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Hi,
I have been trying to acertain exactly how NASA sterilized the Mars Rovers rovers, (to prevent contamination from terrestrial microbes).
Someone told me they used Ethylene Oxide gas, However during the Viking Lander missions they researched into many ways of doing this and Ethylene Ooxide was dicounted as useless due to topographical impracticalities and the fact that it doesnt kill all know microbes.
The Viking research basically said all parts must be stripped down and heat treated etc. Yet when you look at NASA photo's of the rovers being finally assembled, they are not all even wearing facemasks masks ! So how did they ensure total sterility?
'I'd sooner belive that two Yankee professor's would lie, than that rocks can fall from the sky' - Thomas Jefferson, 1807
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I've been looking into this, too, recently.
(For a part related to my studies, art restoration/conservation, where contamination can be a problem...)
There are different approaches, and the most efficient are chemical. The best method... Has been out of use for a while, because it was too toxic, hence forbidden, heh...
-pure alcohol kills off most nasties,
-freezing doesn't do much for simple lifeforms, a lot of them survive fine,
-freeze drying/heating cycles eventually kills all, but is bad news for your hardware in a lot of cases,
-outgassing/'choking' with eg. nitrogen doesn't help for certain spores...
etc etc...
And i share your questions cq the 'cleanness' of the probes, when you see them being handled afterwards...
Rumour has it by the way, that some of the older Russian, and even NASA stuff didn't get more than a very superficial decontamination before being send up to land/crash/...
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Yeah, When you look at the way the assembled systems are handled all the way through the production process, they wear suits but half thier face and their noses aren't even covered! and this is while they pack it into the launch vehicle holder!
I have never got a straight answer from anyone at NASA, it is my belief that it was a 'token effort' sterilization, because as you say previous probes were not sterilized properly on hindsight.
BUT every extra probe we send that is not properly sterilized increases the odds that something survived. We cannot afford to contaminate a whole planet until we know either way wether life exist(ed) on Mars.
There are international agreements in place that are supposed to ensure that contamination doesn't happen, I just hope they have stuck to it, or there is little point in searching for biological life on Mars!
some photo's at [http://athena.cornell.edu/the_mission/rov_saf_gal.html]http://athena.cornell.edu/the_mission/rov_saf_gal.html
'I'd sooner belive that two Yankee professor's would lie, than that rocks can fall from the sky' - Thomas Jefferson, 1807
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