Suppose there is a heat source at Lagrange Point 1 for Europa-Jupiter sends as much energy to Europa as the Sun does to Earth.

Assuming that this "artificial star" is completely sustainable and infinite, and the stability of its orbit is never affected and its brightness does not change no matter how long the time takes, What will Europa's surface and atmosphere and the weather for the light and dark side look like in 50 Million years? (ignoring events such as the has evolution of the sun, asteroids, etc.)

Note: whoever created the artificial star also created a Earth-like magnetic field for Europa in one way or another.

Note 2: The highest temperature in the day side is 60 degrees Celsius

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    $\begingroup$ Have you considered to put it in orbit ? For terraformation tidal lock makes things difficult. One side would get lighted, the back side of Europa remains dark. In the zone between, there will probably be stormy weather. It will all depend on the atmosphere forming and the water available. Much better explanations are given by answers on many existing questions.. worldbuilding.stackexchange.com/search?q=tidal+lock+weather $\endgroup$
    – Goodies
    Commented Nov 20, 2021 at 9:52

2 Answers 2


Jupiter will get big.

This heat source sends more heat to Jupiter than it does to Europa. It is right between them. Jupiter is bigger that Europa.

Currently Jupiter is very cold. You are going to make it hotter than Earth. Jupiter is mostly gas and when gas expands it takes up more space.

In the short term (geologically) Jupiter is going to take up a metric buttload of space. It is an interesting question as to how big Jupiter will actually get during this process. It is also an interesting question as to what will happen to Europa. Could Jupiter actually expand all the way to the orbit of Europa in the short term? Will it slow Europa down? I think probably not - the biggest gas giant is only 1.8x Jupiter size and that is still not out to Europa.

I pictured the heat source as star-like, for simplicity. If it is directional then lay that out in the OP. Also what color it is, likes and dislikes, and star sign.

But Europa! Whither Europa? Europa would lose its oceans once it got to Earth temperature.

escape velocity chart


Check out Titan. It is an order of magnitude more massive than Europa but it can fit into Europa's clothes. If you move Titan to be underneath Earth (same temperature) you will see it is too hot to keep water, or oxygen, or nitrogen. It will keep CO2 in case there is any of that there. If you got it as hot as Earth Europa would lose its oceans and most of its atmosphere.

How fast that would happen is a physics question which would interest me to see worked out, if anyone is capable and willing. It might take longer than 50 million years which could make for an interesting fiction.

  • $\begingroup$ The L1 point is much closer to the smaller body. Europa weighs 0.008 Earths and Jupiter weighs 318 Earths, but I didn't run through all the math above here. Anyway, the difference in heating is the square of the difference in radii. Then, while Jupiter will pick up heat over a larger area because it is larger, it also releases heat over that larger area. Net result: Jupiter doesn't even notice this. $\endgroup$ Commented Nov 20, 2021 at 20:27

Part One of Two

Wilk is right, Europa's ice cover would sublimate into water vapor. It does already sublimate into water vapor which is then lost from Europa, but at a low rate due to the low temperatures on Europa. Drastically warmng up Europa will drastically speed up the loss of ice.

If the new sun emitted as high a percentage of ultrviolet as the Sun does, the water vapor would broken down into hydrogen and oxygen. In any case, with an escape velocity of 2.025 kilometers per second, and an Earthlike surface temperature, Europa could not retain water vapor, hydrogen, oxygen, carbon dioxide, nitrogen, etc. and would lose the water vapor atmosphere to space rather rapidly.

When liquid water is exposed to the vacuum of space, it boils and becomes water vapor. If the water vapor atmosphere of Europa becomes thin enough, the pressure will drop to below the boiling boint of wter at Earthlike temperatures, and the top of the oceans will boil off. In any case a lot of liquid water will evaporate at Earthly temperatures, though it might rain and snow down on the other side of the planet. But considering how vast the subsurface ocean of Europa is, it would conduct heat from the hot side to the cold side and probably melt the vast ice layers on the cold side.

I cannot do the calculations, so I cannot say what the situation on Europa would be after a specific time period such as the 50,000,0000 years in the question.

First possibility: It is possible that after 50 million years only some of the outer ice layer of Europa had been lost into space and the liquid water beneath it still remained. So conditions inside the interior subsurface ocean of Europa would be the same as before. Sunlight could not penetrate an ice layer more than a few centimeters thick to fuel photosynthesis inside the ocean, so the situation for any hypothetical lifeforms would be the same as it is now.

Second Possibility: It is possible that all the ice would have melted after 50 million years and the top of the ocean would be boiling off into space. Thus it would be possible for light to penetrate the top layers of the oceans (unless clouds blocked it) and fuel photosynthesis. So if there was already life in the ocean it might have already evolved to have photosynthesis, or it might take it many tens or hundreds of millions more years to evolve that capability.

If there was not any life already in the ocean, some first primitive forms of life might have developed by 50 million years. Or it could take tens or hundreds of millions of years more for life to evolve.

Third Possibility:

And the third possibility is that the ice caps would be gone and that the ocean would also have been lost into space by 50 million years after the new sun started, making Europa a dead moon. If there had been any life in the subsurface ocean it would have been killed off, except maybe for microbes living in cracks inside the rocks beneath the ocean.

I have always wondered about the logic of magically transforming Jupiter into a star in 2010, which would eventually remove all the ice and water from Europa, Ganymede, and Callisto, which do not have high enough escape velocities to retain the common atmospheric gases.

Part Two of Two.

Wilk is wrong about Jupiter swelling up as the new sun heated it up. If Jupiter was heated up to Earthlike temperatures its atmospheric gases would expand a little. Jupter would have to be very close to a very hot star to have a surface temperature of thousnds of degrees and to swell up like a "puffy planet".


Anyway, a heat source in the L1 position of Jupiter and Europa would not heat up Jupiter as much as it heated up Europa, since the heat source would be much closer to Europa than to Jupiter.

If the heat source was five times closer to Europa than to the nearest part of Jupiter, for example, a spot on the jupiter side of Europa would receive 25 times as much heat from the heat source as a spot on Jupiter directly beneath the heat source, and parts of Jupiter's surface that were farther away from the heat sources would receive even less heat.

The L1 spot for Jupiter-Euo ropa would be rather unstable, so the heat source would have to constantly correct its orbit around Jupiter to say in the L1 position for 50,000,000 years. Thus it would have to be an artificial heat and light source.

And if the purpose of that artificial heat and light source is to heat and light Europa, why design it to broadcast heat and light in every direction, instead of focusing a beam of heat and light at Europa and only at Europa.

So I don't think that Jupiter would be heated up at all by the artificial heat source.

Somone may suggest that an advanced civilization might move 2 large astronomical bodies into orbits around Jupiter that would make them eventually collide and merge into a single object with an orbit in the Europa-Jupiter L1 position. The collison could have melted the entire new object into red hot lava, glowing enough to heat and light Europa for thousans or millions of years. And that would also heat and light Jupiter a little bit.

But a red hot glowing astronomical object large enough to heat up Europa would be very massive, many, many, many times more massive than an artificial "sun satellite" with fusion power plants and giant lamps aimed at Europa would be. So it would take a lot more power to steer that giant heat source to keep it in the L1 position. And how can super giant rockets or ion thrusters to steer it be attached to a red hot glowing astronomical object without melting and becoming useless?


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