TEGA - Round 2 Options

[djellison]

I challenge you not to look at this and make a ping/spring/boing happy sort of a noise.

http://phoenix.lpl.arizona.edu/images/gallery/lg_14223.jpg

[Aussie]

I feel that solving the underlying cause of the sample 'stickiness' is just as important than getting a permafrost sample to the oven. The adhesive quality doesn't seem to be a function of ice as the sample from stone soup showed greater adhesion than the permafrost scrapings. With the lack of H2O from the probe results this seems to rule out H2O as a (major) contributing factor for the clumping.

Regardless, this is not an underperformance of the system. The screen is there to stop the introduction of large particles to the oven entrance where they could jam, so the clumping samples could not have got to the oven in any case. There is still the possibility that the sample will break down as the first one did and penetrate the screen in a few days time - so all is not yet lost.

I'm not sure why trying to make a soil analogue is important. Unlike the rovers where they were trying to experiment with extraction techniques for the bogged vehicle Phoenix is on a very short timescale before the arm usage must be restricted or terminated. A mixture of non representative substances may make a reasonable analogue for the initial 'stickiness', but it would almost certainly not have the same breakdown characteristics over time - particularly when I don't believe we have a clue what is causing the adhesion in the first place. The answer is probably there in the TEGA and MECA results.

[JRehling]

I feel that solving the underlying cause of the sample 'stickiness' is just as important than getting a permafrost sample to the oven. The adhesive quality doesn't seem to be a function of ice as the sample from stone soup showed greater adhesion than the permafrost scrapings.

I've walked through some kinds of mud and come away with clean soles -- the mud adheres to itself. Other kinds seems to suck the shoe off my foot. Is there a science that studies this? There certainly *could* be, but I don't know if anyone actually publishes on it. What would you even call it -- centigeology?

This reminds me of lots of phenomena that take place with ice freezing that on Earth might be more the subjects poets and fishermen study rather than scientists. But on Mars, the equivalent phenomena take on engineering importance, and arguably scientific importance.

But the D:H ratio is of fundamental importance. I'd say there are three things of utmost interest that Phoenix was looking for:

1) The dynamics and history of H2O at this latitude.
2) The possibility of organics in that ice.
3) The identity of the Viking oxidant.

So far, we have apparent success at #3 and we may get good data on #2 out of the data we already have, but #1 probably cannot be done with the trace amounts found in the earlier sample. So the major objectives of this mission will have a very large hole at the top if something doesn't break our way soon, with at most about 15% of the active surface operations to go.

[centsworth_II]

I've seen people try to rate the success/failure of missions that were partial successes, and never saw any good come out of those discussions.

Well you seem to have done a fairly good job of it yourself (see below).

...I'd say there are three things of utmost interest that Phoenix was looking for:

1) The dynamics and history of H2O at this latitude.
2) The possibility of organics in that ice.
3) The identity of the Viking oxidant.

So far, we have apparent success at #3 and we may get good data on #2 out of the data we already have, but #1 probably cannot be done with the trace amounts found in the earlier sample.

According to the Phoenix web site, "Phoenix is designed to study the history of water and habitability potential in the Martian arctic's ice-rich soil."

I would say that "study the habitability potential" is the more interesting aspect of the mission to the public. This part of the mission seems to have been largely successful. Don't let your disappointment ruin a chance to share in the excitement.

[JRehling]

Well you seem to have done a fairly good job of [rating the success]

I cited the mission's own official priorities -- both the programmatic list of success criteria and then, although I paraphrased, their own explanation of the science objectives, in the order they mention them. You or I could have personal objectives for the mission, and it's those I wouldn't see much point in contrasting at length (if we have them), but their own criteria are right to the point.

I don't think it'll be helpful to try to get to the bottom of whether or not my excitement or lack thereof is of the right degree.

[Paul Fjeld]

I cited the mission's own official priorities -- both the programmatic list of success criteria and then, although I paraphrased, their own explanation of the science objectives, in the order they mention them.

I think your approach is the right one to assess the success of Phoenix.

It would be great if there was some way to tell the overall frustration level amongst the science team at the end of the mission and if in fact they would be kicking themselves for making certain assumptions rather than others about the nature of the soil/ice they would be sampling. The TEGA doors are a partial engineering mistake, but it's not clear that that's what's costing them. The 'broken fingers' (nice one) are only broken when it comes to delivering the ice-rich sample, otherwise its been a champ Swiss Army knife.

For me it comes down to 'poor engineering guess' or 'Martian Mystery.' If the former, the whole mission is a success (but with an annoying little fly buzzing around), if the latter, even without the ice it's a great success. Get the ice ratio stuff and it's Heroic.

[centsworth_II]

The 'broken fingers' (nice one) are only broken when it comes to delivering the ice-rich sample, otherwise its been a champ Swiss Army knife.

So why is there a clogged MECA funnel? I assume they didn't use the sprinkle method developed for TEGA deliveries. If they had, I don't think the MECA delivery would have fouled.

[01101001]

So why is there a clogged MECA funnel? I assume they didn't use the sprinkle method developed for TEGA deliveries. If they had, I don't think the MECA delivery would have fouled.

I wouldn't assume that. MECA WCL #3 got two deliveries, because the first failed. They were sol 96, Golden Goose 2, and sol 102, Golden Goose 3.

I think sprinkle has become the standard for delivery to both TEGA and MECA WCL. I'd expect sprinkle was used for the initial attempt to deliver a sample to MECA WCL #3.

JPL Blog: Deborah Bass: Water Ice and Soil Samples on Mars:

[Describing the learning curve:] We tried three methods: de-lumping, sprinkling and agitation.

[...] The sprinkle and agitation methods have been routinely adopted for sample delivery.

The neat consequence of this is that it solves what had always been our worry about how to deliver the same sample to each instrument for comparison of science results. The sprinkle delivery method enables us to put a large sample into the scoop and deliver part of it to MECA microscopy, part to MECA wet chemistry and part to the TEGA instrument. Same sample problem: solved!!

The first delivery to WCL #3 didn't succeed. If they used the routine sprinkle and it still failed, then they might have changed method and attempted a more forceful large dump for the second, also failed, delivery attempt, yielding the mound of soil we now see on the cell mouth.