally & environmentally it has a great many dissimilarities to the Moon. It will be interesting to compare the similarities & differences between hypotheses for the origin of many landforms between the two worlds.

Mercurian hollows are compared to Swiss cheese terrain in the very Science paper Hollows on Mercury: MESSENGER Evidence for Geologically Recent Volatile-Related Activity. The authors note that



moreover, they note that while CO2 sublimation causes Swiss cheese terrain to retreat by about 1 m/year, whatever volatile is involved in hollows formation on Mercury would retreat by 1 cm in about 70,000 years

I thought from the moment I saw that comparison with polar landforms on Mars that it was ridiculous... the geometry is different, the composition is about as different as it could get, and the mechanism is different. On Mars the ground itself (at the pole) is made of the volatile substance (CO2 ice) and it is being eaten away by scarp retreat from the points where it begins - so the small depressions get bigger and coalesce in expanding circles and composite multi-circle shapes.

On Mercury we have depressions looking more like Ina, the famous lunar example, but more widespread, and since then quite a lot of other examples have been found on the Moon. The sharp outlines are in places convex inwards, completely unlike the Mars south polar features. Often they are surrounded by smooth deposits apparently ejected from the hollow, completely unlike the Mars features. Yet the MESSENGER team have said several times that their hollows are not found on the Moon. I think we will be seeing a change of opinion on this pretty soon (especially after my LPSC poster!)

Phil

On Mars, swiss cheese is caused by sublimation of nearly pure CO2 (there's probably some dust contamination) sublimating into the atmosphere due to solar heating. On Mercury, I'd guess the sublimating volatile is less pure, and the halos around the hollows are due to heavier materials being redeposited. I'd also guess that the sublimation is driven not solely by direct insolation - i.e., the whole surface gets pretty hot. That might account for the differences in morphology.

As long as you can make something similar work on the Moon...

Phil

Click to view attachment

WOW Phil...

I can't wait for your LPSC poster! I did not realize there are similar features on the Moon. Really fascinating!

Craig

Yes, fantastic examples. If you didn't say Moon, I would have said 'Mars'.
Is it possible, for some sort of, for want of better words, 'soil liquefaction',
without water being the liquid medium. Caused either by impact, or interior
seismic activity.
It's coming up to Australia Day, so here's a from me.

One idea used for the lunar examples, dating back, I think, to Peter Schulz in his classic 'Moon Morphology' book, is regolith excavation and 'liquefaction' to some extent, by the occasional release of residual volcanic gases or slowly accumulating radiogenic argon. Gas-supported regolith (liquified, if you like to call it that) might account for the sharp meniscus-like boundary on most of them, as the regolith flowed back into the hollow at the end of the eruption. This idea is mentioned in my LPSC abstract. This can work just as well on Mercury - the MESSENGER team is saying there is more volatile content than expected in Mercury. (Volatiles might include sulphur compounds rather than water).

My point here - the MESSENGER folks have said several times now that these hollows are not found on the Moon. They certainly are much more numerous on Mercury, but I believe similar features are seen on the Moon, and any explanation for Mercury ought to be at least considered for the Moon as well. And on the Moon we can explore them directly - even a GLXP team could look at one.

Phil

The new PDS data release is reflected in an update to the Mercury Quickmap interface:

http://messenger-act.actgate.com/msgr_publ...t_quickmap.html

Image search is down right now but will allow downloading of individual images.

Phil

Sheesh, those hollows really look creepy to me, like the planet is infected with some kind of a disease. These are presented in a sRGB display-correct fashion, without any contrast enhancements:

Click to view attachment Click to view attachment

Fantastic! Thanks.

It'll never get well if you pick it! (as they say)

Phil

Here's what it looks like to me. There is a layer just below the surface that easily collapses (evaporates?) at the least provocation. When could such a layer have been laid down? When Mercury had an atmosphere. Could the same apply to the Moon? Why not?

If Earth were suddenly denuded of its atmosphere would hollows form? If so, where and why?

Some of those raised blobs in the crater look like the result of surface tension - something that you might see after a spill of molten metal had solidified.