Rosetta's comet mission discussion thread

[Dotini]

https://agu.confex.com/agu/fm14/webprogrampreliminary/Session1556.html

Click for numerous abstracts to be submitted to the AGU meeting in San Francisco, December 15-19.

"The session welcomes papers on preliminary results from this Rosetta characterization, mapping and landing phase, including simulation and theory papers, implications for comets and solar system origins, as well as results from ground based observations of the Rosetta target comet 67P/Churyumov-Gerasimenko."

 

[lpetrich]

Rosetta fuels debate on origin of Earth’s oceans / Rosetta / Space Science / Our Activities / ESA

Comet 67P has about 3 times as much deuterium (H-2) as the Earth does, and other comets are also enriched, typically by a factor of 2 or 3. Asteroids, however, have amounts of deuterium close to the Earth's, though some of them are enriched up to a factor of 2. Uranus and Neptune, however, have only 1/3 as much, and the Sun, Jupiter, and Saturn only 1/9 as much.

This is likely the result of isotope fractionation in the condensation of water from the protosolar nebula. Heavier isotopes will condense more readily than lighter ones. Heavy water, (H-2)2O, boils at 101.4 C as compared to ordinary water, (H-1)2O, at 100 C. A good check may come from oxygen isotopes, since they also will likely be fractionated. However, oxygen is a major part of rocky materials, which are mostly various metal oxides and metal silicates and silica. That will complicate the history of Solar-System oxygen relative to hydrogen.

 

[Dotini]

Fine structure in the comet's jets.

http://blogs.esa.int/rosetta/2015/01/16/fine-structure-in-the-comets-jets/

OSIRIS wide-angle camera image acquired on 22 November 2014 from a distance of 30 km from Comet 67P/C-G. The image resolution is 2.8 m/pixel. The vertical line in the bottom right of the image, which seems to separate two regions of the coma with slightly different brightness, is the shadow of the nucleus cast onto the coma.
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

 

[OmCheeto]

Apparently the ESA is aware that I'm antsy about the Dawn/Ceres probe, so they provided me with some alternative entertainment today:

http://sci.esa.int/where_is_rosetta/

An interactive application which tracks the Rosetta mission from March 3, 2004 to December 31, 2016.

Hints for anyone like me, who never reads the instructions:

left mouse button: rotate
right mouse button: translate
mouse scroll wheel: zoom
When in play mode, the months take less than a second to fly by. So if you get near an interesting event, push pause, and use the "right" and "left" arrow keys. They will change the date by one day.​

I was so enveloped in the animation this morning, that it was almost like being in a movie.
At one point, I screamed; "Look out! You're going to hit Jupiter!"

January 30, 2008
The comet and Jupiter, from the wrong angle.​

But then I paused the animation, rotated it a bit, and calmed down.

 

[Dotini]

https://www.flickr.com/photos/93308747@ ... hotostream

ESA are calling these jets "collimated", but I'm not sure what that really means in this case.

 

[Dotini]

Links to newly published reports:
http://www.sciencemag.org/site/special/rosetta/
.
Research Article
On the nucleus structure and activity of comet 67P/Churyumov-Gerasimenko
H. Sierks et al.
A comet with an unusual shape has an array of surface features and high porosity, with early outgassing between its two lobes.
.
Research Article
The morphological diversity of comet 67P/Churyumov-Gerasimenko
N. Thomas et al.
Images with better than 1-meter-per-pixel resolution shows a comet’s morphology with evidence for complex active processes.
.
Research Article
Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun
A. Rotundi et al.
Observations of the dust outflow show bound and unbound grains and imply a comparatively high dust-to-gas ratio of 4.
.
Report
67P/Churyumov-Gerasimenko, a Jupiter family comet with a high D/H ratio
K. Altwegg et al.
In situ mass spectrometry reveals a deuterium-to-hydrogen ratio three times that of Earth, which is suggestive of diverse origins for comets in this class.
.
Report
The organic-rich surface of comet 67P/Churyumov-Gerasimenko as seen by VIRTIS/Rosetta
F. Capaccioni et al.
The reflectance behavior of an illuminated comet is consistent with the presence of nonvolatile organics and sparse water ice.
.
Report
Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko
M. Hässig et al.
Mass spectrometry performed in situ shows a highly heterogeneous coma with large diurnal and possibly seasonal variations.
.
Report
Birth of a comet magnetosphere: A spring of water ions
H. Nilsson et al.
The interaction of the solar wind and a comet atmosphere is characterized through detection of the energetic ion environment.
.
Report
Subsurface properties and early activity of comet 67P/Churyumov-Gerasimenko
S. Gulkis et al.
Measurements at a comet yield water production rates and an assessment of low thermal inertia.

 

[Dotini]

Interesting snippets from a NY Times article on Rosetta.
http://www.nytimes.com/2015/01/23/s...-a-comet-even-with-a-wayward-lander.html?_r=0
.
Photo

A close-up of the "neck region" of the rubber-duck-shaped comet. Credit Eureopean Space Agency
.
The high-resolution camera has taken photographs with a resolution as fine as two and a half feet per pixel. The comet, just two and a half miles wide with a two-lobe shape that resembles a rubber duck toy, has a remarkably wide variety of terrain. That includes smooth dust-covered regions, fields of boulders, steep cliffs and large depressions that may have been blown out by underground melting of carbon dioxide. The variety is surprising because many think the comet is, by and large, made of the same material throughout. Scientists are not sure if the shape comes from two smaller comets that bumped and stuck together or one large comet that eroded in an unusual manner.

On the surface of Comet 67P, there are even what look like ripples of sand dunes like those seen on Earth and Mars. That appears befuddling, as a comet has no atmosphere — and so no wind — and only a wisp of gravity.

“You have to ask yourself, is that possible?” said Nicolas Thomas, a professor of experimental physics at the University of Bern in Switzerland and lead author of one of the papers. Dr. Thomas said that back-of-the-envelope calculations indicated that it might be plausible, with the jets of gas acting as wind and the particles held together through intermolecular attraction known as the van der Waals force instead of gravity. “You can convince yourself you can make them move,” Dr. Thomas said. “It’s plausible, at least at the moment.”
.
Photo

A large fracture running across the comet. Credit Eureopean Space Agency
.
In another region, along the comet’s “neck,” is a cliff about 3,000 feet high with fractures hundreds of feet long. The scientists cannot agree on what they are seeing, whether the lines reflect layering in the material making up the comet or cracks caused by the heating and cooling of the material as it passes in and out of sunshine.

In the smooth regions, there are circular structures. “Which look very, very bizarre,” Dr. Thomas said. “To be frank, we don’t know how those things were created. We have no clue.”

 

[Dotini]

http://rosetta.jpl.nasa.gov/sites/default/files/gallery_image/Active_pit.jpg
Active Pit

Active pit detected in Seth region of Comet 67P/Churyumov–Gerasimenko. This is an OSIRIS narrow-angle camera image acquired on 28 August 2014 from a distance of 60 km. The image resolution is 1 m/pixel. Enhancing the contrast (right) reveals fine structures in the shadow of the pit, interpreted as jet-like features rising from the pit.

The images are also available separately:
Left hand image
Right hand image

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Download Active_pit.jpg (12.59 MB)

Active Pit

 

[Dotini]

BBC reports on Goosebumps and Dinosaur Eggs.
http://www.bbc.com/news/science-environment-30931445

A fascinating texture: Comet 67P's "goosebumps" have a preferred scale of about 3m
The data being gathered by the European Space Agency probe is going to keep scientists busy for years, but it is clear already that many of the old ideas about how comets are put together and how they behave will have to change.
It is obvious now that this comet is not a large lump of ice with some dust mixed in. Rather, it has a much more complex construction, incorporating significantly more dust and many rocky components. This is very evident from the ratio of dust to gas being ejected by the comet (four to one), and all those craggy cliff features where stiff, consolidated materials seem to dominate.
"We used to think of comets as 'dirty snowballs'; we now think 'icy dirt-ball' is a much better description," said Simon Green from the UK's Open University. "That's the way 67P looks - a solid object with ice vaporising from somewhere below the surface."

 

[enorbet]

Thanks, everyone, for the links and pics. When I first read that part of the reason for the bounce was that the surface is so much harder than was expected, I knew this was going to be one of the big areas of research. In some ways this information is so fundamental that it is even more exciting than some of the superb data coming off Mars. Once we wrap our heads around how such formations are possible (can Van derWalls actually be this powerful in such conditions is just one example) then what follows is "How could we be so wrong?" in our previous estimates and expectations.

Man! This is exciting stuff!

 

[Dotini]

It's party time for Rosetta and 67P. See the gorgeous photos of cometary jets, glows, streaks and blobs around the active nucleus.

http://www.universetoday.com/119296/dust-whirls-swirls-and-twirls-at-rosettas-comet/

Montage of four single-frame images of Comet 67P/C-G taken by Rosetta’s Navigation Camera (NAVCAM) at the end of February 2015. The images were taken on 25 February (top left), 26 February (top right) and on two occasions on 27 February (bottom left and right). Exposure times are 2 seconds each and the images have been processed to bring out the details of the comet’s many jets. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

This photo taken on Feb. 27 shows the comet with peacock-like display of dusty jets. Below center is a streak that may be a dust particle that traveled during the exposure. Other small white spots are also likely dust or bits of comet that have broken off. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

All were taken between February 25-27 at distances around 50-62 miles (80 to 100 km) from the center of Comet 67P/Churyumov-Gerasimenko. Looking more closely, the comet nucleus appears to be “glowing” with a thin layer of dust and gas suspended above the surface. In the lower left Feb. 27 image, a prominent streak is visible. While this might be a cosmic ray zap, its texture hints that it could also be a dust particle captured during the time exposure. Because it moved a significant distance across the frame, the possible comet chunk may be relatively close to the spacecraft . Just a hunch.

Particularly striking and collimated jets emerge from the comet’s shadowed Hathor region between the two lobes. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

 

[OmCheeto]

OMG!

ROSETTA’S LANDER PHILAE WAKES UP FROM HIBERNATION
​

Yippie!

Rosetta's lander Philae is out of hibernation!

The signals were received at ESA's European Space Operations Centre in Darmstadt at 22:28 CEST on 13 June. More than 300 data packets have been analysed by the teams at the Lander Control Center at the German Aerospace Center (DLR).

"Philae is doing very well: It has an operating temperature of -35ºC and has 24 Watts available," explains DLR Philae Project Manager Dr. Stephan Ulamec. "The lander is ready for operations."

For 85 seconds Philae "spoke" with its team on ground, via Rosetta, in the first contact since going into hibernation in November.
...

 

[Drakkith]

OMG!

ROSETTA’S LANDER PHILAE WAKES UP FROM HIBERNATION
​

Yippie!

From the article: Philae shut down on 15 November 2015 at 1:15 CET after being in operation on the comet for about 60 hours.

My god... NASA invented time travel and didn't tell anyone!

 

[OmCheeto]

From the article: Philae shut down on 15 November 2015 at 1:15 CET after being in operation on the comet for about 60 hours.

My god... NASA invented time travel and didn't tell anyone!

Ah! Hahahaha!
They must have hired Kip Thorne.

 

[Drakkith]

Ah! Hahahaha!
They must have hired Kip Thorne.

"C'mon TARS!"

*Epic music plays*

"C'mon TARS!"

Best docking scene ever!

 

[mfb]

They fixed the date in the article.

Great news!

 

[rootone]

Yay!

 

[Garth]

From the article: Philae shut down on 15 November 2015 at 1:15 CET after being in operation on the comet for about 60 hours.

My god... NASA invented time travel and didn't tell anyone!

Come on you lot - this is Europe not USA! ESA invented time travel - well we have Dr Who to thank for that!

 

[Drakkith]

Come on you lot - this is Europe not USA! ESA invented time travel - well we have Dr Who to thank for that!

Huh... no wonder the spacecraft looked vaguely like a phone booth...

 

[enorbet]

LOL @ Drakkith - as soon as I read your phone booth comment I swear I could hear a synth cranking up crunchy rhythms and ooo-Woooo-oooos. :)

 

[Dotini]

"Our observations show that the distribution of water in the coma is highly inhomogeneous," explains Nicolas Biver, CNRS researcher at LESIA-Observatoire de Paris in Meudon, France, and lead author of the study.

The column density of water around comet 67P/C-G, measured by MIRO. From N. Biver et al. (2015)
"We found the highest density of water just above the neck, close to the north pole of the comet's rotation axis: in this narrow region, the column density of water is up to two orders of magnitude higher than elsewhere in the coma," adds Dr Biver.

http://sci.esa.int/rosetta/56065-miro-maps-water-in-comets-coma/

Date: 19 June 2015
Satellite: Rosetta

The column density of water around Comet 67P/C-G as measured by the MIRO instrument on Rosetta.

From N. Biver et al. (2015)

Last Update: 19 June 2015
http://sci.esa.int/rosetta/56070-the-column-density-of-water-around-comet-67p/

A composite image of four NAV/CAM images taken 19 miles (31 kilometers) from the center of comet 67P/Churyumov-Gerasimenko. A new study has revealed that electrons from the comet, not photons from the sun, are responsible for the breakup of water and carbon dioxide molecules.
Credit: ESA/Rosetta/NAVCAMdiscovery

, which was made using NASA's Alice instrument aboard the European Space Agency's Rosetta spacecraft , was surprising to scientists, who had previously thought that light particles, or photons, from the sun caused these eruptions.Electrons cause the rapid breakup of water and carbon dioxide molecules erupting from the surface of comet 67P/Churyumov-Gerasimenko, new findings reveal.

"The discovery we're reporting is quite unexpected," Alice instrument principal investigator Alan Stern, of the Southwest Research Institute in Colorado, said in a statement. "It shows us the value of going to comets to observe them up close, since this discovery simply could not have been made from Earth or Earth orbit with any existing or planned observatory, and it is fundamentally transforming our knowledge

of comets."
http://www.space.com/29672-rosetta-comet-eruptions-surprising-discovery.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+spaceheadlines+(SPACE.com+Headline+Feed)

 

[OmCheeto]

Some new news:

Philae lander delivers 'ground truth' by touching and analyzing material on a comet's surface [ITV]
30 July 2015 at 7:00pm

...
By firing radio waves through the comet, from Philae to the orbiting Rosetta spacecraft , scientists also know that around 75-85% of comet 67P is empty space.

That isn't in the form of caves but just the space between the individual grains of dust and ice in the body. Whatever 67P is made from, it very loosely packed.
...

So, comets are like cotton candy?

 

[mfb]

A detailed description of the landing process. That crater rim collision sounds dangerous. 1m lower and Philae might have crashed into the crater (just at ~0.3m/s, but then the orientation would have been completely uncontrolled).

 

[Dotini]

http://blogs.esa.int/rosetta/2015/08/11/comets-firework-display-ahead-of-perihelion/

A short-lived outburst from Comet 67P/Churyumov–Gerasimenko was captured by Rosetta’s OSIRIS narrow-angle camera on 29 July 2015. The image at left was taken at 13:06 GMT and does not show any visible signs of the jet. It is very strong in the middle image captured at 13:24 GMT. Residual traces of activity are only very faintly visible in the final image taken at 13:42 GMT. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The decrease in magnetic field strength measured by Rosetta’s RPC-MAG instrument during the outburst event on 29 July 2015. This is the first time a ‘diamagnetic cavity’ has been detected at Comet 67P/Churyumov–Gerasimenko and is thought to be caused by an outburst of gas temporarily increasing the gas flux in the comet’s coma, and pushing the pressure-balance boundary between it and incoming solar wind farther from the nucleus than expected under ‘normal’ levels of activity.
Credits: ESA/Rosetta/RPC/IGEP/IC

During an outburst of gas and dust from Comet 67P/Churyumov–Gerasimenko on 29 July 2015, Rosetta’s ROSINA instrument detected a change in the composition of gases compared with previous days.
The graph shows the relative abundances of various gases after the outburst, compared with measurements two days earlier (water vapour is indicated by the black line).
Credits: ESA/Rosetta/ROSINA/UBern/ BIRA/LATMOS/LMM/IRAP/MPS/SwRI/TUB/UMich

Soon afterwards, the comet pressure sensor of ROSINA detected clear indications of changes in the structure of the coma, while its mass spectrometer recorded changes in the composition of outpouring gases.

For example, compared to measurements made two days earlier, the amount of carbon dioxide increased by a factor of two, methane by four, and hydrogen sulphide by seven, while the amount of water stayed almost constant.

 

[OmCheeto]

This comet strikes me a fodder for either kooks or sci-fi bufs:

1. "75-85% of comet 67P is empty space." [ref]

It's hollow! What could be inside it?​

(it's not really hollow)

2. "...But today we can report that the following have also been detected: Formaldehyde..." [ref]

Formaldehyde? Isn't that what they embalm people with? It's a ship full of dead aliens!​

(Actually, lots of compounds have been found on Comet 67P/C-G. Formaldehyde is just a water molecule that's been dissected, and someone put a carbon atom in the middle. I just found this out, btw. I'm dreadfully bad at chemistry.)

3. "ESA Rosetta Mission ‏@ESA_Rosetta 2h2 hours ago
"T-12 hours to #Perihelion2015! Closest approach to #Sun occurs at 02:03UT on 13 Aug #FinalCountdown"

Something is going to happen! Perihelion is a big word!​

(Ok...)

4.

The alien spacecraft fired an attitude adjusting jet! We knew something was going to happen! And look at Dotini's magnetic field graph that coincides with the jet. Obviously, the aliens withdrew the magnetic energy of the comet to power the jet. ​

(I actually have no idea what is going on with this. But it inspired my post. This is really weird. )

5. "Do you remember where you were on November 12, 2014 when Philae landed on comet 67P/Churyumov-Gerasimenko?
For three nerve-wracking days, the world's attention was focused on the tiny spacecraft , as it bounced its way across the surface of the comet, 300 million miles from Earth.
Though it landed in the wrong place..."

Wrong place? Pfft. It's exactly where the alien spacecraft wanted it, so that could suck the energy from its solar panels. Have we seen any selfies from Philae lately? No!​

Ok. #5 was my lame attempt at humour. My apologies.
But science should be fun. [URL='https://twitter.com/ESA_Rosetta']ESA Rosetta Mission ‏@ESA_Rosetta 9 hours ago[/URL]
<1 day to #67P #perihelion2015 & 185,997,031km to the Sun today! Hope @Philae2014 remembered to pack his sunglasses!

 

[jerromyjon]

Someone could make a great tin-hat salesman!

(I actually have no idea what is going on with this. But it inspired my post. This is really weird. )

Well the jets are towards the sun, right? Perhaps the aliens are inside the sun transmitting the "start destruct sequence" signal which has to penetrate the exterior "decoy" layers. So now you know.

 

[OmCheeto]

Someone could make a great tin-hat salesman!

shhhhhhh! I've already alerted admin that I should not be a member of this forum. I think he thinks I was kidding...

Well the jets are towards the sun, right?

I don't know!

Perhaps the aliens are inside the sun transmitting the "start destruct sequence" signal which has to penetrate the exterior "decoy" layers. So now you know.

That could be.

But I just have so much fun thinking about all this stuff.

I consider the July 29th jet to be a case of fact being stranger than fiction.
Most likely, it is because I have nearly zero knowledge of chemistry.
Why was there a 7 fold increase in hydrogen sulphide? Could this jet have been caused by a thermally induced chemical reaction? Or was that just a freakishly deep pit, with stratified compounds?
I really have no idea.

But PF is filled with freakishly smart people, and I know they will answer, the silliest of questions.

------------------
And hopefully not ban me, for being an idiot.

 

[Dotini]

PF is filled with freakishly smart people, and I know they will answer, the silliest of questions.

Smart, yes, but also cautious and prudent. In the midst of rapid-fire discoveries, nobody wants to be caught saying anything that's seen to be wrong the very next week.

Seriously glad this is fun for you. Me too.

 

[jerromyjon]

Well the jets are towards the sun, right?

Looking at the shadows in the pictures I don't think it could be towards the sun. I was thinking about a comets "tail" being towards or away from the sun but now I forget which way it is. I have to say away since I think the tail tapers out at nearly the angle that a shadow would be cast. Sorry for not just googling it but I need to exercise my memory.

 

[OmCheeto]

Smart, yes, but also cautious and prudent. In the midst of rapid-fire discoveries, nobody wants to be caught saying anything that's seen to be wrong the very next week.

Sad. A thousand silly ideas might yield one good one.
It used to be called "brainstorming", in the olden days.

Do people ever do that anymore? Or have egos gotten so huge, that even the thought of positing an incorrect notion, sends people scurrying, like frightened mice?

Seriously glad this is fun for you. Me too.

 

[jerromyjon]

Do people ever do that anymore?

Now all I can run through my mind is this quote from Nugatory: "In order to broaden the horizons of science, you have to be standing at the frontier"

With that said, we are just sniffing the dust, saying is smells like hydrogen sulfide. I said that out loud earlier (I said "hydrogen sulfide?") and my wife just gave me a blank look and said "What?"... I imagine the greatest minds in the field are in heated conversations over this.

 

[OmCheeto]

Some of the descriptions in the article Dotini posted yesterday indicate that I have a lot to learn, as even the things they describe that they already know, make no sense to me.

Some highlights of things that may not be obvious if you read the article too fast:
1. The comet itself does not possesses its own magnetic field
2. The "diamagnetic cavity" is not a cavity inside the comet, it's a hole in the field that surrounds the comet.
3. That hole/cavity was created by the increased outgassing of the comet.The following excerpt from the article has me the most confused, so I may need to do some research.

...
The solar wind is the constant stream of electrically charged particles that flows out from the Sun, carrying its magnetic field out into the Solar System. Earlier measurements made by Rosetta and Philae had already shown that the comet is not magnetised, so the only source for the magnetic field measured around it is the solar wind.
...

[ref]
Specifically, the bolded portion.

Reading the wiki entry on "Interplanetary magnetic field", it's obvious that I've glossed over the fact that the solar wind, how do I put this, magnifies, is responsible for the sun's magnetic field being 100 times stronger at Earth's orbit, than if the wind did not exist.

I guess it's just hard for me to imagine how it works. But, apparently it does, and I should just shut up. But as most people know, I won't.

Also, looking at the moving GIF again, it looks as the though, from the shadows, that the gas jet was caused by that section rotating towards the sun.
Does anyone know how deep those pits get?
Has anyone counted all the pits? (I guess we could just count the jets)
Has anyone worked out the math on what effect the depth of the pits have on their thermal properties?
Is it possible to measure how much mass was lost from the one pit on July 29th, from the images?

Ok... I'll shut up now.

 

[OmCheeto]

Sad. A thousand silly ideas might yield one good one.
It used to be called "brainstorming", in the olden days.

Do people ever do that anymore? Or have egos gotten so huge, that even the thought of positing an incorrect notion, sends people scurrying, like frightened mice?

hmmm... This just came across my Facebook feed today. A very short interview with Freeman Dyson. One of the questions he answered, reminded me of this thread, and the spirit of PF.

http://scitation.aip.org/content/aip/magazine/physicstoday/news/10.1063/PT.5.3026 [physicstoday]
Jermey N. A. Matthews
12 August 2015
...
PT: Are you ever concerned that your contrarian view of climate science will become as much a part of your legacy as all the other contributions you’ve made to science? Or do you embrace that possibility?

DYSON: I do not care what my legacy will be. To me the most beautiful aspect of science is that it is a collaborative enterprise, with a multitude of people from all over the world taking part. In the long run, it does not matter who discovered what. We all share the joy of discovery even if we do not share the credit. I am happy to be skeptical about the prevailing dogma concerning climate change, whether or not it turns out that I am right. I can disagree vigorously with my colleagues and still remain friends.
...

--------------------
ps. My posts over the last two days should not be construed in any way that I am endorsing a loosening the rules against crackpottery. Thank you very much.

 

[jerromyjon]

My posts over the last two days should not be construed in any way that I am endorsing a loosening the rules against crackpottery.

There are plenty of less rigorous forums in which "crackpottery" runs rampant. I don't think any of us here at PF would enjoy that.

the solar wind, how do I put this, magnifies, is responsible for the sun's magnetic field being 100 times stronger at Earth's orbit, than if the wind did not exist.

Very interesting. Why have I never heard of this? Just when I think I have everything in perspective you throw me another curve ball.

 

[Dotini]

The song of Comet 67P — detected by the http://mashable.com/category/rosetta/ spacecraft last year — is actually caused by oscillations in the magnetic field surrounding the object, the European Space Agency (ESA) said in a blog post Wednesday.

http://mashable.com/2015/08/19/comet-song-rosetta/?utm_medium=feed&utm_source=feedburner&utm_campaign=Feed:+Mashablefrance+(Mashable!+Francais)
Rosetta's magnetometer started to detect the fluctuations when it got to Comet 67P in August 2014, ESA said. Until November, the spacecraft clocked about 3,000 instances of wave activity in the frequencies expected to make these sounds.

Radiation from the sun ionizes neutral particles spit out from the comet, and then those bits of material move perpendicular to the comet's induced magnetic field, ESA said. Scientists found that the current created from that movement is unstable, causing the oscillations that make the comet sing, the agency added.

http://www.ann-geophys.net/33/1031/2015/angeo-33-1031-2015.html
Abstract. We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low-activity state. Quasi-coherent, large-amplitude (δ B/B ~ 1), compressional magnetic field oscillations at ~ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied cometary interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pickup-ion-driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.

 

[Dotini]

"Abundant molecular oxygen in the coma suggests that primordial O2 was incorporated into the nucleus during the comet’s formation...Current Solar System formation models do not predict conditions that would allow this to occur."
http://www.nature.com/nature/journal/v526/n7575/full/nature15707.html'In looking at exo-planets, "the combination of O2 and methane has been taken as a sign that you might have life underneath," she said.

"On this comet we have both, but we don't have life. So having oxygen may not be a very good bio-signature."'
http://news.yahoo.com/discovery-oxygen-comet-big-surprise-181858811.html

 

[Dotini]

"Here we report observations of water ice on the surface of comet 67P/Churyumov–Gerasimenko, appearing and disappearing in a cyclic pattern that follows local illumination conditions, providing a source of localized activity. This water cycle appears to be an important process in the evolution of the comet, leading to cyclical modification of the relative abundance of water ice on its surface."

http://www.nature.com/nature/journal/v525/n7570/full/nature14869.html

 

[Dotini]

Various scenarios of radiolysis are discussed as the origin of molecular oxygen in the comet.
http://blogs.esa.int/rosetta/2015/10/28/first-detection-of-molecular-oxygen-at-a-comet/

High-resolution measurements allowed molecular oxygen (O2) to be distinguished from other species like sulphur (S) and methanol (CH3OH). The detection of the coma gases is stronger closer to the comet nucleus, as expected. The contribution to the detection from contamination from the spacecraft thruster firings during manoeuvres is very low. Data from A. Bieler et al. (2015)

The strong correlation of molecular oxygen abundance with water vapour indicates a shared origin and release mechanism from the nucleus. Data from A. Bieler et al. (2015)

The O2/H2O ratio does not vary significantly over the study period. Short-lived strong variations are attributed to the decrease of the O2 ratio for occasionally higher H2O abundances linked to the daily water-ice cycle. The overall consistent level implies that O2 is not produced today by solar wind or UV interaction with surface ices, otherwise it would rapidly decrease due to the comet's increased activity. Instead the O2 must have been incorporated into the comet's ices during its formation in the early Solar System, and is being released with the water vapour today. Data by A. Bieler et al. (2015)

------------------------

“Regardless of how it was made, the O2 was also somehow protected during the accretion stage of the comet: this must have happened gently to avoid the O2 being destroyed by further chemical reactions,” adds Kathrin.

 

[OmCheeto]

SciAm wouldn't lie to us, would they?

Historic Rosetta Mission to End with Crash into Comet
There were other options, but super close-up shots on descent will provide science bonanza
By Elizabeth Gibney and Nature magazine | November 4, 2015

A year since a probe called Philae made history by touching down on a comet, the team that pulled off the feat is plotting a different kind of landing. Next September, the European Space Agency will crash Philae’s mothership Rosetta into the icy dust ball, but as gently as possible.
...

 

[Imager]

The FAQ on the ESA website says 12 year mission. Although it doesn't look like the FAQ has been updated recently.

How long will the Rosetta spacecraft operate?
Rosetta’s planned lifetime is about 12 years. The nominal mission ends in December 2015, after the comet reaches its closest point to the Sun (in August 2015) and starts heading back towards the outer Solar System.
http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions

November 12, 2015, one year aniversary of Philae's landing, did anyone bake a cake?

 

[Imager]

Sadly, only a couple months remaining for Rosetta, but a big Cheer for the ESA! Job well done!

from Rueters:

The European spacecraft Rosetta will crash-land on the surface of the comet 67P/Churyumov-Gerasimenko and end its 12-year space odyssey on Sept. 30, France's National Centre for Space Studies (CNES) said on Thursday.

 

[1oldman2]

Sad to see the mission end, but what a way to go. Congratulations ESA!

 

[1oldman2]

End of the line today. http://blogs.esa.int/rosetta/2016/07/26/farewell-silent-philae/
Tomorrow, 27 July 2016 at 09:00 UTC / 11:00 CEST, the Electrical Support System Processor Unit
(ESS) on Rosetta will be switched off. The ESS is the interface used for communications between
Rosetta and the lander, Philae, which has remained silent since 9 July 2015.

 

[1oldman2]

It seems the final curtain call is coming up. From, http://www.planetary.org/blogs/emily-lakdawalla/2016/0726-rosetta-end-of-mission-plans.html
"Last week, ESA announced when and where Rosetta is going to touch down, bringing the
mission to an end: within the Ma'at region on the comet's head, at approximately 10:30 UTC
(12:30 CEST / 06:30 EDT / 03:30 PDT) on September 30. It took me a while to figure out its
position relative to the Philae landing locations -- comet geography is challenging! -- but I think this is how they all relate to each other"

 

[Borg]

Philae lander has finally been found.

Philae is seen wedged against a large over-hang. Its 1m-wide box shape and legs are unmistakable, however.
Rosetta had previously surveyed this location - dubbed Abydos - without success.
The difference now is a closer-in perspective and a change in the seasons on the comet, which means the hiding place has become properly illuminated.

Laying on its side with one leg sticking up:

 

[Jonathan Scott]

From information on the ESA site, the top right picture is an earlier wider angle image of the comet's "head" with a red dot to show the approximate location of Philae.

 

[1oldman2]

Micro-gravity landings can be rough!
http://www.space.com/27767-philae-comet-landing-nearly-failed-infographic.html

The action took place 317 million miles (510 million kilometers) from Earth
and 14 miles (22.5 km) from the comet, Rosetta released the lander. Philae
fell towards the comet for seven hours.

Philae hit the surface at 3.3 feet per second (1 meter per second). Harpoons
and a rocket meant to secure the probe to the comet, failed to fire.

In its first bounce, Philae traveled about 0.6 miles (1 km) up and an equal
distance across the comet. Philae ascended with a speed of 15 inches (38
centimeters) per second. Escape velocity from the comet is 19.7 inches (50
cm) per second.

After a second bounce lasting about seven minutes, Philae finally came to
rest on the surface.

 

[OmCheeto]

...

Philae hit the surface at 3.3 feet per second (1 meter per second).

Those speeds didn't really mean anything to me, so I googled them.
They are about 50% slower than an average human's walking speed.

And it made me lol when thinking about walking into a wall, and bouncing back 1/2 a mile, or 1 km.

Exophysics* is funny.
At least, for me, anyways

*Yah, I know... But you know what I mean.

 

[1oldman2]

http://www.planetary.org/blogs/emily-lakdawalla/2016/09091029-rosetta-end-of-mission-update.html

The European Space Agency posted several articles this morning about the plans for the end of the Rosetta mission
scheduled for September 30, just three weeks from now. On September 29, a rocket burn will essentially cancel out
Rosetta's orbital motion around the comet, initiating a free fall from an altitude of 20 kilometers. The spacecraft
will impact the comet at a speed of about 90 centimeters per second at 04:20 PDT / 07:20 EDT / 11:20 UTC / 13:20 CEST, give or take 20 minutes. Upon impact, the spacecraft will automatically "passivate," cutting the radio connection to Earth and ending the mission forever.

http://www.esa.int/Our_Activities/S...setta_s_descent_towards_region_of_active_pits
9 September 2016
Squeezing out unique scientific observations until the very end, Rosetta’s
thrilling mission will culminate with a descent on 30 September towards a
region of active pits on the comet’s ‘head’.

The region, known as Ma’at, lies on the smaller of the two lobes of Comet 67P
/Churyumov-Gerasimenko. It is home to several active pits more than 100 m in
diameter and 50-60 m in depth - where a number of the comet’s dust jets originate.

 

[1oldman2]

Here are links to the live stream, I'm hoping its more than just talking heads, would be great to get video of the approach.
Rosetta - 3:15am to 5:00am EDT 9/30
http://www.ustream.tv/nasajpl2
http://www.nasa.gov/multimedia/nasatv/index.html#public