Water ice found on the surface of comet 67P

January 14, 2016 by Deborah Netburn, Los Angeles Times
Rosetta NAVCAM context images of the two debris falls. Credit: (c) Nature (2016) doi:10.1038/nature16190

For the first time, scientists have spotted large patches of water ice on the surface of a comet, thanks to instruments aboard the European Space Agency's Rosetta orbiter.

The finding, published Wednesday in Nature, solves a long-standing mystery about in comets. Scientists already knew that the coma - the expansive cloud of gas surrounding the comet's nucleus - is dominated by water molecules. They also knew that water ice is one of the main components of the nucleus. But until now, traces of water ice on the of the comet had been difficult to detect.

"First, not finding ice was a surprise; now, finding it is a surprise," said Murthy Gudipati a planetary scientist at the Jet Propulsion Laboratory in La Canada Flintridge, Calif., and an author on the paper. "It is exciting because now we are starting to understand the upper dynamic layers of the comet and how they evolved."

The surface of comet 67P, like most comets, is primarily covered by dark organic materials that appear almost black. That's because as comets fly toward the sun, they are exposed to warm temperatures that cause volatiles like water ice on their surface to sublimate - or go directly from solid to gas.

What remains on the crust are what are known as refractory materials. These include silicates similar to rocks, sand and dirt on Earth and carbonaceous materials. Because these materials do not sublimate, the comet's surface becomes increasingly organic and silicate rich over time, said Michael Combi, who studies comets at the University of Michigan and co-authored the paper.

The surface water ice on comet 67P Churyumov-Gerasimenko was discovered in two places several tens of feet across in a region known as Imhotep, on the bottom part of the main lobe of the comet. It was found using the VIRTIS infrared instrument, which scanned the area looking for water ice spectra signals not long after the Rosetta orbiter caught up with 67P in the fall of 2014.

In both cases the ice appeared on cliff walls and debris falls, and appeared as noticeably bright patches in visible light.

"It looked like there was a breakage, or something fell down on the surface of the comet, and a large, new inside area that had water ice was exposed," Gudipati said. "Although we knew water ice had to be in the nucleus, this was our first direct detection of that interior ice."

Further analysis of the VIRTIS data revealed the water ice grains in the newly exposed areas came in two different sizes.

The small grains that are in the micrometer range are likely associated with a thin layer of frost that forms as a function of the comet's rotation. As this region of the comet turns away from the sun, water ice condenses out of the coma and onto the nucleus, the authors wrote. During the "day" the water goes back into the coma.

The larger ice grains, which are a few millimeters across, probably have a more complex origin story, the authors said. One possibility is that water ice in the shallow subsurface of the comet might vaporize as the comet flies closer to the sun, and then move downward into the cooler lower surface lawyers where it condenses again in the voids.

"Keep in mind that comets are very porous, like cotton candy," Gudipati said. "Seventy percent of this comet is a void, and because of that, the heat from the surface does not go that deep."

It should be noted that water ice made up just a small percentage of the material scanned by VIRTIS, suggesting that it is mixed in with the refractory materials in the upper layers of the comet.

The research team, lead by Gianrico Filacchione of the Institute for Space Astrophysics and Planetology in Rome, is now analyzing data captured by the same instrument later in the mission to see how the amount of ice exposed on the surface changed as the comet zoomed closer to the sun.

In the meantime, Gudipati said the new findings have already given comet scientists a lot to work with.

"We knew water ice made up the majority of the , but we didn't know how deep or in what condition it was," he said. "This shows that it not very deep at all - perhaps just a few feet beneath the surface."

Explore further: ESA's Rosetta data reveals evidence for a daily water-ice cycle on and near the surface of comets

More information: G. Filacchione et al. Exposed water ice on the nucleus of comet 67P/Churyumov–Gerasimenko, Nature (2016). DOI: 10.1038/nature16190

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14 comments

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Doc Moore
3.3 / 5 (4) Jan 14, 2016
Water is weird stuff, that much I remember from Thermodynamics 101, but, this comet has almost no gravity and no atmosphere, and yet it seems to be little more than a large chunk of frozen water. How can that be? In the void of space, how can ice survive? What does this tell us about the potentials for water on Mars? That would make an enlightening story.
jonesdave
3.4 / 5 (8) Jan 14, 2016
@Doc,
"In the void of space, how can ice survive?"
Well, the formation location for comets would have been sufficiently cold for it not to sublimate. i.e. well beyond the ice line (protoplanetary disc; dense interstellar molecular clouds). The vast majority of comets spend their lives well beyond the ice line. Only those that are perturbed into closer heliocentric orbits will exhibit this behaviour. Current thinking is that the thermal skin depth will prevent them from outgassing after a certain number of orbits. After that the heat cannot reach beyond that depth, due to the continued depletion of volatiles.
Then they will become difficult to distinguish from asteroids on elliptical orbits, without a closer look.
A closer look would, of course, show their density to be inconsistent with asteroids, i.e. rocks.
Solon
2.1 / 5 (11) Jan 14, 2016
They can't let the dirty ice ball model die can they, too much at stake for mainstream science. If they are wrong here, what else are they wrong about? No doubt there are processes at work that might produce a surface film of ice at some locations, but for the most part 67P is a rock being eroded by electron beam etching. It will end up as a silicon aerogel carcass before finally dissolving away to dust.
jonesdave
3.9 / 5 (11) Jan 14, 2016
They can't let the dirty ice ball model die can they...............No doubt there are processes at work that might produce a surface film of ice at some locations.........


They've already detected subsurface ice using MIRO (many centimeters). And the solid ice ejected from Tempel 1 and Hartley 2, and around 17P Holmes after an outburst. Where else would you like them to find it?
Remember, according to EU there is no water of any description. These useless scientists were just confusing it with OH. And Wal, the eejit, was still coming out with that BS 24 years after the first unambiguous detection of H2O at Halley by the KAO.
Only one person making up stories here. How does it feel to have been conned?
wduckss
1 / 5 (3) Jan 14, 2016
The surprise is that at a distance of 185,980,000 km (Perihelion) someone claims that
"That's because as comets fly toward the sun, they are exposed to warm temperatures that cause volatiles like water ice on their surface to sublimate .."

Max. temperature, comet is -43 C.
So is been solved, why deep freezing quickly evaporate (especially water because the ice melts).
Solon
1.7 / 5 (11) Jan 14, 2016
They can't let the dirty ice ball model die can they...............No doubt there are processes at work that might produce a surface film of ice at some locations.........


They've already detected subsurface ice using MIRO (many centimeters). And the solid ice ejected from Tempel 1 and Hartley 2, and around 17P Holmes after an outburst. Where else would you like them to find it?
Remember, according to EU there is no water of any description. These useless scientists were just confusing it with OH. And Wal, the eejit, was still coming out with that BS 24 years after the first unambiguous detection of H2O at Halley by the KAO.
Only one person making up stories here. How does it feel to have been conned?


It's not that simple, and you should know that. There are still unanswered questions about the nature of space water, one being the Ortho-to-Para ratio discrepancy.
Search "Interstellar Water Chemistry: From Laboratory to Observations" for a fairly recent pdf.
jonesdave
3 / 5 (11) Jan 14, 2016
It's not that simple, and you should know that. There are still unanswered questions about the nature of space water, one being the Ortho-to-Para ratio discrepancy.
Search "Interstellar Water Chemistry: From Laboratory to Observations" for a fairly recent pdf.


Yes, sh*t for brains, it really is that simple. Want me to start posting links to the 'EU Electric Comet Theory'? As proposed by the well known f*ckwits Thornhill & Talbott?
Like I said, where else do you want them to start discovering ice, that that haven't in the last 10 years?
Want me to start quoting that sh*t back to you? Linking to it, maybe?
You've lost. End of.
Now for f*cks sake, shut up.
jonesdave
2 / 5 (8) Jan 14, 2016
The surprise is that at a distance of 185,980,000 km (Perihelion) someone claims that
"That's because as comets fly toward the sun, they are exposed to warm temperatures that cause volatiles like water ice on their surface to sublimate .."

Max. temperature, comet is -43 C.
So is been solved, why deep freezing quickly evaporate (especially water because the ice melts).


Where did you read that sh*t? Maximum temperature is around 350 Kelvin. Either get your sh*t right or f*ck off. No offence. And nothing melts. No liquid in vacuum. Not rocket science. Eh?
jonesdave
3.1 / 5 (9) Jan 14, 2016
It's not that simple, and you should know that. There are still unanswered questions about the nature of space water, one being the Ortho-to-Para ratio discrepancy.
Search "Interstellar Water Chemistry: From Laboratory to Observations" for a fairly recent pdf.


Perhaps you'd like to start listing the EU predictions for this, or any other comet that have actually been right? Maybe throw in the evidence to back it up? As you well know by now, you've got f*ck all, and that is the way it will stay.
Want me to quote the idiot Thornhill to you about comets? Let's be honest; how wrong can one be?
R.I.P. Electric Comet. Bye bye. Close the door on your way out.
jonesdave
3.2 / 5 (9) Jan 14, 2016
"It's not that simple, and you should know that. There are still unanswered questions about the nature of space water, one being the Ortho-to-Para ratio discrepancy.
Search "Interstellar Water Chemistry: From Laboratory to Observations" for a fairly recent pdf."

It's still effing water, and it's still on a comet. Game over. As it was in 2005 when a shed load of solid ice was blasted out of Tempel 1.
Now give us all a break and p*ss off back to la-la land.
wduckss
1 / 5 (3) Jan 15, 2016
The surprise is that at a distance of 185,980,000 km (Perihelion) someone claims that
"That's because as comets fly toward the sun, they are exposed to warm temperatures that cause volatiles like water ice on their surface to sublimate .."

Max. temperature, comet is -43 C.
So is been solved, why deep freezing quickly evaporate (especially water because the ice melts).


Where did you read that sh*t? Maximum temperature is around 350 Kelvin. Either get your sh*t right or f*ck off. No offence. And nothing melts. No liquid in vacuum. Not rocket science. Eh?


https://en.wikipe...asimenko
Besides the speech should be used little evidence and logic. Distance comet in perihilu 186 million what automatically means lower the temperature of the Earth. Instead laboratories on Earth should be use Cosmic lab and will not be confusion.
Maggnus
5 / 5 (3) Jan 21, 2016
They can't let the dirty ice ball model die can they, too much at stake for mainstream science. If they are wrong here, what else are they wrong about? No doubt there are processes at work that might produce a surface film of ice at some locations, but for the most part 67P is a rock being eroded by electron beam etching. It will end up as a silicon aerogel carcass before finally dissolving away to dust.

Wow, talk about crank posting. If nothing else, an interesting example of extreme confirmation bias, Pretty typical for the eu crowd.
Maggnus
5 / 5 (2) Jan 21, 2016
It's not that simple, and you should know that. There are still unanswered questions about the nature of space water, one being the Ortho-to-Para ratio discrepancy.
Search "Interstellar Water Chemistry: From Laboratory to Observations" for a fairly recent pdf.
Actually, it IS that simple, and a quick read of an elementary level chemistry book (about grade 4 level) would provide you with the necessary rudimentary information to know this.

The van Dishoeck paper you are referencing does not say what you seem to think it says.
cantdrive85
1 / 5 (2) Jan 21, 2016
Water ice found on the surface of comet 67P

It's about time being as this is what they were looking for...

http://i.dailymail.co.uk/i/pix/2015/09/17/10/2C6A94F800000578-3238186-Comets_are_composed_of_frozen_gases_mixed_with_dust_giving_the_n-a-32_1442483569166.jpg

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