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How cold is it on Mars, really?

Vox Humana

Thinker
Joined
Jul 19, 2006
Messages
206
I recently watched ep 2 of the National Geographic miniseries 'Mars', and one of the major plot points was the danger posed to the astronauts by the cold temperatures of the planet, especially at night. It's common in popular media to portray Mars being a dangerously cold place, and the numbers seem to support that - average temperatures around -55 C.

But with only 1% of the atmosphere of Earth, it would seem the effect of convective heat loss would be significantly lower than what we're used to. I also recall from thermodynamics courses (vaguely, as it was a half a lifetime ago) that a properly insulated body loses heat very slowly due to radiative heat transfer. If these assumptions are accurate, it seems possible that a person in a suit designed for survival on Mars would stay warm with moderate activity, and may actually overheat without active cooling systems, regardless of the outside temperature.

So am I missing something, or is the cold on Mars not as big a challenge as portrayed in popular media?
 
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The coldness is probably not high on the list of problems. Although I suppose it could be one more problem to contend with. Would it maybe take a lot of energy to keep the indoors at a comfortable temperature? Thermal insulation of the living spaces would be necessary.
 
I recently watched ep 2 of the National Geographic miniseries 'Mars', and one of the major plot points was the danger posed to the astronauts by the cold temperatures of the planet, especially at night. It's common in popular media to portray Mars being a dangerously cold place, and the numbers seem to support that - average temperatures around -55 C.

But with only 1% of the atmosphere of Earth, it would seem the effect of convective heat loss would be significantly lower than what we're used to. I also recall from thermodynamics courses (vaguely, as it was a half a lifetime ago) that a properly insulated body loses heat very slowly due to radiative heat transfer. If these assumptions are accurate, it seems possible that a person in a suit designed for survival on Mars would stay warm with moderate activity, and may actually overheat without active cooling systems, regardless of the outside temperature.

So am I missing something, or is the cold on Mars not as big a challenge as portrayed in popular media?

Warning - there be spoilers here!

If you recall, they have overshot their landing target by 75 km, the overloaded rover only got them part way to the Workshop Module before it broke down, so they were facing a 16 hour walk in -35°C dropping to -70°C. The question would really be, how efficient are their EVA suits?

I have to say that I am very disappointed in the series so far. Yes, the sets and special effects are very good, but the script has the characters making fundamental errors that defy belief.

1. The mission commander had to leave his command seat to perform emergency maintenance during re-entry. With only seconds to go before retro-thruster firing, instead of climbing down to safety, he tried to climb up, and when the RTs fired, he lost his grip and fell about 15 feet at high G, sustaining an injury that was eventually fatal,. If he had climbed down, he would not have fallen.

2. The crew communications back to mission control is a shambolic mess. They are unclear in what they are saying. The second in command mumbles a lot instead of making her decisions and commands clear and concise.

3. In episode three, one of the crew members finds a panel missing from a piece of equipment he is responsible for. He finds that another crew member has cannibalized some parts for another job, and has left exposed wires inside. When the crew member reaches in to find out why the equipment is not working, it sparks and he gets a shock.

4. Also in episode 3, they have to winch a member of the crew 200m down into a lava tube to look for a flat area so they can erect their living area dome. Its very, very dark when she gets to the bottom, and what does she do? She unhooks herself from the winch cable, and with spotlights only on the front of her EVA helmet, she takes a a few steps backwards and almost drops into a deep canyon.

Now, I know that there is a need for some dramatic license to make things a bit exciting for the viewers, but some of this is beyond ridiculous. These people are supposed to be highly trained ASTRONAUTS!!!

- no astronaut would make such a poor decision as the commander did;

- no astronaut would mumble incoherently when communicating with other crew members and with Mission Control,

- no astronaut would cannibalize a piece of equipment without following a strict procedure and without the express knowledge of the crew member responsible for that piece of equipment.

- and finally, no astronaut would ever, ever, ever step backwards in the pitch dark in a completely unfamiliar area.
 
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The coldness is probably not high on the list of problems. Although I suppose it could be one more problem to contend with. Would it maybe take a lot of energy to keep the indoors at a comfortable temperature? Thermal insulation of the living spaces would be necessary.

It would take a lot of energy to keep the evil solar radiation at bay.

That's the biggest issue with Mars.

McHrozni
 
Their plan in the series is to set up the habitation dome 200m underground in a lava tube to minimise their exposure to radiation.

It could work. Assuming there are available lava tubes on Mars, that is. Energy generation and storage might become an issue though.

McHrozni
 
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Does it have to be that deep?

Probably not, but there's no particular reason not to be that deep. You're better insulated for heat but most important are radiation, micrometeorites and other unpleasantness. Mars is not Earth and if you go underground you might as well go all the way and get all the bonuses from being a mole.

You'll need surface solar cells in either case, and a way to reach and maintain them. It doesn't really matter that much if the elevator shaft is 200 m deep instead of 20 m.

McHrozni
 
Warning - there be spoilers here!

If you recall, they have overshot their landing target by 75 km, the overloaded rover only got them part way to the Workshop Module before it broke down, so they were facing a 16 hour walk in -35°C dropping to -70°C. The question would really be, how efficient are their EVA suits?

I have to say that I am very disappointed in the series so far. Yes, the sets and special effects are very good, but the script has the characters making fundamental errors that defy belief.

1. The mission commander had to leave his command seat to perform emergency maintenance during re-entry. With only seconds to go before retro-thruster firing, instead of climbing down to safety, he tried to climb up, and when the RTs fired, he lost his grip and fell about 15 feet at high G, sustaining an injury that was eventually fatal,. If he had climbed down, he would not have fallen.

2. The crew communications back to mission control is a shambolic mess. They are unclear in what they are saying. The second in command mumbles a lot instead of making her decisions and commands clear and concise.

3. In episode three, one of the crew members finds a panel missing from a piece of equipment he is responsible for. He finds that another crew member has cannibalized some parts for another job, and has left exposed wires inside. When the crew member reaches in to find out why the equipment is not working, it sparks and he gets a shock.

4. Also in episode 3, they have to winch a member of the crew 200m down into a lava tube to look for a flat area so they can erect their living area dome. Its very, very dark when she gets to the bottom, and what does she do? She unhooks herself from the winch cable, and with spotlights only on the front of her EVA helmet, she takes a a few steps backwards and almost drops into a deep canyon.

Now, I know that there is a need for some dramatic license to make things a bit exciting for the viewers, but some of this is beyond ridiculous. These people are supposed to be highly trained ASTRONAUTS!!!

- no astronaut would make such a poor decision as the commander did;

- no astronaut would mumble incoherently when communicating with other crew members and with Mission Control,

- no astronaut would cannibalize a piece of equipment without following a strict procedure and without the express knowledge of the crew member responsible for that piece of equipment.

- and finally, no astronaut would ever, ever, ever step backwards in the pitch dark in a completely unfamiliar area.

You hit the nail on the head. This is a dramatisation not a documentary or a dramatisation of a real event like Apollo 13 movie is. The intent foremost is to attract viewers and keep them coming back for the benenfit of NatGeo, is advertisers and stockholders. With that in mind as co director subject to the direction of the executive producers how would you be able to do it differently?
 
You hit the nail on the head. This is a dramatisation not a documentary or a dramatisation of a real event like Apollo 13 movie is. The intent foremost is to attract viewers and keep them coming back for the benenfit of NatGeo, is advertisers and stockholders. With that in mind as co director subject to the direction of the executive producers how would you be able to do it differently?

Thus my decision not to watch it because dramadey is not the business of Nat. Geo. Reality is.
 
Probably not, but there's no particular reason not to be that deep. You're better insulated for heat but most important are radiation, micrometeorites and other unpleasantness. Mars is not Earth and if you go underground you might as well go all the way and get all the bonuses from being a mole.

You'll need surface solar cells in either case, and a way to reach and maintain them. It doesn't really matter that much if the elevator shaft is 200 m deep instead of 20 m.

McHrozni

All the extra cable to connect to your panels and radio antenna, all the energy, effort and risk of lowering your habitation and the climbing up and down the extra 180 metres?
 
Thus my decision not to watch it because dramadey is not the business of Nat. Geo. Reality is.

Nat. Geo actually is capable of coming up occasionally with something worthwhile. It just doesn't happen very often.

Just look at Georgio Lunatic hair. (Discovery I think). All of the "scientific" channels have reached out to the LCD. Pretty pathetic. This is why I pay them no heed anymore. They are promoting crap intentionally. For ratings.
 
So am I missing something, or is the cold on Mars not as big a challenge as portrayed in popular media?

For the purpose of heating and cooling, the surface of Mars is essentially a vacuum. Thus, suits worn on the surface would closely resemble those used in space. And as in space, the prime concern would be to avoid overheating. The suit must draw heat away from the human body, not provide it to the person wearing it.

Similarly, a Mars habitat would lose heat very slowly to its environment (at least to the atmosphere) and I don't think keeping its temperature would require a lot of energy.
 
Nat. Geo actually is capable of coming up occasionally with something worthwhile. It just doesn't happen very often.

Just look at Georgio Lunatic hair. (Discovery I think). All of the "scientific" channels have reached out to the LCD. Pretty pathetic. This is why I pay them no heed anymore. They are promoting crap intentionally. For ratings.


Londo Molari is usually on The Hitler History Channel with his Ancient Aliens rubbish, but NatGeo has its fair share of crap too, not least of which is "America Unearthed", in some ways worse than Ancient Aliens as junk archaeology goes.
 
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Their plan in the series is to set up the habitation dome 200m underground in a lava tube to minimise their exposure to radiation.

Does it have to be that deep?

Not at all. A layer of 2.5m of regolith (dirt) would be sufficient to reduce cosmic radiation exposure to Earth levels.

Some mission designs include a layer of sandbags on the hab, which would already cut radiation exposure by about 30%.

Unsheltered, the cosmic radiation dose on the surface of Mars would be about 10rem per year.
 
For the purpose of heating and cooling, the surface of Mars is essentially a vacuum. Thus, suits worn on the surface would closely resemble those used in space. And as in space, the prime concern would be to avoid overheating. The suit must draw heat away from the human body, not provide it to the person wearing it.

Similarly, a Mars habitat would lose heat very slowly to its environment (at least to the atmosphere) and I don't think keeping its temperature would require a lot of energy.
The research being carried out at the moment is mainly dealing with the low air pressure:

http://www.space.com/27214-skintight-spacesuit-biosuit-photos.html

If it incorporated a hood you could probably reduced the helmet down to a faceplate. Then you have to deal with the cold. This could be a heated fluid oversuit or even just plain old Antarctic boots, salopettes, parka, gloves and hat.
 
If it incorporated a hood you could probably reduced the helmet down to a faceplate. Then you have to deal with the cold. This could be a heated fluid oversuit or even just plain old Antarctic boots, salopettes, parka, gloves and hat.

The post you responded to asserted that the problem is more shedding heat than preventing heat loss, so why the "heated fluid oversuit"? I can understand a need to prevent conductive heat loss if, for instance, a hand comes in contact with the ground, but the question is, do we actually have to worry about convective or radiative heat loss?

It seems that the answer is no and actually there's more concern with overheating than with preventing heat loss, though I haven't done the math to see who is right here.
 
All the extra cable to connect to your panels and radio antenna, all the energy, effort and risk of lowering your habitation and the climbing up and down the extra 180 metres?

The length of cable will be way more than 200 meters anyway. You'll need quite a few solar panels anyway. Once you live underground pretty much all the time it doesn't really matter so much if it's 20 or 200 meters. 200 meters underground should also be safer from meteorites and other such unpleasantness that don't even register on Earth.

McHrozni
 
Unsheltered, the cosmic radiation dose on the surface of Mars would be about 10rem per year.

Compared to about 0.04 on Earth, or 0,5 rem total yearly dose.

Sheltering is necessary, but it also assumes Mars doesn't have radionuclides in soil in dangerous levels.

McHrozni
 
The post you responded to asserted that the problem is more shedding heat than preventing heat loss, so why the "heated fluid oversuit"? I can understand a need to prevent conductive heat loss if, for instance, a hand comes in contact with the ground, but the question is, do we actually have to worry about convective or radiative heat loss?

It seems that the answer is no and actually there's more concern with overheating than with preventing heat loss, though I haven't done the math to see who is right here.
Looks like it may need to both functions, heating and cooling. The Spirit and Opportunity rovers measured temperatures from -80 to +30 (:jaw-dropp) deg C and that the temperature swings were enough to damage the rovers:

http://mars.nasa.gov/mer/spotlight/20070612.html
 
But the rovers don't produce much heat of their own, whereas a human body does. Even at -80, do we really need to worry much about heat loss?

As I said I can see issues with conductive heat loss when touching the ground, for instance. Probably easy to get frost bit without decent protection in that case, but aside from actual contact with very cold materials, in general I'd suspect that even in very cold temperatures the issue would be more one of how to get rid of excess heat, not how to insulate and prevent heat loss.
 
Looks like it may need to both functions, heating and cooling. The Spirit and Opportunity rovers measured temperatures from -80 to +30 (:jaw-dropp) deg C and that the temperature swings were enough to damage the rovers:

http://mars.nasa.gov/mer/spotlight/20070612.html

From something I read a while ago (probably a sci-fi story), I believe the ~30C temperature would be (literally) a surface temperature. At, say, 1.8m (head height for an astronaut), it would be considerably less. Viking measured soil temps of about 27C from infrared, but the air temperature at 1.5m was roughly -17C.
http://www-k12.atmos.washington.edu/k12/resources/mars_data-information/temperature_overview.html
 
This is why I don't think Mars should be our first choice for the first large scale, permanent or semi-permanent (i.e the first thing that could properly be thought of as a settlement or colony instead of a "base" or expedition or scientific outpost or whatnot) and Europa or Titan or our Moon should be our areas of focus.

But at times I also wonder if the effort into settling on a planet wouldn't just be an equal sunk cost as being a large self sufficient space station.
 
But at times I also wonder if the effort into settling on a planet wouldn't just be an equal sunk cost as being a large self sufficient space station.

A planet has lots od readily available land and mineral resources. A planet with water should have rich mineral veins just waiting to be harvested. These two alone are more than enough to make a planet a better choice for colonization than a space station could.

McHrozni
 
This is why I don't think Mars should be our first choice for the first large scale, permanent or semi-permanent (i.e the first thing that could properly be thought of as a settlement or colony instead of a "base" or expedition or scientific outpost or whatnot) and Europa or Titan or our Moon should be our areas of focus..

1. How would the moon be any better? Solar radiation exposure would as great if not greater. (no atmosphere at all and closer to the Sun)

2. Europa is years of traveltime, and in any case, its bombarded with 540 rem of radiation per day in the form of high-energy electrons and ions, mostly from Jupiter. That is around 18,000 times what the surface of Mars receives.

3. Titan? That is at least a ten year trip just to get manned spacecraft there. Yes, other unmanned missions have got there quicker, but that was using gravity assist from Jupiter that accelerated them to a speeds from which it would be difficult to slow down and get into orbit.
 
But the rovers don't produce much heat of their own, whereas a human body does. Even at -80, do we really need to worry much about heat loss?

As I said I can see issues with conductive heat loss when touching the ground, for instance. Probably easy to get frost bit without decent protection in that case, but aside from actual contact with very cold materials, in general I'd suspect that even in very cold temperatures the issue would be more one of how to get rid of excess heat, not how to insulate and prevent heat loss.
It appears that the human body ditches heat primarily by radiation (approx. 65%), how that is changed by wearing a suit I don't know.

One idea could also use the body itself to help maintain the suit environment. Use wicking base layers and draw off the damp air and de-hydrate it, recover the water, scrub the CO2, and recirculate the air as much as possible. The perspiration is one hell of a way to keep the body temperature down.
 
1. How would the moon be any better? Solar radiation exposure would as great if not greater. (no atmosphere at all and closer to the Sun)

Because the moon is right next door astronomically speaking. We'd be facing the same (or only slightly worse) issues with radiation, temperature, etc but that would be, in my opinion, highly offset by a 2-3 day travel time (versus a travel time so long it pretty much every scenario I've seen requires a one way trip) and (near) instantaneous communications. We took off and landed on the moon nearly 50 years ago. It's a proven place we can get to and get back to. If we had a permanent moon base we could get emergency supplies to it in a pinch. We could medevac someone from it in a pinch. We could talk them through problems in (more or less) real time. They wouldn't be quite as "on their own."

Europa is years of traveltime, and in any case, its bombarded with 540 rem of radiation per day in the form of high-energy electrons and ions, mostly from Jupiter. That is around 18,000 times what the surface of Mars receives.

Probable liquid water which to me at least offsets pretty much any other issue beyond "populated by a race of sentient Youtube comments"

There is no such thing as a perfect (or even good if you want to be honest) site in our solar system for a permanent human settlement with our current technology, any place is going to take a lot of work.
 
I've read that mars is colder than the earth. The parts of Mars have been known to drop as low as 123 C.

Yeah, I've even heard that it's so cold there I heard that there have been times where some places on the planet's surface have reached below the boiling temperature of water!
 
How cold is it on Mars? Well, see for yourself: http://www.space.com/16907-what-is-the-temperature-of-mars.html

"On average, the temperature on Mars is about minus 80 degrees F (minus 60 degrees C). In winter, near the poles temperatures can get down to minus 195 degrees F (minus 125 degrees C). A summer day on Mars may get up to 70 degrees F (20 degrees C) near the equator, but at night the temperature can plummet to about minus 100 degrees F (minus 73 C)"​

I believe that in scientific terms, it's called 'colder than a brass monkey's balls.' ;)
 
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Looks like it may need to both functions, heating and cooling. The Spirit and Opportunity rovers measured temperatures from -80 to +30 (:jaw-dropp) deg C and that the temperature swings were enough to damage the rovers:

http://mars.nasa.gov/mer/spotlight/20070612.html

Hmmm, reminds me of home.
Our temp swings here are between extremes of <-40C to +35C.
Vehicles just don't behave well at -40 and below.
 
How cold is it on Mars? Well, see for yourself: http://www.space.com/16907-what-is-the-temperature-of-mars.html

"On average, the temperature on Mars is about minus 80 degrees F (minus 60 degrees C). In winter, near the poles temperatures can get down to minus 195 degrees F (minus 125 degrees C). A summer day on Mars may get up to 70 degrees F (20 degrees C) near the equator, but at night the temperature can plummet to about minus 100 degrees F (minus 73 C)"​

I believe that in scientific terms, it's called 'colder than a brass monkey's balls.' ;)

"Cold enough to freeze the balls off a brass monkey"
 
But the point of this thread, right from the start, is that temperature alone says very little. Temperature alone does not say how much heat will be transferred away from bodies. For that you need thermal capacity of the surrounding medium .. and we know it is very low on Mars, mostly due very low pressure and thus density of the surrounding medium.
So while brass monkey's balls would indeed over time get down to minus 60, live monkey's balls would not.
 
Looks like it may need to both functions, heating and cooling. The Spirit and Opportunity rovers measured temperatures from -80 to +30 (:jaw-dropp) deg C and that the temperature swings were enough to damage the rovers:

http://mars.nasa.gov/mer/spotlight/20070612.html

But the rovers don't produce much heat of their own, whereas a human body does. Even at -80, do we really need to worry much about heat loss?

Don't underestimate the RTGs, they're typically <6% efficient at converting the decay heat into electricity so most of the energy produced is heat. The eight plutonium modules each produce about 250W of thermal energy (and in total about 110W of electric power). That's a lot more waste heat than a human.
 
But the point of this thread, right from the start, is that temperature alone says very little. Temperature alone does not say how much heat will be transferred away from bodies. For that you need thermal capacity of the surrounding medium .. and we know it is very low on Mars, mostly due very low pressure and thus density of the surrounding medium.
So while brass monkey's balls would indeed over time get down to minus 60, live monkey's balls would not.

Live monkey (or any primate) lungs might suffer from the low pressure though.
 
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