4 ms·

For those, like me, wondering how this is even possible: In order to remain liquid in such cold conditions (the research team estimate between -10 and -30 Cels

For those, like me, wondering how this is even possible: In order to remain liquid in such cold conditions (the research team estimate between -10 and -30 Celsius where it meets the ice above), the water likely has a great many salts dissolved in it.

ryanmercer 8y ago
It is also quite possible Mars still has 'hot spots' as geologically it was very 'recently' volcanically active. Every now and then there's little anomalies that possibly hint at subsurface hot spots that might allow for hot springs and similar. In Robert Zubrin's fictional (but hard-science) book "First Landing" on the first manned Mars mission they actually find a hot spot and drill into it resulting in a geyser (which obviously, the water instantly freezes creating a snow-like effect). All of Zubrin's books are worth reading if you are at all interested in manned missions to Mars. He has some non-fiction looks (that are a bit outdated now due to scientific discoveries, like finding the polar caps are lousy with water ice) but he goes into the math and gets you in the right mindset. The fiction book is similar in nature to The Martian (came out well before The Martian) and he also has a short little fiction book meant to be sold to future colonists called 'How to Live on Mars: A Trusty Guidebook to Surviving and Thriving on the Red Planet' which also takes a hard-science fiction approach to the subject.
- yellowapple 8y ago
  "that are a bit outdated now due to scientific discoveries, like finding the polar caps are lousy with water ice" They are? The north cap has more than 800,000 cubic kilometers of water in it. Not much compared to Earth, but in space terms that seems pretty abundant to me.
  - Quinner 8y ago
    Lousy is used in this sense to mean "full of".
    - asavadatti 8y ago
      Never seen it used like that but it's (somewhat) correct usage lousy 1. very poor or bad; disgusting. "the service is usually lousy" 2. infested with lice; teeming with (something regarded as bad or undesirable). "the town is lousy with tourists"
  - ryanmercer 8y ago
    What Quinner said lousy like 'lousy with lice' (infested with lice). From memory the Northern cap alone would cover Mars with something like 14 inches (it's close to 15 I think) of water :)
nickspacek 8y ago
Very interesting; I presume there is a way to determine the concentration of salts that "great many" represents. Would be interesting to compare with known halotolerant lifeforms' salt tolerance (https://en.wikipedia.org/wiki/Halotolerance https://en.wikipedia.org/wiki/Halotolerance).
hossbeast 8y ago
It seems like, being under ground, it would also be subject a higher than normal pressure, which would also help
- simias 8y ago
  I was wondering about that, how deep is it exactly? If TFA mentions it I missed it. Given the planet's low gravity and very thin atmosphere I presume it must be pretty deep in order to remain liquid. They mention Lake Vostok at the end of the article which is 4km deep but it's probably not directly comparable.
  - AnimalMuppet 8y ago
    It says 1.5 km down. I'd expect there to be significant pressure down there. Enough to make it liquid at -10C? I suspect so, but I'm not an expert on the pressure gradient on Mars...
    - gmueckl 8y ago
      Mars only has a surface gravity of about 3.71m/s^2 compared to Earth's 9.81m/s^2. This means that 1.5km of ice will just create something like 0.38 times the pressure the same column of ice of the same density would create here on Earth. If this ice were densely packed, the mass of a 1m^2 column of ice that high would be a bit less than 1400 tons. This creates a pressure of 5.1MPa or around 51 bar. Now if I could get my hand on a phase diagram for water on which I could find that point (263K, 5.1MPa) I could tell you how close pure ice is to melting under these conditions.
      - the8472 8y ago
        The melting point does not really budge much for standard water. https://upload.wikimedia.org/wikipedia/commons/0/08/Phase_diagram_of_water.svg https://upload.wikimedia.org/wikipedia/commons/0/08/Phase_di...
- Tushon 8y ago
tbabb 8y ago
This is one reason why I am VERY skeptical of this conclusion. From my reading of the article, the primary evidence they have is a bright radar reflection. That is the long-wavelength equivalent of saying "we found some white stuff, it's probably water ice!" There are other things besides water which reflect strongly. The fact that the conditions at the site are extremely non-conducive to liquid water tempers the idea that there's water there. AFAICT, there is nothing null-hypothesis rejecting here. In fact, it seems barely as good as "it's not impossible that it's water." I suspect the current hoopla is premature at best.

ryanmercer 8y ago

It is also quite possible Mars still has 'hot spots' as geologically it was very 'recently' volcanically active. Every now and then there's little anomalies that possibly hint at subsurface hot spots that might allow for hot springs and similar. In Robert Zubrin's fictional (but hard-science) book "First Landing" on the first manned Mars mission they actually find a hot spot and drill into it resulting in a geyser (which obviously, the water instantly freezes creating a snow-like effect). All of Zubrin's books are worth reading if you are at all interested in manned missions to Mars. He has some non-fiction looks (that are a bit outdated now due to scientific discoveries, like finding the polar caps are lousy with water ice) but he goes into the math and gets you in the right mindset. The fiction book is similar in nature to The Martian (came out well before The Martian) and he also has a short little fiction book meant to be sold to future colonists called 'How to Live on Mars: A Trusty Guidebook to Surviving and Thriving on the Red Planet' which also takes a hard-science fiction approach to the subject.

yellowapple 8y ago
"that are a bit outdated now due to scientific discoveries, like finding the polar caps are lousy with water ice" They are? The north cap has more than 800,000 cubic kilometers of water in it. Not much compared to Earth, but in space terms that seems pretty abundant to me.
- Quinner 8y ago
  Lousy is used in this sense to mean "full of".
  - asavadatti 8y ago
    Never seen it used like that but it's (somewhat) correct usage lousy 1. very poor or bad; disgusting. "the service is usually lousy" 2. infested with lice; teeming with (something regarded as bad or undesirable). "the town is lousy with tourists"
- ryanmercer 8y ago
  What Quinner said lousy like 'lousy with lice' (infested with lice). From memory the Northern cap alone would cover Mars with something like 14 inches (it's close to 15 I think) of water :)

nickspacek 8y ago

Very interesting; I presume there is a way to determine the concentration of salts that "great many" represents. Would be interesting to compare with known halotolerant lifeforms' salt tolerance (https://en.wikipedia.org/wiki/Halotolerance https://en.wikipedia.org/wiki/Halotolerance).

hossbeast 8y ago

It seems like, being under ground, it would also be subject a higher than normal pressure, which would also help

simias 8y ago
I was wondering about that, how deep is it exactly? If TFA mentions it I missed it. Given the planet's low gravity and very thin atmosphere I presume it must be pretty deep in order to remain liquid. They mention Lake Vostok at the end of the article which is 4km deep but it's probably not directly comparable.
- AnimalMuppet 8y ago
  It says 1.5 km down. I'd expect there to be significant pressure down there. Enough to make it liquid at -10C? I suspect so, but I'm not an expert on the pressure gradient on Mars...
  - gmueckl 8y ago
    Mars only has a surface gravity of about 3.71m/s^2 compared to Earth's 9.81m/s^2. This means that 1.5km of ice will just create something like 0.38 times the pressure the same column of ice of the same density would create here on Earth. If this ice were densely packed, the mass of a 1m^2 column of ice that high would be a bit less than 1400 tons. This creates a pressure of 5.1MPa or around 51 bar. Now if I could get my hand on a phase diagram for water on which I could find that point (263K, 5.1MPa) I could tell you how close pure ice is to melting under these conditions.
    - the8472 8y ago
      The melting point does not really budge much for standard water. https://upload.wikimedia.org/wikipedia/commons/0/08/Phase_diagram_of_water.svg https://upload.wikimedia.org/wikipedia/commons/0/08/Phase_di...
Tushon 8y ago

tbabb 8y ago

This is one reason why I am VERY skeptical of this conclusion. From my reading of the article, the primary evidence they have is a bright radar reflection. That is the long-wavelength equivalent of saying "we found some white stuff, it's probably water ice!" There are other things besides water which reflect strongly. The fact that the conditions at the site are extremely non-conducive to liquid water tempers the idea that there's water there. AFAICT, there is nothing null-hypothesis rejecting here. In fact, it seems barely as good as "it's not impossible that it's water." I suspect the current hoopla is premature at best.