Frankly, I think you'll see the U.S. split up into several smaller polities before you see a Uranian orbiter... *sigh*...

-the other Doug

Well, I will turn 82 that year. It's (barely) within the realm of possibility that I could see it. But I ain't holding my breath.

-the other Doug

Hmm... I'd say just the opposite, Paul. I see the white layer forming a small ledge where Oppy is currently looking at it. The only way a rock layer can form a ledge is if it is *more* resistant to erosion than the layer below it.

-the other Doug

I really, really believe that statement needs to be in future tense, Doug, not present tense. Not a single Falcon has yet had a successful flight. Not even a Falcon 1, much less a Falcon 9.

I understand that some of us grew up being told about how wonderful the Saturn series was going to be, and watched as a $25 billion (in 1960's dollars) pile of chips was shoved to the center of the table, with the still-nonexistent Saturn V being one of the trump cards in our hand. But even then, even after some of the Saturn V technology (such as the S-IVB) was proven on earlier flights on smaller rockets, the capabilities of the Saturn V were *always* described in future tense, right up until it finally flew.

Until capabilities are demonstrated, they remain planned or virtual, and as such must be spoken of in the future tense. Please.



-the other Doug

Hah! You're talking to someone who owns four or five virtual "I Corrected Henry" t-shirts... *grin*...

-the other Doug

Here's a thought -- assuming you can make a heat shield that can take multiple dips into the atmosphere, you could reduce your orbital speed to the minimum possible by making several aerobraking passes. It wouldn't reduce your overall final entry speed by a lot, but there is a measurable difference in the total energy you need to bleed off from LMO than from a direct entry from your trans-Mars trajectory, or even from a higher orbit.

The whole idea is to use the atmosphere's braking capability to the fullest, I would think. And as long as Mars has an atmosphere and can support braking, we need to figure out how to maximize it.

-the other Doug

Has everyone managed to come up with flat-field corrections for the horribly dusty optics? Or, dare I say it, are these streak-free pancam mosaics indicative of a major cleaning of those optics?

-the other Doug

Jeez, Mike! References? I mean -- this is just an Internet forum, my friend. Really.



However, if you ever feel like you're writing to yourself alone in this thread, always know that the feeling is incorrect. I may sometimes slog through some of your posts, but I have learned a tremendous amount about organic and inorganic chemistry and the great variety of Titanian cryo-ices, and your observations and speculations on how these strange (yet familiar) landforms came to be fill my mind in my spare moments.

You really need to be putting this work up for publication in peer-reviewed journals. It's that well done.

-the other Doug

I don't suppose anyone would believe me if I said that entire list was compiled from memory? It was, but I doubt anyone would actually believe me... (For that list, I could have given the full names, in fact, not just their informal names. Including middle names. How many people know that Charlie Duke's middle name is Moss? Or that Jack Schmitt's given name is Harrison Hagan Schmitt? )

In fact, the number of days spent outside of LEO cites, admittedly approximate in the post, are also from memory. I could be off by a half a day or so either way.

-the other Doug

My own memories from childhood include the 3" reflector I got for Christmas in 1969. The most dangerous thing that happened to me in my youth was using the sun filter on that scope to look at sunspots. I was gazing intently into the eyepiece, watching with fascination as the sunspots slowly slid across the sun's face, when the filter cracked with a loud snap and full, magnified sunlight came streaming through the eyepiece.

Darned good thing I flinched when I heard the crack, or I'd be blind in one eye right now.

I also remember using that same scope to study Comet Bennett in 1970. It was the first comet I ever saw that I can remember (Ikeya-Seki having disintegrated close to the sun before coming around to be visible to those of us in the northern hemisphere), and I was (barely) able to see the tiny dot of the nucleus within the coma.

As a slightly older teen, I was a member of my home town's astronomy club, which included rights to check out the keys to the club's 8" reflector located about 10 miles outside of town and away from most of the light pollution. I was able to find the valley at Taurus-Littrow on the Moon with that scope, as well as seeing Syrtis Major and Sinus Meridiani on Mars. Plus a wondrous view of banded Jupiter and its attendant moons, and ringed Saturn. I also for the first time was able to directly see structure in the smudge that is M31.

It's been a long while since I have actually looked into the eyepiece of a telescope... but those childhood experiences molded my interest and enthusiasm for the rest of my life.

-the other Doug

The show didn't emphasize expense, really. There were actually some nice segments with people describing how they built their own scopes, cheap. One fellow showed off a scope built with materials left over from a canoe-building project, another spoke of grinding his own mirror in the aftermath of a hurricane, when "there wasn't no power, so I didn't have anything better to do."

It emphasized that making your own equipment could take a lot of perseverance and practice, but showed all sorts of people who were reaping the rewards of those virtues and were well-pleased with themselves.

All in all, I saw a lot of good role models who didn't spend an arm and a leg on their hobby. A good thing, I think.

-the other Doug

Ah, but did they make the sky *just* the right shade of pink?



-the other Doug

I recorded an interesting documentary this last Thursday, and I'm just now getting a chance to watch it. (Gotta love these digital video recorders...)

It's entitled "Seeing in the Dark," and it discusses the current state of amateur astronomy, with some nice information about its history. The biggest, most interesting thing is how many amateurs are now pulling their data from remote sources; there are tons of "time-share" 'scopes out there, which are financed by hundreds or thousands of eager amateur users, that collect photons onto digital camera systems and deliver their images to the amateur investigators via the internet.

It ran on PBS. I would hope it gets re-run at some point.

-the other Doug

That's why I have such a hard time understanding the gut reaction a handful of planetary scientists seem to have at this apparent fact. Their reaction, instead of trying to constrain the time frames, the extent of standing water, the processes by which that water has been buried or trapped at the poles or sputtered way into the void, etc., etc., seems to be: "Well, wait -- there *must* be another explanation for this. There simply must. Let's see how many improbable theories we can generate to explain this, since it simply *cannot* be liquid water which made these landforms. Utterly impossible."

Every theory I hear, from "White Mars" to "insignificant capillary action and frosts", tries to explain away one tiny fragment of a growing body of overwhelming evidence, first and foremost of which is the morphological evidence. Yes, capillary action involving tiny amounts of water could have produced some of the alteration we've seen in rocks at Gusev -- but it doesn't explain the massive outflow channels. Yes, dry ice phase change physics can explain some aspects of some erosional features -- but it does not explain the meandering river valleys. And so on, and so on. The whole approach begs Occam's Razor to cease to exist -- it's like they want to abandon the obvious, simplest, most probable answer in favor of *anything* else.

It's like standing in the middle of the American southwest, pulling up abundant marine fossils from the ground, and spending the rest of your life feverishly trying to convince everyone that they must have somehow been transported there from some currently existing ocean. That the American southwest could *never* have been a seafloor, for the simple reason that it isn't one now.

Mars may have been like it is now, more or less, for a long time. But it was, for some period of time, a lot different. It's time to accept that and not feverishly argue that it couldn't have been...

-the other Doug

I am coming to the conclusion that everything -- and I mean *everything* -- that I see on Iapetus, be it dark or light surface, exhibits flow features of some sort.

You don't see those features on the other moons. Occasional things, yes, but not like this.

Another way in which Iapetus is entirely unique.

We're going to be scratching our heads over this place for decades to come. Who was it that said this close flyby might well pose more questions than it answers? Whoever it was, he/she just won the Grand Prize...

-the other Doug

Whereas Verdana has always been my font of choice, and I have truly enjoyed having it here. To me, Arial is ugly and hard to read.

-the other Doug

Oh, I agree, it's a statistically insignificant sample. And I would dearly love to get a statistically significant sample -- something like hundreds of thousands.

However, just to set the record straight, only 24 humans have traveled beyond LEO. Yes, nine three-man Apollo crews were sent to the vicinity of the Moon, but of those 27 crewmen, three went twice. So Lovell, Young and Cernan have spent the most time outside of the van Allen belts. (I guess you could claim that the Gemini 10 and 11 crews left *low* Earth orbit, but neither did more than graze the inner edge of the van Allen belts, and besides, all four of those men -- Youmg Collins, Conrad and Gordon -- eventually went to the vicinity of the Moon. So the count remains 24.)

Of those three, Lovell spent the least time, only 12 days. Young spent the next most time, about 19 days. And Cernan spent the most time, roughly 21 days. Note that all of these people are happy and healthy, their worst medical complaints these days being the standard complaints of advanced age. The one Apollo astronaut who died directly of cancer, at an early age, was Jack Swigert, and he died 10 years after his flight in the late 40's. Shepard died (IIRC) of a leukemia-related blood disease, a cancer-like illness but not a "standard" cancer, at a much more advanced age.

-the other Doug

p.s. -- the list of humans who have traveled beyond LEO, in case anyone is interested, is as follows:

Buzz Aldrin
Bill Anders
Neil Armstrong
Al Bean
Frank Borman
Gene Cernan
Mike Collins
Pete Conrad
Charlie Duke
Ron Evans
Dick Gordon
Fred Haise
Jim Irwin
Jim Lovell
Ken Mattingly
Ed Mitchell
Stu Roosa
Jack Schmitt
Dave Scott
Al Shepard
Tom Stafford
Jack Swigert
Al Worden
John Young

See? Only 24.

DVD

Very true -- which is why humans living on Mars will have to dig in. The HEDS experiments have not yet been flown successfully, so we still don't have hard data on the radiation environment on Mars' surface -- but the atmosphere there is not thick enough to provide a lot of protection. So, the answer is to give yourself a couple of meters worth of soil as a shield. The same will be true of a lunar base.

This is why the current plans for a lunar base make little sense to me -- they have the hab modules sitting right up on the surface. That simply isn't going to work, long-term.

As it is, two of the humans who have traveled out of LEO have died of cancer-related illnesses (Al Shepard and Jack Swigert). That's just under 10% (two out of 24). It's impossible to say if these illnesses were caused by cosmic ray exposure, and of the two, Shepard developed his illness well after his return from the Moon. But without a larger population to study, we really don't know just how serious the risk will be, we only have theoretical warnings that traveling beyond LEO is a dangerous situation in which to place a crew. But if we lose the first Mars crews to cancers within 10 to 20 years of their flights, the common wisdom will be that we ought to have known better.

-the other Doug

Well, Earth's magnetic field does block some galactic cosmic rays -- or more accurately, it deflects some of them. And the mass of the Earth blocks some -- you're close enough to Earth in LEO that it provides a pretty fair shielding effect. The overall exposure is less in LEO than in interstellar space, though not by a huge amount.

The atmosphere is our best protection from them -- it presents enough mass to keep most (though not all, of course) from getting through. And, obviously, the mass of the Earth blocks a lot from any given point on Earth's surface. However, airline pilots have restrictions on how many total hours of flight time they can log in their careers, with flight times near and poleward of the antarctic and arctic circles counting greater in a weighted average. Beyond a certain time frame, airline pilots face unhealthy long-term exposure to cosmic rays. This is why many airline pilots are forced to retire in their 50's -- they've logged as many high-altitude hours as they're allowed for their lifetimes.

I think the maximum NASA is prepared to allow a single human to spend in LEO is on the order of 18 to 24 months -- any longer than that and you accumulate too many rads from cosmic rays. That's why most ISS expedition members are allowed to fly on two and only two long-term expedition crews. Russia has flown some of its cosmonauts for longer periods, and AIUI some of those guys have shown deleterious effects from the radiation exposure.

-the other Doug

I don't have a link, but I do have a cite:

"When you look at the Pancam pictures we took from the top of Karatepe a couple of weeks, ago, the upper part of the slope is a jumbled dog's breakfast, made up of blueberry-laden rocks that look like the same stuff we've been seeing for months. A few meters down the slope, though, everything changes. The rock becomes contiguous and regularly banded, the jumble giving way to intact stratigraphy."

Steve Squyres, "Roving Mars," First Edition (hardback), © 2005 Steven W. Squyres. pp.346-347

-the other Doug

I have to disagree with Alan -- this is not the first ejecta blanket we've had a chance to study. The first couple of meters down into Endurance were what Squyres called a "dog's breakfast" of jumbled ejecta, and Oppy also skipped down past that until she got down into the intact layered stratigraphy.

The whole point is that intact bedrock tells you a much more complete story than jumbled ejecta. Yes, the science teams *may* take a good look at anything they see in the jumbled ejecta as they exit the crater that looks different or unusual, but even if they do, they'll have no clue from what stratigraphic section anything in the ejecta came. So simply, from a geological standpoint, it makes a lot more sense to study the intact bedrock.

-the other Doug

I just can't reconcile the huge outflow channels (where, I will point out, two of the five successful landers have touched down), the obvious water-carved channels and riverbeds, and the north-south dichotomy with a Mars that has almost never seen liquid water flowing on its surface.

It might not have been wet there for three and a half billion years, but *massive* amounts of liquid water once flowed on Mars. The morphological evidence is overwhelming. Those who continue to try and find alternatives serve a useful purpose, but it's time that we actually accept the evidence of our eyes and spend our energy constraining the time frames during which Mars was wet, and stop denying that it ever happened.

IMHO.

-the other Doug

Way to go, bud! Now, hoist a few for me, since I can't be there to celebrate with you!

-the other Doug

Exactly, tasp -- for every dark slope in the bright terrain that you can say of, "It's a sun-facing slope, so the dark material must always underlay the white material," I can point to thousands of slopes facing the same way that are white.

It ain't *just* the solar orientation, guys.

-the other Doug

The total energy required to land on Mars may be less than on the Moon, in relation to the mass you wish to land, because you can use the atmosphere to provide a good deal of your braking. However, you still have to deal with the Mach 5 problem, as is being discussed in another thread. The atmosphere just can't slow a large body to a velocity under Mach 5 before you have to start using rocket braking, and by that time you're so close to the ground you don't have enough time for rockets to slow you down to a zero landing velocity.

You need to start rocket braking earlier in the trajectory, going faster than Mach 5, and you need to apply that braking *into* the aerodynamic pressure pushing at you faster than Mach 5. That's the real challenge. The total energy required to achieve the landing is far less of an issue than figuring out how to apply that energy into a hypersonic slipstream.

-the other Doug