Well if the six percent figure is typical of martian soils (although I suspect it's not or we would have seen it before?) I imagine there must have been a lot. If the impactor that made heimdall just happened to bullseye, or near bullseye, a carbonate deposit from ancient times would that produce carbonate particles in the soil like phoenix sees? Or would the effects of the impact alter the carbonates?
I wonder if there are any impact craters on earth that are known to have hit carbonate deposits for comparison.

To me it looks less like a basin with dark spots, more like a basin with a mottled floor. Thats a bit pedentic I know but I wonder if there's a partial covering of dark lava flows on the basin (mottled) or if later impacts have excavated darker material (spots).

Thats genuinely cool! I bet it's been playing tourist for a bit, sunbathing at mercury, cloud surfing venus, and meeting 'characters ' in dimly lit asteroid belt bars... It's enough to make a planet bound buggalo jealous!

Edit: Tasp, sorry for the plagarism, the idea of 'seedy asteroid belt bars' caught my imagination. Makes me think of some of some of the bars in salford where you need the confidence of a veteran space explorer to set foot!

Thats fascinating, and I wish I had the organic chemistry knowledge to ask you some intelligent questions about it! I've submitted abstracts with much less substance behind them than that! Are you planning to publish, or have you posted it here so it's here for all to see?
Edit: I didn't mean to grill you all of a sudden mike, It's just a surprise how much work you put in!

So the soil is now bone dry but has minerals in it that must have formed in the presence of water? Interesting. I'd got the impression that the warming due to mars axial tilt was to slow for the ice to melt , it would simply sublimate and re-condense somewhere else without ever reaching the liquid phase. Is this evidence against that, or could there have been melting from volcanic or impact heat that lasted long enough to leave this impression? There is a large crater just down the plain. How long does the observed amount of calcium carbonate take to form? Mars throws us more mysteries....

And two more, here and here.

They seem to have a good handle on the sodium contamination, would they not take it into account before claiming they had found sodium in the E-ring?

I've decided against badgering the Cassini team (the right and obvious decision but impatience skews my perception sometimes), I'm sure they've got enough on their plates.

I know I'm being impatient, and I know that the cassini team have a lot of work to do, but, well I was wondering if it would be worth e-mailing the team and asking if they planned to hold onto the most recent flyby data until after the next two Enceladus flybys. It wouldn't surprise me if they did but, well, I'm just wondering whats happened to it?

Hmmm, to throw a thought out at random, perhaps there is another way of looking at the question of the tholins structure:
Since organic matter has such a wonderful affinity for long chains and ring structures it might make more sense to ask what structures, in a given area of titans atmosphere, are likely to survive the conditions in that region. Anything too heavy will be drawn down to the surface, anything vulnerable to UV wil get broken apart, and anything very eager to combine with other material will likely get pulled into another larger tholin structure.

There might be interesting exceptions, for example not all the ten thousand dalton ions in the upper atmosphere need be wide boys heading down.A few might have structures lending themselves to lower density, or other properties, that allows them to remain at that altitude.

To speculate wildly: If the tholin factory in the upper atmosphere has been running long enough it might even be dominated by a relative few structures that have the best survivability there, with others being pulled down to lower levels or smashed up by UV.
There might be the next few generations of lightweight plastic floating up there waiting to be found...

Thanks Mike! I've been doing some more research and I found this interesting paper, i hope you can access it. It gives me the impression of tholins being shards of wire mesh (PAH's) tangled into bundles of string (chains)!:



It also mentions near the end that tholin production at lower pressures (higher altitudes) more accurately matches titans smog.

My apologies for resurrecting this thread but re-reading the organic building blocks article posted by ngunn there's something I hope someone can clear up:



He makes it sound as if the 10,000 dalton ion may act as the basis for a PAH, but unless I've seriously misremebered my atomic weights 10,000 daltons ought to be a huge sheet or stack of aromatic rings anyway . I get the feeling I'm seriously misintepreting him but I've had no luck finding clarification, can anyone help?

Thats what I'm talkin' about! Go oppy! Mars is along way off so: GO OPPY!

I thought this was a pretty nifty little video on one of ESA's plans to do a sample return mission to an asteroid, possible in collaboration with the Japanese. You have to scroll down a bit to find the video. To be fair it was posted first on sicknicks favorite stomping ground, but some people don't know it so i thought I'd spread the word

I was planning on using Fortran, mainly because its the only language i have any experience with and I already have a compiler, and starting from scratch. I haven't made any solid plans yet though. I'm still going through my old uni notes on things like transfer orbits. Does anyone know where I might look for some details on how launch windows for gravitational assists are calculated? My notes only skim over it briefly.

You never know...I've never trusted the things!
Actually to get myself a bit less computer phobic i've been thinking of writing a fortran program to recreate the new horizons mission, basically calculating the trajectory and fuel requirments for earth to jupiter to pluto and beyond. Does anyone have any idea where I could go for some resources, or any suggestions on where to start?

I hesitate to post this as it could well begin one of those circular 'what is/isn't lifeand could it be in spot x' debates, but I feel it is an interesting idea that may generate some interesting discussion.
This is a paper describing how a prebiotic system could show natural selection and evolution without replication.
I don't have the background to judge the idea, but it seems reasonable from what I understand. Do people here see any reason why such a selection process couldn't take place on Titan, and if it did, what effect might that have on titans 'goo-ology'?
Essentially I am wondering: would Titans pre-biotic, organic rich, environment be a good place to test this idea?

I have a feeling they will wait to release the results, but I hope they don't!

A story on how long the rains lasted on mars popped up last night, no mention of when the wet period occoured but it fits best with the chronology of mars at the end of the late heavy bombardment.

My ignorance is at least equal to yours here nprev, but I am under the impression that forming frost requires a mobile, or 'liquid' monolayer at the forming surface of the crystals, kept liquid by the pressure of the van der waals forces between the atoms. I think SickNick or Dburt would have some knowledge on whether this is always true. I don't know if any studies have been done to see if frost forms without the monolayer under mars-like conditions?

If it is always true this implies some difference between the surface and near surface material.

Surfaces without thin films of (usually but not always) water experience much higher friction coefficients, as high relief areas, known as asperities, on the two surfaces bond together. This might explain some of the clumping, but not why the clumping seems to lessen over time.

EDIT: Actually it might. If the regolith beneath the surface is ultra dry, and the atmosphere in the soil pores to, then soil freshly removed from the subsurface will have no water monolayers and particles will be held together by cold welds between asperities. After some days exposed to the atmosphere above the surface, which does have some water content, monolayers will start to form, lubricate the particles and hey presto the stickiness goes away.
If there's enough H2O in the Martian air to make that a possibility (no idea myself) then this could be tested by scooping up some subsurface, testing it for monolayers, leaving it in a heap on the deck for a few days then testing it again. If the soil becomes 'damp' after a few days on the deck then we have an explanation in the making and I shall buy myself a new bottle of absinthe! END EDIT.

It's been pointed out to me on the the yellow and black rover forum that relative humidity is temperature dependent and would be expected to vary significantly as the temperature changes, as relative humidity is the partial pressure of the water vapour divided by the saturation vapour pressure of water at a given temperature. Is it possible there has been a misinterpretation somewhere, and the change in relative humidity is entirely due to temperature, and little or no vapour is coming off the ice? Again my ignorance of humidity and atmospheric physics s pretty profound

Thanks!

Gallen 53 could you expand on that for me? What I mean is; what is it about the decomposition of olivine that causes dryness? Or do you mean that the presence of olivine is a sign of extreme dryness?

I'm curious that no thin films form at all when the water vapour, presumably coming from the ice beneath, is rising through the soil. It suggests there is something in the soil repelling the water, either a compound or an electrostatic charge...?

Agreed! I do have a preference (Titan, no Europa, no Titan!) but I could be easily talked out of, and back into, it by anyone who shared my dribbling enthusiasm for either mission! Just wanted to say to the guys who do this work how much I admire and envy them, it really is the kind of stuff that makes me glad to be alive in this time.

Well this conversations been done to the death on every space forum I've ever looked at, so I won't post again on this thread. The main counter-arguments I'd give you for a near surface habitable zone are:

1:Low temperature bacteria I've covered in the links in my last post, they are actually quite common in some places and survive of tiny amounts of water too contaminated with salts to freeze.

2: The atmospheric pressure at the phoenix site is usually above the triple point pressure for water, and any water present at -20 ( which would need to be saturated with a natural antifreeze such as sodium chloride salt) would have a vapour pressure so low it might persist even below that. The pressure needed to give pure water a liquid phase is only 6.7 millibars, and that can be provided by any atmospheric gas, so the absurdly low partial pressure of water in the martian atmosphere doesn't affect the argument. Although in dry air water will evaporate faster it can still form a liquid phase, and at martian polar temperatures I guess evaporation rates would be low even in bone dry air.

3:Most bacterium would be well protected from UV radiation by only a millimetre of Martian regolith.

That leaves whatever chemical nasties might be lurking in the soil, and high energy radiation like cosmic rays. For an example of a species that can survive several extreme conditions at once, including dessication, radiation, and oxidising chemicals I give you the absurdly tough Deinococcus radiodurans, probably the best know polyextremophile but not the only one!

I will point out myself, before I'm embarrassed by someone doing it for me, that even if a microbe might survive on mars if introduced to the right spot, conditions may well still be to harsh for it to grow. Hence the critter wouldn't be able to 'go' anywhere, however as some microbes can metabolise and synthesis proteins at -15 deg c, a warm midsummer day at phoenix's location, I wouldn't rule out very slow reproduction entirely.

Or as I said above, it's right on the edge of possibility, but we've been surprised by micro organisms before...

Edit: I'm sure I've read that there might be a habitable zone in Venus upper cloud layer, but I can't find the article, I'll post a link for you If I can find it.

Yes but regions that have those kinds of ground temperatures have little unbound H2O and visa versa. However there hasn't been found a hard lower temperature limit to biological processes as far as I know. Everything just gets slower and slower and activity tails off (even for the hardiest), without ever completely stopping, around -15 to - 20. There is some activity going on even at minus 40 deg C. So it's right down at the edge of couldn't happen, but on an unusually warm day if the right little critter got carried there, maybe......

Has anyone heard how long it will take for the CIRS data to be released? I remember for the march flyby it being about a month, has there been any hints whether it will be the same length of time? If I was six I'd be shouting 'are we nearly there yet?'. I'd really like to know which mechanism for the plumes the temperature data supports. I do appreciate it takes time to get these things right, and they need to be right before they get released, but if anyone has a time frame for it it might help control my inner child!