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22

tl;dr Miki Sudo Using JPL's SPICE toolkit, I computed the positions of Earth and Europa for the times in question. On 1983-Nov-25, Earth and Europa are 935.2 million km apart, while 1985-Jul-22, they are 612.5 million km apart. Miki Sudo wins by 323 million km, given the assumed date for her birthday. If we don't trust famousbirthdays.com for Sudo's ...


18

According to this 2007 paper, the current research as of the time of their own research had a huge range in possible concentrations of $\text{MgSO}_4$, magnesium-sulfate, with over four orders magnitude (approximately times $30,\!000$) differences between the extreme ends of the predictions. It conducts its own analyses and near the end of the paper makes ...


12

Any online planetarium or equivalent mobile app will tell you that on 1983-11-25 Jupiter was near to its conjunction with the Sun: while on 1985-07-22 it was close to opposition: So on Miki Sudo's birthday, Europa was about 300 million kilometers closer to the Earth than on Joey Chestnut's birthday. images taken from the Star Walk iOS app


11

Technically those aren't "geysers" on Europa, they're cryovolcanos. Though that definition may be a bit imprecise as well, but the 100 km eruptions on Europa probably have more in common with volcanic eruptions on Earth than geysers. Europa undergoes significant tidal flexing which, in combination to it's solid icy crust, could be compared to explosive ...


11

For a liquid, hydrostatic pressure is $\rho g h$ where $\rho$ is density (this is always the same for all water) g is gravitational acceleration and h is depth. The gravitational acceleration on Europa is 1.3 $\text{m/s}{}^2$ (compared with 9.8 $\text{m/s}{}^2$ on Earth). But on Europa there is 20km of ice floating on the water. As a rough estimate, the ...


9

No, nothing on Europa could possibly be photosynthesizing as we know it. Jupiter doesn't emit light, and what it reflects from the sun is not enough, plus there's no significant amount of carbon dioxide there. However, the first life on Earth was not plants, it was chemotrophs. These bacteria gained their energy from the heat of hydrothermal vents, and if ...


9

From your first link, the definition is: "The circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.[1][2][3][4][5] The bounds of the CHZ are based on Earth's position in the Solar System and the amount of ...


8

Use an orrery that will let you specify a specific epoch and vantage point. There are some quite fancy ones online, for example this Solar System Scope: What you do in this particular tool is click on the calendar bar below and enter date and time of your observation (if you forgot that, there's a good chance your photograph has a time stamp, either of the ...


8

It's a pretty straight forward calculation of 3 factors. Distance from the sun, apparent size and albedo. I'm going to compare Jupiter to our full moon, since we're all familiar with that. Jupiter averages between 4.95 and 5.45 AU from the sun. That puts it, in comparison with our full moon (about 1.02 AU on average), that means individual square ...


7

I wanted to throw my hat into the mix to flesh out another contributing factor. One reason these "geysers" are so capable of achieving great heights is a lack of atmosphere on Europa to slow them down (and to a lesser extent, weaker gravity). I wrote a basic "physics simulation" in Python 3 which illustrates this purpose, the code for which is below. import ...


7

Yes Tidal locking is a mutual process, and both the satellite and the parent body will eventually permanently face each other. However, while tidal locking of a satellite can happen relatively quickly (that is, within the life span of the solar system), tidal locking of the parent body is extremely slow and will in a practical sense never happen (the ...


6

One option is to sketch (or photograph) their approximate positions at the start of the night and again 4-5 hours later, if this is possible. Then repeat the next night. It should be easy to at least identify Io and Europa that way (they're the fastest moving). (That's a pretty good picture for a beginner by the way!)


5

Nope. (Sorry, the other answer beginning with yes, I wanted to begin one with no), but both answers are correct from a certain point of view. Jupiter's rotation is speeding up because it's contracting. See here. Jupiter does slow down due to it's tidal bulge and tugging from it's moons, but the bigger factor is that Jupiter loses more heat than it ...


4

The most popular hypothesis for explaining the various zigzagged lines (lineae) that cover Europa’s surface is that they are caused by cracks appearing in the ice shell because of tidal deformations, and that these cracks are then filled by water oozing out from the interior. The dark, reddish color of these lineae is thought to be due to magnesium sulfate, ...


4

Since water on all planets is in contact with impurities, I would think that the default for water is salty, and a small percentage on Earth (2.5%) gets desalinated by going through the evaporation/condensation cycle. Since no similar cycle is operating on Europa, I imagine its ocean is salty.


4

I'll pick up on your example as it can be used very well for illustrating the main points: First: The solar intensity in Jupiters orbit is less than 4 percent compared to Earths. So much less energy comes from the Sun which limits possible sublimation significantly Second: Sure tidal flexing leads to fountains. These fountains blow material into space. But ...


4

Apparently they have been inferred to be "220 meters". See the references in: S. D. Kadel, S. A. Fagents, "TROUGH-BOUNDING RIDGE PAIRS ON EUROPA", , Lunar and Planetary Science XXIX. (PDF)


3

A geyser is a water volcano, they are familiar and fairly common on Earth. By analogy, a water volcano on other planets can also be called a geyser, although the mechanism may be rather different. Geysers on Earth are caused by heating of sub-surface water by magma chambers. On Enceladus, there is no magma. The energy of the volcanos of Enceladus is ...


3

Question: I would know why the words "geysers" and "jets" would be used interchangeably. Is this because it hasn't been confirmed yet what they are, and the authors don't wish to show favoritism by choosing one or the other, or are they synonymous and can always be used interchangeably, or is there some other reason ? A jet is a generic ...


3

There is no feasible way for a human-made probe to crush through Europa's ice layer. "It is predicted that the outer crust of solid ice is approximately 10–30 km (6–19 mi) thick." (Wikipedia) It's not even known, whether there is a liqud ocean at all under Europa's ice layer. Instead of drilling one could try to slowly melt trough the ice.


3

The surface of Europa gets some sunlight direct from the sun and some long wave radiation from Jupiter so it's not in darkness. It's also in Jupiter's radiation belt so it gets hit with high energy charged particles and the surface of Europa, despite being bombarded by particles is still a vacuum. The surface of Europa is a terrible place to look for life, ...


3

If Europa was the only large moon orbiting Jupiter then it wouldn't have tides, or, more accurately, it would have a permanent tidal bulge and no moving tides, so it depends on what you call a tide. A permanent tide is still a tide IMHO. There's still a tidal force creating a bulge. It also doesn't have to have a liquid surface. Land tides or crustal ...


2

From this NASA FAQ page about Europa: Theory and observation indicate that Europa's icy shell is around 15 to 25 kilometers (10 to 15 miles) thick, overlying an ocean approximately 60-150 kilometers (40 to 100 miles) deep. Support for this hypothesis comes from observations of pits, domes, and spots on Europa's surface. The size and spacing of the features ...


2

The easiest way is to look it up, e.g. here: http://www.skyandtelescope.com/observing/a-jupiter-almanac/ Because the moons' positions change, and they are too small to distinguish in a small telescope, there are no general rules.


2

The one far away is Ganymede, the brightest is Europa but not much of a way for the others (from any angle) I did find a diagram that lines up pretty well with your picture though.


1

You can use Sky and Telescope's interactive tool for observing Jupiter's moons. This website describes how to use it to determine the positions of the Galilean moons. It works in the past or future.


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