Enceladus: More Evidence of Liquid Water

by Paul Gilster on July 29, 2009

I’m pushed for time this morning but do want to catch up with Cassini news, in particular the recent findings from Enceladus. The plumes of water vapor and ice particles erupting from the moon continue to capture the imagination. Cassini’s Ion and Neutral Mass Spectrometer was used during Enceladus flybys in July and October of 2008, with results just released in Nature. Out of all this we get this interesting find, as discussed by Hunter Waite (SwRI), who is lead scientist on the instrument involved:

“When Cassini flew through the plume erupting from Enceladus on October 8 of last year, our spectrometer was able to sniff out many complex chemicals, including organic ones, in the vapor and icy particles. One of the chemicals definitively identified was ammonia.”

William McKinnon (Washington University, St. Louis) calls ammonia “sort of a holy grail for icy volcanism,” noting that this is our first unambiguous detection of ammonia on an icy satellite of a giant planet. Finding it is intriguing because the presence of ammonia can keep water in liquid form at lower temperatures than we might expect.

enceladus_1008

Image: The Cassini spacecraft acquired this view of Enceladus just after the spacecraft passed within 25 kilometers (15 miles) of the surface on Oct. 9, 2008. Remarkably, only a handful of craters are visible in this view, indicating the relatively young age of this surface. Credit: NASA/JPL/Space Science Institute.

This JPL news release talks about ammonia as a natural antifreeze, and notes that with the right amount of ammonia, water can exist in a liquid state at temperatures as low as 176 Kelvin (-143 degrees Fahrenheit). Waite again:

“Given that temperatures in excess of 180 Kelvin (-136 degrees Fahrenheit) have been measured near the fractures on Enceladus where the jets emanate, we think we have an excellent argument for a liquid water interior.”

Cassini has already racked up five Enceladus flybys, with two more scheduled for November and another two in the spring of 2010. We know we have organics and a strong possibility of liquid water within the Saturnian moon. The amount of water involved is still unknown, but potentially habitable environments are still in play.

The paper is Waite et al., “Liquid water on Enceladus from observations of ammonia and 40Ar in the plume,” Nature 460 (23 July 2009), pp. 487-490 (abstract).

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{ 13 comments }

george scaglione July 29, 2009 at 9:12

funny thing.i see more and more about the potential of liquid water on this moon!seems to make it a major place we might want to go.funny thing too,the presidents panel which is studying manned spaceflight suggests visiting the moons of mars.well this one is a “little” further away…but i say,if it is a major facinating question mark and we think that the moons of mars are attractive anyway – then why not?! as i have said before,at this juncture,i think it is more important to push further into the solar system than it just may be to redo the moon.now let me hasten to add,yes we must go back to the moon also.however whats the rush.my god i’d rather do something new than redo the work of 1969! thank you very much,george

philw1776 July 29, 2009 at 9:40

Interesting…was ammonia detected by Galileo around Europa?

george scaglione July 29, 2009 at 14:22

phil,thank you but i don’t know.however i am pretty sure that water would be more of a draw than ammonia.although lol it just occured to me…might be aliens to whom ammonia just might be a bigger draw! :) thanks very much your friend george

andy July 29, 2009 at 14:24

Cassini shows us just what a loss Galileo’s main antenna was.

James M. Essig July 29, 2009 at 18:38

Hi George;

I most certainly agree with your above comments.

We have about a couple of hundred moons within our solar system, many of which might be accessible via manned expeditions.

With the Ad Astra Rocket Companies VASIMR engine, probably all of the moons within our planetary solar system that do not have dangerous radiation fluxes around them could be explored.

I can see a coming opportuinity for the glory days of the exploration of planetary moons wihin our solar system, as we simultaneously develop real star ships.

Ammonia water on Enceladus. Now that can be a recipie for life.

Thanks;

Jim

NS July 30, 2009 at 3:04
george scaglione July 30, 2009 at 9:16

ns,hate to be a party poopper and i wasn’t so happy about this news either when i first heard it,but,i understand that tv broadcasts break down to static after two years! kinda throws cold water on alot of cool sf as well!! maybe we should be glad that the aliens will not see alot of the tripe that our intelligence cranks out!!!!!!!! it is kinda too bad however that they won’t see other things ,like carl sagan’s cosmos series for example! thank you very much your friend george ps,oh! and jim…yes we need to as i see it go on exploring the solar system most certainly to include the habitable moons.as you say,while,we work on star ships! in fact the solar system exploration could only help! imagine how much we will learn about space flight and propulsion in the meantime! fusion engines would be a good bet…and a big step up while we strongly consider warp drive at the same time.i recall my “prediction” of the first starship by 2075! i mean that leaves us “only” 66 more years,and taking exponential growth into account just maybe we could start to see it all as a “done deal”! as always,good to talk to everybody.your friend george

Administrator July 30, 2009 at 16:44

philw writes:

was ammonia detected by Galileo around Europa?

I’m hoping someone else has a firm answer on this — my impression is that no substantiated detection of ammonia has been made around Europa, but I can’t verify it.

NS July 30, 2009 at 20:33

I’m aware that TV signals really couldn’t be detected very far from Earth (and in fact the complete web page accompanying the map has a caveat about this). I’ve also heard our own SETI efforts couldn’t detect radio leakage (as opposed to a deliberate beacon) even from a star as close as Alpha Centauri. Still, I thought the map was so eye-catching enough to be worth sharing.

ljk October 15, 2009 at 1:01

A Sensitivity Study of the Enceladus Torus

Authors: B. L. Fleshman, P. A. Delamere, F. Bagenal

(Submitted on 12 Oct 2009)

Abstract: We have developed a homogeneous model of physical chemistry to investigate the neutral-dominated, water-based Enceladus torus.

Electrons are treated as the summation of two isotropic Maxwellian distributions$-$a thermal component and a hot component. The effects of electron impact, electron recombination, charge exchange, and photochemistry are included. The mass source is neutral H$_2$O, and a rigidly-corotating magnetosphere introduces energy via pickup of freshly-ionized neutrals. A small fraction of energy is also input by Coulomb collisions with a small population ($<$ 1%) of supra-thermal electrons. Mass and energy are lost due to radial diffusion, escaping fast neutrals produced by charge exchange and recombination, and a small amount of radiative cooling.

We explore a constrained parameter space spanned by water source rate, ion radial diffusion, hot-electron temperature, and hot-electron density.

The key findings are: (1) radial transport must take longer than 12 days; (2) water is input at a rate of 100–180 kg s$^{-1}$; (3) hot electrons have energies between 100 and 250 eV; (4) neutrals dominate ions by a ratio of 40:1 and continue to dominate even when thermal electrons have temperatures as high as $\approx$ 5 eV; (5) hot electrons do not exceed 1% of the total electron population within the torus; (6) if hot electrons alone drive the observed longitudinal variation in thermal electron density, then they also drive a significant variation in ion composition.

Comments: 9 pages text, 3 tables, 9 figures

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:0910.2243v1 [astro-ph.EP]

Submission history

From: Bobby Fleshman [view email]

[v1] Mon, 12 Oct 2009 21:23:52 GMT (347kb,D)

http://arxiv.org/abs/0910.2243

ljk November 2, 2009 at 23:37

November 2, 2009

Fabulous! Enceladus Raw Flyby Images

Written by Nancy Atkinson

Carolyn Porco, the lead for Cassini’s imaging team, warned on Twitter that the flyby of Saturn’s moon Enceladus performed by the spacecraft on Nov. 2 wasn’t really an “imaging” flyby, and that we might have to wait until the Nov. 21 flyby for really good images.

But just take a look the images returned so far, with stunning looks at the jets shooting from the moon! Another image takes a close look at the surface.

These are raw, unprocessed images, but what images they are! This is the second image from today’s flyby returned by the spacecraft. See below for more.

Full article here:

http://www.universetoday.com/2009/11/02/fabulous-enceladus-raw-flyby-images/

ljk November 30, 2009 at 1:12

Cassini Flyby Shows Enceladus Venting

Credit: NASA/JPL/SSI; Mosaic: Emily Lakdawalla

Explanation: What’s happening on the surface of Saturn’s moon Enceladus?

Enormous ice jets are erupting. Giant plumes of ice have been photographed in dramatic fashion by the robotic Cassini spacecraft during this past weekend’s flyby of Saturn’s moon Enceladus.

Pictured above, numerous plumes are seen rising from long tiger-stripe canyons across Enceladus’ craggy surface. Several ice jets are even visible in the shadowed region of crescent Enceladus as they reach high enough to scatter sunlight. Other plumes, near the top of the above image, appear visible just over the moon’s sunlit edge.

That Enceladus vents fountains of ice was first discovered on Cassini images in 2005, and has been under close study ever since. Continued study of the ice plumes may yield further clues as to whether underground oceans, candidates for containing life, exist on this distant ice world.

http://antwrp.gsfc.nasa.gov/apod/ap091124.html

ljk January 10, 2010 at 1:39

Modeling the Enceladus plume–plasma interaction

Authors: B. L. Fleshman, P. A. Delamere, F. Bagenal

(Submitted on 5 Jan 2010)

Abstract: We investigate the chemical interaction between Saturn’s corotating plasma and Enceladus’ volcanic plumes. We evolve plasma as it passes through a prescribed H2O plume using a physical chemistry model adapted for water-group reactions. The flow field is assumed to be that of a plasma around an electrically-conducting obstacle centered on Enceladus and aligned with Saturn’s magnetic field, consistent with Cassini magnetometer data.

We explore the effects on the physical chemistry due to: (1) a small population of hot electrons; (2) a plasma flow decelerated in response to the pickup of fresh ions; (3) the source rate of neutral H2O. The model confirms that charge exchange dominates the local chemistry and that H3O+ dominates the water-group composition downstream of the Enceladus plumes. We also find that the amount of fresh pickup ions depends heavily on both the neutral source strength and on the presence of a persistent population of hot electrons.

Comments: 10 pages, 1 table, 2 figures

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:1001.0787v1 [astro-ph.EP]

Submission history

From: Bobby Fleshman [view email]

[v1] Tue, 5 Jan 2010 22:50:52 GMT (687kb,D)

http://arxiv.org/abs/1001.0787

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