The extremes of potential cryofluids Options

[Nafnlaus]

Our solar system has done much to show us that water and silicate magmas are not the only things that can flow on a planet and shape its surface. Io sees flows of liquid sulfur among its silicate flows. Titan, methane and other hydrocarbons. Even places where water has been found to be sculpting the landscapes it's often quite different - for example, enceladus's geysers erupt "seawater" as basic as household ammonia. And for Pluto, scientists have been speculating about bodies of neon and eutectics of nitrogen:

http://www.planetary.org/blogs/emily-lakda.../2011/3182.html

(Although, as the link notes, they couldn't exist fully exposed to the surface, as the pressure is too low).

I started thinking, how extreme could this potentially go?

We really don't know how cold planets / dwarf planets cam get. as we have limits to how far out we can detect these sized bodies. 2012 VP113 has the highest known perihelion at about 80 AU, although Sedna is close at around 76 AU. Objects around this range have the potential for liquid hydrogen on / near the surface (requires 7kPa pressure to hit the triple point). But how much further out can they be without us seeing them? Long period comets, after all, have apohelions as high as 70000 years. It seems quite natural to expect that there would be numerous objects much further out from the sun - or even in interstellar space - which could thus reach very cold temperatures, perhaps even close to thie cosmic microwave background. This is cold enough to condense liquid helium - which can exist on the surface without any pressure at all.

But can we go more exotic?

The cosmic microwave background temperature is 2.72548K, tantalizingly close to helium-4's lambda point of 2.172K. How do we get 4He down to its lambda point? Often by evaporative cooling - a process that most definitely can occur in nature, with the caveat that the gas lost has to be actually *lost* (such as taken away by the solar wind, captured into the gravity of a mutually tidally locked companion, escaping without external help, or whatnot) in order to keep the pressure down to allow it to continue. Evaporative cooling, with perfect removal of the gas, can reach down to about 1,3K, well below the lambda point.

The problem is, my first thoughts were that no realistic gas loss rate from such a body could manage to overcome radiative exchange with the cosmic microwave background, except possibly in very deep, very well insulated situations (where the pressure would probably be too high). But then I started thinking about it more. The smaller the body, the easier it becomes in all respects - less surface area, less gravity to hold onto the gas, etc. And radiative exchange at cosmic microwave background temperatures is extremely slow. Could it be possible?

A Charon-sized body has about 4 million square kilometers surface area, so let's consider a 1 million square kilometer body, cold and dead with no relevant geothermal heating and far enough from the sun that it seems nothing more than a bright star. Let's consider a radiative heat loss rate that needs to be achieved of 5uW/m² (the cosmic microwave background exchanging with lambda point helium would on its own require only 1.8uW/m² with perfect emissivity - in the real world with lower emissivity, less, potentially significantly less). We're assuming no insulating ground cover. Helium has a latent heat of vaporization of 20.754 kJ/kg. This means that the body would only need to lose about 240 kilograms of helium per second. Now, obviously such a body wouldn't be exposed to Pluto-intensity solar wind, or anything close to it. But Pluto (which loses 500 tonnes/s of its atmosphere to the solar wind) also is losing nitrogen, a much heavier gas, and has far more gravity than the thought experiment body described above. And there's other methods to lose gas apart from the solar wind - in short, I could envision such a rate of helium loss in some scenarios. And one can both decrease the required rate of helium loss and the rate of radiative exchange simply by reducing the size of the body in question.

In short, if such a situation were to exist, the helium on the surface could theoretically hit its lambda point and exist as superfluid oceans. And that's something really crazy to envision because superfluids have all sorts of bizarre behaviors.

* Flow with zero viscosity.
* Usually exists as both a fluid and superfluid component mixed together - but the superfluid moves straight through the fluid component without resistance.
* Heat is distributed extremely rapidly throughout the entire body, and (in part) flows in waves like sound.
* Bodies of superfluid at higher elevation tend to rapidly drain themselves over the edges of their contours into lower bodies in a powerful film-flow siphon effect.
* Superfluids can leak through incredibly tiny holes, and do so at incredible speeds - micron-scale holes and dozens to hundreds of meters per second velocity in a "beam" of tiny droplets that act as quantum solvents.
* Application of tiny amounts of heat can cause a powerful fountain effect
* Rotating superfluids contain an array of evenly distributed rotating vortices (rather than rotating as a whole). These vortices exist only in quantized energy states and are arranged in patterns to evenly distribute themselves.
* Waves have extremely low dissipation and seem to be very prone to "rogue waves".

It's hard to picture a world with weirder surface properties than that

[Daniele_bianchin...]

extremely extremely interesting. I am very fascinated by super fluids different from water..
You can assume dimensions and pressures for these possible Exotic worlds? or planet size does not affect?