Now, *that* ain't a tinted-blue B&W pic of Earth! Very nice.

-the other Doug (With my shield, not yet upon it)

Thank you, serpens. I've been saying this for many years, just in regards the photogeology of the Martian surface vs. what the geologists focusing solely on surface-level measurements keep trying to say.

In essence, even before the chemical cues you mention were confirmed, mapping as early as Mariner 9 clearly showed vast catastrophic flow plains, well-developed river and delta patterns -- many, many macroscopic evidences of liquid water carving the surface at some time in the (as now is known, quite distant) past. And once these extremely convincing pieces of evidence for liquid water became known, it seems like a branch of planetary geology became fixated on proving that these aqueous erosional features just had to have an explanation that didn't require large quantities of liquid water, solely on the basis that since liquid water cannot exist on the surface now, we must assume that it could never have existed there.

But, over and over, we see that in both additional orbital imagery and data from surface assets, the empirical evidence points to the presence of abundant liquid water in ancient times. And the theorists step back, very reluctantly and with great inertia holding them back, with new theories that, well, maybe it was some other fluid carving channels... or maybe there was a little tiny bit of water that only existed on the surface for hours, not thousands or millions of years.... or maybe, just maybe, if you push us really hard, we'll admit that in a very few places some water persisted for longer than a few days... And yet, the empirical evidence keeps pointing to relatively long-lived streams, rivers, pools and lakes. Long enough lived to have created rounded and sorted populations of pebbles, long enough to create conglomerate rocks with clay-like matrices... et cetera, et cetera.

Maybe it is the theorists' jobs to creep very slowly back from their best-understood hypotheses as new empirical data comes in to to challenge them. But at some point, you just have to admit defeat and start to look for a new hypothesis that actually fit the empirical data. Heck, even Harold Urey was able to do so (if not with terribly good graces) when the first lunar samples were returned by Apollo. Urey, a cold-Mooner, had predicted that the Moon and its rocks would be primitive and chondritic, without any volcanic transformation. But when the well-described rocks were initially analyzed, one of Urey's staffers came in to tell him the results, and Urey, in a very irritated voice, cut him off and said "Don't tell me, I know, they're basalts, right?" The staffer confirmed that, and Urey just grunted, seeing his entire set of theories of lunar origin and composition fly completely out the window with the first truly empirical results.

I think we still need that moment to pass through the planetary science community in re Mars, and I'll be interested to see what finally tips them over the edge...

-the other Doug (With my shield, not yet upon it)

Yeah, possibly a monitor issue. But there are no colors in that image except blue -- not even white. The clouds are just a lighter blue than the rest of the image. If it's a color image, there are no land masses visible and the white clouds have been heavily tinted.

It still looks like a tinted gray-scale image to me, to be honest. I get the feeling that if you just drew the blue channel down to where the clouds are white, the rest of the image would become gray.

-the other Doug (With my shield, not yet upon it)

Looks like a black-and-white picture of Earth that has been tinted blue.

-the other Doug (With my shield, not yet upon it)

Interesting, from the shadow patterns it looks like the sensor head on the end of the arm moves at various points during the drive. I always thought the arm and the sensor head were kept immobile during drives -- I guess not.

-the other Doug (With my shield, not yet upon it)

Sadly, by the time I ran across this topic, the voting had closed. But any such listing that doesn't include the Soviet Luna probes or the American Ranger probes and especially the Surveyor and Lunar Orbiter programs is just plain ignoring the word "historic." IMHO.

-the other Doug (With my shield, not yet upon it)

Wasn't MOD looking for shooting stars in Mars' night atmosphere? I haven't seen anything from that, yet, either. (Of course, the raw jpegs might not show a whole lot on this, it might take some real heavy image processing to find those.)

-the other Doug (With my shield, not yet upon it)

HiRISE got it.

HiRISE Images of Comet C/2013 A1 Siding-Spring

-the other Doug (With my shield, not yet upon it)

ps -- and now I see I was scooped by two hours. Sigh. Gotta get off these painkillers, dammit...

Excellent work, Damia! I can't tell, of course, how much of this might be some kind of image artifacting, but in this image you posted it almost looks like sheets of dust are being ejected -- very fine sheets.

It's a real imaging challenge to show the surface details of the nucleus and also see the jet and dust action. You *really* captured that with this one!

-the other Doug (With my shield, not yet upon it)

Thanks, Nick! It's awful darned good to be back. Though, with all that I've gone through in the past year and a half (I'm not going to go into the gory details, it just suffices to say that there was a fair amount of luck involved in me being here today to once again share this marvelous forum with y'all), I think that the "With my shield, not yet upon it" phrase is going to become a permanent part of my sig. I've been through the battles, and I'm back home to tell about it, by the gods!

As for the electrical field structures around Saturn, I will note that the magnetic field obviously develops a strong "static electricity" component as it travels along in its rotation around the planet. Look at what happens in the rings as the magnetic field passes through them -- the electrical effects cause enough particle separation from the ring plane to produce the spokes phenomenon. A larger mass, like an electrically conductive spacecraft, would definitely notice that kind of effect if it passed through that area. So I guess it's not surprising that most of the bodies in the Saturn system are sufficiently charged electrically to cause arcing on Cassini as it passes through.

All of that said, we've passed closer to Enceladus than we passed Hyperion. Heck, I think we'e had closer passes of Titan (albeit above the deep atmosphere) and Rhea, among other moons. Any signs of arcing at those points, I wonder? It might also be good to run through Galileo close approaches, especially with Io, to look for such phenomena.

-the other Doug (With my shield, not yet upon it)

A flux tube was my first thought, too. But the only flux tube I've heard of around an outer planet's moon (or at least through which the moon travels) is Io's, and that one is generated (AIUI) more than anything else by the sulfur ring caused by Io's volcanoes. I would think Hyperion would have to be venting something with a high dialectric constant for it to have generated a flux tube...

-the other Doug (With my shield, not yet upon it)

Very nice! You can make out crater rim structures that have obviously been buried for millions, if not billions, of years. That's exactly what you'd expect to see, of course, but it is cool beyond description to actually see it.

-the other Doug (With my shield, not yet upon it)

Okay, kewl. A rather less robust geological exploration in re the sample return, then. As with the Soviet Luna sample return spacecraft, your selection of samples is limited to the variety available within reach of an arm attached to the lander. Certainly, this is more robust than, say, the seminal APXS systems flown on Surveyor, which had a variety of targets limited to an area less than a square foot (and that only when improvised operations using Surveyor's digging scoop arm to push the APXS sensor away from the ground directly below its deployment housing -- without that improvisation, Surveyor would have a target selection pre-determined by the single spot over which the APXS sensor was located after landing).

It *is* nice that the Chang'e return scheme, as per the illustration, will be a deep core. Such was returned by the final Luna sample return craft, as well (though perhaps not as deep as the Apollo deep cores). But we're not looking at the kind of exploration flexibility and variety, in terms of returned samples, that you could get by roving around and selecting the most interesting samples (both those that represent the common rocks and soils that define the overall area geologically plus the unique and exotic samples that represent rocks thrown into the area from other geological units far away). Yes, you would need to acquire very small samples of each type of rock you find, but that's the same challenge MSR will be facing in the next couple of decades.

I guess the good news is that China is developing an infrastructure for unmanned lunar exploration that can be exploited in a number of ways in the future. Perhaps after the deep-core sample return process has been proven out, we will see the LSR-style rover-cache-plus-separate-return-vehicle architecture developed to provide a truly robust geological exploration capability. At least, one can hope...

-the other Doug (With my shield, not yet upon it)

"Blackstar" on that forum is a science and aerospace writer/historian named Dwayne Day, who has more connections in the industry than most NASA administrators... He may occasionally pass along rumors (as we all do on occasion), but his rumors are usually more reliable than press releases from the various agencies, universities and aerospace firms.

The best information I've heard is that Chang'e 4 will be not only a revamped version of Yutu, but will also test the sample collection and caching systems. Chang'e 5 will then be the sample return mission. What I've not heard is whether the lander that carries the Chang'e 5 rover will also carry the ascent vehicle that will rendezvous with the orbiter with the Earth return capsule.

If they send separate flights with the rover lander, the ascent vehicle and the Earth return orbiter, the rover will have to be able to make its way to the ascent vehicle to deliver its samples. This would make this a combination LOR/LSR mission architecture -- lunar orbit rendezvous plus lunar surface rendezvous.

I'll be very interested in seeing what they end up doing. If they do it that way, though, they can really do some robust recon and sample return work on the Moon, which will be really interesting to see.

-the other Doug (With my shield, not yet upon it)

Hey, guys -- been gone a while, had some rather serious issues recovering from the second surgery that I needed, but rest assured I've been following y'alls discussion and comments (and wonderful image processing) of the arrival of Rosetta at C-P. I've avoided logging in and posting because the rather high doses of painkillers I had to be on for quite a while kept me feeling that I wasn't able to compose coherent posts, but I'm at a much lower level of the painkillers now, so I've decided to venture back into posting comments to the forum.

As for C-P, my first reaction to the overall look of the sides of the main lobes on either side of the neck region remind me of glacial striations, or striations formed by mass movement along the neck-facing sides of the lobes. I can sort of imagine a large chunk of comet being blown away from the main body in slow motion, tearing the striations into the remaining faces of the lobes as it departed. Mass wasting since that event and movement of the departing mass as it was ejected could account for the discontinuities and alterations of the striations we see at this point in C-P's history and development.

Just an observation, from a possibly-still-befuddled brain...

-the other Doug (with my shield, definitely not yet upon it)

Thanks, it's appreciated.

-the other Doug (with my shield, not yet upon it)

On 6/21, PDP8E made a post in the general Mars forum in the thread "geology of Gale Crater and Mount Sharp," but the thread doesn't appear in the list of threads and when I click on the thread title from the main index page I get an error that some of the files required to display the thread are missing.

Did the thread get deleted or moved? I haven't been able to find it in the MSL forum, and IIRC it wasn't the kind of thread that would lend itself to needing to be completely deleted. I guess I would have assumed that if the thread had been completely deleted, it wouldn't show up as the last activity in that forum on the main index page.

Just curious, more than anything...

-the other Doug (with my shield, not yet upon it)

I've seen the Martian equivalent of "sea level" called the "mean elevation" but, more appropriately in a scientific sense, it is called a "zero-elevation datum" and defined as an air pressure of something like 610 Pa, or about 6 mB, which is basically the triple-point that defines the pressure required for liquid water to exist.

Since air pressure does regularly vary on Mars (bi-annually, in fact, as the CO2 sublimates from the thawing spring pole and refreezes at the autumn pole), it's not the best way to define a specific altitude. As Phil mentioned, the best way to do this is to have orbital assets define actual elevation against a concrete mean zero elevation and then use inertial devices (platform plus accelerometers) to keep track of subsequent changes as the rover moves around.

-the other Doug (with my shield, and, after another visit to the hospital and operating room, just resting on it for a while but still not on it for good)

Ah, but is it a deposit of conglomerates, or of breccia? They look rather similar, and each has about an equal chance of showing up here in Gale.

-the other Doug (with my shield, not yet upon it)

I always feel like
That rock is watching me!
(And I have no privacy...)



-the other Doug (with my shield, not yet upon it)

OK, thanks for the replies. I guess a lot of it does come down to the "cool factor," plus engineering studies of the limits of the imaging systems plus low-light observations of Martian phenomena (aerial dust structuring, etc.).

I was simply struck by the question "why use MSL's cameras for functions for which they were not really designed?" But thanks for the explanations as to the motivations, they make a lot of sense.



-the other Doug (with my shield, not yet upon it)

Maybe I'm really missing something, here, but... of what possible use is it (except for a certain "cool factor") to be able to separate out magnitude 7 and fainter stars from the noise in MSL nighttime images?

What scientific value can you get from MSL in terms of imaging faint stars that you can't get one huge heck of a lot easier (and far more cheaply) with other resources? You know, like going in the back yard with a pair of binoculars?

I guess I just don't understand the point of it. If I'm just being unenlightened, I apologize and am always receptive to further enlightenment...

-the other Doug (with my shield, not yet upon it)

Aren't these characteristics of all of the iron meteorites we've seen on the surface? I can recall several examples at Meridiani.

They all seem to be perched directly on top of the current surface, not even partially buried by lag deposits. They do all seem to show up on deflated surfaces, though, which is certainly consistent with your observations about the surface deflation at Gale.

I have a gut feeling that there is more to the story, but as to the specifics of what that "more" is, there are no working theories that have come to mind yet...

-the other Doug (with my shield, not yet upon it)

Yep, that's exactly why it looks to me like this used to be a blocky ejecta field that has been eroded down to the ground, so to speak. Because the base rocks all appear to be highly brecciated.

I appreciate the comments, though -- to let a small cat out of the bag, I'm in the middle of a very difficult recovery from the first of two major abdominal surgeries. (The second surgery will happen as soon as I'm well enough recovered from the first one, and I keep developing post-op infections that are getting badly in the way of my recovery). This means that I have had more time and such to read and post to the forum -- but it also means that, at least at times, I'm on some pretty serious painkillers. I check anything I post three or four times to make certain it's not the product of a drug-addled brain, but just to let y'all know, if I post something that seems more incoherent than normal for me, it's likely because of the ocycodone.

But anyway, thanks Phil, I'm happy to see that I'm not the only person who noticed that the base rocks here at Murray Ridge all seem to be breccias, implying this is the remnants of a thickly bouldered ejecta field.

-the other Doug (with my shield, not yet upon it)

More than just about anywhere else here at Meridiani (or even at Gusev or Gale), this area looks like it was a heavily populated block field which has been worn down to just the nubs of boulders after eons of wind erosion.

This appears to go beyond Steve Squyres' "dog's breakfast" of eroded, jumbled rocks. This area was a huge GIANT dog's breakfast...

-the other Doug (with my shield, not yet upon it)