Could there be a foam planet

[Everten P.]

Is it possible to have a naturally made foam planet?

[Nuke]

if you have enough foam to make a planet, it wont maintain its foaminess for long. it will collapse into a liquid or solid (depending on the composition of the foam, you can make foam out of everything from soapy water to aluminum) near the core. you might have a sea of foam near the surface though.

[Everten P.]

I mean a natural one with no human interaction so is it possible to have one with a foamy aspect to it?

[phoenix_ca]

Pretty sure Nuke answered that.

[KerbMav]

Like bathing foam? No.

Very porous rock? Maybe, but:

The IAU...resolves that planets and other bodies, except satellites, in the Solar System be defined into three distinct categories in the following way:

(1) A planet is a celestial body that (a) is in orbit around the Sun, (has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and © has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, ( has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, © has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies"

The bolded part makes it impossible to have a foamy planet, as it means that the body transforms itself into a sphere by its own gravity, which would inevitably destroy the foam.

So, maybe a foamy asteroid? Not enough gravity to keep an atmosphere to prevent the foam to pop instantly in the vacuum of space.

I see no possible way to have any stellar body that is made of foam to the core, a big layer of foam on the surface might be possible.

[Nuke]

this thread reminds me of this:

https://what-if.xkcd.com/4/

[lajoswinkler]

Solid foam planet, no

Liquid foam planet, no.

Solid foam asteroid, possibly yes.

Liquid foam asteroid, no.

An example of solid foam is pumice.

Also, it really depends on the size of the voids. A loose rubble-pile asteroid might be called a solid foam object.

[Idobox]

Pumice is basically stone foam, it exists in the real world, and parts of Earth are covered with it. So it is plausible to have a planet covered in it.

Dust can also, in certain conditions, turn into highly porous rock.

Now, if you're thinking of something like bubble bath or sponge, the story is different. Bubble bath type of foam is intrinsically unstable, the liquid slowly flowing down, the bubbles bursting, so you would need a process generating gas bubbles to replace the foam.

For the sponge type of foam, you will need something flexible, which pretty much restricts you to organic matter, which in turn will necessitate life to produce in large quantities. Life forms looking like sponge exist (for example, sponges), but it's going to require some imagination to justify the whole planet being covered.