Alice obtains first far ultraviolet spectra of comet 67P/C-G

The Alice ultraviolet (UV) spectrograph aboard Rosetta has delivered its first scientific discoveries, making the first far ultraviolet spectra of a cometary surface.

Alice is probing the origin, composition and workings of comet 67P/Churyumov-Gerasimenko, gaining sensitive, high-resolution compositional insights that cannot be obtained by either ground-based or Earth-orbital observations.

From data collected over the last month, the Alice team discovered that the comet is unusually dark in the ultraviolet and that the comet’s surface – so far – shows no large water-ice patches. Alice is also already detecting both hydrogen and oxygen in the comet’s coma, or atmosphere.

We’re a bit surprised at just how unreflective the comet’s surface is and how little evidence of exposed water-ice it shows,” says Dr. Alan Stern, Alice principal investigator and an associate vice president of the SwRI Space Science and Engineering Division.

As the mission progresses, we will continue to search for surface ice patches and ultraviolet color and composition variations across the surface of the comet,” says Dr. Lori Feaga, Alice co-investigator at the University of Maryland.

Alice was developed by Southwest Research Institute and is one of three instruments funded by NASA flying aboard Rosetta.

Read more: NASA Instrument aboard European Spacecraft Returns First Science Results



  • Ross says:

    Well isn’t that SHOCKING, no water ice detected on the surface, yet hydrogen and oxygen exist in the coma. How can this be without photodissociation of water?? Solar wind’s electrical influence is eroding the comet surface. The silicates in the nucleus release oxygen, which react with hydrogen of the solar wind and you’ve got hydroxyl, which scientists in the past so eagerly used as evidence of water. If you haven’t at least tried to “debunk” the electric comet theory, I recommend looking it over so you can get a head start for when we observe it directly.

    • Marco says:

      What silicates? The visible surface is black. The observed elements are being ejected from jets that originate below the surface. Noting that the surface is “dry” doesn’t tell us anything about what is below the surface. A lot of gas gets generated in comets over an orbital cycle. I think phase change (evaporation or sublimation) , or even chemical reactions within the comet can explain more than a vague, unobserved electrical process.

      • Ross says:

        If the jets (which are active right now, protruding from the “neck” area of the comet) are due to material inside the comet then where are the vents? The coma is supposed to be caused by sublimation of surface ice, yet there has been ZERO water ice detected yet. Therefore, according to the standard model, for there to be a coma and active jets all produced by cleverly hidden materials inside the nucleus, there should be open vents everywhere. I see ZERO. In reality, the jets are cathodic etching in response to the comet’s increasing potential difference as it nears the sun. This explains why the nucleus has such low albedo, its surface is being continuously eroded by discharges. Standard comet theory is proving to be more unfalsifiable with every surprising observation.

      • Dave says:

        Hi Marco,
        The comet is cut to ribbons, some of the escarpments are a couple of hundred meters high, where the faces have been eroded or cut by some kind of mechanism, posibly electric.
        If there was ice under the surface, we would be ablle to see it by now, either on those steep escapments, or in the neck regions where so much material has been eroded away to reveal yet more rock.
        So it is very hard to emagine how water ice would sublimate from below the surgface and escape though the rock with out there being signs of possibly explosive fissures (due to pressure of sublimation, ot at least some jet holes. Even then to belive the theory that everything is coming from below the surface, we have to imagine how the ecape of sublimated wate can miraculously leave the comet as a filiment instead of expanding in all directions one free from the jet.
        If you can explain all that, Im with you

    • James McCarthy says:

      All observations,and these discussions are fascinating…and only add to the beauty,and mystique of the comet itself,to say nothing of the novelty of the circumstances by which we are afforded these windows. That said,no apologies for my gushing amazement,I have an thoughts are ,that a kind of dehydration is occurring to the outermost layer of the comet,induced by the extreme cold,and low density of the outermost ice layer.I believe that the over dried,drained ice layer is ablating in the frictional impacts of its tumbling.I also contend that the neck is frictionally eroding,at an increased rate,proportionate to its flexing as conduit of two larger elements.

  • Chris Dennis says:

    I’m not a scientist by any imagination, but what I am seeing in the imagery is that the comet surface shows ablation features similar to what is observed with snow/ice in the wind. That is sharply eroded features.

    Curious that the “neck” shows more smoother textures and yet OSIRiS image showed that is where the coma is sourced.

    My guess would be that the comet will fragment at the neck once we observe renewed ablation during perihelion and increased gravity stress,

    Just a lay mans observation

    • Donald says:

      It would be pretty AWESOME if the comet split while Rosetta orbits it.

  • frankebe says:

    I am curious to see how many more of these predictions end up being true:

    And here:

    So far, no ice, lots of solid rock, a sculpted surface, and dark albedo.

    Well, it’s worth a small wager against the standard theory predictions, perhaps—nothing like getting empirical evidence in place of mathematical theories, eh?

    • Donald says:

      That’s the beauty of science. Make theories based upon current knowledge and observations. Make better observations and refine knowledge then update the theories. Nothing is ever set in stone, even comet ice. The more we explore the more we discover how much we still don’t know.
      It wouldn’t surprise me if we find that many of these ‘comets’ are just very wet asteroids and that many of what we call asteroids are just dry comets.

  • Marco says:

    If you look at this quantitatively, the amount of gas ejected (one glass a second water equivalent over the whole comet) the speed and directionality of the jet, the vents are necessarily smaller than the resolution can show, yet, and reasonably separated. Quantitatively again, electrical potentials required for what you are talking about come to contradictory conclusions. I agree with you that standard cometary theory is on very shaky ground – electric comet theory is on even shakier falsifiability grounds. Physics has a good hold on how electricity works – it has little to nothing to do with the observed jets and coma.

  • morganism says:

    Thunderbird has landed !

    Actually, my favorite hypo on formation of this body .

    I think they are going to find that the apple core shape is due to the impact on the ducks head, spalling out the chunks in the neck. Am trying to find some models of hydrates under impact to see if there is compression of the already expanded mesh/lattice.

    As for composition, i am sticking with the methane clathrate model. This provides for plenty of carbon, making a progression of hydrocarbons all the way up to graphite.

    Once you are to graphite, then graphene can self assemble. once to graphene, you can get lots of interesting structures and chemistry, notably using UV, you can get hydroxyls to work making CO2 and water. Add some things to change PH, and you can even make lipospheric type polymers.

    If this is indeed expanded methane clathrate/hydrate, you can have argon and other exotics trapped inside the lattice structures.

    nano diamonds are a tough thing to explain in space
    They sometimes make up 10% of dust, making them some of the most plentiful minerals in the solar system. But if you are going nearer the sun…

  • morganism says:

    oops, forgot to point out that expanded methane solves the density problem that has been found for most small bodies in the solar system.

    numerous studies this year have shown that the “brazil nut” problem works in any disturbed system, even in microgravity.

    This would tend to put the “rubble pile” model to the fiery death it deserves. Any impact on a body, would tend to “smooth” out any other impact craters, and bring all large rocks to the surface.

    Expanded methane hydrate has the density of packing peanuts, no voids needed.

  • Chad says:

    It’s quite silly that the likes of ESA keep insisting that comets are icy water worlds. One sure observation from Rosetta is that comets are clearly not dirty snowballs and nowhere near it. Comets are not icy, snowy, or watery. They are asteroid-like and very dark, dry bodies. Why do the scientists keep insisting, in their culture of glib press releases to the general pubic, on the negligent and false idea of “icy comets” when comets have proven not to be anything like that from the past 5 comet encounters with probes? When will “icy comets” finally stop being printed by modern science publications and agencies?

  • Dave says:

    Do we have any analisis of the surface, or better still analysis from the dust collecter that can give some clues as to what the comet is made of?

  • Jorge R says:

    sorry, i´m chemist, not a planetary scientist, and I think all of your comments are very interesting.
    Can the comet have something like a porous carbon surface that permits the slow sublimation of subsurface ice -heated by sun and conducted inwards by thermal conductivity?
    The jets in the comet must be due to fractures in the surface? (the seems to be more “violent” from a far away view than a close-up view)
    Thanks for your reponses. i apologice i I´m sayng something abvious or stupid.

    • Marco says:

      Hi Jorge, I do believe that the scientist are suggesting exactly what you are saying. However, there are contradictions in that the surface appears to be very insulating, thus thermal conductivity to subsurface would be limited, especially this far from the sun. The temperature of the surface is still well below freezing so I do not understand why jets would form on the basis of solar thermal energy sublimating water ice. Something else is obviously happening, and hopefully we will have that Eureka moment somewhere and it will all make sense.

  • THOMAS says:

    I would certainly agree with Marco in saying that “standard cometary theory is on very shaky ground” (though I find this something of an understatement). The images being provided by Rosetta have indeed completely blown away Fred Whipple’s “dirty snowball” model (particularly as they come as spectacular confirmation of the images already available for five other comet nuclei, all displaying the same rocky appearance). It would be hard to imagine a rockier, more battered, less snowball-like object (even an asteroid…) than comet 67P. In addition no trace whatever has been detected of surface ice or of H2O, being “outgassed”, in whatever form.

    I no longer agree with Marco, however, when he claims that “Physics has a good hold on how electricity works”. It is certainly true that we have harnessed electricity for a full range of from basic to extremely sophisticated purposes (otherwise we wouldn’t be having this internet exchange, for example…). On the other hand, biophysicists, to take just one example of our merely dawning understanding of other realms where separation of electric charge is fundamental, are only now just beginning to understand the crucial role played by electric dipoles in the basic functioning of both the brain and the body.

    But the real problem is that “science” still knows very little about how electricity actually “works” as regards its more extreme naturally-occurring, unharnessed, manifestations, even in something as common as the lightning that strikes in our own back-yard. Lightning-connected phenomena such as ultra high-altitude red sprites, blue jets and elves have only been observed in the last few years, let alone understood: “science” has as yet absolutely no fundamental understanding of how the overall system works.

    It thus seems to me a little premature and rather too dismissive to claim, as Marco does, that electricity “has little to nothing to do with the observed jets and coma”. Hopefully, as increasingly precise images and information pour in from Rosetta, more and more people will understand over the coming weeks and months that the “jets and coma” of comet 67P are in fact most likely an electric discharge phenomenon due to charge difference which is driven by the same fundamental principles (albeit in a less spectacular discharge mode) as lightning is down here on Earth. My only fear is that the Rosette probe may itself fall victim to such discharge activity and suddenly fall silent in the coming days as the result of its circuits being shorted out by a spark from the comet. As for the lander Philae, I fear, for the same reasons, that it unfortunately has scant chance of escaping being zapped big time as it approaches the surface… It will be very interesting to see if Rosetta manages to get pictures of any flash in that case.

    We’re truly getting into money time for model confirmation or falsification!

    • Marco says:

      @Thomas Re: Electricity. We are talking about positive and negative charges, electrons, protons etc.? I remember learning about lightning in high school physics – It all made sense and still does, while you make it sound all mysterious and magical. I certainly trust the scientists to know what they are doing with regards to “ionised materials” ie. yes, there are plenty of electrical potentials floating around – None particularly mysterious. If you are talking about some other mysterious force which is like electricity but different, stop calling it electricity.
      I think it is important to note that current models are wrong, but it is important to stick with the physical laws we understand, together with whatever new data we get, to decide what new model we should pursue.

  • Dave says:

    To Marco
    Please have a glance into how plasmas work. It’s not mysterious. Try youtube you may be surprised what comes up.

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