Can You Walk on Mercury?

[SezMe]

My mate Ellen (http://www.ellenjackson.net/), (for what it's worth, that is me with her on the About Ellen page (and here is a real challenge to the photogs: that dog has black fur, black nose, black eyes, and black sh... never mind. How do you get a photo of her?)) has been commissioned to write a book for kids (~7-11) about the planets and moons in our solar system. It is NOT sci-fi, but it does attempt to use imagery to convey to kids what the environments on other planets and moons are like. It is intended to be scientifically accurate but allow for literary license to convey the wonder and magnifigance to young adults of our solar system and, by inference, our world.

The book imagines a kid astronaut who travels to several planets and moons in our solar system and tries to portray what he would actually see/experience. One of planets he visits is Mercury.

Here is the question: What would happen to the sneakers of an astronaut who walked on the surface of Mercury. OK, ok, forget all the technical/scientific conundrums and just imagine someone walking on the surface of Mercury and focus on his sneakers. Would they melt? Would they ignite? Would they harden, blister and crack? Or what?

What say you...and, possibly more importantly, do you have any urls which back up your opinion?

Thanks a lot in advance

[RCNelson]

Google on planet mercury sun facing OR faces.

[BillC]

They wouldn't ignite, Mercury having no appreciable atmosphere to supply the oxygen needed for combustion. The Nine Planets (http://www.nineplanets.org/mercury.html) gives a range of 90K to 700K for the surface of Mercury, so it would be quite possible to find a locale with a "comfortable" ground temperature. At 700K, most synthetic rubbers aren't going to last long, but there's no shortage of alternate materials that will.

[SezMe]

Originally posted by BillC
They wouldn't ignite, Mercury having no appreciable atmosphere to supply the oxygen needed for combustion. The Nine Planets (http://www.nineplanets.org/mercury.html) gives a range of 90K to 700K for the surface of Mercury, so it would be quite possible to find a locale with a "comfortable" ground temperature. At 700K, most synthetic rubbers aren't going to last long, but there's no shortage of alternate materials that will.
Bill, I'll take it that synthetic rubbers won't last long, but the question is, "How will the degradation manifest itself?" Melting? Burning (ignoring the lack of oxyent)? Hardening? Other?

[Matabiri]

Originally posted by SezMe
Bill, I'll take it that synthetic rubbers won't last long, but the question is, "How will the degradation manifest itself?" Melting? Burning (ignoring the lack of oxyent)? Hardening? Other?

Hardening (and cracking) occurs when you get significant additional crosslinking between the rubber molecules: this is probably most likely for artificial rubber, which is Vulcanised (crosslinked) with sulphur, and is essentially one big molecule. It's also accelerated by high UV exposure - this is what causes degradation in rubber left in the sun on Earth.

Burning in the absence of an atmosphere is most unlikely, unless the rubber can supply its own oxidation source - not really.

Natural rubber would melt at high temperature, as it's not significantly cross-linked.

[Rolfe]

Oh! I thought this thread was going to be about whether it would be possible to walk on the surface of a "lake" of liquid elemental mercury.

Sorry. Normal service will now be resumed....

Rolfe.

[PixyMisa]

Originally posted by Rolfe
Oh! I thought this thread was going to be about whether it would be possible to walk on the surface of a "lake" of liquid elemental mercury.

Uh, yeah. :o

There's a another question with the same words, though, that might be significant to the book.

You can't walk on the moon, because the motion of walking requires a certain minimum gravitational force. That's why Armstrong and Aldrin and co bounded all over the place: Not out of exuberance, but because walking didn't work.

But I can't recall what the minimum gravity is. Mercury's gravity is more than twice that of the moon (roughly the same as Mars, in fact), so you might well be able to walk on Mercury.

Definitely not on Pluto, though, which has rather less gravity than the moon.

[PixyMisa]

Actually, I'll correct that: You can walk on the moon, but only very slowly.

http://www.clavius.org/gravleap.html

[Matabiri]

Originally posted by PixyMisa
You can't walk on the moon, because the motion of walking requires a certain minimum gravitational force. That's why Armstrong and Aldrin and co bounded all over the place: Not out of exuberance, but because walking didn't work.

But they were exuberant as well, right? I like to think that they said, "Whee!" every so often. Probably because I would have (http://tinyurl.com/3q7fm).

[neutrino_cannon]

Mercury wouldn't seem to be as much of a problem as Venus. It's a wicked planet when lead melts from the ambiant temperature.

[PixyMisa]

Originally posted by Matabiri
But they were exuberant as well, right? I like to think that they said, "Whee!" every so often. Probably because I would have (http://tinyurl.com/3q7fm).

Well, yeah. ;) And of course you can play golf on the moon. :)

[patnray]

Originally posted by SezMe
(and here is a real challenge to the photogs: that dog has black fur, black nose, black eyes, and black sh... never mind. How do you get a photo of her?)) [/B]
Use highlighting lights: Shine lights that are narrow beams onto the subject from behind and above the subject. This creates light highlights, even in black hair, that make the subject stand out from the background. Use fill in light in front to eliminate the shadows.

The photo on your link might have worked if you put the sun behind them both, positioning them so it creates highlights on the dog, and used an on camera flash to fill in the shadows.

[Pragmatist]

Simple answer, yes. Remember that Mercury doesn't rotate, one side is permanently hot, the other permanently cold. So there has to be somewhere where you can walk.

[Luke T.]

Originally posted by Rolfe
Oh! I thought this thread was going to be about whether it would be possible to walk on the surface of a "lake" of liquid elemental mercury.

Sorry. Normal service will now be resumed....

Rolfe.

I was thinking the same thing when I saw the topic title and even most of the way through the opening post.

Talk about disappointed!

[CurtC]

I too thought the question would be about the element Mercury, to which my answer was already "hell no." You'd sink up to your knees, then would have no way to keep yourself upright, and you'd fall over, with about 1/14 of your volume below the surface level.

Originally posted by Pragmatist
Simple answer, yes. Remember that Mercury doesn't rotate, one side is permanently hot, the other permanently cold. So there has to be somewhere where you can walk.You sure about that? I thought that Mercury was tidally locked so that its rotation and revolution rates were some rational number, just not 1.

[BillC]

CurtC is right. It was originally believed that Mercury was tidally locked to the sun, with its day equal to its year and thus keeping one face permanently turned towards the sun. Doppler radar measurements in the 1960's showed otherwise.

From Starry Night:
sidereal day=58.6 (earth) days
year = 88 days

So there's for every two orbits, it turns 3 times on its axis, a 3:2 rotation/revolution resonance, something unique in the solar system. Though it's not known if this is just a coincidence.

I guess you could make a landing on the night side shortly after nightfall and before the ground had got too cold.

I can't answer the question about rubber cracking since my chemistry has long gone dormant.. However, 700K is about the temperature of a soldering iron, so if anyone wants to run a hot soldering iron back and forth over the soles of a pair of trainers in the name of science, they can report back to us all. :)

[Pragmatist]

Originally posted by BillC
CurtC is right. It was originally believed that Mercury was tidally locked to the sun, with its day equal to its year and thus keeping one face permanently turned towards the sun. Doppler radar measurements in the 1960's showed otherwise.

From Starry Night:
sidereal day=58.6 (earth) days
year = 88 days

So there's for every two orbits, it turns 3 times on its axis, a 3:2 rotation/revolution resonance, something unique in the solar system. Though it's not known if this is just a coincidence.

I guess you could make a landing on the night side shortly after nightfall and before the ground had got too cold.

I can't answer the question about rubber cracking since my chemistry has long gone dormant.. However, 700K is about the temperature of a soldering iron, so if anyone wants to run a hot soldering iron back and forth over the soles of a pair of trainers in the name of science, they can report back to us all. :)

To CurtC: No, I'm not sure about that, looks like I was wrong, my apologies.

To BillC.: Thanks for that, apologies for the mistake. All my astronomy books are from the 1960's so I'm not exactly up to date! :)

[SezMe]

Thanks for all the comments. Very helpful. And sorry to Luke, Rolfe, et. al. for not including the word "Planet" in the title. The other interpretation never ocurred to me. You musta wondered, "What kind of dumb**** question is that?" :)

[CurtC]

Originally posted by BillC
CurtC is right. It was originally believed that Mercury was tidally locked to the sun, with its day equal to its year and thus keeping one face permanently turned towards the sun. Doppler radar measurements in the 1960's showed otherwise.Just to be completely nitpicky, a "day" is usually the amount of time it takes for the sun to make a whole circle around the sky, where the reference frame is on the surface of whatever planet you're talking about. A day on Earth is 24 hours, but the Earth does one complete spin in something like 23 hours, 56 minutes. So if Mercury were tidally locked at 1:1, "day" would have no meaning.

I checked out the Wikipedia site about the older belief about how Mercury was locked, and its 3:2 discovery in the 1960s. They said that it was thought to be locked because, at peak observation times (when it's angle with the Sun is greatest from our point of view), they would always see the same side. But with a 3:2 ratio, with one revolution, it would rotate 1.5 times. Of course, the Earth's position around the Sun would change some in that time, but it still doesn't make sense that it would look like they were seeing the same face each time. What's up with that?

[epepke]

Originally posted by Rolfe
Oh! I thought this thread was going to be about whether it would be possible to walk on the surface of a "lake" of liquid elemental mercury.

I, too.

I bet you'd slip and fall. But my father once worked in a chemical plant, and there were huge open vats of liquid mercury. The workers used to amuse themselves by throwing a Crescent wrench into the vats and watching it bob on the surface.

This is what people did before television.

[Goshawk]

To assist Ellen in breaking it down to a kid's level of comprehension...walking on the surface of Mercury wouldn't even be as bad as walking across red-hot lava.

If the ground temp on Mercury is 90K to 700K, that converts (http://www.sengpielaudio.com/calculator-fahrenheit.htm)to about -297 to 800 Fahrenheit.

According to the NoDak Volcano Guys (http://volcano.und.edu/vwdocs/frequent_questions/top_101/Lava/Lava5.html) the temperature of the coolest hot lava is about 1292 F.

So what else out there is about 700K, or 800 F?

Well, after a wildfire, the ground can be still hot enough to melt the soles of your shoes.

http://www.co.san-diego.ca.us/enterprise_portal/announcements/WhatToDoSfterAWildFire.pdf
What To Do After a Wildfire

... Avoid tennis/running shoes, whose soles can melt or be punctured

http://www.nature.ca/sila/dvtr/frstfr_e.cfm
Ground temperatures below a wildfire like this can exceed 400 degrees Celsius.Which is 752 F.

I would assume that the same thing would happen on the surface of Mercury.

[Johnny Pneumatic]

Originally posted by epepke
I, too.

I bet you'd slip and fall.

Me as well. If anyone wants to foot the bill for the sealed suit to keep the mercury from coming in contact with me and provide a closed respiration system so I won't breath highly toxic mercury oxide in the air above the pool; and the huge cost of that much mercury I'll try it out.

[Xeriar]

During the moon langings, astronauts landed on the edge between 'day' and 'night' on the Moon, so that the surface temperature would be bearable. I imagine this would also be the case on Mercury.

Walking might be difficult - certainly not at any brisk pace, but bounding about could certainly be fun. Walking and running are controlled falls, and humans are naturally tuned to Earth's gravity.

[BillC]

(To CurtC)

Just to be totally, completely, utterly nitpicky, the time take for the sun to reach the same meridian in the sky is one solar day. The time taken for the body to rotate on its axis relative to the distant stars is one sidereal day (= one "star" day). So a sun-locked Mercury would have had one sidereal day = one year.

But I'm stumped on the resonance issue. A table I found gave the interval between greatest eastern (or western) elongations of Mercury (when viewing is most favourable) as about 117 days. This is 2 sidereal days, 2/3 of a solar day, and 4/3 of a Mercurian year. So, one elongation later, Mercury will have revolved round the sun by 120 degrees (plus one orbit), and would have rotated twice relative to the stars (hence presenting the same face to the stars). But it would have rotated 240 degrees relative to the sun. According to my reckoning, this would leave you thinking that was locked relative to the stars (hence the sidereal day would be infinite), not to the sun.

Maybe The BA can sort this one out.

[LucyR]

To all those who misunderstood:

Capital "M" in title.

You would of course float on the surface of a mercury lake. If you stood up you'd probably sink in about 15 cm or so. Walking would presumably be difficult because there'd be very little friction.

[CurtC]

LucyR - both the planet and the element begin with a capital "M".

BillC - let's see if I can take a stab at this. I figure the time between elongations ought to be 116 days, which is close enough to your number. Both the Earth and Mercury would be 115 degrees along in their orbits at that time, Mercury having lapped Earth.

In 116 days, Mercury should have rotated 1.97 times, almost exactly twice. So the stars would see the same face of Mercury at that time as before, but the Earth would see it from an angle 115 degrees off from what it did before, not the same. This doesn't add up.

Aha - I just found a site (http://dml.cmnh.org/1995Jun/msg00135.html) that mentions "astronomers relied on visual and
photographic evidence collected during the short periods when the angular distance between Mercury and the sun, as seen from the earth, was as large as possible and the physical distance between Mercury and the earth as small as possible." Since Mercury's orbit is pretty eccentric, these conditions would happen about once a year on Earth, with Mercury revolving around the Sun four times, and rotating on its axis six times, therefore once a year, at its greatest elongation, Mercury would have the same face toward the Sun.

About trying to stay in the part where it's not too hot and not too cold: a solar day on Mercury is 176 Earth days, and its circumference around the equator is 9550 miles, so you would have to walk only about 2.3 mph, or one mile every 26.5 minutes, to stay in the same place relative to the Sun.

[LucyR]

Originally posted by CurtC
LucyR - both the planet and the element begin with a capital "M".


Since when?

[epepke]

Originally posted by LucyR
To all those who misunderstood:

Capital "M" in title.

Like the capital "Y" in "You" and the capital "W" in "Walk"?

[LucyR]

Originally posted by epepke
Like the capital "Y" in "You" and the capital "W" in "Walk"?

So you assumed he made three mistakes? I prefer to be generous.

[SezMe]

Thanks, LucyR :)

I just assumed thread titles are like book titles.

[jj]

Originally posted by Rolfe
Oh! I thought this thread was going to be about whether it would be possible to walk on the surface of a "lake" of liquid elemental mercury.

Sorry. Normal service will now be resumed....

Rolfe.

Is it just me, or does the poison-factor in that idea just overwhelm all else?

[wollery]

Originally posted by LucyR
To all those who misunderstood:

Capital "M" in title.I don't know for sure what the protocol is, but I was severely told off by my thesis examiners for using capitals for hydrogen, lithium, deuterium and a couple of other elements.

[LucyR]

Originally posted by wollery
I don't know for sure what the protocol is, but I was severely told off by my thesis examiners for using capitals for hydrogen, lithium, deuterium and a couple of other elements.

Right, and some people on this thread would probably give them an apoplectic attack.

Btw. can you tell us what your thesis was about?

[Interesting Ian]

Originally posted by LucyR
So you assumed he made three mistakes? I prefer to be generous.

You've got a great sense of humour LucyR :)

[LucyR]

Originally posted by Interesting Ian
You've got a great sense of humour LucyR :)

I know I'm going against the grain but I must say that you sir are a scholar and a gentleman. Well, perhaps not a scholar exactly, but certainly a gentleman. :D

Btw. what's your avatar of?

[Interesting Ian]

Originally posted by LucyR
I know I'm going against the grain but I must say that you sir are a scholar and a gentleman. Well, perhaps not a scholar exactly, but certainly a gentleman. :D

Btw. what's your avatar of?

Well, your humour is always something I've really appreciated, kinda a bit like mine. Not sure how many other people actually get it though :confused:

My avatar? Vastly better than yours isn't it? :D

Here's a bigger version. I'm sure you'll be able to make out what it is with the bigger version.

http://visionaryrevue.com/webmedia/bosch.light.300.jpeg

[Interesting Ian]

Originally posted by Interesting Ian
Well, your humour is always something I've really appreciated, kinda a bit like mine. Not sure how many other people actually get it though :confused:

My avatar? Vastly better than yours isn't it? :D

Here's a bigger version. I'm sure you'll be able to make out what it is with the bigger version.

http://visionaryrevue.com/webmedia/bosch.light.300.jpeg

Ascent of the Blessed by Hieronymus Bosch.

[wollery]

Originally posted by LucyR
Btw. can you tell us what your thesis was about? The title was, "A high proper motion search for low mass stars".

In laymans terms, I looked in a big area of sky for stars that move fast.

[Interesting Ian]

Originally posted by wollery
The title was, "A high proper motion search for low mass stars".

In laymans terms, I looked in a big area of sky for stars that move fast.

Exciting stuff! ;)

[wollery]

Originally posted by Interesting Ian
Exciting stuff! ;) Yeah, to about 20 people worldwide. :p

Earth-shattering it ain't, but I enjoy it.

[Soapy Sam]

21

[wollery]

I said about! :p

[Art Vandelay]

Originally posted by Xeriar
During the moon langings, astronauts landed on the edge between 'day' and 'night' on the Moon, so that the surface temperature would be bearable. Interestingly enough, the name of that edge appeared in the title of a movie about a robot made from liquid metal.

[pauldmin]

In theory, it would be possible to walk in one of the craters at the poles of Mercury, since it has very little axial inclination and the crater bottom would be permanently dark.

It would be pretty cold though.