ESA’s Rosetta spacecraft has made the first in situ detection of oxygen molecules outgassing from a comet, a surprising observation that suggests they were incorporated into the comet during its formation.
Rosetta has been studying Comet 67P/Churyumov–Gerasimenko for over a year and has detected an abundance of different gases pouring from its nucleus. Water vapour, carbon monoxide and carbon dioxide are the most prolific, with a rich array of other nitrogen-, sulphur- and carbon-bearing species, and even ‘noble gases’ also recorded.
Oxygen is the third most abundant element in the Universe, but the simplest molecular version of the gas, O2, has proven surprisingly hard to track down, even in star-forming clouds, because it is highly reactive and readily breaks apart to bind with other atoms and molecules.
For example, oxygen atoms can combine with hydrogen atoms on cold dust grains to form water, or a free oxygen split from O2 by ultraviolet radiation can recombine with an O2 molecule to form ozone (O3).
Despite its detection on the icy moons of Jupiter and Saturn, O2 had been missing in the inventory of volatile species associated with comets until now. ...
One year since Philae made its historic landing on a comet, mission teams remain hopeful for renewed contact with the lander, while also looking ahead to next year’s grand finale: making a controlled impact of the Rosetta orbiter on the comet.
Rosetta arrived at Comet 67P/Churyumov–Gerasimenko on 6 August 2014, and after an initial survey and selection of a landing site, Philae was delivered to the surface on 12 November.
After touching down in the Agilkia region as planned, Philae did not secure itself to the comet, and it bounced to a new location in Abydos. Its flight across the surface is depicted in a new animation, using data collected by Rosetta and Philae to reconstruct the lander’s rotation and attitude. ...
Meanwhile, Rosetta continues to return unique data with its suite of instruments, analysing changes to the comet’s surface, atmosphere and plasma environment in incredible detail.
“We recently celebrated our first year at the comet and we are looking forward to the scientific discoveries the next year will bring,” says Matt Taylor, ESA’s Rosetta project scientist.
“Next year, we plan to do another far excursion, this time through the comet’s tail and out to 2000 km. To complement that, we hope to make some very close flybys towards the end of the mission, as we prepare to put the orbiter down on the comet.”
The plan is to end the mission with a ‘controlled impact’ of Rosetta on the surface. This idea emerged around six months ago, when an extension of operations from December 2015 to September 2016 was announced. ...
MPS: Colors of a Comet
Posted: Fri Nov 13, 2015 12:02 am
by bystander
Colors of a Comet
Max Planck Institute for Solar System Research | 2015 Nov 12
OSIRIS, the scientific imaging system of ESA’s Rosetta mission to comet 67P/Churyumov-Gerasimenko, shows a surface with subtle, but significant color variations.
[img3="Depending on the viewing geometry between Rosetta, the comet, and the Sun, different amounts of light reach Rosetta. When all three objects are nearly aligned (small phase angle = 0) the comet appears especially bright. With increasing deviation from this geometry (larger phase angle) the comet looks darker and darker. Credit: ESA/Rosetta/MPS for OSIRIS Team
MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA"]http://www.mps.mpg.de/4274808/standard_sans_both.jpg[/img3][hr][/hr]
To the naked eye comet 67P/Churyumov-Gersimenko, destination and by now longtime companion of ESA’s Rosetta spacecraft, is rather unremarkably colored: black as a piece of coal all over. However, with the help of OSIRIS, Rosetta’s onboard scientific imaging system, scientists can make visible subtle, yet comprehensive differences in surface reflectivity. The newest analysis, presented today at the annual meeting of the Division of Planetary Sciences (DPS) of the American Astronomical Society (AAS) in National Harbor (Maryland, USA), thus paints a much more diverse picture of 67P. Not only is the neck region between the comet’s two lobes apparently richer in frozen water than surrounding areas. OSIRIS data also show the body to be covered by a porous layer of fine grains and suggest the presence of frozen sulfur dioxide.
Cometary nuclei and other primitive bodies populating the outer regions of the Solar System commonly reflect red light slightly more effectively than light of other wavelengths. The effect is believed to be one of the results of space weathering. Images obtained during and shortly after Rosetta’s approach phase in July and August of last year with different color filters have now been extensively analyzed and confirm this effect also for 67P.
“Like most cometary nuclei, 67P’s reflectivity spectrum is rather smooth and featureless”, says OSIRIS team member Sonia Fornasier from the LESIA-Observatoire de Paris/University of Paris Diderot in France, who presented the new results today. Characteristic fingerprints of certain chemical compounds, so-called absorption bands, cannot be found in the wavelengths sampled by OSIRIS – except for a feature centered around 290 nanometers. “This feature lies in the ultraviolet range where instrument calibrations tend to be tricky and need still to be confirmed”, says Fornasier. If the feature proves to be real, it is compatible with the presence of frozen sulfur dioxide on the comet’s surface”, she adds. The gaseous products of sulfur dioxide have been detected in several cometary comae including 67P.
Many of the OSIRIS images analyzed in the new study offer a high spatial resolution of up to almost one meter per pixel. Rosetta can therefore observe differences in surface reflectivity in far greater detail than previous cometary missions. “Using the reflectivity in different wavelengths as a criterion, we were able to identify three different groups of terrains on 67P”, Fornasier sums up the extensive analyses. All three terrains occur on both the comet’s lobes, but are often clustered in certain regions. These sometimes, but not always roughly coincide with the 25 different morphological regions so far identified on the comet’s surface. ...
Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko
from the OSIRIS instrument onboard the ROSETTA spacecraft - S. Fornasier et al
There are no large caverns inside Comet 67P/Churyumov-Gerasimenko. ESA's Rosetta mission has made measurements that clearly demonstrate this, solving a long-standing mystery.
Comets are the icy remnants left over from the formation of the planets 4.6 billion years ago. A total of eight comets have now been visited by spacecraft and, thanks to these missions, we have built up a picture of the basic properties of these cosmic time capsules. While some questions have been answered, others have been raised.
Comets are known to be a mixture of dust and ice, and if fully compact, they would be heavier than water. However, previous measurements have shown that some of them have extremely low densities, much lower than that of water ice. The low density implies that comets must be highly porous.
But is the porosity because of huge empty caves in the comet's interior or it is a more homogeneous low-density structure? ...
A homogeneous nucleus for comet 67P/Churyumov–Gerasimenko from its gravity field - M. Pätzold et al
Silent since its last call to mothership Rosetta seven months ago, the Philae lander is facing conditions on Comet 67P/Churyumov-Gerasimenko from which it is unlikely to recover.
Rosetta, which continues its scientific investigations at the comet until September before its own comet-landing finale, has in recent months been balancing science observations with flying dedicated trajectories optimised to listen out for Philae. But the lander has remained silent since 9 July 2015.
"The chances for Philae to contact our team at our lander control centre are unfortunately getting close to zero," says Stephan Ulamec, Philae project manager at the German Aerospace Center, DLR. "We are not sending commands any more and it would be very surprising if we were to receive a signal again." ...
Rosetta's comet has been seen changing colour and brightness in front of the ESA orbiter's eyes, as the Sun's heat strips away the older surface to reveal fresher material.
[img3="The colour-changing comet. Credits: Spacecraft: ESA/ATG medialab; Data: ESA/Rosetta/VIRTIS/INAF-IAPS/OBS DE PARIS-LESIA/DLR; G. Filacchione et al.(2016)"]http://sci.esa.int/science-e-media/img/ ... 07_625.jpg[/img3][hr][/hr]
Rosetta's Visible and InfraRed Thermal Imaging Spectrometer, VIRTIS, began to detect these changes in the sunlit parts of Comet 67P/Churyumov-Gerasimenko – mostly the northern hemisphere and equatorial regions – in the months immediately following the spacecraft's arrival in August 2014.
A new paper, published in the journal Icarus, reports on the early findings of this study, up to November 2014, during which time Rosetta was operating between 100 km to within 10 km of the comet nucleus. At the same time, the comet itself moved along its orbit closer to the Sun, from about 542 million km to 438 million km.
VIRTIS monitored the changes in light reflected from the surface over a wide range of visible and infrared wavelengths, as an indicator of subtle changes in the composition of the comet's outermost layer.
When it arrived, Rosetta found an extremely dark body, reflecting about 6% of the visible light falling on it. This is because the majority of the surface is covered with a layer of dark, dry dust made out of a mixture of minerals and organics.
Some surfaces are slightly brighter, some slightly darker, indicating differences in composition. Most of the surface is slightly reddened by organic-rich material, while the occasional ice-rich material shows up as somewhat bluer. ...
The global surface composition of 67P/CG nucleus by Rosetta/VIRTIS. I) Prelanding mission phase - Gianrico Filacchione et al
Studying comets provides clues to the early history of our solar system
[img3="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)"]http://www.swri.org/press/2016/images/comet-67.png[/img3][hr][/hr]
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. ... “If the building blocks 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. ...
The Presence of Clathrates in Comet 67P/Churyumov-Gerasimenko - Adrienn Luspay-Kuti et al
Ingredients crucial for the origin of life on Earth, including the simple amino acid glycine and phosphorus, key components of DNA and cell membranes, have been discovered at Comet 67P/Churyumov-Gerasimenko.
The possibility that water and organic molecules were brought to the early Earth through impacts of objects like asteroids and comets have long been the subject of important debate.
While Rosetta’s ROSINA instrument already showed a significant difference in composition between Comet 67P/C-G’s water and that of Earth, the same instrument has now shown that even if comets did not play as big a role in delivering water as once thought, they certainly had the potential to deliver life’s ingredients.
While more than 140 different molecules have already been identified in the interstellar medium, amino acids could not be traced. However, hints of the amino acid glycine, a biologically important organic compound commonly found in proteins, were found during NASA’s Stardust mission that flew by Comet Wild 2 in 2004, but terrestrial contamination of the collected dust samples during the analysis could not be ruled out. Now, for the first time, repeated detections at a comet have been confirmed by Rosetta in Comet 67P/C-G’s fuzzy atmosphere, or coma. ...
Prebiotic chemicals—amino acid and phosphorus—in the coma of comet 67P/Churyumov-Gerasimenko - Kathrin Altwegg et al
Rosetta is set to complete its mission in a controlled descent to the surface of its comet on 30 September.
The mission is coming to an end as a result of the spacecraft’s ever-increasing distance from the Sun and Earth. It is heading out towards the orbit of Jupiter, resulting in significantly reduced solar power to operate the craft and its instruments, and a reduction in bandwidth available to downlink scientific data.
Combined with an ageing spacecraft and payload that have endured the harsh environment of space for over 12 years – not least two years close to a dusty comet – this means that Rosetta is reaching the end of its natural life. ...
Instead of risking a much longer hibernation that is unlikely to be survivable, and after consultation with Rosetta’s science team in 2014, it was decided that Rosetta would follow its lander Philae down onto the comet.
The final hours of descent will enable Rosetta to make many once-in-a-lifetime measurements, including very-high-resolution imaging, boosting Rosetta’s science return with precious close-up data achievable only through such a unique conclusion.
Communications will cease, however, once the orbiter reaches the surface, and its operations will then end. ...
[img3="Profile of a Primordial Comet - Credit: Centre: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0; Insets: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; Fornasier et al. (2015); ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S; Langevin et al. (2016)"]http://sci.esa.int/science-e-media/img/ ... ic_625.jpg[/img3][hr][/hr]
Detailed analysis of data collected by Rosetta show that comets are the ancient leftovers of early Solar System formation, and not younger fragments resulting from subsequent collisions between other, larger bodies.
Understanding how and when objects like Comet 67P/Churyumov-Gerasimenko took shape is of utmost importance in determining how exactly they can be used to interpret the formation and early evolution of our Solar System. ...
If comets are primordial, then they could help reveal the properties of the solar nebula from which the Sun, planets and small bodies condensed 4.6 billion years ago, and the processes that transformed our planetary system into the architecture we see today.
The alternative hypothesis is that they are younger fragments resulting from collisions between older 'parent' bodies such as icy trans-Neptunian objects (TNOs). They would then provide insight into the interior of such larger bodies, the collisions that disrupted them, and the process of building new bodies from the remains of older ones. ...
The Primordial Nucleus of Comet 67P/Churyumov-Gerasimenko - B. J. R. Davidsson et al
In unprecedented observations made earlier this year, Rosetta unexpectedly captured a dramatic comet outburst that may have been triggered by a landslide.
Nine of Rosetta’s instruments, including its cameras, dust collectors, and gas and plasma analysers, were monitoring the comet from about 35 km in a coordinated planned sequence when the outburst happened on 19 February.
“Over the last year, Rosetta has shown that although activity can be prolonged, when it comes to outbursts, the timing is highly unpredictable, so catching an event like this was pure luck,” says Matt Taylor, ESA’s Rosetta project scientist.
“By happy coincidence, we were pointing the majority of instruments at the comet at this time, and having these simultaneous measurements provides us with the most complete set of data on an outburst ever collected.” ...
The 19 Feb. 2016 Outburst of Comet 67P/CG: An ESA Rosetta Multi-Instrument Study - E. Grün et al
Less than a month before the end of the mission, Rosetta's high-resolution camera has revealed the Philae lander wedged into a dark crack on Comet 67P/Churyumov-Gerasimenko.
The images were taken on 2 September by the OSIRIS narrow-angle camera as the orbiter came within 2.7 km of the surface and clearly show the main body of the lander, along with two of its three legs.
The images also provide proof of Philae's orientation, making it clear why establishing communications was so difficult following its landing on 12 November 2014. ...
ESA: Rosetta's Descent Towards Region of Active Pits
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.
The walls of the pits also exhibit intriguing metre-sized lumpy structures called ‘goose bumps,’ which scientists believe could be the signatures of early ‘cometesimals’ that assembled to create the comet in the early phases of solar system formation.
Rosetta will get its closest look yet at these fascinating structures on 30 September: the spacecraft will target a point adjacent to a 130 m-wide, well-defined pit that the mission team has informally named Deir el-Medina, after a structure with a similar appearance in an ancient Egyptian town of the same name. ...
Since 9 August, Rosetta has been flying elliptical orbits that bring it progressively closer to the comet – on its closest flyby, it may come within 1 km of the surface, closer than ever before. ...
The final flyover will be complete on 24 September. Then a short series of manoeuvres needed to line Rosetta up with the target impact site will be executed over the following days as it transfers from flying elliptical orbits around the comet onto a trajectory that will eventually take it to the comet's surface on 30 September.
The collision manoeuvre will take place in the evening of 29 September, initiating the descent from an altitude of about 20 km. Rosetta will essentially free-fall slowly towards the comet in order to maximise the number of scientific measurements that can be collected and returned to Earth before its impact. ...
And Phil continued to pray to the Blue Fairy there before him, she who smiled softly, forever...she who welcomed forever. Eventually the floodlights dimmed and died, but Phil could still see her palely by day, and he still addressed her, in hope. He prayed until all the sea anemones had shriveled and died. He prayed as the ocean froze and the ice encased the caged amphibicopter, and the Blue Fairy too, locking them together where he could still make her out - a blue ghost in ice - always there, always smiling, always awaiting him. Eventually he never moved at all, but his CIVA camera always stayed open, staring ahead forever all through the darkness of each night, and the next day...and the next day...
[img3="Comet outbursts. Credit: OSIRIS: ESA/Rosetta/MPS for OSIRIS Team
MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA;
NavCam: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0"]http://sci.esa.int/science-e-media/img/ ... rs_625.jpg[/img3][hr][/hr]
Brief but powerful outbursts seen from Comet 67P/Churyumov–Gerasimenko during its most active period last year have been traced back to their origins on the surface.
In the three months centred around the comet's closest approach to the Sun, on 13 August 2015, Rosetta's cameras captured 34 outbursts.
These violent events were over and above regular jets and flows of material seen streaming from the comet's nucleus. The latter switch on and off with clockwork repeatability from one comet rotation to the next, synchronised with the rise and fall of the Sun's illumination.
By contrast, outbursts are much brighter than the usual jets – sudden, brief, high-speed releases of dust. They are typically seen only in a single image, indicating that they have a lifetime shorter than interval between images – typically 5–30 minutes.
A typical outburst is thought to release 60–260 tonnes of material in those few minutes. ...
Summer Fireworks on Comet 67P - J.-B. Vincent et al
So you link to articles that are two years old and older to prove asterisk is yesterday ???
Uptod8t wrote: Of course this post will be deleted as Asterisk's vainglorious moderators continue their ancient tradition of deleting information which makes ancient amateur science fans wonder why they spent so much time reading and believing in error. Sad really, rather you should be happy at new knowledge.
Your posts get deleted because you are a known troll and have been banned many times in many guises, yet you keep coming back to a forum you profess to hate. Just go away and stay away, please!
Re: ESA: Rosetta: Comet 67P/Churyumov–Gerasimenko
Posted: Mon Sep 26, 2016 8:07 pm
by geckzilla
bystander wrote:Your posts get deleted because you are a known troll and have been banned many times in many guises, yet you keep coming back to a forum you profess to hate. Just go away and stay away, please!
That's because they're actually a bully who can't handle it when they're either wrong or someone disagrees with them regardless of whether they're right or wrong. They just gotta come back and try to force us to accept their rightness. Too bad for them we have moderation tools, so the effect is completely lost here. Must be infuriating.
Re: ESA: Rosetta: Comet 67P/Churyumov–Gerasimenko
Posted: Mon Sep 26, 2016 10:33 pm
by Uptod8t
bystander wrote:
Uptod8t wrote: Asterisk is SO yesterday!
So you link to articles that are two years old and older to prove asterisk is yesterday ???
Uptod8t wrote: Of course this post will be deleted as Asterisk's vainglorious moderators continue their ancient tradition of deleting information which makes ancient amateur science fans wonder why they spent so much time reading and believing in error. Sad really, rather you should be happy at new knowledge.
Your posts get deleted because you are a known troll and have been banned many times in many guises, yet you keep coming back to a forum you profess to hate. Just go away and stay away, please!
Asterisk's yesterday includes the three year old NASA post, "Comets are the primitive building blocks of the Solar System and the likely source of much of Earth’s water ..." My urls included a more recent NASA link showing comets are NOT the source of earth's water, and another non-amateurish scientifici link that shows earth's water has been around as long as the planet. Except for Neufer, your regular participants' and moderators' archaic and brittle grey matter DEMANDS: "NO NEW INFORMATION!!!!!"
As far as being a 'known troll' goes, in the early days of internet forums 'trolls' were thought to be annoying mindless things, but they have proven to be necessary prods stimulating archaic dustithinkers to rejuvenate and make flexible again their atropyhying thought processes. So it is now an honour to be called a Troll, and I thank you. Soon Old Timers shall pass away, and hopefully New TImers will refresh American and British science so they can catch up.
You, however, will never catch up as long as "Rocky Planet" remains your mantra even though new discoveries which you forbid yourself to believe prove that immense quantitities of water inside the earth demand a reclassification of 'rocky planet' to 'water planet.' And of course this brings proof that the biblical Genesis account of earth's formation is correct .. dry land rising up out of the planet wide oceans .. the waterball becoming a planet.
So then, if I go away, who is to remind you of your need to correct your personal and scientific failings? And if you are not reminded, you will never recover your intellect from its moribund condition. I am her to serve.
Re: ESA: Rosetta: Comet 67P/Churyumov–Gerasimenko
Posted: Mon Sep 26, 2016 10:40 pm
by Uptod8t
geckzilla wrote:
bystander wrote:Your posts get deleted because you are a known troll and have been banned many times in many guises, yet you keep coming back to a forum you profess to hate. Just go away and stay away, please!
That's because they're actually a bully who can't handle it when they're either wrong or someone disagrees with them regardless of whether they're right or wrong. They just gotta come back and try to force us to accept their rightness. Too bad for them we have moderation tools, so the effect is completely lost here. Must be infuriating.
Who has professed to hate this forum? Nasty attitude that. Much better to be constructive, as I repeatedly do, believing the Asterisk foundation is worth building on rather than tearing down, which is the attitude of the regulars and moderators here .. all but Neufer that is, that TRUE scientist AND gentleman.
If you, Geck, call what I include here "force (full) it is because your firmest convictions have been made unstable by new scientific discoveries you are aware of but choose to ignore .. to your own mental incapacitation.
Re: ESA: Rosetta: Comet 67P/Churyumov–Gerasimenko
Posted: Tue Sep 27, 2016 12:13 am
by geckzilla
Uptod8t wrote:
geckzilla wrote:
bystander wrote:Your posts get deleted because you are a known troll and have been banned many times in many guises, yet you keep coming back to a forum you profess to hate. Just go away and stay away, please!
That's because they're actually a bully who can't handle it when they're either wrong or someone disagrees with them regardless of whether they're right or wrong. They just gotta come back and try to force us to accept their rightness. Too bad for them we have moderation tools, so the effect is completely lost here. Must be infuriating.
Who has professed to hate this forum? Nasty attitude that. Much better to be constructive, as I repeatedly do, believing the Asterisk foundation is worth building on rather than tearing down, which is the attitude of the regulars and moderators here .. all but Neufer that is, that TRUE scientist AND gentleman.
If you, Geck, call what I include here "force (full) it is because your firmest convictions have been made unstable by new scientific discoveries you are aware of but choose to ignore .. to your own mental incapacitation.
I've been at this for a lot longer than you have. We used to have practically nothing but pseudoscience debates here. It was as open as it could be and no one learned anything other than the fact that it is, as they say, many orders of magnitude easier to come up with manure than it is to refute it. The only way to even the playing field is with moderation. I like new scientific discoveries, but I don't like you, and you are terrible at delivering such news to us, because you're a jerk about it and all you try to do is prove some kind of point we moved past a long time ago because you're wrong. So, please, get out. I'm sure Art enjoys the rump osculation you are giving him, but really, we're fine without you.
NASA TV to Provide Live Coverage of Rosetta Touchdown
NASA Television and the agency’s website will air the conclusion of ESA’s (European Space Agency’s) Rosetta mission from 6:15 to 8 a.m. EDT Friday, Sept. 30, with NASA commentary, interviews and analysis of the successful mission. The Rosetta mission will end with the controlled decent of the spacecraft onto the surface of comet 67P/Churyumov-Gerasimenko at around 7:20 a.m. ...
Farewell Rosetta: ESA Mission to End on Comet Surface NASA | JPL-Caltech | Rosetta | 2016 Sep 29
[img3="This view shows Comet 67P/Churyumov–Gerasimenko as seen by the OSIRIS wide-angle camera on ESA's Rosetta spacecraft on September 29, 2016, when Rosetta was at an altitude of 14 miles (23 kilometers). Credits: ESA/Rosetta/MPS for OSIRIS Team
MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA"]http://www.jpl.nasa.gov/images/rosetta/ ... 160929.jpg[/img3]
[img3="The OSIRIS narrow-angle camera aboard the European Space Agency's Rosetta spacecraft captured this image of comet 67P/Churyumov-Gerasimenko on September 30, 2016, from an altitude of about 10 miles (16 km) above the surface during the spacecraft's controlled descent. The image scale is about 12 inches (30 cm) per pixel and the image itself measures about 2,000 feet (614 meters) across. Credits: ESA/Rosetta/MPS for OSIRIS Team
MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA"]http://rosetta.jpl.nasa.gov/sites/defau ... _16_km.jpg[/img3]
When the Rosetta spacecraft successfully touched down on comet 67P/Churyumov-Gerasimenko on September 30, 2016, the news was shared globally via Twitter in dozens of languages. Citizens the world over were engaged by the astronomical achievement, and now the European Space Agency and NASA are eager to learn as much as possible about the critically important celestial body of ice.
Using statistical analysis and scientific computing, astronomers at Western University have charted a path that most likely pinpoints the very origins of comet 67P/Churyumov-Gerasimenko, which is vital information in discovering what kind of material it is made from and just how long it has been present in our solar system. ...
Galiazzo and Wiegert think that 67P/Churyumov-Gerasimenko is relatively new to the inner parts of our solar system, having only arrived about 10,000 years ago. Prior to this time, the comet would have been inactive in frozen storage far from the Sun.
Previous studies show that similar comets — known as Jupiter Family comets — historically stay in the inner parts of our solar system for 12,000 years, therefore recognizing comet 67P/Churyumov-Gerasimenko as a member of the Jupiter Family makes sense. ...
PSI: Avalanches, Not Internal Pressure, Cause Comet Nuclei Outbursts
Outbursts of comet nuclei are likely caused by surface avalanches rather than geyser-like eruptions from within, research by Planetary Science Institute’s Jordan Steckloff shows.
Rapid asymmetric brightening events of comets have been observed for decades, and have long been thought to be the result of some sort of eruption of materials from deep within the interior of a comet, said Steckloff, a PSI Associate Research Scientist. ...
High-resolution images from Rosetta observations of 67P/Churyumov-Gerasimenko show outbursts that resemble plumes of material from geysers on Earth.
“However, there is a major problem with this model. There is no internal heat source on comets to power geyser-like eruptions,” Steckloff said. “Instead, these outburst plumes are the natural result of avalanches.”
The surfaces of comets have regions at the base of slopes and cliffs that are rich in icy materials, and are actively sublimating, with ice turning directly into gas. As this gas leaves the surface of the comet, it produced a weak breeze, Steckloff said. When granular materials on comets slide downslope or over a cliff, they enter this sublimation breeze and are blown into a tightly collimated plume of material that leaves the surface of the nucleus.
This model is consistent with data collected by the Rosetta spacecraft, and provides a physical mechanism that allows these outbursts to be studied to determine where on the surface they came from and how much material avalanched downslope. ...
