9

Is it scientifically possible to briefly walk on the moon bare footed?

What possible side effects could there be?

Are these side effects mild enough to make it worth it?

kim holder
  • 21,377
  • 9
  • 85
  • 188
Charles Okwuagwu
  • 191
  • 1
  • 5
  • 1
    Possible duplication of Puncturing space suit during EVA. What would happen? or Reaction to taking a glove off in space. – ForgeMonkey May 16 '15 at 12:07
  • 1
    @ForgeMonkey sorry, i did not see any of those suggestions this question just caught my fancy and i googled and came up blank – Charles Okwuagwu May 16 '15 at 12:18
  • 1
    I would put a pressurized tent over the area to walk on. And I would walk around barefoot on Earth for about a year before that to build up my calluses. Then it shouldn't be a problem at all. – Mark Adler May 16 '15 at 16:19
  • Make that a heavy/well anchored tent... – DJohnM May 16 '15 at 18:58
  • Hi Mark - how can you know that? The material of the moon seems tremendously different from the material of the organic soil we walk on on earth. (Great idea about the tent though!) – Fattie May 18 '15 at 03:26
  • 1
    Why would it have to be heavy? In case of earthquakes? There is absolutely no wind on the moon, I believe. – Fattie May 18 '15 at 03:27
  • I'm not talking about walking on soil. I should have been more clear. By "Earth" I didn't mean "earth". I meant a human urban environment. I walked barefoot for a few years, built up thick calluses, and had no problem walking on scorching hot pavement, frozen ground, sharp rocks, thorns, broken glass, etc. – Mark Adler May 18 '15 at 06:10
  • 1
    The tent would either have to be attached to the ground really well, be very heavy, or both. Just multiply, say, 5 psi by the area of the inside of the tent. That is the force on the tent trying to push it away from the ground. – Mark Adler May 18 '15 at 06:10
  • @MarkAdler, please explain the need for a heavy tent. Moons windless environment seems to make it unnecessary. I understand it would be only 1/6th its earth weight. – Charles Okwuagwu May 18 '15 at 06:24

2 Answers2

13

There are 3 main threats you'd have to account for:

  1. Vacuum. This is discussed in the questions @Forgemonkey linked to. Conclusion: brief exposure of the feet only is survivable.
  2. Temperature. Surface temperatures on the Moon swing between + 120 and - 150 °C, so you'd have to pick your spot carefully to have a survivable temperature.
  3. Cuts and abrasion. Lunar regolith is very sharp. It'd be like walking across glass shards. On Earth, dust and sand are subject to erosion from wind and water, which tends to make everything smooth. On the Moon these forces are absent, so e.g. the debris from a meteorite impact all keeps its sharp edges indefinitely.

All in all, not a pleasant experience, I'd think.

Hobbes
  • 127,529
  • 4
  • 396
  • 565
  • @3 do we have proof of this? i mean that regolith is that sharp and why? – Charles Okwuagwu May 16 '15 at 15:32
  • Yes, we have proof. Lunar dust proved a major problem during the Apollo missions. Lots of samples were taken home, some of it unintentionally (as dust adhering to the outside of spacesuits, for instance). – Hobbes May 16 '15 at 16:11
  • 4
    Speaking as someone who routinely walks barefoot (on Earth!) in a variety of environments, I'm not convinced (3) would be a problem if you can find a nice thick layer of dusty regolith to walk on. Even if the individual pieces are sharp, only a small fraction of your weight will be available for each of them to pierce the skin with, because the dust redistributes itself to the shape of your foot. But you would want to dust off your soles extremely carefully before you step onto a smooth hard surface afterwards! – hmakholm left over Monica May 16 '15 at 17:48
  • 2
    The vacuum would be a greater problem -- even though not immediately fatal (I'm assuming good ankle seals on the footless spacesuit), inflating the skin with several hundred millibars relative to ambient is going to stiffen the foot a lot; in particular the toe joints would suffer, but perhaps also the ankle. Possibly the lower gravity would partially make up for that, possibly the two effects would combine to make it even harder to walk naturally. – hmakholm left over Monica May 16 '15 at 17:58
  • 2
    @HenningMakholm I think. a short period of airless environment can be tolerable, until around a half minute it isn't even too unconfortable. And around the terminator (on the border of the dark and light side) the temperature could be even around the room temperature. The shards are also not very problematic as you write. I think, it could be done, although it would be like a highly extreme sport and would require a very fast gate. – peterh May 16 '15 at 19:59
  • 1
    A curious effect, not a huge problem, but worth mentioning, is that in gravity that low, your body can get confused which way is down. You might find the moon a little hard to walk on because of a lack of orientation. http://www.space.com/27029-moon-gravity-falling-astronauts.html Ofcourse, the falls wouldn't hurt, but you might look silly. – userLTK May 16 '15 at 22:09
  • 1
    Hi Hennig - I just don't think you can generalise from barefoot on Earth to barefoot on moon. the fact that lunar regolith is very sharp is a really interesting insight, I had not known this. Also as I understand it lunar dust or "fines" are very fine indeed. And some sources say that that dust itself is very "sharp" like tiny glass shards. regarding the general mix of dust/shards/whatever on a typical lunar surface area, it does seem to be INCREDIBLY different from any earth surface (which, don't forget, is mostly organic what you're feeling - ... – Fattie May 18 '15 at 03:19
  • ...even "dry" soil is essentially a wet spongy stuff packed with micro-worms and what have you.) the lunar surface is (as i understand it) totally dry and totally inorganic. If you imagine on earth a swimming pool fool of fine and not-fine shavings and bits of (say) metal or ceramics (totally dry inorganic stuff), perhaps the lunar surface is more like that? – Fattie May 18 '15 at 03:20
  • @peterh +3 my feeling exactly! And we will have a permanent foot print on the moon! Totally worth it – Charles Okwuagwu May 18 '15 at 04:09
  • 1
    I think the greatest problem is temperature. – Anixx May 19 '15 at 20:29
  • http://en.wikipedia.org/wiki/Walking_on_Broken_Glass – Keith Thompson May 20 '15 at 01:51
  • 1
    According to [DOI 10.1029/2005RG000184] and http://curator.jsc.nasa.gov/lunar/letss/regolith.pdf, about 50% of the surface material has a grain size smaller than 0.074 mm, and only 10% of the grains are larger than 1 mm. I would therefore expect that the skin should easily be able to absorb any sharp edges that are present. On a longer walk, they would of course suffer from abrasion. I would worry more about the risk of getting cancer from the smallest particles, but that's probably not a problem until you wash your feet afterwards. – JulianHzg May 29 '15 at 09:39
3

For the record here's a direct quote, from the same article Hobbes discovered:

“The dust was so abrasive that it actually wore through three layers of Kevlar-like material on Jack [Schmitt’s] boot.”

– Professor Larry Taylor, Director of the Planetary Geosciences Institute, University of Tennessee (2008)

I observe that the "ground" on Earth is soil, which is an organic substance and (even in the driest places) very wet and springy. What we think of as "very dry, hard" earth (in the "outback") is nothing compared to, say, imagine a try with an inch of tiny and large metal filings. I suggest the issue of what the lunar "soil" feels like is somewhat unknown. We do know it wore-through three layers of kevlar, even in the low gravity, in about 20 hours.

Fattie
  • 1,614
  • 1
  • 14
  • 27
  • 1
    Harrison H. "Jack" Schmitt's total EVA time during Apollo 17 was a record 22 hours 6 minutes and they drove with LRV for 35 km at top speed of about 13 km/h. So they probably had about 16-18 hours of foot time. Quite a lot. My favorite moonwalk is from Apollo 16 tho, towards the House Rock. Watching it for the first time, you'd never guess how far that rock is. Lots of abrasive action too. :) – TildalWave May 18 '15 at 03:54