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#140 by robertross on 09 Aug, 2012 02:27
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Is Curiosity going to examine its own crashed descent stage? In addition to getting us some really cool crash pictures, it would also present the opportunity to study some of that big pile of dirt the stage kicked up. Maybe the stage will have even dug some distance down into the ground, allowing subsurface sampling.
Asked at the second press conference. Answer: no.
And the main reason: risk of contamination from Hydrazine fuel -
#141 by Sesquipedalian on 09 Aug, 2012 02:58
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Asked at the second press conference. Answer: no.
And the main reason: risk of contamination from Hydrazine fuel
Thanks for the responses, especially for the reason, which would have been my next question.
One more question. Is this a new requirement or something unique to the descent stage? Because Opportunity investigated its own heat shield. Even if the heat shield didn't have fuel on it, it still would presumably have had chemicals from the trip through the atmosphere. -
#142 by kschachn on 09 Aug, 2012 03:35
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When we look at these pictures from Mars how much are they "lightened" up from what the human eye would see? In other words, how bright would it be on the surface of Mars as compared to the surface of earth during the daytime? Is this what it would look like to an astronaut or would it be dimmer?
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#143 by spectre9 on 09 Aug, 2012 04:38
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The risk of contamination isn't for hydrazine it's for everything except the tungsten weights.
I don't know how many times JPL will have to answer this same question. -
#144 by Lars_J on 09 Aug, 2012 05:45
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When we look at these pictures from Mars how much are they "lightened" up from what the human eye would see? In other words, how bright would it be on the surface of Mars as compared to the surface of earth during the daytime? Is this what it would look like to an astronaut or would it be dimmer?
There is no fixed light level for the human eye. Our eyes adjust and adapt to light levels continuously, and also have a much wider dynamic range than almost any digital camera. But what you see is probably close to how it would appear in person. -
#145 by iamlucky13 on 09 Aug, 2012 06:19
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When we look at these pictures from Mars how much are they "lightened" up from what the human eye would see? In other words, how bright would it be on the surface of Mars as compared to the surface of earth during the daytime? Is this what it would look like to an astronaut or would it be dimmer?
I took some time to quantify that question a while back when I was asked elsewhere.
Sparing all the technical details, the brightness of sunlight at Mars is a little under half the brightness of at earth, but because the human eye can perceive a very wide brightness range, and adjusts very easily to changes in brightness, if you were there, you would not have an impression that it was more than a little bit dimmer. You'd have no trouble seeing at all.
The brightness is equivalent to a lightly overcast day on earth, and actually quite a bit brighter than a typical kitchen, which is usually the best lit room in a house.
If you could perceive two scenes side-by-side, one under earth lighting, and the other under Mars lighting, you would notice the Mars scenario being slightly, but not impressively darker.
All because the human eye is a fantastically capable instrument. -
#146 by iamlucky13 on 09 Aug, 2012 06:23
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Asked at the second press conference. Answer: no.
And the main reason: risk of contamination from Hydrazine fuel
Thanks for the responses, especially for the reason, which would have been my next question.
One more question. Is this a new requirement or something unique to the descent stage? Because Opportunity investigated its own heat shield. Even if the heat shield didn't have fuel on it, it still would presumably have had chemicals from the trip through the atmosphere.
Spirit and Opportunity didn't have any instruments with anywhere close to the sensitivity as those in the Sample Analysis at Mars (SAM) suite. If they contaminate SAM, they'll have trouble telling which molecules are genuine discoveries, and which are from earth. -
#147 by robertross on 09 Aug, 2012 14:47
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Asked at the second press conference. Answer: no.
And the main reason: risk of contamination from Hydrazine fuel
Thanks for the responses, especially for the reason, which would have been my next question.
One more question. Is this a new requirement or something unique to the descent stage? Because Opportunity investigated its own heat shield. Even if the heat shield didn't have fuel on it, it still would presumably have had chemicals from the trip through the atmosphere.
You do understand the orders of magnitude difference between the seriousness of hydrazine contamination versus the miniscule trace amounts that might be on the heat shield, right?
And to add, since they said there was106.4 kg140.6 kg of propellant remaining, and there was (perhaps) some visual evidence of a larger debris field at the descent stage's location (indicating the propellant may have dispersed from the vehicle), there is a high probability of an extreme hazard.
If they can image it from afar (looking down on it), then they may do that (IIRC from the presser they might), so we have a chance to see something (maybe). -
#148 by jtrame on 09 Aug, 2012 15:01
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Asked at the second press conference. Answer: no.
And the main reason: risk of contamination from Hydrazine fuel
Thanks for the responses, especially for the reason, which would have been my next question.
One more question. Is this a new requirement or something unique to the descent stage? Because Opportunity investigated its own heat shield. Even if the heat shield didn't have fuel on it, it still would presumably have had chemicals from the trip through the atmosphere.
1. Future passes of the MRO may show the crash site in greater detail.
2. Different instrumentation on Curiosity vs. MERs, Curiosity more sensitive to contamination issue. Others may be able to elaborate on that. -
#149 by Kaputnik on 09 Aug, 2012 15:40
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Also, the MSL heatshield was instrumented, so less need to actually examine it.
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#150 by Sesquipedalian on 09 Aug, 2012 16:54
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One more question. Is this a new requirement or something unique to the descent stage? Because Opportunity investigated its own heat shield. Even if the heat shield didn't have fuel on it, it still would presumably have had chemicals from the trip through the atmosphere.
You do understand the orders of magnitude difference between the seriousness of hydrazine contamination versus the miniscule trace amounts that might be on the heat shield, right?
I did recognize that the heat shield is likely to have no hydrazine, or only trace amounts, compared to the descent stage, which is why I said "Even if the heat shield didn't have fuel on it". But surely the heat shield does have all kinds of chemicals caused by heat shield ablation.
Now the possibility of chemicals on the heat shield didn't stop Opportunity from looking at it, which is why I asked the question. In other words, is the contamination risk from a heat shield qualitatively different from the contamination risk from hydrazine? Or is there a new requirement to avoid contamination from any source?
It is also possible that my assumption is wrong and that the heat shield carries no risk of chemical contamination whatsoever; if this is so, I should very much like to learn why.Spirit and Opportunity didn't have any instruments with anywhere close to the sensitivity as those in the Sample Analysis at Mars (SAM) suite. If they contaminate SAM, they'll have trouble telling which molecules are genuine discoveries, and which are from earth.
Okay, thanks. It sounds like this is would qualify as a new requirement driven by increased instrument sensitivity.And to add, since they said there was 106.4 kg of propellant remaining, and there was (perhaps) some visual evidence of a larger debris field at the descent stage's location (indicating the propellant may have dispersed from the vehicle), there is a high probability of an extreme hazard.
If they can image it from afar (looking down on it), then they may do that (IIRC from the presser they might), so we have a chance to see something (maybe).
And this is also helpful, as you say that hydrazine contributes a chemical hazard, whereas the heat shield presumably wasn't actually hazardous, even if it could be hypothetically a contamination risk.
So between iamlucky13's and robertross's answers, it sounds like the answer to my question is "both".
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#151 by Kaputnik on 09 Aug, 2012 17:39
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RobertRoss- did you introduce a typo on the reported value of 140.6kg hydrazine remaining at DS sep, or is that a new figure estimating how much would have remained after ECO?
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#152 by Norm38 on 09 Aug, 2012 20:18
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Since use of the laser was brought up today, about how deep into the rock can the laser "dig"?
Does it just vaporize a thin layer off the surface, or can it actually make a pit into the rock? -
#153 by Jim on 09 Aug, 2012 21:18
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Since use of the laser was brought up today, about how deep into the rock can the laser "dig"?
Does it just vaporize a thin layer off the surface, or can it actually make a pit into the rock?
thin layer -
#154 by iamlucky13 on 09 Aug, 2012 21:43
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Since use of the laser was brought up today, about how deep into the rock can the laser "dig"?
Does it just vaporize a thin layer off the surface, or can it actually make a pit into the rock?
According to this site, they can etch up to half a millimeter (very much "thin layer" territory) into the surface, and compare how readings change as they do so to see if on the smallest scales there is variation in the rock that tells them a little bit about how it weathers.
http://msl-scicorner.jpl.nasa.gov/Instruments/ChemCam/
It says going that deep takes 500+ laser pulses. Each pulse lasts less than a millionth of a second, but is repeated multiple times per second. A normal analysis would use 50-75 pulses. -
#155 by robertross on 09 Aug, 2012 23:17
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RobertRoss- did you introduce a typo on the reported value of 140.6kg hydrazine remaining at DS sep, or is that a new figure estimating how much would have remained after ECO?
Yes, sorry. Corrected now. Thanks.
(I reverted back to the originally reported Sol 0 landing value of 140.6 kg) -
#156 by robertross on 10 Aug, 2012 00:11
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Here's something for those interested:
They just reported on Canadian television that Weaver industries built the heat shield for MSL (after something about the original (design?) fell through?). They had to keep it under their hats and could only announce it now after landing
I found this article on the net:
http://ephratareview.com/2012/08/weaver-industries-journey-to-mars/
Company:
http://www.weaverind.com
edit: another source/link
http://www.cw15.com/news/local/story/Mars-rover-lands-with-some-help-from-two-local/n2DbbbGJdkyzc4-n8oIcHw.cspx -
#157 by scienceguy on 10 Aug, 2012 04:03
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How does MSL's power supply work? i.e. how do they get an electric current from the plutonium?
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#158 by iamlucky13 on 10 Aug, 2012 04:24
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How does MSL's power supply work? i.e. how do they get an electric current from the plutonium?
Thermocouples.
In a nutshell, dissimilar metals joined together at one end, with the free ends exposed to a different temperature, will experience a small voltage across the free ends. Stack a bunch of them together with a significant heat difference and you can get useful amounts of power.
http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator -
#159 by scienceguy on 10 Aug, 2012 04:55
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cool. thx.
