Hubble presents strong evidence for massive underground ocean on Ganymede

[Cirocco]

Just thought I'd share:

http://www.nasa.gov/press/2015/march/nasa-s-hubble-observations-suggest-underground-ocean-on-jupiters-largest-moon/index.html#.VQJqWo6G_h4

An underground ocean on Ganymede has been theorized for decades, but now Hubble has shown some of the stongest evidence yet for its existence. Pretty good new for possibility of finding extraterrestrial microbiological life too

[peadar1987]

With all of this water and geothermal activity going on, I would be very surprised and intrigued if there wasn't some other form of life in our solar system. When it was just Europa, I thought it was a long shot, but when it's Europa, Enceladus, and now Ganymede and possibly Triton and even Pluto, I think the chances are becoming higher and higher. We live in exciting times!

[-Velocity-]

With all of this water and geothermal activity going on, I would be very surprised and intrigued if there wasn't some other form of life in our solar system. When it was just Europa, I thought it was a long shot, but when it's Europa, Enceladus, and now Ganymede and possibly Triton and even Pluto, I think the chances are becoming higher and higher. We live in exciting times!

Me too. There are quite likely to be Earth life forms that could actually live in some of these conditions, and if not, an Earth life form could probably be engineered that could survive using current or near future technologies.

However, while we have a decent grasp on what constitutes habitability, we still don't know under what conditions life could arise. For all we know, conditions under the surface of those moons are very hostile to the formation of life. Martian life could conceivably have a common origin with Earth life, but the outer solar system moons almost certainly cannot be seeded via meteorites. They sit at the bottom of huge gravity wells, so meteors impact at very high speeds, and with the exception of Titan, they do not have atmospheres to cushion their impacts. All outer solar system moons have surface conditions that are lethal to all forms of life as we know it. Add to that, they are very far away, so materials blasted off of Earth (or Mars) has an extremely, incredibly low probability of impacting into, say, Europa, and even if a Earth/Mars meteoriod were so lucky, it would still most likely happen only after it had been floating around in space so long that all the biologicals it was carrying had died. So if we find anything living out there, it will almost assuredly be the result of a separate genesis of life.

Edited March 13, 2015 by |Velocity|

[lajoswinkler]

If you have a body large enough to establish a decent hydrostatic equilibrium to turn itself into a proper ball, and it's far away making it possess ancient nebula H2O, chances are very high (I'd say 100% for all intents and purposes) there will be at least one pocket of liquid water at some depth where the heat is trapped and pressure is high enough. It's not surprising at all.

[Elthy]

The size of this supposed ocean is amazing. But exploring it will be realy, realy hard since a submarine would have to deal with even bigger pressures than on earth...

[Technical Ben]

With all of this water and geothermal activity going on, I would be very surprised and intrigued if there wasn't some other form of life in our solar system. When it was just Europa, I thought it was a long shot, but when it's Europa, Enceladus, and now Ganymede and possibly Triton and even Pluto, I think the chances are becoming higher and higher. We live in exciting times!

Show me the trees. Until then, I'm not even contemplating any fruit existing.

The results are really interesting. Is it a nice view, or a cloudy smog of an ocean? Some of the images from below the ice shelves are amazing. Would be great to see what it is like on Ganymede.

Though to be honest, I'm not sure if they have ruled out other possibilities yet, such as other substances or minerals causing such effects.

[vger]

This is really making me wonder if we should be looking at gas giants in a different way. With all the intense tidal forces at work, it's almost starting to be reasonable to assume that any body close enough to a gas giant, could be harboring subsurface liquid.

[lajoswinkler]

This is really making me wonder if we should be looking at gas giants in a different way. With all the intense tidal forces at work, it's almost starting to be reasonable to assume that any body close enough to a gas giant, could be harboring subsurface liquid.

That is exactly what's been presumed ever since we've visited those bodies for the first time. The new thing is that HST gave more evidence to support the hypothesis, but the hypothesis exists for a long time and is very solid.

[Hcube]

This is really awesome !

Yeah, at the moment Europa is the new hype planet for life research. NASA is studying a Europa mission with the SLS, and ESA is planning missions there too after the Rosetta success.

The problem about Europa though is that its ocean is well under the surface : There is no way you can drill deep enough to get to the actual liquid water when the delta-V needed restricts the mass of the probes you can send there to some hundred kgs...

[Scotius]

But there are cryovolcanoes on Europa They spew water so high, a probe can dip into such a plume while orbiting the moon, and catch samples without landing. Sure, there is not much chance for multicellular organism flying so high, but even a single microbe would be a huge deal. Or even organic substances.

[vger]

This is really awesome ! Yeah, at the moment Europa is the new hype planet for life research. NASA is studying a Europa mission with the SLS, and ESA is planning missions there too after the Rosetta success.

If it's just life you're looking for, surely SOME evidence of it would be present on the surface. Some of what those cryovolcanoes are spitting out has to come back down. There should be a nice surface layer of ejected oceanic material to sift through. If there's microbes, even if they're dead, there shouldn't be much trouble in locating them.

[Lohan2008]

Very exciting news. I wonder if any probes will be sent to Ganymede ?

[Hcube]

Very exciting news. I wonder if any probes will be sent to Ganymede ?

I think that since the trend right now is Europa, probes will be sent there instead for now. But then, why not Ganymede too ? (or later)

I think that the issues with those life-research missions are that sending a probe to jupiter, and to ganymede/europa is fairly easy, but the landing must be very hard without an atmosphere. Apart from the Apollo landings, i don't think any landing was made on a body without a decent atmosphere.

[vger]

I think that since the trend right now is Europa, probes will be sent there instead for now. But then, why not Ganymede too ? (or later)

I think that the issues with those life-research missions are that sending a probe to jupiter, and to ganymede/europa is fairly easy, but the landing must be very hard without an atmosphere. Apart from the Apollo landings, i don't think any landing was made on a body without a decent atmosphere.

It's not like we haven't done partial powered-landings on Mars though. And IMO that would actually be slightly more complicated because of the possibility of winds "playing" with the descent.

Once we've picked a good landing site from all the topography data (preferably an area that is flat for some distance, just in case of miscalculations), the only big problem I can think of is the extra dV needed in the absence of aerobraking. We shouldn't have any trouble programming an A.I. that can land itself.

Edited March 15, 2015 by vger

[Bill Phil]

It's not like we haven't done partial powered-landings on Mars though. And IMO that would actually be slightly more complicated because of the possibility of winds "playing" with the descent.

Once we've picked a good landing site from all the topography data (preferably an area that is flat for some distance, just in case of miscalculations), the only big problem I can think of is the extra dV needed. We shouldn't have any trouble programming an A.I. that can land itself.

Which maps? They had pretty accurate maps for Apollo, but they found some boulders on the site. Are we just "better" now?

[vger]

Which maps? They had pretty accurate maps for Apollo, but they found some boulders on the site. Are we just "better" now?

Unsure, but sensors on the probe will provide it more detailed info on the way down. The only problem would be if there literally is NO good place to land. A human pilot would be in just as much trouble in that case though.

[Bill Phil]

Unsure, but sensors on the probe will provide it more detailed info on the way down. The only problem would be if there literally is NO good place to land. A human pilot would be in just as much trouble in that case though.

It would need to recognize it...

Pretty easy, I guess. Using radar you could determine the jagged-ness of the landing when you're near, and you could keep doing so for each new one. The problem would be choosing one.

Orbiting really close is possible, to map it out. With the orbiter part, I mean.

[KerikBalm]

I agree with velocity. We have no idea how favorable the conditions are to the formation of life.

At any rate, Europa and Enceledus are both much better targets. While Ganymede may have a subsurface ocean, it has a much thicker crust, and it seems there has been no recent interaction between the surface and the ocean underneath

Enceledus on the other hand has liquid water much much closer to the surface, with frequent cryovolcano eruptions. Europa also seems to have areas of this crust where much more heat escapes, and perhaps cryocolcanism too.

While there may be other bodies with subsurface liquid water... these are the only two that seem to be doing the hard job of getting samples from that subsurface ocean to the surface or even to space where they are much more accessible.

It also means that panspermia would be easier. If a microbe laden rock crashed on ganymede, and something survived the impact... it would still be very far from the liquid water, and would die/not be viable long before it ever got close to water.

In contrast, if something impacted at one of these three fissures (the "tiger stripes" of enceledus), maybe, just maybe, a microbial population would make it to the subsurface ocean, and maybe a few of them would be able to survive.

[Cirocco]

my two cents on the whole "search for life" thing:

the fact that there's liquid water 100km under the crust of ganymede doesn't necessarily mean that there is (or could be) life on Ganymede. We have no idea of the conditions down there. What is does tell us that as we start to find more and more places in our solar system where liquid water exists, the higher the odds are becoming that one of those spots has conditions suitable to life.

Plus of course, water is pretty much a necessity for colonization attempts, so if there's water, colonization becomes more plausible. Again, that doesn't mean we can/should go to Ganymede in particular, but it does mean that if water is more abundant than previously believed, then more places than previously believed may also be alligible for colonization .

[Hcube]

It's not like we haven't done partial powered-landings on Mars though. And IMO that would actually be slightly more complicated because of the possibility of winds

What i was talking about was not the landing itself, but the arrival to the planet and the circularization. Without aerobraking you need crazy delta-v to slow down from interplanetary speeds... i cant remember of anything landing on a body without an atmosphere (not counting stuff like rosetta/philae and the moon, obviously)

Or you could do a jupiter aerobrake and then continue towards ganymede/europa maybe ?

A jupiter aerobrake must be very risky, you dont want to get too deep in its atmosphere... What do you guys think ?

[SeaDog]

What i was talking about was not the landing itself, but the arrival to the planet and the circularization. Without aerobraking you need crazy delta-v to slow down from interplanetary speeds... i cant remember of anything landing on a body without an atmosphere (not counting stuff like rosetta/philae and the moon, obviously)

Or you could do a jupiter aerobrake and then continue towards ganymede/europa maybe ?

A jupiter aerobrake must be very risky, you dont want to get too deep in its atmosphere... What do you guys think ?

In the JUICE mission details, getting too close to Jupiter is avoided because of radiation. It might be possible to do an aerobreak, but it might not be worth it because of the new mission specs that would require.

[peadar1987]

What i was talking about was not the landing itself, but the arrival to the planet and the circularization. Without aerobraking you need crazy delta-v to slow down from interplanetary speeds... i cant remember of anything landing on a body without an atmosphere (not counting stuff like rosetta/philae and the moon, obviously)

Or you could do a jupiter aerobrake and then continue towards ganymede/europa maybe ?

A jupiter aerobrake must be very risky, you dont want to get too deep in its atmosphere... What do you guys think ?

Also you would have to carry a heat shield to avoid burning to a crisp (and considering the depth of Jupiter's gravity well, probably quite a chunky one). I'd guess that the delta-V savings from the aerobrake are probably almost completely negated by the cost of having the heat shield. If there was a clear advantage to doing it, then we would be.

Anybody know if we use gravity assists from moons to capture at Jupiter and Saturn?

[jfull]

This is why we needed the Jupiter Icy Moons Orbiter

Its reactor would not only be able to power its ion engines, but also an ice-penetrating radar system, something you just can't do on solar or RTGs.

We could get subsurface scans of both Europa and Ganymede.

[KerikBalm]

"I'd guess that the delta-V savings from the aerobrake are probably almost completely negated by the cost of having the heat shield"

If this were true in general, there'd generally never be a craft that used a heat shield on a planet with an atmosphere, but instead would fire retrorockets before entering the atmosphere.

Its not what we do on Earth, its not what we do on Mars, and with jupiter's much larger radius, you can go in much shallower and not have to go so deep (because your path is longer).

It should work.

As for the radiation belts... I'm not sure they'd be a problem for aerobraking, getting really close to jupiter should actually get you shielded from the radiation, as the radiation is channeled to the poles, but loops between the poles further out, similar to Earth's radiation belts anf our auroras - if I understand correctly.

However, there is a lot more that can go wrong with an aerobrake vs a retrorocket, and for some conditions, the retrorockets don't have that much more mass.

[peadar1987]

"I'd guess that the delta-V savings from the aerobrake are probably almost completely negated by the cost of having the heat shield"

If this were true in general, there'd generally never be a craft that used a heat shield on a planet with an atmosphere, but instead would fire retrorockets before entering the atmosphere.

Its not what we do on Earth, its not what we do on Mars, and with jupiter's much larger radius, you can go in much shallower and not have to go so deep (because your path is longer).

It should work.

As for the radiation belts... I'm not sure they'd be a problem for aerobraking, getting really close to jupiter should actually get you shielded from the radiation, as the radiation is channeled to the poles, but loops between the poles further out, similar to Earth's radiation belts anf our auroras - if I understand correctly.

However, there is a lot more that can go wrong with an aerobrake vs a retrorocket, and for some conditions, the retrorockets don't have that much more mass.

I found a paper so I did: http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/11319/1/03-1622.pdf

Looks like the effectiveness of an aerobrake depends on the mass of the body and how much delta-V you could save by gravity assists from moons. A low circular orbit around Jupiter is greatly improved by aerobraking. A higher, more elliptical orbit, and the cost of the heatshield rapidly outweighs the benefit in fuel savings, which I suppose makes sense.