Europa

Spider-Man · 2003-11-08 00:02:35

No, that wouldn't work, I'm afraid, to come from the "far" side of Europa, as it's not Jupiter itself that's emitting any radiation (Jupiter is just a bunch of helium and other gasses; there isn't anything Jupiter directly does other than make a tremendous magnetic field). However, due to Jupiter's emmense gravitational field, it has collected solar radiation over the course of aeons. Earth has done the same; the Van Allen belt is a perfect terrestrial example. The Earth doesn't actually emit any radiation, but it can collect it from the sun through the millenia. However, sustainedly staying in the Van Allen belt or Jupiter's main radiation belt (which envelops the orbit of Europa) is very dangerous for almost anything. The built up stores of charged particles just love to burn you from the inside out, kind of like a microwave oven.

Palomar · 2003-11-08 11:15:25

*Europa's "freckles" [how cute!]:
http://antwrp.gsfc.nasa.gov/apod/ap021101.html
I really hope to see the landing of a probe *on* Europa in my lifetime.
--Cindy

*More news about Europa, from a very short article in the most recent issue of "Astronomy" magazine (received yesterday in the mail).

Included is a small circular photo of one of the "freckles." The story is entitled "Dirt makes ice mounds on Europa" and reads:

"Jupiter's moon Europa has a skin of ice perhaps 13 miles (20 km) thick. It covers a global ocean of brine that may be 60 miles (100 km) deep. The moon's icy surface displays many geological features, including domes.

These are hills of ice up to 4 miles (6 km) across and 300 feet (100 meters) high. In the past, scientists thought warm ice had sufficient buoyant force to raise the domes by itself.

However, researchers Robert Pappalardo and Amy Barr (University of Colorado) have found that making a dome also demands chemical impurities, such as salt or sulfuric acid, mixed into the ice. The source of such impurities would be Europa's global ocean.

'We're excited,' says Pappalardo. 'We now think it's possible that any past or present life in the ocean, or just the chemicals from it, may be lifted to the surface. Essentially, it would be like an elevator ride for microbes.'"

--Cindy

atitarev · 2003-11-08 19:49:58

Spider-man, thanks for answering my question. So it is a lot of radiation on either side of the Jovian moons. The closer to Jupiter, the worse. Hopefully scientists will make human missions to Europa possible in the future.

Would be good if Plus Ultra Technologies missions became a reality. I read about their Mars, Jupiter, Uranus and beyond missions. Interesting ideas, but are they serious about what they write? I can also say that I am going to Mars but I don't have a spaceship to do it. :;):

RobS · 2003-11-08 22:16:12

There are figures for the daily radiation dosage in the four moons in Zubrin's book about exploring the solar system. Callisto is outside the belts and okay. Ganymede radiation is 7 or 8 rems a day, I think; that would kill someone outside in about a month. Europa is much higher, Io even higher,

But I bet those figures don't take into account the fact that Europa and Ganymede both have weak magnetic fields of their own. The radiation should be diverted to their poles and the equatorial areas would be relatively less bombarded. Maybe Ganymede would be habitable at the equator. The other moons will be visited only robotically, I suspect.

-- RobS

atitarev · 2003-11-09 02:17:28

But I bet those figures don't take into account the fact that Europa and Ganymede both have weak magnetic fields of their own. The radiation should be diverted to their poles and the equatorial areas would be relatively less bombarded. Maybe Ganymede would be habitable at the equator. The other moons will be visited only robotically, I suspect.

I agree that only Ganymede and Callisto could be considered for human settlement for the next 100 and more years starting with Callisto. Europa is interesting as a candidate for some primitive extraterrestrial life, so people may just study it. In the future it could be (along with Ganymede and Callisto) the largest supplier of water for newly terraformed or paraterraformed (domed) worlds - Mars, Venus, Mercury and Luna (the Moon).
Problem would be supplying enough solar heat to Ganymede and Callisto but as already discussed in Mercury Terraformation (not quite related to Mercury) it could probably solved with large mirrors.

I am optimistic and I hope that a few planets and satellites could be terraformed with more or less effort to a better or worse extent, if not terraformed, some planets could be paraterraformed to have a sustainable, self-dependant life.

Let me express my views about each terraformable/colonizable planet/moon apart from the Jovian moons:

Mercury:
Negative: too close to the Sun, bad rotation.
Positive: Heavy as Mars, rich metals.
To terraform one very difficult option is to move it further away from the Sun (min. 90 mln km, or even further and make it Venusian satellite). If not possible to move, some people offer to lock its rotation, so that it always faces the Sun and settle the dark side of it.
Venus:
Negative: slow rotation.
Positive: high gravity, a lot of nitrogen.
Terraformable if rotation could be increased. Question: imagine Venus had Earth's atmosphere and water but the same distance from the Sun and rotation same as it is now. How bad would it be? Too hot during the long day and too cold during the long night? That's for sure but maybe genetic engineering would help to create plants and maybe animals that can survive in such environment. Speeding up Venus's rotation is desirable but might be impossible with current technology.
Luna:
I believe rotation is a problem but not as big as on Venus. Problem is low gravity. Perhaps the Moon can hold an atmosphere but it has to be topped up every few thousand years. In my opinion, the terraformed Moon would be a better value that keeping it as a site for telescopes and some production in vacuum.
Mars would be the "easiest" to terraform.

...

RobS · 2003-11-09 15:21:40

Somewhere, once upon a time, I saw an estimate that the moon's gravity would lose an entire atmosphere in just a few thousand years. Hence my formula for terraformation would be "one dome at a time." Such a system, like the draining of Dutch polders, would provide land in increments. Private industry could pressurize a crater, or a few square kilometers of mare, recoup their investment, and use it to pressurize more. The Apollo landing sites could be preserved as "national parks." Astronomy would still be maintained (though domes leak, and enough of them would produce a very tenuous atmosphere). The domes would be interconnected by tunnels and train service. The same system could be used to terraform Mercury's poles, where there is evidence of ice and plenty of solar power on mountain peaks (or very tall towers). The Mercurians would explore the rest of their world at night. They could terraform the whole thing one cavern at a time. The caves could even have small openings to admit the proper amount of sunlight.

I have my doubts about moving planets around because they gravitationally perturb each other over time. They are spread out for a reason.

I doubt it makes sense to get water from the Galilean moons, the ice is too deep in Jupiter's gravitational well. But the Centaurs, which are basically asteroids made of cometary material orbiting out by Pluto, could be moved into the inner solar system by using the gravity of Neptune and other outer planets, thereby bringing them into the inner solar system with relatively small delta-vees. You'd probably want to surround them with an aluminized plastic envelope to reflect away the solar heat of the inner solar system and trap any vaporized gasses.

-- RobS

atitarev · 2003-11-09 16:36:11

So, the Moon and the Mercury could only be parateraformed, rather than fully terraformed. At least it's more realistic. I would also dump some ice asteroids on poles of both Luna and Mercury to increase water reserves, it might stay for quite some time where it is in a shadowed cool place.

I doubt it makes sense to get water from the Galilean moons.

Yes, I agree that using asteroids could be more efficient but the Centaurs are also too far away, maybe we'll have the technology to dig and and ship ice sooner than we get to move the asteroids in the right direction. For the Galileans moons colonies it might be a profitable trade in water.

I still would like to know if a terraformed Venus, that is Venus with Earth's atmosphere and water but with its current rotation could support life. Someone calculated that its average temperature would be about 25 C, not bad, it would probably be quite comfortable, especially around the poles but the calculation assumed the Earth's rotation as well. What if people are never able to change the rotation? Is that it? No point in terraforming Venus? On Earth day and night could be very long in the polar regions, and there are still plants, animals and people who live in those regions. Large oceans, a lot of wind, rains would also soften the problem with very long days and nights on Venus (from dawn to dawn 8 Earth months). Will the slow rotation destroy an Earth-like atmosphere on Venus? Can life be sustainable without installing orbital shades and mirrors in such environment? Can someone comment on this? Any ideas how to estimate weather on such a Venus?
I think, the difficulty in changing rotation will deter humans from terraforming Venus more than its current hellish atmosphere and lack of water but I can't see the problem with the rotation resolved quickly.

Important correction to my previous posts: The solar day on Venus is 116.8 Earth days, much shorter than its rotational day (243 Earth days). It is still too long but it's less than four months from dawn to dawn, rather than 8 months.

Venus

Palomar · 2003-11-11 11:29:32

*Hey guys. Don't mean to be a nit-picker, but we've already got at least 1 thread established elsewhere at these message boards, devoted to the topic of terraforming Venus, etc.

Can you please move the Venus discussion over there? I'd like to keep this thread focused on Europa (and perhaps, peripherally-speaking, on other Jovian moons).

Thanks!

--Cindy

Palomar · 2004-03-17 07:30:05

[=http://www.spacedaily.com/news/jupiter-europa-04b.html]A new class of planetary tools...

*I'm NOT keen, however, on the "radioactive heating unit" idea (futuristic)...unless someone can explain this would be completely safe and NOT compromise whatever life might be there.

The probe -currently- being tested can melt through ice at a rate of 6 feet per hour; Europa's ice crust is "as much as 18 miles deep" (I presume, based on the wording used, that the depth of the ice crust varies).

--Cindy

::EDIT:: Another article says Europa reflects 5 times as much light as our Moon.

Marineris Sauce · 2004-03-17 11:18:36

There are figures for the daily radiation dosage in the four moons in Zubrin's book about exploring the solar system. Callisto is outside the belts and okay. Ganymede radiation is 7 or 8 rems a day, I think; that would kill someone outside in about a month. Europa is much higher, Io even higher,
But I bet those figures don't take into account the fact that Europa and Ganymede both have weak magnetic fields of their own. The radiation should be diverted to their poles and the equatorial areas would be relatively less bombarded. Maybe Ganymede would be habitable at the equator. The other moons will be visited only robotically, I suspect.
-- RobS

I could be wrong on this but I seem to remember reading recently about Europa being protected from solar and cosmic radiation by Jupiters magnetic field which envelopes the watery moon completely. I'll try to find where I read that...

atomoid · 2004-03-17 14:50:53

[http://www.spacedaily.com/news/jupiter-europa-04b.html]A new class of planetary tools...
*I'm NOT keen, however, on the "radioactive heating unit" idea (futuristic)...unless someone can explain this would be completely safe and NOT compromise whatever life might be there.
The probe -currently- being tested can melt through ice at a rate of 6 feet per hour; Europa's ice crust is "as much as 18 miles deep" (I presume, based on the wording used, that the depth of the ice crust varies).
--Cindy
::EDIT:: Another article says Europa reflects 5 times as much light as our Moon.

6 feet per hour sounds really fast at first, but even if they can land in a place where Europa's ice is only 10 miles deep, it will still take over a year of non-stop melting to get the probe through to the liquid H2O zone!

i assume theyre talking RTGs on the melt system and not a reactor, RTGs are well-sheilded and protected against damage, even so, the species of radiation they emit is weak and cant even make it halfway through a layer of skin. but if its a reactor, thats another story...

i havent read up on the europa melt-probe, but is it supposed to string some data cable behind attached to the lander through which it is to comminucate? won't the melt-hole fill and freeze up behiind it (that water has to go somewhere)?

Palomar · 2004-03-17 15:04:06

atomoid: "i havent read up on the europa melt-probe, but is it supposed to string some data cable behind attached to the lander through which it is to comminucate?"

*The article doesn't state that explicitly, but I gather it'd be so.

atomoid: "won't the melt-hole fill and freeze up behiind it (that water has to go somewhere)?"

*That's a really good question. Hopefully someone more knowledgeable than I can answer it.

--Cindy

::EDIT:: Instead of actually -drilling- down into the crust, can't something similar to an ultrasound device detect the possibility of life in the European waters? But then I'm not sure of the properties of ultrasound...plus, that crust is mighty thick. Hmmmmm. ~thinking~

Yang Liwei Rocket · 2004-03-17 15:42:57

There are many plans about going to Europa moon of Jupiter but none have gotten started. There are great ideas from the German Aerospace , is this ESA going to look below, I wonder why NASA haven't tried to do something like this earlier? [http://news.bbc.co.uk/2/hi/science/nature/3548139.stm]http://news.bbc.co.uk/2/hi/science/nature/3548139.stm
Once they do get a probe below the ice.. it would be wonderful it if there data on the composition of the water and were photos of maybe a sub-surface ocean of water, can u imagine the images?
[http://newsimg.bbc.co.uk/media/images/3 … rob203.jpg]http://newsimg.bbc.co.uk/media....203.jpg
[http://www.newscientist.com/news/news.jsp?id=ns99993421]http://www.newscientist.com/news/news.jsp?id=ns99993421
[http://news.bbc.co.uk/olmedia/895000/im … opa300.jpg]http://news.bbc.co.uk/olmedia/895000/im … opa300.jpg

SBird · 2004-03-18 12:12:27

I think that the idea for a umbilical cable is that it feeds off a reel on the back of the probe so that when it gets frozen into the ice, it's no big deal.

As for ultrasound or sonar, the projected thickness of the ice is much too thick to be able to penetrate unless you're using nukes or something to generate the sound.

Palomar · 2004-03-18 13:19:15

I think that the idea for a umbilical cable is that it feeds off a reel on the back of the probe so that when it gets frozen into the ice, it's no big deal.

*But how could it continue downward if the length of cable running -behind- the copper melting head becomes frozen in previously melted water frozen again into ice?

--Cindy

Byron · 2004-03-18 13:33:12

I think that the idea for a umbilical cable is that it feeds off a reel on the back of the probe so that when it gets frozen into the ice, it's no big deal.
*But how could it continue downward if the length of cable running -behind- the copper melting head becomes frozen in previously melted water frozen again into ice?
--Cindy

I'm assuming he means after the cable has been spooled down through the ice before the water freezes...as long as part of the cable is above the ice (held in place by some sort of surface anchor, I would guess), I would imagine that the probe with the cable spool would still be able to melt its way down the ice, with the trailing cable held in place by the freezing water behind the probe.

At least this is how I'm seeing it...anyone is welcome to correct me if I'm wrong on this...lol...

B

SBird · 2004-03-18 13:50:39

I think that's how it's presently envisioned. Basically, imagine tying a string to a tree and walking away with the spool. Even though the string behind you stays still, you can just keep playing out the string as you walk along.

In this case, the wire left behind is refrozen into the ice which probably actually increases the longetivity and lifetime of the wire. 10 km of thin wire isn't too big of a challenge. (in fact, I think that fiber optic would be the way to go for good data transmission.)

RobS · 2004-03-18 14:08:01

I was under the impression they planned to use radio transmission to send data back up, because any wire would be frozen solid into the ice and wouldn't be able to play out. I suppose if the reel were on the probe, that wouldn't be a problem.

-- RobS

Palomar · 2004-03-18 14:52:00

10 km of thin wire isn't too big of a challenge.

*My father worked for an electricity company, so I'm familiar with wires (thin and thick), and the spools (I think that was the correct name) they were wrapped around and stored by. Even if it's thin, that's still A LOT of wire (article says ice as much as 18 miles deep). :-\ How much weight would that be, approximately? And what would be the size, bulk-wise (on the spool)? It'd take a rather hefty, large probe to handle all that...(even if they can melt down into thinner ice, say "only" 10 miles deep)...

--Cindy

SBird · 2004-03-18 15:39:23

You're right that the mass won't be insignificant. However, there's really no good way to send data through the ice itself. It'll block light and radar and pretty much all other EM radiation at those thicknesses. Perhaps ELF radio transmissions might make it but you'd need a super powerful transmitter to punch through. The only way to communicate other than wire would be sonar but again you'd need a LOT of power to be able to be heard on the surface. Perhaps with the nuclear power source they plan to have enough power to be able to do this but it seems questionable. Also, both ELF and sonar have lousy data transmission rates. You'd be waiting days to upload a single picture.

As far as cable, as long as you don't have to worry about the cable breaking (probably not a problem as it will be encased in ice), you can make it very thin. In the Earth to LEO thread, I was talking about the idea of space tethers ( the rotating kind or electropropulsion kind, not the space elevator kind) with insane lenghts. The tether I was using for a model was 100 km long but only weighed about 8000 kg. That was for a tether that was impact reistant and could hold a weight of 3 TONS. Check out Tethers Unlimited [http://www.tethers.com]here - that's where I got the data from. They've got a nice site that explains things pretty well.

I'd expect that you could probably get a fiber optic info cable 20 km long that was a few dozen kg if you were careful. Telecom fiber is about 0.3 mm in diameter without the protective covering. Assuming a total thickness with protective sheath of 0.5 mm, that's a total of 0.002 cubic meters of material per 10 km. A 50 km line, assuming you get about 50% packing efficiency (I have no idea how realistic that number is) it would all fit into a cube 27 cm on a side or about a cubic foot. Pulling a density of 6 g/cm^3 completely out of my butt, the cable masses 59 kg.
Heavy but doable.

As for the concerns about radioactive contamination of Europa I saw in another post - it's non-issue. Europa is already exposed to radiation levels from Jupiter's radiation belts that would kill a human on the surface in a few seconds. While the ice stops most of this radiation, it is ridiculous to assume that none of it has made it into the interior over the last few billion years. Also, the volume of Europa's oceans are estimated to be 10 TIMES the Earth's. We released thousands of kilograms of radioisotopes in the 60's nuclear testing and failed to seriously hurt our ecosystems here. 20 kg of thermal radioisotopes in a shielded container area non-threat to a potential ecosystem of that size. I'm much more worried about Earthly contamination hitching a ride on the probe.

atomoid · 2004-03-19 05:33:26

Thanks for the in-depth analysis.
But maybe there is no need to worry about dealing out a cable after all. According to [http://news.bbc.co.uk/2/hi/science/nature/3548139.stm]the BBC article:

Once the probe is through the ice and into the ocean underneath, it could open a compartment to take a sample of the water and release some of its ballast to give it a positive buoyancy.
If the craft were based on a spherical shape it could easily turn round, float back up to the ice cover and begin melting back up to the surface.
...could analyse the water while the craft floated in the ocean and the results could then be transmitted to Earth through the ice with a type of powerful transmitter used by submarines.

Not sure what submarine transmitters use, but sounds better than hastling with a cable for a probe that might roam and collect samples, image different subsurface terrain, then change its bouyancy and float/melt back up through the ice.

But are there good reasons to go back up?
...maybe to put the [http://www.thesamples.com]samples into analyzer equipment that couldnt be put in the probe and so would be housed in the lander at the surface? -but it seems to imply it would melt a new hole that would pop up somewhere very far out of reach of its lander. But then the lander should of course be a rover anyway, imagine the surface views!

Palomar · 2004-03-19 10:16:01

*Europa's "freckles" [how cute!]:
[http://antwrp.gsfc.nasa.gov/apod/ap021101.html]http://antwrp.gsfc.nasa.gov/apod/ap021101.html
I really hope to see the landing of a probe *on* Europa in my lifetime.
--Cindy

*I was hoping to relocate this information, and was hoping it'd be in -this- thread.

Check out the link in the quote box, relative to sampling a "freckle" versus burrowing through the ice crust. What do you think of this?

Atomoid, I really enjoyed the info you provided us with in your post! SBird, too [thanks especially for answering regarding wire, bulk, etc.]!

--Cindy

::EDIT:: An exquisite image of Europa:

[http://rsd.gsfc.nasa.gov/pub/goes/galileo.europa.jpg]red veins, blue webs

I posted this pic a long time ago; it's worth a repeat (what the heck, I'm in edit mode anyway):

[http://antwrp.gsfc.nasa.gov/apod/ap030919.html]lovely

SBird · 2004-03-19 11:04:00

Having the probe resurface is a good idea. All you'd have to do is have a big tank that you fill with ballast. When you want to resurface, dump the ballast and refill the tank with air or vacuum. The proble will then head back up. However, I think that the probe's return will be much slower than its descent because you can't get all that much lift from buoyancy compared to the descent rate from dense ballast.

I'm not too sure about having a rover rendezvous with the emerged probe, though. I don't know what Europa looks like from a rover's point of view but the sattelite images make it look pretty rugged. Unless your probe resurfaced pretty close, I'd be afraid that it would hav a big canyon or something in the way. Of course, if you have a tether, you can just follow the tether back up to the surface.

The submarine communications they refer to are ELF - Extremely Low Frequency radio communication that can punch through lots of water. If you remember the movie Crimson Tide, the sub gets the partial message at the beginning from an ELF transmission. However, if you remember, the message came in the form of a telegram. ELF has such low data transmission rates because of the slow wavelength - it's not good for much more than Morse code. I also wonder if it can punch through 20 km of solid ice. I know very little about the technical side of ELF so I don't know what the answer to that is.

Of course, it would be better to try and find a thinner section of the ice for the probe such as a 'freckle' or one of those big rift faults. The transit times will go down and your ability to communicate goes way up as the ice gets thinner.

As for mobility, when the probe breaks through the bottom of the ice, it can just leave behind a base station that's attached to the communication tether. Some sort of robotic sub can then tool around, checking stuff out and occasionally head back to base to upload the latest data for transmission to the surface.

What would probably be best is some sort of tether that can carry information rich data like pictures. An ELF transmitter on the sub would then act as a backup transmitter and a way to transmit smaller data chunks like temperature and chemical composition without having to return to the base station.

atomoid · 2004-03-20 16:59:35

And that ELF signal, in order to reach earth (or an orbitter) would have to be pretty strong. is there any differnce in transparency to the ELF whether the water is liquid or ice phase, and all the other contstituants of the Europa ice vs Earth water?

On another note, one potential drawback to using a tether for data is if Europa has any ongoing ice plate fault shifting due to tidal or other causes (as seems likely) and the tether happened to be across a fault it would get snapped, although its probably not that great a risk considering all the other risks involved..

ERRORIST · 2004-03-20 21:16:37

How about moving Europa closer to Jupiter. Just slow the orbit it has around Jupiter, and should fall closer to Jupiter. The tidal forces would melt the ice, and now it would become a real water world like the movie. More easy for life to form in a warm Ocean.

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