Rosetta's comet mission discussion thread

In summary: The landing is expected to occur on Wednesday, November 12th at 12:35am PST.The Rosetta mission is a European Space Agency (ESA) mission with some US instruments on board. It carries a lander that will descend onto the comet surface, take pictures at the surface, and study the comet. The lander's feet will have to drill into the comet material in order to be anchored firmly, because the gravity is very slight.
  • #141
Get out your 3D glasses. From the APOD. Today's picture is 67P in 3D.

Astronomy news on
  • #142
  • #143
The above image is from

"We have found extremely high-temperature minerals coming from the coldest place."
Early analysis revealed minerals that included magnesium iron silicate, known as olivine, or, in its gem-quality variety, peridot; magnesium aluminum oxide, also called spinel; and titanium nitride. Brownlee said all these form at temperatures of at least 2,000 degrees Fahrenheit.
Last edited:
  • Like
Likes marcus
  • #144
So much slick surface area makes it look like a gold nugget from a river bed oo)

  • #145
Unfortunately, the image posted is not yet an official true color image. The official one will be released Dec 15, supposedly.

It seems the instrument makers have the rights to all their data for the first 6 months. ... black.html
  • #147
I would have thought that the make-up of gases near the surface would be very strongly affected by their volatility, in that even slightly lighter molecules would have greater velocity for the same energy and hence would be likely to escape more rapidly than heavier ones, altering the concentrations of what was left. On that basis, one would expect normal water molecules to escape slightly more easily than heavy ones, potentially increasing the deuterium ratio in what was left later on the warming side of the orbit.

So unless I've missed something, I don't see any good reason to believe that the deuterium ratio near the surface is likely to give a fair indication of the deuterium ratio within the body of the ice. The latter would be much more interesting and convincing.
  • Like
Likes Yashbhatt
  • #148
The escape velocity is of the order of 1 m/s - well below the thermal motion of molecules (even at 3 K). Only chemical bonds keep them on the asteroid, so binding energy is relevant. Is that different for heavy water? It has a slightly higher melting and boiling point at standard pressure, but that difference is small.
  • Like
Likes Yashbhatt
  • #149
mfb said:
The escape velocity is of the order of 1 m/s - well below the thermal motion of molecules (even at 3 K). Only chemical bonds keep them on the asteroid, so binding energy is relevant. Is that different for heavy water? It has a slightly higher melting and boiling point at standard pressure, but that difference is small.

Good point - this is not like an atmosphere situation.

The Wikipedia entry on deuterium has this to say (unfortunately with no good references as far as I can see):
Wikipedia said:
However, different astronomical bodies are found to have different ratios of deuterium to hydrogen-1, and this is thought to be as a result of natural isotope separation processes that occur from solar heating of ices in comets. Like the water-cycle in Earth's weather, such heating processes may enrich deuterium with respect to protium.
  • #150
There are no large water ice patches detected on 67P. spacecraft -returns-first-science-results
The provenance of water and organic compounds on the Earth and other terrestrial planets has been discussed for a long time without reaching a consensus. One of the best means to distinguish between different scenarios is by determining the D/H ratios in the reservoirs for comets and the Earth’s oceans. Here we report the direct in situ measurement of the D/H ratio in the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA mass spectrometer aboard ESA’s Rosetta spacecraft , which is found to be (5.3 ± 0.7) × 10−4, that is, ~3 times the terrestrial value. Previous cometary measurements and our new finding suggest a wide range of D/H ratios in the water within Jupiter family objects and preclude the idea that this reservoir is solely composed of Earth ocean-like water.

A NY Times science writer, citing a few papers, helpfully suggests Earth may have been wet from (almost) the beginning.'s-water.html?_r=0
Last edited:
  • #151

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."
  • #152
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.
  • Like
Likes Yashbhatt
  • #153
Fine structure in the comet's 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.
  • Like
Likes Borg and OmCheeto
  • #154
Apparently the ESA is aware that I'm antsy about the Dawn/Ceres probe, so they provided me with some alternative entertainment today:

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. :redface:
  • Like
Likes Yashbhatt
  • #156
Links to newly published reports:
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.
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.
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.
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.
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.
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.
Last edited:
  • #157
Interesting snippets from a NY Times article on Rosetta.

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.”

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.”
  • #158
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

Download Active_pit.jpg (12.59 MB)

Active Pit
  • #159
BBC reports on Goosebumps and Dinosaur Eggs.
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."
  • Like
Likes OmCheeto
  • #160
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!
  • Like
Likes Dotini
  • #161
It's party time for Rosetta and 67P. See the gorgeous photos of cometary jets, glows, streaks and blobs around the active nucleus.

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
  • Like
Likes mfb, OmCheeto, DennisN and 1 other person
  • #162


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.
  • Like
Likes enorbet, harrylin and mfb
  • #163
OmCheeto said:

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!
  • Like
Likes enorbet and OmCheeto
  • #164
Drakkith said:
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.
  • #165
OmCheeto said:
Ah! Hahahaha!
They must have hired Kip Thorne.

"C'mon TARS!"

*Epic music plays*

"C'mon TARS!"

Best docking scene ever!
  • Like
Likes OmCheeto
  • #166
They fixed the date in the article.

Great news!
  • Like
Likes OmCheeto
  • #167
  • #168
Drakkith said:
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!:-p
  • Like
Likes OmCheeto
  • #169
Garth said:
Come on you lot - this is Europe not USA! ESA invented time travel - well we have Dr Who to thank for that!:-p

Huh... no wonder the spacecraft looked vaguely like a phone booth...
  • Like
Likes harrylin
  • #170
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. :)
  • #171
"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.

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

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."
Last edited:
  • Like
Likes rfpn1968 and OmCheeto
  • #172
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? :biggrin:
  • Like
Likes marcus
  • #174

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).

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.
  • Like
Likes OmCheeto
  • #175
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!


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. :redface:
But science should be fun. :oldbiggrin:[URL='']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!

  • Like
Likes marcus, Dotini, Yashbhatt and 1 other person

Similar threads

  • Aerospace Engineering
  • General Discussion