Team identifies clathrate ices in comet 67P

SwRI-led team identifies clathrate ices in comet 67P
Southwest Research Institute scientists led an international team studying the composition of comet 67P’s coma to better understand the ice structures and the possible origin of its nucleus. The team found evidence of water ice clathrates that could indicate the comet formed closer to the Sun than originally thought. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

For decades, scientists have agreed that comets are mostly water ice, but what kind of ice—amorphous or crystalline—is still up for debate. Looking at data obtained by ESA's Rosetta spacecraft in the atmosphere, or coma, around comet 67P/Churyumov-Gerasimenko, scientists at Southwest Research Institute (SwRI) are seeing evidence of a crystalline form of ice called clathrates.

"The structure and phase of the ice is important because it tells us a lot about how and where the comet may have formed," says Dr. Adrienn Luspay-Kuti, a research scientist in SwRI's Space Science and Engineering Division. She is the lead author of a paper titled "The presence of clathrates in comet 67P/Churyumov-Gerasimenko" published in the April 8 issue of the journal Science Advances. "If the of 67P were predominantly crystalline ices and clathrates, then 67P likely agglomerated from chunks of ice closer to the Sun. The protosolar nebula closer to the Sun experienced higher temperatures and more turbulence where crystalline ices could form as the nebula cooled. More pristine amorphous ices likely dominated the colder outskirts of the rotating disk of dust and gas that surrounds the core of a developing solar system."

Amorphous water ice efficiently traps large amounts of volatile compounds, which are released simultaneously upon warming. Water clathrates are crystalline structures containing gas molecules. The volatiles locked inside the water actually create the stable clathrate structure. These structures release gases at characteristic temperatures, dependent on the gas-phase volatile locked inside the clathrate. Luspay-Kuti led an international team of cometary experts that interpreted Rosetta spacecraft data, and found that the observed outgassing pattern indicates the nucleus of 67P contains clathrates.

"Without direct sampling of the nucleus interior, evaluating the composition of the coma provides the best clues about the structure and, as a result, the possible origin of cometary nuclei," said Luspay-Kuti. "Thought to closely reflect the composition of the building blocks of our solar system, comets carry important information about the prevalent conditions in the solar nebula before and after planet formation. These small icy bodies help us understand the big picture."

The multi-institute team of cometary scientists analyzed mass spectrometer data from the southern region of 67P from September to October 2014, before equinox. 67P is a Jupiter family comet thought to originate from the Kuiper Belt. Scientists are comparing these new data with data from the flyby of Hartley 2—considered cometary kin in family and origin to 67P—and finding correlations. If these comets formed closer to the Sun than originally thought, these data could help refine solar system formation models.

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Type of ice reveals the age of comets

More information: "The presence of clathrates in comet 67P/Churyumov-Gerasimenko"
Journal information: Science Advances

Citation: Team identifies clathrate ices in comet 67P (2016, April 8) retrieved 21 July 2019 from
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Apr 08, 2016
Is this the same type of clathrate ice that is found near volcanic vents under the oceans of Earth? I think those have Methane gas.

Apr 08, 2016
@OS - clathrates are a general class of traps for molecules - basically one type of molecule is embedded within a matrix or lattice composed of some other type of molecule, without the guest and host exchanging electrons or sharing covalent bonds.

One type of clathrate is a hydrate clathrate, where the 'cage' is made up of water molecules, of which the clathrates that this article refers to are an example. And yes, this is the same family of clathrate as the methane hydrate clathrates found on the sea floor.

But the article does not say which small molecules were found to be emerging from 67P's hydrates clathrates, and it is a large family. One can have hydrogen trapped in a hydrogen clathrate, or methane trapped in a methane clathrate, and even ethane is sometimes found in clathrates (usually with methane). Many other small molecules can form hydrate clathrates at low enough temperatures or high pressures.

Apr 09, 2016
^^^ The molecules identified in this study were CH4 (methane) & C2H6 (ethane). There was another recent paper which came to the same conclusions based on N2/CO & Ar/CO ratios:

"A protosolar nebula origin for the ices agglomerated by Comet 67P/Churyumov-Gerasimenko"


Apr 09, 2016
But the article does not say which small molecules were found to be emerging from 67P's hydrates clathrates
No but the original article cited above does - ethane, among other things.

Hydrocarbons are found throughout the solar system. We might expect to find reservoirs on the Moon and Mars just as we do here.

Just a suggestion rs - if you are conveying info you got from looking it up, it is more useful (and honest) to copy/paste excerpts or post links rather than giving the impression you actually know the stuff?

Apr 09, 2016
So much for the Oort cloud dirty snowball guess....Epic fail!

Apr 09, 2016
So much for the Oort cloud dirty snowball guess....Epic fail!

And who said JFCs formed in the Oort cloud? Epic fail of research, as usual.

"Comets are rocks blasted off rocky planets by interplanetary lightning bolts. They are just asteroids on elliptical orbits." T & T. Now, that is an epic fail!

Apr 09, 2016
Just a suggestion rs - if you are conveying info you got from looking it up, it is more useful (and honest) to copy/paste excerpts or post links rather than giving the impression you actually know the stuff?

I agree (and your comments are often excellent examples of having links).

However I usually don't comment unless someone asks a question or there is a mistake or significant omission in an article, and it happens to be a subject that I know fairly well. In this case I have looked at clathrates for many years both as a potential energy source and as a potential greenhouse feedback, so I already knew that in addition to methane, hydrogen and ethane also form clathrates, as do other gasses.

In such cases I often check to see if my knowledge is out of date (I'm an old codger), and if I find a source that adds significant information (or is very well written), I do include a link, but if what I find confirms what I thought I do not include a link.

- continued -

Apr 09, 2016
- continued -

The main time that I rely on external sources is when someone like JVK or Benni challenges I comment I have made, and we get down into the details of a subject. In such cases I do include links.

The other time is that even if I don't know a subject well, if I am very curious and look something up and the results turn out to be interesting, I comment. In such cases I generally include a link to the best source(s). However if no source explains things succinctly, and I take the time to understand and summarize the results of many sources, then I only include a link if a source stands out as well worth reading.

If I had more time, I probably would take the time to hunt down more links, so I appreciate it when people do (I often give 5* to someone who provides good links or hunts down a non-paywalled copy of an article – heck I even gave JVK a 5* twice when he had great links and no insults).

Fair enough?

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