Wikipedia:Reference desk/Archives/Science/2016 August 28

= August 28 =

What material is Curiosity's wheels made of?
Given that the skin of Curiosity's wheels (0.75 millimeters thick) did not hold as well as expected, what material is it made out of?

Is it 100% pure aluminium or some alloy (harder and thus more durable), like 6061-T6?

--Mortense (talk) 14:16, 28 August 2016 (UTC)


 * This is the most comprehensive source that I could find, and it simply states "aluminum". Although American aluminum is far superior to European "aluminium", I agree that it is very likely to be an alloy, or at least doped. (If not then it should have been).  2606:A000:4C0C:E200:1821:CD59:E35A:CB68 (talk) 15:32, 28 August 2016 (UTC)
 * says "aviation grade", but I don't know if that has a technical meaning with regards to alloy, vs just overall quality and purity at the stated alloy. DMacks (talk) 20:27, 28 August 2016 (UTC)
 * says "aviation grade", but I don't know if that has a technical meaning with regards to alloy, vs just overall quality and purity at the stated alloy. DMacks (talk) 20:27, 28 August 2016 (UTC)


 * Just for the record, the incredibly puerile language jab made above does not mean there is significant difference in aluminium depending on the continental origin. 86.28.195.109 (talk) 21:34, 28 August 2016 (UTC)
 * A comment by The Mirthless Colonel, It seems. 2606:A000:4C0C:E200:1821:CD59:E35A:CB68 (talk) 23:35, 28 August 2016 (UTC)


 * If it is "aircraft grade" as mentioned above, then it is most likely 6061 aluminium alloy, which is what is primarily used for aircraft. 209.149.113.4 (talk) 12:39, 29 August 2016 (UTC)
 * The Curiosity rover has sent pictures showing probable debris dumped on Mars by the spacecraft itself and it blithely continues to distribute random fragments of its wheels. This hardly adheres to the letter of the 1967 Outer Space Treaty Article IX that requires signatories to avoid contaminating Mars. While aluminium is an abundant element, its affinity for oxygen means that finds of the pure metal are taken as evidence for industrial refining processes begun in the 19th century on Earth and would, only if genuine, be crucial in researching a possible Martian extinct civilisation. AllBestFaith (talk) 14:04, 29 August 2016 (UTC)


 * That is incredibly off topic and unfounded. Simply landing on Mars will alter it in some way. Curiosity hasn't even traveled 10 miles yet. Anyone searching for aluminum on Mars could easily avoid that tiny speck of land and search elsewhere. 209.149.113.4 (talk) 14:49, 29 August 2016 (UTC)
 * Or, if they were just incredibly suspicious, perform isotopic analyses of any refined aluminum they find. I would bet the isotopic ratios of Mars and Earth aluminum would differ.
 * Since one of the two naturally-occurring isotopes of aluminum on Earth (the radioactive one) is actually made when cosmic rays are captured by argon in the Earth's atmosphere, the comparative densities of the Martian and Terran atmospheres and different abundances of argon in those atmospheres seem to assure different isotopic ratios of aluminum, in the unlikely chance ancient Martians discovered how to refine and work that metal independently). loupgarous (talk) 20:57, 30 August 2016 (UTC)
 * The 27Al:26Al ratio is extremely lopsided towards the former. CIAAW does not even deem 26Al significant enough to include as a natural isotope. Double sharp (talk) 05:18, 31 August 2016 (UTC)
 * One reason for suspecting that 26Al might be more abundant on Mars, as the atmosphere there's significantly thinner (0.6% Earth sea level pressure - see Atmosphere of Mars) and has higher levels of argon, both pointing to a higher rate of 26Al formation by cosmic ray capture of atmospheric argon. Argon's comparatively incompressible; it and the other less-compressible gases in the Martian atmosphere may comprise up to 30 percent of the atmosphere over the southern pole during Mars's winter solstice.  See  Forget, 2004. loupgarous (talk) 12:20, 31 August 2016 (UTC)


 * I may be misreading the graphs, but I don't think that the temperature/pressure on Mars is such that the compressibility of any gas differs significantly from an ideal gas. See Compressibility factor. --Guy Macon (talk) 19:21, 31 August 2016 (UTC)

Have I prevented a potential disaster?
Earlier today I stopped my girlfriend from trying a mixture of nail polish remover and peroxide to remove paint stains from a wooden floor. I vaguely remember reading somewhere that peroxide and acetone are involved in very unstable explosive chemical reactions. Is this true, have I saved her from horrible injury (or worse) or am I confusing poorly remembered facts and merely delayed getting the floor clean? BTW what is a good way to get water-based PVA paint spots out of pine floor-boards? Roger (Dodger67) (talk) 20:14, 28 August 2016 (UTC)
 * You are probably remembering (and trying to avoid) the synthesis of TATP. I don't know much about various stripping products. DMacks (talk) 20:22, 28 August 2016 (UTC)


 * We're not giving advice here - Neither Wikipedia nor I accept any responsibility if we get something wrong and you blow yourself up. That said, I found some MSDSes that say that for example 3% hydrogen peroxide is "Non-explosive in presence of open flames and sparks, of shocks, of heat, of reducing materials, of combustible materials, of organic materials, of metals, of acids, of alkalis."  By contrast T-Stoff, basically 80% hydrogen peroxide, was legendarily reactive with just about everything, will spontaneously set clothes on fire, and I assume it would make explosive organic peroxides at any opportunity.  In between are industrial bottles of 30% H2O2, which are certainly good for making hazardous substances.  There's even a "food grade 35% hydrogen peroxide" described online ... I quail to think of what they might do with it.  Usually it is hard for consumers to get ahold of 30% hydrogen peroxide, hence the number of hits that come up in those searches for people who want to concentrate their disinfectant.  That said, there are definitely applications like hair bleach that can use more.  So without a clear indication of the concentration, I can't give an answer, though I bet that it is 3% and I bet that any inadvertent act of terrorism is unlikely.


 * While I'm at it, it's worth saying that paint uses a lot of simple inorganic pigments like titanium dioxide that AFAIK would laugh at your H2O2. The floor, or at least the varnish on it, might not be so resilient.  The nail polish remover is a slightly better bet, but it's not really a paint thinner which is typically more hydrophobic.  Either way the varnish seems at risk, but in the latter approach at least you're dissolving it and not reacting it - I don't know if the reacted varnish would discolor or not. Wnt (talk) 20:42, 28 August 2016 (UTC)
 * Alright, actually paint thinners do include acetone. And the OP specified a water based paint, which might not need the hydrophobic stuff, not sure.  And at this point I should admit that I don't know what I'm talking about where paint and floors are concerned and strike it all as a bad job. Wnt (talk) 12:22, 30 August 2016 (UTC)
 * In sum, the OP is correct that the combination of Acetone and Hydrogen Peroxide, can, in theory, create TATP, which is highly explosive. But this usually requires a third agent, such as sulphuric acid or hydrochloric acid to get the two to react. Still, I commend you for remembering not to mix your acetones with your peroxides.
 * As to removing the paint, worst comes to worst, you could always physically shave it off with a Plane (tool), re-sand and revarnish that spot in the floor. But I'm sure others may have better ideas for removing the paint. Eliyohub (talk) 10:18, 30 August 2016 (UTC)
 * There is a more concentrated solution of hydrogen peroxide in water which has been used to make TATP.  Having lost a son to a terrorist explosion, I won't make another terrorist's life easier by saying more (except the concentration's much lower than rocket-grade hydrogen peroxide).  It's probably safer not to mix acetone (nail polish remover's main ingredient) with anything else unless that's your job (and you have great health insurance).  OP did well by deterring his girlfriend from doing something unwise (but not explosive, since there's something else she would have had to add to the mix).  Can't recommend anything specific for that job but perhaps a sharp plastic scraper (which MIGHT leave the varnish on the floor behind).  None of the solvents which come readily to mind are very safe for untrained personnel without VOC-rated breathing masks. loupgarous (talk) 20:38, 30 August 2016 (UTC)