Further evidence for subsurface liquid ocean on Enceladus.

[RGClark]

Hidden Ocean Found on Saturn's Icy Moon Enceladus, Could Potentially Support Life.
By Mike Wall, Senior Writer | April 03, 2014 02:01pm ET
http://www.space.com/25340-saturn-moon-enceladus-ocean-discovery.html

Bob Clark

 

[Kyle]

I'm confused, is the article saying we've for certain found an ocean on Enceladus, or just evidence to suggest the possibility? The headline certainly leans towards the forward.

 

[dumbo2007]

...and lies beneath a shell of ice 19 to 25 miles (30 to 40 km) thick,

that will require one helluva drill to verify !

 

[Andy44]

that will require one helluva drill to verify !

Maybe you could crash something large onto the surface, or blow something up, and measure siesmic shock waves from various points to build a model of the interior. I think that's what they did with the moon; crashed S-IVB stages into it and measured the response from sensors placed on the surface.

 

[Castor]

I think that's what they did with the moon; crashed S-IVB stages into it and measured the response from sensors placed on the surface.

Yep, S-IVB stages from Apollo 13-17 as well as the LM's ascent stages (from Apollo 12 onwards).

 

[Unstung]

Maybe you could crash something large onto the surface, or blow something up, and measure siesmic shock waves from various points to build a model of the interior. I think that's what they did with the moon; crashed S-IVB stages into it and measured the response from sensors placed on the surface.

A ground penetrating radar is also a possibility and is requires a far less massive payload. Just knowing that there is an ocean underneath Enceladus leads to a much stronger case for life and a sample return. The ocean appears to be long lived and in contact with the silicate core which is a bonus. The mission architecture for a sample return is simple, but complying with Planetary Protection will be difficult and expensive.

 

[N_Molson]

... and Saturn is not exactly next door !

 

[Castor]

A ground penetrating radar is also a possibility and is requires a far less massive payload.

NASA is considering the proposal of sending up a Enceladus mission, but again faces a lack of funds.

---------- Post added at 09:50 AM ---------- Previous post was at 09:46 AM ----------

Just knowing that there is an ocean underneath Enceladus leads to a much stronger case for life and a sample return.

The Cassini spacecraft had shown the existence of ice and water plumes in 2005. By about 2006, scientists had confirmed that there was a reservoir of water under the moon, from its shape and gravitational attraction. However NASA has been struggling to get funding for even a bare bones sample return mission. I seriously doubt that this news is going to change the situation.

 

[Unstung]

... and Saturn is not exactly next door !

The long flight time will increase the prime mission length and cost money but is doable.

NASA is considering the proposal of sending up a Enceladus mission, but again faces a lack of funds.

---------- Post added at 09:50 AM ---------- Previous post was at 09:46 AM ----------



The Cassini spacecraft had shown the existence of ice and water plumes in 2005. By about 2006, scientists had confirmed that there was a reservoir of water under the moon, from its shape and gravitational attraction. However NASA has been struggling to get funding for even a bare bones sample return mission. I seriously doubt that this news is going to change the situation.

Read this proposal. A basic sample return does not need to cost billions of dollars, but it hinges on the availability of ASRGs, a technology that is nearly ready to be demonstrated but currently shelved due to the extreme lack of funds. With Planetary Science funding levels from a few years ago, it would certainly be possible. LIFE is a valid mission to test the ASRG technology, something that is required no matter what cheap, risky mission the new generator is flown on. It's a Discovery mission, and Discovery-class missions were made to be selected frequently, every two or three years. Funds for frequent Discovery missions will be possible in the 2020s even with these incredibly low budgets. In fact, restoring the Discovery program is what's planned in the future but at the cost of the New Frontiers program.

What really has the potential to stop such a sample return is Planetary Protection. The sample return would be an unprecedented restricted Category V. Containing an Enceladus sample would no doubt be costly and may require new facilities. The mission is very unlikely to be selected this decade, but even at this rate the 2020s provides plenty of opportunities. After the development of InSight, OSIRIS-REx, and Mars 2020, there will be plenty of funds. However, the launch window will be something of concern by then instead of funding.

 

[Andy44]

ASRG technology,

And this is?

 

[DaveS]

And this is?

Advanced Stirling Radioisotope Generator: [ame="http://en.wikipedia.org/wiki/Advanced_Stirling_radioisotope_generator"]Advanced Stirling radioisotope generator - Wikipedia, the free encyclopedia[/ame]

 

[Unstung]

It looks like NASA is "considering making MMRTG Pu-238 power systems available for the next Discovery mission", and a candidate mission is the Enceladus sample return. This will stretch the plutonium supply, but there should be enough for the sample return (1 MMRTG), Mars 2020 (1 MMRTG), and Europa Clipper (4 MMRTGs). The source also elaborates on Planetary Protection (along with many other things I wrote):

Sample return missions like this proposal were considered by the last Decadal Survey, and two key challenges were identified. The first was to ensure that the Earth could not be contaminated with any life brought back from Enceladus. The Survey report assumed that an expensive sample containment facility would have to be built. The current mission concept proposes to address this problem by tuning "the sample impact velocity such that large molecules would survive, but structures such as bacteria or viruses would not." However, NASA still could decide that any sample return from a potential life-bearing world requires expensive new facilities.

Anyway, potential missions to Enceladus are a bit off topic. The discovery is exciting, and hopefully it results in an affordable Saturn mission to continue studying the Saturnian system in the near future.

 

[RGClark]

that will require one helluva drill to verify !

It might be possible to travel through the tiger stripes to the liquid ocean:

Bob Clark

 

[Unstung]

It might be possible to travel through the tiger stripes to the liquid ocean:

https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-prn2/t1.0-9/10169351_10152130820034387_101619080_n.png

Bob Clark

The energy generated by the tiger stripes is 5-6 GW of power and there's four of them. That's about 1.21 gigawatts each. Landing near a geyser and entering it seems too dangerous. The tiger stripes themselves don't connect to the ocean, they're tectonic fractures. Remote sensing of the ocean is much safer.

 

[RGClark]

The energy generated by the tiger stripes is 5-6 GW of power and there's four of them. That's about 1.21 gigawatts each. Landing near a geyser and entering it seems too dangerous. The tiger stripes themselves don't connect to the ocean, they're tectonic fractures. Remote sensing of the ocean is much safer.

IF that model is true they do connect to the ocean.

Bob Clark

 

[dumbo2007]

What exactly is heating the water to keep it liquid ? Some sort of geo-thermal energy ?

 

[Castor]

What exactly is heating the water to keep it liquid ? Some sort of geo-thermal energy ?

The energy most likely comes from the high intensity radiations emitted by Saturn. The heating could also be tidal in nature.

 

[Urwumpe]

IF that model is true they do connect to the ocean.

Yes, but they are not the easiest way to get to the ocean, because they are geologically active. Just like you should not drill through an active volcano (except you know what you are doing, see Unzen Scientific Drilling Project), drilling through these regions will likely only destroy your only drill - and the spare part is many million kilometers away.

 

[Unstung]

What exactly is heating the water to keep it liquid ? Some sort of geo-thermal energy ?

The warming of Enceladus' interior is done by tidal heating and radioactive decay within the moon. Interestingly, it has been calculated that Enceladus currently does not receive enough energy in its eccentric orbit around Saturn to maintain a subsurface liquid ocean for long. It is possible that Enceladus' orbit was changed, making it less elliptical.

 

[RGClark]

Dr. Caroline Porco also posted to her Facebook page a link to an article she co-wrote on the astrobiological possibilities on Enceladus:

Follow the Plume: The Habitability of Enceladus
Christopher P. McKay, Ariel Anbar, Carolyn Porco, and Peter Tsou
ASTROBIOLOGY
Volume 14, Number 4, 2014
Mary Ann Liebert, Inc.
DOI: 10.1089/ast.2014.1158
Abstract
The astrobiological exploration of other worlds in our Solar System is moving from initial exploration to more focused astrobiology missions. In this context, we present the case that the plume of Enceladus currently represents the best astrobiology target in the Solar System. Analysis of the plume by the Cassini mission indicates that the steady plume derives from a subsurface liquid water reservoir that contains organic carbon, biologically available nitrogen, redox energy sources, and inorganic salts. Furthermore, samples from the plume jetting out into space are accessible to a low-cost flyby mission. No other world has such well-studied indications of habitable conditions. Thus, the science goals that would motivate an Enceladus mission are more advanced than for any other Solar System body. The goals of such a mission must go beyond further geophysical characterization, extending to the search for biomolecular evidence of life in the organic-rich plume. This will require improved
in situ investigations and a sample return. Key Words: Ice—Life detection—Icy moon. Astrobiology 14, xxx–xxx
http://online.liebertpub.com/doi/pdfplus/10.1089/ast.2014.1158

Bob Clark