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Could Venusian greenhouse gas effects keep a TNO like Pluto warm? (lemmy.world)

submitted 4 days ago* (last edited 4 days ago) by [email protected] to c/[email protected]

16 comments fedilink hide all child comments

TNO = trans neptunian object, basically far out dwarf planet

Obviously there would be less sun to greenhouse, but theoretically could that be a way to have closer-to-earth habitats far away from a star?

edit: the TNO does not have to be like Pluto, it can be bigger or have different conditions

top 16 comments

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[–] [email protected] 22 points 4 days ago* (last edited 4 days ago) (2 children)

I don't think so.

Even out at Mars you already have significantly diminished solar incidence.

I think that past Saturn you probably start to have so little incoming solar energy that it's almost impossible to retain it.

EDIT:

Saturn receives around 1% of the solar irradiance of earth.

Pluto receives 0.064%. less than 1W/m2.

With a radius of 1188km, the absolute maximum incident solar energy is 3.8E12 W. (Assuming no efficiency loss as the angle of incidence decreases due to curvature)

The radiating surface is the full sphere, and using Earth's black body temperature of 254K.

Therefore, Pluto would be radiating approximately 5.67E-8 x 254^4 x 4 x pi x 1188000 ^2 = 7.38 E14.

In other words, you would need to retain at least 99.5% of all energy emitted by pluto. Mirrors reflect around 95% of visible light, and infrared is even more difficult to reflect.

[–] [email protected] 5 points 4 days ago* (last edited 4 days ago)

Data comes from NASA planetary fact sheets (amazing resource btw).

Overall equation structure:

Circular area that can receive sunlight: pi x radius ^ 2

Total incoming power : solar irradiance x circular area

Spherical area : 4 x pi x radius ^ 2

Black body radiation : stefan-boltzmann constant x Area x Temperature ^ 4

You know have incoming power and outgoing power.

Percentage : 100 x (Outgoing - incoming) / outgoing

[–] [email protected] 4 points 4 days ago (2 children)

Shouldn't the greenhouse effect be trapping whatever does make it though? I thought greenhouse effects could lead to a positive feedback loop scenario

[–] [email protected] 14 points 4 days ago (2 children)

The greenhouse effect won't even start if the greenhouse gases are frozen on the surface

[–] [email protected] 2 points 4 days ago (1 children)

So what if there is a temporary heat source (nuke or something) or it originated from closer to the sun?

[–] [email protected] 2 points 4 days ago

Intuitively I would assume that a single event would either not release enough energy to start a feedback loop or destroy the planet altogether, but I have no idea how to calculate that.

[–] [email protected] 1 points 4 days ago

That too 😂

[–] [email protected] 2 points 4 days ago

The greenhouse effect still has a limit to how much it can trap.

At the end of the day infrared radiation is still basically light.

Even on the cloudiest day, or when there is super dense smoke or ash, it is still not pitch black out. Some light gets through. If you are looking into a mirror, it might seem like it reflects 100% of light. But they only reflect around 95%.

You would require something which can let through 100% of all sunlight, but still trap 99.5% from leaving.

You could have a look at how one-way mirrors work, to understand the percentages of light passed through and reflected.

[–] [email protected] 9 points 4 days ago (1 children)

I think a problem would be Pluto not having the gravity to hang onto much atmosphere.

[–] [email protected] 3 points 4 days ago (2 children)

Not Pluto specifically, in fact "TNO like Pluto" was kind of a misspeak because mass and density are flexible. I basically just want a slightly-more-habitable place than the average terrestrial world and work backwards from there. Things like moons of gas giants are explored, but I was thinking how to make things even more remote.

[–] [email protected] 2 points 4 days ago* (last edited 4 days ago)

Well, if you want an atmosphere to start with, might try running numbers for sulfur hexafluoride. I don't know if it'd be your best option, but I'd guess that it'd be up there if you can keep the object warm enough for it to be a gas.

https://www.epa.gov/eps-partnership/sulfur-hexafluoride-sf6-basics

Sulfur hexafluoride (SF₆) is a synthetic fluorinated compound with an extremely stable molecular structure. Because of its unique dielectric properties, electric utilities rely heavily on SF₆ in electric power systems for voltage electrical insulation, current interruption, and arc quenching in the transmission and distribution of electricity. Yet it is also the most potent greenhouse gas known to date. Over a 100-year period, SF₆ is 23,500 times more effective at trapping infrared radiation than an equivalent amount of carbon dioxide (CO₂).

I don't know how to calculate albedo, but I'm sure that there are Web pages out there talking about it.

EDIT: If all you care about is keeping the body warm via solar radiation and you don't care about it specifically using purely the greenhouse effect, you could use space mirrors in orbit.

[–] [email protected] 1 points 4 days ago

How about a space station? Lot easier to keep things livable if you just contain everything. Would probably end up being easier to build a station and fly it out there than try to terraform something that distant.

[–] [email protected] 6 points 4 days ago (1 children)

Most chemicals that are gasses this close to the sun are solids that far out. Carbon dioxide freezes at just -79 C at one atmosphere of pressure. The energy coming in from the sun would not be enough to keep good greenhouse gasses from precipitating out of the atmosphere.

[–] [email protected] 1 points 4 days ago

If we are starting the the chemicals being cases, through external means or the TNO not starting as a TNO, would it be able to sustain enough heat to keep it that way?

[–] [email protected] 2 points 3 days ago* (last edited 3 days ago)

No, the greehouse effect involves the atmosphere trapping the sun's heat, and at the distance of Neptune the sun just looks like another bright star - too far away to provide enough heat even to keep an atmosphere in a gaseous state. BUT... if a faraway planet (I'm just gonna go ahead and use that word) generates enough internal heat to keep its atmosphere gaseous, it wouldn't need a greenhouse effect, or even a sun. It could roam around between stars and still maintain an atmosphere, and who knows... living things could evolve that get all their energy from heat instead of sunlight.

[–] [email protected] 1 points 3 days ago

It's so unbelievably cold out there, gases tend to liquify, liquids become solids.