# From which notable Europa's surface features could be possible to observe Jupiter eclipsing the sun?

I'm currently writing a story happening on Jupiter's moon Europa in the distant future and am looking for a location of the settlement where it takes place. As the protagonist likes to observe Jupiter eclipsing the sun before her workday, it should be a location from which it's possible to observe this occurrence.

I tried to browse WolframAlpha, Wikipedia and USGS databases, looking at coordinates and considering this location should be in the moon's hemisphere facing Jupiter and in the Western part of it so that Jupiter wouldn't be right overhead and blocking the entire sky (also it would be aesthetically much better view with Jupiter being close to the horizon). But I don't understand these coordinate systems.

I asked ChatGPT to brainstorm which features would fit, and tried to define the criteria as both "the sun setting behind Jupiter" and "Jupiter eclipsing the sun". But that requires fact-checking.

Ideas ChatGPT offered:

• Conamara Chaos
• Pwyll Crater
• Thera Macula
• Agenor Linea
• Minos Linea
• Katreus Linea

So I have a two-fold question:

Which of these locations fits better? As a fact-checking: is any of these in the wrong location to observe Jupiter eclipsing the sun?

Which other location(s) would also fit the criteria, and maybe better than any of these?

• Probably all of the locations, you can calculate the visibility based on the "latitude" of those locations and the orbital inclination of Europa. Commented Jul 24 at 11:25
• @Polaris5744 I don't know how to calculate this. Commented Jul 24 at 11:41
• Okay, give me some time and I will try my best to calculate this. Commented Jul 24 at 11:43

The orbital inclination of Europa is $$0.470^{\circ}$$, so it is safe to ignore this inclination. Also, Jupiter has a axial tilt of $$3.13^{\circ}$$.

The mean orbital radius of Europa is $$670,900$$km and the radius of Jupiter is $$69,911$$km, that means observed on Europa, the apparent diameter of Jupiter is $$12^{\circ}$$,(it is just trig function). Way bigger than the Sun apparent diameter observed in Jupiter (in context, the apparent solar diameter observed on Earth is around $$0.5^{\circ}$$).

This means that Jupiter can cover the entire Sun's disk. Also the Europan latitude (compare to declination of Equatorial system) of Sun will not exceed a maximum of $$\pm 4^{\circ}$$ while Jupiter is always on the Europan Equator (compare to celestial equator of Equatorial system).

In conclusion, everywhere on Europa can see Jupiter eclipsing the Sun, location does not matter here, only day/night matter, you can choose whatever location you prefer and use it in your story.

This may also be interesting: libration

• Thank you! Just a correction. As far as I have read until now, Europa is tidally locked to Jupiter, like the Moon is to Earth. Then Jupiter can be observed from anywhere in the hemisphere permanently facing Jupiter but not from the other, which is permanently turned away, right? Commented Jul 24 at 12:19
• Neglecting libration, what you are saying is correct. Considering this effect, places on the edge of the side facing Jupiter and close to north and south pole of Europa can also see Jupiter, but I doubt they can see an eclipse. Commented Jul 24 at 12:21
• Also, you get an eclipse every night/month? Commented Jul 24 at 22:55
• that is correct Commented Jul 25 at 1:42
• I know for a fact that there are plenty of places on our Moon that will never witness Earth eclipsing the sun, and those places are ... at the backside of our moon :-) I have no idea whether Europa has tidal locking around Jupiter, but if this were the case, all your calculations might be pointless :-) Commented Jul 25 at 14:28

== Just an addition to Polaris' excellent answer. The specific locations you ask about would see Jupiter nearer to the horizon in proportion to that location's angular distance from the (fixed) Europa terminator.

From the phase angle seen by this spacecraft, Conamara Chaos appears to be pretty near the terminator, so it would see Jupiter eclipse the sun near or on the horizon: