Printable Version of Topic

Posted by: nprev Mar 28 2007, 02:16 AM

An ambitious astronomer takes advantage of a rare opportunity to photograph the hemisphere of Mercury we almost never get to see via telepresence in Chile. Article http://skytonight.com/news/wires?id=104620675&c=y.

Posted by: stevesliva Mar 28 2007, 04:01 AM

I believe the best images I have heard of are radar images from Arecibo. It would be interesting to compare to visual or IR.

edit: ah, of course, from this very forum.

Posted by: JRehling Mar 28 2007, 11:47 PM

No picture?!

Given the time the work was done, the image should include the 25% or so of Mercury that is just west of the Mariner hemisphere -- that will include pretty much the entire Caloris Basin. The exciting thing there is the possibility of relief visible at the rim.

Let's see the image!

Posted by: nprev Mar 29 2007, 03:42 AM

Can't find any pics yet...assuming that he's working on publishing his results. Don't expect much, though; pretty much every ground-based optical image of Mercury I've seen looks like a bad pic of Mars with nothing evident but gross albedo features.

However, he did acquire something like 300,000 images, so maybe image stacking & other techniques will bring out some good stuff. Lots of data-crunching needed, though.

Hell, here's a wild thought: does he need some help? Some of the incredibly talented imagesmiths among us might be able to simplify the process considerably; why not contact him & ask? He's a state university prof, can't imagine that he has an abundance of resources...

Posted by: J.J. Mar 29 2007, 03:47 AM

^
Or another way, the best the pictures of Mercury today look like the best film pictures of Mars 30 years ago.

Posted by: Rob Pinnegar Mar 29 2007, 12:29 PM

That's a nice sentiment -- but if he's working on publishing it, which seems very likely, I think he'd probably be nervous about turning the data over to a bunch of Internet people.

Also, in a publication, he would have to be able to describe in detail all of the data processing steps -- which generally would mean no use of "black box" commercial processing software. (There are people out there who write their own processing code in Fortran or C because they don't even trust Matlab -- and although I *do* trust Matlab, I can understand this.)

Posted by: nprev Mar 30 2007, 01:37 AM

Ah; the perils of academia. Yeah, Rob, that sounds about right.

Pity, though. The Internet provides an opportunity for a whole new level of pro-am collaboration above & beyond what astronomy has enjoyed for decades with respect to comet, asteroid and nova/supernova discoveries as well as planetary observation & variable star monitoring. Few if any other scientific disciplines have such a connection with the general public, and it has proven quite profitable. There is an extremely lucrative resource for data processing just waiting to be tapped by the pros with the enthusiastic participation of amateurs...some smart cookie somewhere's gonna figure this out!

Posted by: PhilHorzempa Mar 31 2007, 04:33 PM

This might be a good thread to post images of the "Far Side" of Mercury,
the side not imaged by Mariner 10. The bulk of the high-res images are
probably the Radar ones. However, the visible Earth-based telescopic views
of the Far Side would be nice to see. Then we can wait only a few more months
and see what Messenger reveals about that Far Side.
To start, could anyone in UMSF post those detailed Radar images? I have
seen one of a large crater (with ejecta blanket?) - does anyone have access
to a digital version of that?

Another Phil

Posted by: angel1801 Mar 31 2007, 05:47 PM

I have checked my harddisk and I do have an radar image on Mercury centred at 35S 345W which looks just like the image you're wanting.

Is this it?

Posted by: tedstryk Mar 31 2007, 06:12 PM

There is a lot of good stuff in http://www.unmannedspaceflight.com/index.php?showtopic=946&st=45thread.

Posted by: nprev Apr 2 2007, 02:43 PM

Thanks, Ted; good stuff indeed!

Kind of interesting that there don't seem to be any volcanic constructs on Mercury at all; even the Moon seems to have more of that sort of thing. I know Mercury's crust is thought to be inordinately thick, but it also has a huge core & a magnetic field, so you'd think there'd be a bit more surface activity evident. Maybe we'll see some small domes around Caloris from Messenger.

Posted by: J.J. Apr 3 2007, 03:47 PM

^
Mercury's "intercrater plains" are often cited as analogues of lunar maria, but to me they appear much more subtle.

Posted by: dvandorn Apr 3 2007, 04:53 PM

The most common theory I've heard in re Mercury is that it encountered one or more "big whack"-sized impacts, but that being so close to the Sun and being intrinsically less massive than Earth or Venus, a majority of the ejected material (including most of Mercury's original crust and mantle) never re-accreted onto the planet.

With only a small percentage left of its original silicate mantle, I can imagine that volcanic processes on Mercury would have resulted in landforms that don't look distinctively volcanic -- especially when compared to bodies such as Earth, Luna or Mars.

For example, let's say that only the densest portion of Mercury's mantle was retained. This, and the crystallization of the outer layers of the remnant mantle to form a new crust, could leave only highly viscous, iron-rich lavas available for subsequent extrusion. And since the new crust formed late in the accretion process, you don't see big pile-ups of lava -- as it extruded onto the already thin crust, the whole thing flattened out and the flow features were made very subtle. Thus the distinctive, low-and-rolling landforms of the intercrater plains.

-the other Doug

Posted by: JRehling Apr 3 2007, 05:16 PM

My own post-digested view of the literature on Mercury is best expressed in terms of contrast with the Moon.

The Moon, about a quarter the mass of Mercury, lost its interior heat more quickly, and by 4.2-4.0 GYA, was a mainly solid world with just a bit of volcanic heat left to lose (roughly like Earth and Venus today). Most of its crust was hardened as far as endogenous factors went, so it was shaped primarily by the saturation bombing of impacts. When the bombardment ended, the highlands ended up in their terminal state -- utterly rugged chaos of craters on craters. Meanwhile, the lowlands which began that way were paved smooth by the last vestiges of lunar volcanism.

On Mercury, with a larger world radiating its heat more slowly (not to mention the fact that one side is baked by the Sun and the larger crust probably had more radiogenetic heat), the crust was still more malleable as the bombardment from impacts died out. Neither process ended abruptly in a few hours, but the two gradually died down at the same time, leaving a crust with smooth areas that melted flat after their last impact. Meanwhile, the contraction of the huge core led to some interesting topographic features so that the smooth areas are not glassy smooth like a frozen sea. Of course, some impacts still continued to strike, leaving the Mercurian highlands much more cratered than the lunar maria, but not nearly so completely as the lunar highlands. Finally, Mercury's volcanic heat also created a few smooth maria there.