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Posted by: Juramike Oct 9 2009, 09:52 PM

Now being picked up by the news, but here is the original press release regarding an estimate of oxygen in Europa's subsurface ocean:

http://dps.aas.org/press/2009/Greenberg_9_October_2009.pdf

So how could this estimate affect the instrument package for the Jupiter-Europa flagship mission?
Are there ways to quantify oxygen in fresher ice from orbit?

(RADAR determination? Weird dielectric properties? Metal oxidation states? Rust?)

Posted by: Juramike Oct 9 2009, 10:07 PM

Thinking about this some more, it would also imply that the geochemistry of the subsurface and on-surface (top few m) of both Europa and Enceladus would be oxidizing, while the on-surface and subsurface geochemistry of Titan would be reducing (no ionizing flux).

Maybe the flyby's of Enceladus are giving us our first taste of what's inside Europa?

Is the chemistry of Enceladus organics resulting from oxidative or reductive mechanisms?

Posted by: nprev Oct 10 2009, 05:00 AM

It's an interesting proposition, but I'm always skeptical of detailed, elegant explanations without ground truth. Remember how Io's "sodium torus" was thought to be the result of "sputtered" atoms off of its surface from Jupiter's radiation belts before Voyager?

We always seem to find major, very unexpected surprises, esp. in the outer Solar System.

Posted by: MarsIsImportant Oct 12 2009, 03:13 AM

Yeah, we definitely need a robotic mission to Europa, to include an ice probe that will reach the ocean and release another robotic submarine. The problem would be communication with Earth by the sub. If we can get pass that hurdle, we have a viable mission that could be done fairly soon (certain within my lifetime).

Such a mission would be on the order of magnitude greater than the MER. I'd also like to see a significant improvement in power source efficiency so that the mission could be at least as long or longer than the MER. (Oppy & Spirit raised the bar fairly high) I want a big bang for the buck.

We need a dedicated mission that can survive the extreme pressures near the boundary of the lithosphere. If we are going, we might as well go all the way. The potential science advancement would be enormous. After all, in a few hundred million years Europa might be our descendant's new home away from home - depending upon what we find.

Posted by: Hungry4info Oct 12 2009, 03:54 AM

Please realise that the Jovian environment isn't exactly friendly. If anything sent to Europa lasts more than a month, to be honest, I will feel we got a good "bang for our buck/euro/ruble."

Posted by: centsworth_II Oct 12 2009, 06:15 AM

That's THE problem? Well, what are we waiting for!

Posted by: nprev Oct 12 2009, 06:48 AM

Let's kinda reel this in a bit. Think what Mike was talking about is how to check for oxygen enrichment in Europan surface ice via remote sensing.

The first order of business would seem to be identifying fresh ice--stuff that might have been pushed up recently & therefore more likely to have been in contact with any postulated ocean. Old ice has gotta be heavily contaminated with effluents from Io; that material must really paint Europa quite regularly.

(Another thing to do is a high-res mini-plume search. IIRC, Europa does outgas a bit, but not much. If we could find one active geyser then there's the sweet spot for this investigation.)

As far as oxygen enrichment signatures...I dunno. Cold water can hold much more O2 in solution than warmer water. Does dissolved O2 show in the visible or IR spectral properties of ice in any way, and if so is it detectable via passive remote sensors?

Posted by: Julius Oct 12 2009, 10:34 AM

I believe the thin oxygen atmosphere was attibuted to interaction of solar wind with water ice surface ...how sure are we about that?Can the oxygen originate from europas interior?

Posted by: Juramike Oct 12 2009, 01:23 PM

The oxygen atmosphere and oxygen in the subsurface ocean both would originate from irradiation of the the surface ice.

The solar wind (and other ionizing radiation) penetrates a little into the surface ices and causes the some water molecules to break up and form oxygen (probably in the form of reactive oxygen species to start off with) encapsulated in ice.

As the ice falls into cracks or gets recycled into the subsurface ocean, the ice matrix melts and effectively releases oxygen and other oxidizing species.

...which can then run around and oxidize up any of the other species that exist in the water. So when the water shoots up from underneath, there might be a plethora of oxidized compounds (sulfates rather than sulfides) sitting in "stains" on the surface.

'Course any stuff from Io painting up Europa (IIRC these would be sulfides from Io) would get oxidized up by the surface ices (kinetics????), but that should be a fairly diffuse background.

Posted by: Julius Oct 12 2009, 03:26 PM

Full inline quote removed - ADMIN

To me it sounds a bit far fetched but i'm no mathematician or physics expert so i cant comment about this hypothesis...i would think the thickness of the ice layer would affect to what extent this process oygenates the underlying water ocean?!

The fact that Io can be a source of sulphates detected on the surface of Europa,there's no way of finding out by an orbiter (except pattern of distribution)unless we have direct sampling of the water underneath Europas crust??

Posted by: MarsIsImportant Oct 13 2009, 06:40 AM

Remote sensing is good...but when you talk about ground proof I couldn't think of anything better than a direct sample from the ocean below the ice on Europa. The robotic submarine mission is not my fantasy; it is really being discussed as a possible future mission. It is based upon the technology being developed for this Earthly robotic submarine.

http://www.planetary.org/news/2007/0516_Robotic_Sub_Makes_Final_Dive_To_Reach.html

A few weeks ago I saw a program on a science related channel about using it for a mission on Europa. They discussed in detail how they would penetrate the ice and insert the sub into the body of water below. The basic technology is already here with a few additional innovations. It would be difficult to pull off because it would require several different types of robotic technology working in autonomous coordination together. The payload would have to be rather massive. Miniaturization will be necessary to make it doable and cost effective.

The very real possibility of there being high concentrations of oxygen within that Europa ocean gives us more reason to move forward on such an extensive robotic surface and subsurface mission. Who knows what we will find. Even if there is no life whatsoever down there, that's good to know. A highly oxygenated hydrosphere protected from radiation by a mile or two of ice doesn't sound like a such a hostile environment that it would prevent exploration to me. It sounds like an interesting place to go to study extreme cold liquid water chemistry.

The radiation is not causing oxygen to form directly in the ocean. It is being transported from the surface to that ocean from the constantly reforming ice. But we don't know for sure how long that transfer process would take to penetrate 2 miles of ice crust. Let's find out.

Posted by: nprev Oct 13 2009, 07:19 AM

See http://www.unmannedspaceflight.com/index.php?showtopic=1937 for a good thread on Europa landers/subs/etc. & the technical challenges thereof.

Posted by: Juramike Oct 13 2009, 11:19 AM

I keep thinking of a place like http://en.wikipedia.org/wiki/Conamara_Chaos and all the neat things that might've gotten pulled up along with it.

The top surface of the ocean should be in equilibrium with the lower surface of the ice crust. I'm wondering if you would get nifty layers of different chemical species trapped in the under layer of ice. (The oxygen content of the ocean would depend on activity of the transfer of surface crust into the subsurface ocean.)

As some of those blocks rotatated around and blobbed up to the surface, there might be chemically distinct layers sitting at random angles of view in blocks sitting on top.

(F'r example: http://www.coolantarctica.com/gallery/scenic/icebergs1/Antarctica_iceberg5.htm)

Could an uber hi-res HiRise VIMS instrument pick this up from orbit if it was laying on it's side?

-Mike

Posted by: Julius Oct 13 2009, 12:50 PM

For sure it would be sensible if we're sending a mission to Europa, it should initially consist of an orbiter equipped with high resolution camera ,VIMS and most important ice penetrating radar to be able to determine the thickness of the icy crust and variations in thickness.This would spot the best locations where to attempt drilling thru the Europan crust for access to the underlying watery ocean.Follow up mission including hydrobot could then be properly designed depending on the findings from the orbiter mission.

PS:Havent read Greenbergs book on Europa, but has the role of impacts been given importance as to causing oxygen enrichment to the water ocean??

Posted by: Juramike Oct 13 2009, 02:11 PM

I'm guessing a sequence of missions to Europa: high res orbiter/spectrometer to find the easy places to land/penetrate. Then a lander/rover to taste the ice and get an idea of physical properties, and finally (maybe) a submersible.

I think an intermediate-lander/rover is a minimum to ensure no funky ice properties before drilling in a submersible.

Plus, the rover could check out the low-hanging fruit of previously subsurface ice brought up to the surface.

Posted by: john_s Oct 13 2009, 02:53 PM

We've detected oxygen on Europa's surface (probably trapped in the ice) with ground-based spectroscopy- see http://adsabs.harvard.edu/abs/2002AJ....124.3400S. It's hard to say just how much is there, because the strength of the absorption band depends on how close the molecules are to each other, but it's definitely present.

Posted by: nprev Oct 13 2009, 03:14 PM

Aha! Thanks, John. Interesting. So high-res visible band spectroscopy from a Europa orbiter could presumably find small areas of high O2 concentration? You could probably use the same instrument for broadband terrain mapping & try to correlate oxygen enrichment with fresh-looking ice. Such sites would also be dandy places to look for geysers.

Posted by: MarsIsImportant Oct 13 2009, 03:14 PM

There is no need to drill to get the submersible through the ice. Use a reactor core to create the heat necessary to melt through. This would make it dual purpose.

I'm also wondering whether the oxygen in the environment can be used somehow as a secondary power source (I don't know how to do that little trick). It could be done in combination with solar power, but that won't be an option under the ice. Tethering for power and communication would require too much mass for just the cord and would be impractical to unwind (high probability that something would get stuck). Maybe a lead-oxygen cell of some sort. Regardless, it would have to be fairly novel. A lot would depend upon how much is in the environment and could be captured.

The orbital missions have already been approved. That should give us a better feel for the oxygen answer before a more extensive dedicated mission below. Depending upon the results from that exploration, a narrow mission lander may or may not be necessary. Personally I think the combination of lander and submersible is a good idea and doesn't have to wait too long before becoming practical. The radiation would require shielding of some sort for any orbital or surface mission. A little extra weight for a self contained subsurface mission should be cost effective given the enormous dollar amount necessary to get the entire package to Jupiter.

My question is how much oxygen can really be expected in the ocean below. Although this paper suggests an extraordinary amount, is that real? What about potential ammonia in the water? How will that effect things?

Posted by: infocat13 Oct 15 2009, 01:10 AM

Does not ' LIFE" as we know it faver certain isotopes of oxygen or other ions? and what effect would cycling through the ice and radiation on the surface have on this? and could a orbiter tell us what was what?

Posted by: Juramike Oct 15 2009, 03:48 AM

Hmmmm. Thinking this through from a purely physical standpoint:

Water ice on surface with isotopic ratio. Ionizing radiation hits. (Isotopic effect on ionization energy?? Would this matter to an appreciable extent??)
Oxygen reactive species created with (assumed) isotopic ratio as original ice.
Dioxygen (and ozone) forms in ice matrix.
Lighter forms have better chance of flying and escaping matrix and escaping off to space (but not much; difference for 18O=16O vs 16O=16O is m.w. 34 vs. m.w. 32)

Ice chunks with new ratio (favoring the heavier 18O=16O) go into the ocean which is a sealed environment.

So any oxidized compounds coming up should still have the oxygen isotope ratio that existed on the surface.
Not sure about sequestering into oxidized compounds. Theoretically at least, the 18O=O16 would be less reactive (stronger bond) and so O16 would be preferred to be oxidized into materials.

I don't think there will be an obvious isotope effect due to interaction with ocean materials. I think the isotope setting at the surface ice stage will be the defining moment.

Posted by: centsworth_II Nov 12 2009, 08:08 AM

What about other gasses in the Europan ocean, perhaps released from the interior of the moon? There must be a buildup of such gasses beneath the surface of the ice. Perhaps huge pockets exist from which gasses can work their way up to the surface through cracks in the ice layer. Maybe some day events similar to the methane releases on Mars could be observed on Europa.

Posted by: Hungry4info Nov 12 2009, 09:29 AM

Could that explain the "chaotic terrain" observed in Galileo images?

Posted by: Juramike May 27 2010, 06:19 PM

Article on space.com describing an article soon to be in May issue of Astrobiology magazine (link to magazine website http://www.liebertonline.com/ast).

Also released in http://www.astrobio.net/exclusive/3506/europa%E2%80%99s-churn-leads-to-oxygen-burn

The new information released provides a better mechanism for crustal turnover, the tidal flexing due to Jupiter. And suggests that most of Europa's crust is less than 50 million years old. (Impact gardening, the synopsis states, would only distribute oxygen to about 10 m depth.). The tidal/tectonic cycling idea can thus distribute oxygen throughout the crust and the subsurface ocean.

There are some additional details in the news release regarding tectonic cycling and the formation of chaotic terrain of Europa. Especially interesting is how about 2 billion years would be required to saturate the crust in oxygen.

(Therefore the chemistry of the icy crust is oxidizing).

'"Spectroscopy done by telescopes on Earth or in orbit can tell what substances are mixed into the ice," Greenberg said.'

Posted by: MaDeR Jul 17 2010, 10:08 AM

Astrobio is reported as having Trojan in Avast. I already sent email to them. I do not know if it is false positive, but I do not want go there again.

Posted by: Hungry4info Jul 17 2010, 11:21 AM

I confirm. A javascript in there is picked up by Avast as a trojan. Dunno if it's a false-positive or not either.

Posted by: Greg Hullender Jul 17 2010, 02:13 PM

Sophos reports it as well, but claims to deal with it.

--Greg