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# Icy Explanation: Newsletter Challenge (February 2014)

Posted February 01, 2014 12:00 AM

This month's Challenge Question: Specs & Techs from GlobalSpec:

Isabella is living in an outpost on the surface of a super-Earth-sized exoplanet. The air temperature has been a constant -7.6°F (-22°C) for a month. Outside sits a glass of water. Occasionally a thin layer of ice can be seen at the bottom of the glass, other times the ice is floating on top, and sometimes there is no ice at all. What is causing this?

The atmospheric pressure of the exoplanet at the habitat must be around 209.9 MPa (2071 atm). Ice has a triple point between ice Ih (regular ice), ice III, and water at a temperature of 251.165 K and a pressure of 209.9 MPa. Ice Ih is less dense than water, whereas ice III is denser than water. Small fluctuations in the atmospheric pressure at the habitat are causing the changes. The pressure fluctuations must be transient since only a small layer forms.

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#1

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/01/2014 2:43 AM

Slightly different triple points for the various ice types. Researching it could find the best temperature/pressure combination that would allow this. "Super-Earth-sized" suggests a higher pressure than Earth's atmospheric pressure.

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#2

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/01/2014 4:28 AM

Only constant is temperature, suggested as unvarying, gravity suggested greater than the earths, atmospheric pressure not stated, variable with quantity of gasses, and what is one month on a exoplanet ? out with the charts, anyones guess? Are there any variables?

Regards JD

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#4

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/01/2014 1:52 PM

The variable is pressure. A triple point occurs approximately where that temperature, intersects with an approximate pressure of 200MPa.

Slight variations can take it from, ice heavier than water, to water only, to water heavier than ice.

I obtained this information from a very interesting paper (it is something I never looked at before) here.

I'm not going to guess what causes the changes of pressure.

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#5

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/01/2014 11:32 PM

Ga to you and SE. Your posts were posted nearly simultaneously and the same good link. My guess for the variance of pressure on a large exoplanet would be similar to those found on earth during weather changes of high pressure and low pressure. On a large planet with much greater than 1 earth atmosphere, these fluctuations of atmospheric pressure would be enough of a swing to make ice or not that will be in different phases.

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#3

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/01/2014 1:47 PM

"The minimum temperature that liquid water can exist without ever freezing is -21.985 °C at 209.9 MPa; at higher pressures water freezes to ice-three, ice-five,ice-six or ice-seven at increasing temperatures..."

During this planet's orbit the atmospheric pressure is fluctuating both above and below the 209.9 MPa...when above, it forms a heavier than water ice form...when below it forms regular ice....and sometimes it's in between forming no ice....

ref.... (http://www1.lsbu.ac.uk/water/explan2.html - sorry, link no longer available)

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#13

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/03/2014 10:17 AM

Since this is an engineering forum, and not a pure science forum, we will assume for now that the temperature is slightly above the point where any form of liquid water can exist (for the sake of settling arguments, the correct temperature is -21.985 °C, and certainly not -22.000 °C. This way Solar Eagle, and others, who were onto the answer have it nailed down without any necessary further explanation. An uber-sized planet with have a high atmospheric pressure at the surface (provided it has an atmosphere at all - and this is a requirement to the solution of this month's riddle), and also must have some water present in the atmosphere (not saying that is vapor at the moment). Pressure swings (as stated by others) would be large by earth standards, enough to swing the glass of water from one state to another. The various forms of high pressure ices have been well enough explained.

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#6

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/02/2014 2:02 AM

It appears that perhaps the water in the glass is phasing in and out of a supercritical state by gravitational changes in atmospheric pressure due to an orbiting moon

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#7

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/02/2014 7:21 AM

this could be caused by the sun...cloudy days vs sunny days...night and day could also be a factor..

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#10

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/02/2014 5:55 PM

The problem there is that the OP mentioned the temperature is constant.

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#8

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/02/2014 10:45 AM

Martin the Martian peed into the water glass....

Just saying.

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#9

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/02/2014 11:39 AM

If temp is minus 22 at all times then what is it floating on- if water it would be always frozen.

Score 1 for Off Topic
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#11

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/02/2014 9:29 PM

Well - gotta say I'm glad to see an actual thought-provoking challenge question. It's been a while.

I'm curious what kind of exoplanet will have an atmospheric pressure 2000 times a standard Earth atmosphere, where water and water-ice can be found, and I'd really like to know who put that glass of water out there. Perhaps Isabella is a sentient robot.

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#12

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/03/2014 1:34 AM

I cried "pressure" but than I saw the replies..

No need to be a copycat :(

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#14

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/03/2014 4:23 PM

Theoretically, any change in pressure that moves up and down within the narrow red box on the diagram below would cause the phenomenon described. More 'realistically' (if you can call this realistic), it would be the movement up and down along the small green line.
The explanation for this change in pressure needs to be given. I think the change in atmospheric pressure due to a moon (tidal pressure) [reply #6] is a good answer. For just a small layer of ice (Ice I) to form on top, melt, and then have another thin layer of ice (Ice III) form on the bottom, the glass must be water most of the time. It is also likely the area is shrouded in clouds to prevent 'solar' heating of the water.

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#15

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/03/2014 4:49 PM

"Isabella is living in an outpost on the surface of a super-Earth-sized exoplanet."

The OP does not mention the impracticality of actually having a person on station on this planet to place the water/glass, much less witness the effects of local pressure changes. I do believe the pressure is well above any technology we have now for large pressure vessels, including (most) submarines? And we need this to be landing craft (as a minimum) from a mother ship in space? 200MPa is 29,000 psi. Isabella must a robot, and not requiring a pressure suit, then the possibility is limitless.

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#20

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/18/2014 10:38 AM

Isabella cannot be a robot. Consider that Isabella is living... When we get to the point that robots are considered living, I fully anticipate that we will also be able to provide pressure vessels that will allow humans to man an outpost in such a hostile environment. (And although advanced robots would make it unlikely we would NEED to man such an outpost with a human, I'm sure that some Isabella somewhere would jump at the opportunity to do so. People are infinitely curious.)

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#23

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/19/2014 4:59 AM

Sorry I know I am out of time and late with this comment but I only just read the GlobelSpec email / found this forum. : )

I might point out that the technology needed to actually reach this super Earth probably precludes any problems with handling high pressures like 200 MPa. The only way to get out there is basically some kind of FTL technology - and that will require at a minimum things like the ability to create and manipulate black holes, and probably sci-fi force fields and so on.

It seems rather more likely to me that Isabella is a local.

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#16

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/04/2014 8:10 PM

Should there be a sun that rises and sets then then the answer is obvious. The glass water is frozen solid from the night without sun. As the sun stays in the sky, the heat from the sun warms the top of the ice first leaving water on top with ice below. As the day progresses the entire glass of ice melts leaving all water, Then as the sun disappears the ice starts to form once again, starting from the top, due to its exposure to the air.

Off Topic (Score 7)
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#17

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/04/2014 11:31 PM

pressure, radiation, gravitation, any thing else?

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#18

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/04/2014 11:32 PM

hot spot in the ground?

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#19

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/04/2014 11:41 PM

frozen water breaks (normal) glass

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#22

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/18/2014 11:22 PM

a cycling planet at an elliptical orbit has seasons

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#21

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/18/2014 4:05 PM

At 251.16 K and 209.9 MPa (remember that this is a super planet) we have a water / ice triple point: Ice III + Ice Ih + Water.

Ice III is denser than water, it sinks. Ice Ih is normal ice, it floats.

Shifting pressure slightly you shift from Ice III to Ice Ih. Shifting temperature slightly you shift from ice to water.

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#24

### Re: Icy Explanation: Newsletter Challenge (February 2014)

02/26/2014 1:13 AM

First Isabella must either b an alien or living in a pressure vessel, sort of submarine type thing.

-22C is the right temperature for water to exist in several phases depending on the pressure.

Now if the pressure is some 210MPa then the water may be liquid w/o the formation of ice.

However is the atmospheric pressure is increased Ice is formed known as ICE III which is denser than the water and will sink at the bottom but if the pressure goes down from 210 MPa ordinary ice is formed floating on the water.

Or did I get this upside down:>)

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