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TEGA - Round 2
Paul Fjeld
post Jul 29 2008, 01:47 AM
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QUOTE
Smith said, "While we continue with determining the best way to get an icy sample, we intend to proceed with analyzing dry samples that we already know how to deliver. We are going to move forward with a dry soil sample."

I read that as "we're not as scared of the short circuits as we were." Glass half-full interpretation?

Paul
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centsworth_II
post Jul 29 2008, 02:13 AM
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QUOTE (Paul Fjeld @ Jul 28 2008, 09:47 PM) *
I read that as "we're not as scared of the short circuits as we were."

It does seem quite different from the 'we're treating the next TEGA test as the last' philosophy. If there is any reason to suspect the next TEGA sample would be the last, the next sample MUST be an ice sample.
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Shaka
post Jul 29 2008, 02:26 AM
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blink.gif Just how vital is it to boil some water vapor from a pristine "ice sample"? We know the ice is there; that white stuff that disappears couldn't be anything else, right? What we want to learn about is what's left behind after the ice vaporizes - organics, or heaven knows what? So why not just position the scoop over the screen and let the sample drop out when it's good and ready? Then cook the important stuff.

smile.gif Innocence is bliss.


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Juramike
post Jul 29 2008, 02:48 AM
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I read that as, "Well, the stuff is in the oven anyway. If we do manage to deliver ice how are we going to interpret the data with a mixed sample? Might as well cook this one up and be done with it."


With regards to Shaka's question, can they determine the H/D ratio from the evolved stuff?
(If they can, the H/D ratio of the ice would be lost since both would probably sublime equally well within experimental error. So they'd need a fresh ice sample in the oven, not a used and abused concentrate.)


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Paul Fjeld
post Jul 29 2008, 03:20 AM
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Okay, I'm a bit confused.

Peter's comments implied fresh delivery of a dry sample, no? Like oven #0 has spoiled stuff in it. Would they just dump new dry stuff in #0 till it's finally full and then, how do you characterize the result in regard to its context? As NotLurkingAnymore suggests, could #0 just be a delivery test site now? I admit to profound ignorance of the chemistry of all this.

Paul
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centsworth_II
post Jul 29 2008, 03:23 AM
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QUOTE (Juramike @ Jul 28 2008, 09:48 PM) *
With regards to Shaka's question, can they determine the H/D ratio from the evolved stuff?

That's my reason for anxiously awaiting TEGA analysis of an ice sample, though I am ignorant as to what info is expected to be gleaned from the ice. I wonder if detecting ice-bound volatile organics is in anyone's wildest dreams as even a small possibility.

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CosmicRocker
post Jul 29 2008, 04:04 AM
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How about picking up some dry soil and tipping it into the back and bottom of the scoop. Then collect the ice cuttings, which would presumably land on top of and/or in front of the dry stuff. Hopefully the layer of dry sediment would prevent the ice from sticking to the metal and it would potentially facilitate the pouring/sprinkling of the ice cuttings from the scoop. unsure.gif Alternatively, perhaps they could "shake up" a mixed sample of ice cuttings and dry sediment by manipulating the scoop/arm. A mixed sample might be easier to deliver to the oven.

It may be that they would prefer to have a sample that was mostly ice, but it seems that they could never assume that any ice sample did not have some admixed soil, so using a little soil to facilitate the sample delivery is probably not a terrible thing.


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Aussie
post Jul 29 2008, 09:01 AM
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QUOTE (Paul Fjeld @ Jul 29 2008, 04:20 AM) *
Peter's comments implied fresh delivery of a dry sample, no?
Paul

I would anticipate that they will try and get what is left in the scoop in to top up the oven. This will mean that all the material in the oven will have come from from the rasping of the ice material layer. We know that (water) ice is only a part of this layer. I wouldn't like to guess what percentage, but there seems to be a lot of material left after sublimation. So having got rid of all that pesky haich two oh we are left with some pretty valuable material to analyse. Is it the same as the dry upper layer of the regoloth? What surprises does it hold? If there are any organics then they had a better chance of surviving in the opaque ice than in the regolith. Get some to the wet chemistry lab. What is the Ph of this material? Drop a bit into the OM.

Even if the system does fail after the event at least we will have two separate, and valuable data points.
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jmknapp
post Jul 29 2008, 10:56 AM
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QUOTE (CosmicRocker @ Jul 28 2008, 11:04 PM) *
It may be that they would prefer to have a sample that was mostly ice, but it seems that they could never assume that any ice sample did not have some admixed soil, so using a little soil to facilitate the sample delivery is probably not a terrible thing.


Seems like some good ideas. If placing some dry material at the back of the scoop is a go, I think that precludes delivering rasped material by the main route (through the back of the scoop around the baffles), but they could still scrape up the icy tailings with the front blade & they'd end up on top of the dry material. Said material might also act like an insulator if the problem is that the scoop itself is warm & melting the sample.

It depends on whether this material is just inherently clumpy/sticky no matter what Phoenix does (like floam laugh.gif) or, say, if it's the heat generated by rasping and/or the rasp motor that causes it to clump. Maybe they could produce a good bit of tailings and leave them on the surface for a little while. Assuming they are granular and ingestible by TEGA at that stage, put the scoop in the shade for an hour or whatever to let it cool off completely, and then scrape up the tailings. They would have sublimed to some extent, but not completely, and maybe the grains would be a bit smaller--better to get through the screen.


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MahFL
post Jul 29 2008, 12:19 PM
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My take is they can't get an icy sample into the oven, despite their best efforts . It makes sense to go ahead with a "dry" sample as the clock is ticking. Also the spacecraft could at anytime fail, and that would be the end of the mission.
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centsworth_II
post Jul 29 2008, 01:06 PM
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QUOTE (Shaka @ Jul 28 2008, 09:26 PM) *
Just how vital is it to boil some water vapor from a pristine "ice sample"?


This article sums it up pretty well:
One of the key measurements Phoenix is designed to make is the abundance of the different isotopes of hydrogen and oxygen in the water ice.... Phoenix's mass spectrometer will measure the ratios of the isotopes of these two elements, "and that should be a signature of the processes involved in making that ice," Arvidson said.

Here is what those details could reveal about ice on Mars: One theory is that the ice is in equilibrium with the scant amount of water vapor in Mars' atmosphere and froze out of the air and into the pore spaces between the soil grains.... If the mass spec examines the isotopic ratios of the water and the air "and if they're identical, it means that the water in the atmosphere is in contact, in equilibrium with the ice," Arvidson explained.

"But suppose it's a different isotopic composition — it means that ice was inplaced in some other time, when water in the atmosphere had a different isotopic composition," Arvidson told SPACE.com. "So we're trying to get at the past history and the role of water at the high latitudes."
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Shaka
post Jul 29 2008, 07:43 PM
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Good answer! Thanks, $.02.
Both the H2O and the residue are interesting, and we will, hopefully, get to cook up both from a single sample.
But we also have strategies for doing them separately.


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Ant103
post Jul 30 2008, 11:54 AM
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Color pan of the deck on Sol 61 smile.gif



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nprev
post Jul 30 2008, 12:01 PM
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Absolutely beautiful, Ant; just like being there! Thank you. smile.gif


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remcook
post Jul 30 2008, 12:43 PM
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Indeed! Seeing lots of Earth-based stuff in the frame makes it more 'real'. Great colors.
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