A Day on Europa

I put my imagination to a little exercise and tried to picture what a day on Jupiter’s moon, Europa, would be like. Let’s pretend we’ve landed on Europa. The following is a simple description of a day, without going into too many details.

Diurnal  measurements: A day on any moon is the time it takes to orbit its host planet. So, a Europan day is 3.5 days. This is the same time it sees the Sun reappear after a sunset, naturally. The Sun is not too dim here. Jupiter/Europa is approximately 5 AU from the Sun (1 AU is the distance of the Earth from the Sun). Europa’s thin atmosphere might make the Sun hazier, but it would still be quite bright. But the heat coming off the Sun would be minimal owing to the distance.

This is approximately how bright the sunlight would be:

(Image source: JonLomberg.com Giclee Prints)

Skies and views: However, Europa is tidally locked to Jupiter, so one half of the moon always faces the planet. Since Jupiter is not close enough to cover the sky completely, the part facing Jupiter would also see the Sun.    However, conversely, the part facing away from Jupiter will never see   Jupiter.  Every part of Europa will see the other moons of Jupiter at some point. Ganymede will be regularly seen every two Europan days, and the part facing Jupiter would very commonly see Io transit Jupiter every half Europan day. This is because Io, Europa, and Ganymede are in a 1:2:4  resonance.  However, the illumination caused due to brightness of Jupiter is not even as much as that of our Moon (Jupiter/Europa are very cold, so despite Jupiter’s high albedo, the light reflected off  it  is in the far infrared). So the Jovian side is in  relative  darkness  always. Of course, when Jupiter is between Europa and the  Sun, it’s  pitch black. At this time, the anti-Jovian side would frequently, if  not perennially, see other satellites.

This is how Jupiter might look from Europa:

(Image source: voices.nationalgeographic.com)
In fact, it would be even smaller.

This is a good approximation of what the anti-Jovian side might look like with multiple moons and the Sun:

(Image is about Earth’s moon positions wrt Venus. Ignore the days. Source: Page on areavoices.com)

Because there is minimal atmosphere, Sunlight will not be diffused at all. So, just like the Moon, there is no transition between light and shadow. You will pass suddenly from bright light into dark shadows, and back, hurting your eyes.

Temperatures: Europa’s albedo is a whopping 0.6. This is hardly surprising, considering the moon looks like this:

(Image source: science & space friday | West Chester Technology Blog | Page 3 )

Albedo is the tendency of a body to to reflect sunlight back into space.   Albedo is measured between 0 to 1, and the higher the albedo, more   sunlight is reflected and less is absorbed, making the body very cool.   Earth’s is 0.3 on an average. The thick surface of ice makes Europa reflect sunlight back almost entirely.

Europa’s mean surface temperature is a 100K or -170 deg C. It gets colder towards the poles.

Climate: Much like Mercury, owing to the lack of a well defined atmosphere, Europa does not have a climate. Earth does, mostly due to water vapor. But Europa’s oceans are hidden below the solid surface ice and do not regulate the temperatures of the moon. So there are no seasons at all.

Other natural phenomenon:
The theory that Europa has liquid oceans underneath its surface received much validation when it was discovered recently that water vapor escapes  the surface of the moon in the form of geyser-like plumes. These plumes can be up to 200km in height (20 times the height of Mt. Everest). This is mainly because of Europa’s low gravity, which is nine times lesser than Earth’s.

(Image source: Vanished! Mystery of Europa’s 200-Kilometer High Geysers (Today’s Most Popular) Note that Jupiter is conceptualized as being much larger than it actually is on Europa.)

Europa’s surface is full of crisscrossed lines, that are actually ridges up to  20km wide. These are caused due to plate tectonics (the only other body  apart from Earth and Saturn’s moon Enceladus where there are similar ice tectonics). There are sudden “earthquakes” because Europa is geologically active.

(Image source: The Solar System, a little more clear.)

Coupled with the buoyancy of water and Europa’s low gravity, if any life is found on the moon, it would be quite massive for their  equivalents here on Earth.

More reading/references:
Vanished! Mystery of Europa’s 200-Kilometer High Geysers (Today’s Most Popular)
A paper on Rossby waves that keep the subsurface ocean liquid due to tidal tugs : Europa’s Shifting Surface
NASA’s facts about Europa: About Europa
An excellent reddit thread that talks about the brightness of the Sun on Europa: If  I was standing on the surface of Europa, how bright would the day be,  comparatively to earth? Would Jupiter’s vastness in it’s Horizon  compensate in reflective lighting for the large distance away from the  sun? • /r/askscience


One comment on “A Day on Europa

  1. Ila Pandiyan

    So do you or do you not want to ice fish on Europa, like NdGT does? And do you think there could be life in that liquid ocean?

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