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  • richardmitnick 7:29 am on September 13, 2017 Permalink | Reply
    Tags: , , , , , Does organic material in comets predate our solar system?, , ESA Rosetta   

    From EarthSky: “Does organic material in comets predate our solar system?” 

    1

    EarthSky

    September 13, 2017
    Deborah Byrd

    “If cometary organic molecules were indeed produced in interstellar space—and if they played a role in the emergence of life on our planet—might they not also have seeded life on many other planets of our galaxy?”

    1
    Comet 67P/Churyumov-Gerasimenko as seen by ESA’s Rosetta spacecraft.

    On September 4, 2017, researchers in Paris announced the results of their study of the organic compounds – combinations of carbon, hydrogen, nitrogen, and oxygen – in comet 67P Churyumov-Gerasimenko. This is the comet studied up-close and in detail by ESA’s Rosetta spacecraft for two years, beginning in August 2014.

    ESA/Rosetta spacecraft

    The sorts of organic molecules found in this comet and others have long been proposed by scientists as possible building blocks for life on Earth. Published in late August in the peer-reviewed journal Monthly Notices of the Royal Astronomical Society, the French researchers advance the theory that this organic matter has its origin in interstellar space and predates the birth of our solar system.

    The Rosetta mission found a large amount of organic material in the nucleus of the comet, which some people simply 67P and others call Chury for Klim Ivanovich Churyumov, one of its discovers. The Rosetta mission found that organic matter made up 40% (by mass) of the nucleus of the comet. According to researchers Jean-Loup Bertaux and Rosine Lallement, not only were the organic molecules were produced in interstellar space, well before the formation of the solar system, but also other astronomers are already very familiar with the source of this matter. Their statement explained:

    “For 70 years, scientists have known that analysis of stellar spectra indicates unknown absorptions, throughout interstellar space, at specific wavelengths called the diffuse interstellar bands (DIBs). DIBs are attributed to complex organic molecules that American astrophysicist Theodore Snow believes may constitute the largest known reservoir of organic matter in the universe.

    This interstellar organic material is usually found in the same proportions. However, very dense clouds of matter like presolar nebulae are exceptions. In the middle of these nebulae, where matter is even denser, DIB absorptions plateau or even drop. This is because the organic molecules responsible for DIBs clump together there. The clumped matter absorbs less radiation than when it floated freely in space.

    Such primitive nebulae end up contracting to form a solar system like our own, with planets . . . and comets. The Rosetta mission taught us that comet nuclei form by gentle accretion of grains progressively greater in size. First, small particles stick together to form larger grains. These in turn combine to form still larger chunks, and so on, until we have a comet nucleus a few kilometers wide.

    Thus, the organic molecules that formerly populated the primitive nebulae—and that are responsible for DIBs—were probably not destroyed, but instead incorporated into the grains making up cometary nuclei. And there they have remained for 4.6 billion years. A sample-return mission would allow laboratory analysis of cometary organic material and finally reveal the identity of the mysterious interstellar matter underlying observed patterns in stellar spectra.

    If cometary organic molecules were indeed produced in interstellar space—and if they played a role in the emergence of life on our planet, as scientists believe today—might they not also have seeded life on many other planets of our galaxy?”

    Bottom line: French researchers advance the theory that the organic matter found in comets – possible building blocks for earthly life – has its origin in interstellar space and predates the birth of our solar system.

    See the full article here .

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  • richardmitnick 1:22 pm on September 6, 2017 Permalink | Reply
    Tags: , , DIBs-diffuse interstellar bands (DIBs), ESA Rosetta   

    From CNRS: “Does the organic material of comets predate our Solar System?” 

    CNRS bloc

    Centre Nationnal de la Recherche Scientifique [The National Center for Scientific Research]

    4 September 2017
    Contacts:
    CNRS researcher
    Jean-Loup Bertaux
    jean-loup.bertaux@latmos.ipsl.fr

    Paris Observatory researcher
    Rosine Lallement
    rosine.lallement@obspm.fr

    CNRS press officer
    Julien Guillaume l
    (+33) (0)1 44 96 46 35 / 51 51 l
    julien.guillaume@cnrs-dir.fr

    The Rosetta space probe discovered a large amount of organic material in the nucleus of comet “Chury.” In an article published by MNRAS on August 31, 2017, two French researchers advance the theory that this matter has its origin in interstellar space and predates the birth of the Solar System.

    ESA/Rosetta spacecraft

    1
    67P Churyumov-Gerasimenko, a.k.a. Chury

    The ESA’s Rosetta mission, which ended in September 2016, found that organic matter made up 40% (by mass) of the nucleus of comet 67P Churyumov-Gerasimenko, a.k.a. Chury. Organic compounds, combining carbon, hydrogen, nitrogen, and oxygen, are building blocks of life on Earth. Yet, according to Jean-Loup Bertaux and Rosine Lallement—from Laboratoire Atmosphères, Milieux, Observations Spatiales (CNRS / UPMC / Université de Versailles Saint-Quentin-en-Yvelines) and the Galaxies, Étoiles, Physique et Instrumentation department of the Paris Observatory (Observatoire de Paris / CNRS / Université Paris Diderot), respectively—these organic molecules were produced in interstellar space, well before the formation of the solar system. Bertaux and Lallement further assert that astronomers are already very familiar with the source of this matter.

    For 70 years, scientists have known that analysis of stellar spectra indicates unknown absorptions, throughout interstellar space, at specific wavelengths called the diffuse interstellar bands (DIBs). DIBs are attributed to complex organic molecules that American astrophysicist Theodore Snow believes may constitute the largest known reservoir of organic matter in the universe. This interstellar organic material is usually found in the same proportions. However, very dense clouds of matter like presolar nebulae are exceptions. In the middle of these nebulae, where matter is even denser, DIB absorptions plateau or even drop. This is because the organic molecules responsible for DIBs clump together there. The clumped matter absorbs less radiation than when it floated freely in space.

    Such primitive nebulae end up contracting to form a solar system like our own, with planets . . . and comets. The Rosetta mission taught us that comet nuclei form by gentle accretion of grains progressively greater in size. First, small particles stick together to form larger grains. These in turn combine to form still larger chunks, and so on, until we have a comet nucleus a few kilometers wide.

    Thus, the organic molecules that formerly populated the primitive nebulae—and that are responsible for DIBs—were probably not destroyed, but instead incorporated into the grains making up cometary nuclei. And there they have remained for 4.6 billion years. A sample-return mission would allow laboratory analysis of cometary organic material and finally reveal the identity of the mysterious interstellar matter underlying observed patterns in stellar spectra.

    If cometary organic molecules were indeed produced in interstellar space—and if they played a role in the emergence of life on our planet, as scientists believe today—might they not also have seeded life on many other planets of our galaxy?

    See the full article here .

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    CNRS encourages collaboration between specialists from different disciplines in particular with the university thus opening up new fields of enquiry to meet social and economic needs. CNRS has developed interdisciplinary programs which bring together various CNRS departments as well as other research institutions and industry.

    Interdisciplinary research is undertaken in the following domains:

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  • richardmitnick 10:21 am on December 18, 2016 Permalink | Reply
    Tags: , , , ESA Rosetta,   

    From ESA via Daily Minor Planet: “How Comets are Born” 

    ESA Space For Europe Banner

    European Space Agency

    minor-planet-center

    Minor Planet Center

    28 July 2016
    Markus Bauer








    ESA Science and Robotic Exploration Communication Officer









    Tel: +31 71 565 6799









    Mob: +31 61 594 3 954









    Email: markus.bauer@esa.int

    Bjorn Davidsson
    Email: bjorn.davidsson@jpl.nasa.gov

    Matt Taylor
    ESA Rosetta Project Scientist
    Email: matt.taylor@esa.int

    1
    Comet 67P/Churyumov–Gerasimenko, ESA Rosetta

    ESA/Rosetta spacecraft
    ESA/Rosetta spacecraft

    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.

    A new study addressing this question led by Björn Davidsson of the Jet Propulsion Laboratory, California Institute of Technology in Pasadena (USA), has been published in Astronomy & Astrophysics.

    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.

    “Either way, comets have been witness to important Solar System evolution events, and this is why we have made these detailed measurements with Rosetta – along with observations of other comets – to find out which scenario is more likely,” says Matt Taylor, ESA’s Rosetta project scientist.

    During its two-year sojourn at Comet 67P/Churyumov–Gerasimenko, Rosetta has revealed a picture of the comet as a low-density, high-porosity, double-lobed body with extensive layering, suggesting that the lobes accumulated material over time before they merged.

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    Profile of a primordial comet
    Released 28/07/2016 4:00 pm
    Copyright 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)

    Evidence that Comet 67P/Churyumov–Gerasimenko is composed of ancient material preserved from the formation of the early Solar System and that came together under low speed. The evidence collected by Rosetta lies in the comet’s structural properties, the gases detected leaving the nucleus, and observations of surface features.

    Earlier work showed that the head and body were originally separate objects, but the collision that merged them must have been at low speed in order not to destroy both of them. The fact that both parts have similar layering also tells us that they must have undergone similar evolutionary histories and that survival rates against catastrophic collision must have been high for a significant period of time.

    Merging events may also have happened on smaller scales. For example, three spherical ‘caps’ have been identified in the Bastet region on the small comet lobe, and suggestions are that they are remnants of smaller cometesimals that are still partially preserved today.

    At even smaller scales of just a few metres across, there are the so-called ‘goosebumps’ and ‘clod’ features, rough textures observed in numerous pits and exposed cliff walls in various locations on the comet.

    While it is possible that this morphology might arise from fracturing alone, it is actually thought to represent an intrinsic ‘lumpiness’ of the comet’s constituents. That is, these ‘goosebumps’ could be showing the typical size of the smallest cometesimals that accumulated and merged to build up the comet, made visible again today through erosion due to sunlight.

    According to theory, the speeds at which cometesimals collide and merge change during the growth process, with a peak when the lumps have sizes of a few metres. For this reason, metre-sized structures are expected to be the most compact and resilient, and it is particularly interesting that the comet material appears lumpy on that particular size scale.

    Further lines of evidence include spectral analysis of the comet’s composition showing that the surface has experienced little or no in situ alteration by liquid water, and analysis of the gases ejected from sublimating ices buried deeper within the surface, which finds the comet to be rich in supervolatiles such as carbon monoxide, oxygen, nitrogen and argon.

    3
    How are comets born? No image credit.

    These observations imply that comets formed in extremely cold conditions and did not experience significant thermal processing during most of their lifetimes. Instead, to explain the low temperatures, survival of certain ices and retention of supervolatiles, they must have accumulated slowly over a significant time period.

    “While larger TNOs in the outer reaches of the Solar System appear to have been heated by short-lived radioactive substances, comets don’t seem to show similar signs of thermal processing. We had to resolve this paradox by taking a detailed look at the time line of our current Solar System models, and consider new ideas,” says Björn.

    Björn and colleagues propose that the larger members of the TNO population formed rapidly within the first one million years of the solar nebula, aided by turbulent gas streams that rapidly accelerated their growth to sizes of up to 400 km.

    Around three million years into the Solar System’s history, gas had disappeared from the solar nebula, only leaving solid material behind. Then, over a much longer period of around 400 million years, the already massive TNOs slowly accreted further material and underwent compaction into layers, their ices melting and refreezing, for example. Some TNOs even grew into Pluto or Triton-sized objects.

    Comets took a different path. After the rapid initial growth phase of the TNOs, leftover grains and ‘pebbles’ of icy material in the cold, outer parts of the solar nebula started to come together at low velocity, yielding comets roughly 5 km in size by the time gas has disappeared from the solar nebula. The low speeds at which the material accumulated led to objects with fragile nuclei with high porosity and low density.

    This slow growth also allowed comets to preserve some of the oldest, volatile-rich material from the solar nebula, since they were able to release the energy generated by radioactive decay inside them without heating up too much.

    The larger TNOs played a further role in the evolution of comets. By ‘stirring’ the cometary orbits, additional material was accreted at somewhat higher speed over the next 25 million years, forming the outer layers of comets. The stirring also made it possible for the few kilometre-sized objects in size to bump gently into each other, leading to the bi-lobed nature of some observed comets.

    “Comets do not appear to display the characteristics expected for collisional rubble piles, which result from the smash-up of large objects like TNOs. Rather, we think they grew gently in the shadow of the TNOs, surviving essentially undamaged for 4.6 billion years,” concludes Björn.

    “Our new model explains what we see in Rosetta’s detailed observations of its comet, and what had been hinted at by previous comet flyby missions.”

    “Comets really are the treasure-troves of the Solar System,” adds Matt.

    “They give us unparalleled insight into the processes that were important in the planetary construction yard at these early times and how they relate to the Solar System architecture that we see today.”

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 12:23 pm on November 7, 2016 Permalink | Reply
    Tags: , , , ESA Rosetta, , Thirty comet chemical 'fingerprints' identified from Earth   

    From COSMOS: “Thirty comet chemical ‘fingerprints’ identified from Earth” 

    Cosmos Magazine bloc

    COSMOS

    07 November 2016
    Belinda Smith

    1
    A false-colour image of the long-period Comet Hale-Bopp. An enormous dust jet emanates northwards of the nucleus. ESO

    The European Space Agency’s Rosetta probe’s decade-long mission told us more about Comet 67P/Churyumov-Gerasimenko than we could have ever discovered from Earth.

    ESA/Rosetta spacecraft
    ESA/Rosetta spacecraft

    2
    Comet 67P by Rosetta’s OSIRIS narrow-angle camera on 3 August 2014. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

    But it turns out we can pick out aspects of a comet’s chemical fingerprint without leaving the planet – and those “dirty snowballs” are quite the diverse bunch.

    Planetary scientists from the US and Japan, led by Johns Hopkins University’s Neil Dello Russo, examined the chemicals in 30 comets, focusing on the coma – the hazy halo of material around the solid nucleus – and tail of each.

    Writing in Icarus, they found each comet had its unique chemistry – but those that whiz around the sun more often tend to have lower levels of the most volatile substances.

    “When NASA or [the European Space Agency] sends a mission to a comet, we can learn a tremendous amount of detail on that specific comet,” Dello Russo says.

    His work, he adds, puts those findings into a larger chemical context: “We can help answer where an individual comet fits into the population of comets.”

    Comets are thought to be largely unchanged clumps of rock and ice leftover from the formation of the solar system 4.6 billion years ago. Knowing where and how comets formed, evolved and were stored can give insights into the solar system’s youth.

    The solar system has two main comet storage reservoirs.

    Just beyond Neptune is the Kuiper belt – a region thought to contain mainly icy bodies such as comets. It’s a disc roughly 30 to 50 astronomical units away (where one astronomical unit is the distance between the sun and Earth).

    But far beyond that is the Oort cloud, a vast spherical shell icy bodies – such as comets – that surrounds the sun between 2,000 and 50,000 astronomical units away.

    Sometimes, a comet makes the journey towards the sun, loops around and whizzes back out again.

    Those with a round trip of more than 200 years are called long-period comets; if the journey is made in less than 200 years, it’s in the short-period group. (Comet 67P/Churyumov-Gerasimenko, which skirts around the sun every 6.5 years, is a short-period comet, while the long-period Comet Hale-Bopp takes more than 2,500 years.)

    Uncovering the chemical composition of these primordial bodies has only recently been made possible with advances in infrared detection methods.

    Seeing comets in the visible part of the spectrum is pretty, but it’s the infrared that unveils their chemistry.

    Different infrared wavelengths correspond to different molecules – particularly symmetric hydrocarbons such as methane.

    As volatiles sublime (transition from solid to gas) they form the coma and tail, giving planetary scientists a proxy for the chemical composition of the frozen nucleus.

    So from 1997 to 2013, Dello Russo and colleagues gathered data from four Earth-based telescopes on molecules such as methane, formaldehyde, ammonia and carbon monoxide from 21 Oort cloud comets and nine Kuiper belt comets.

    While each comet had its own chemical fingerprint, they noticed short-period comets were relatively depleted in the most volatile molecules measured: acetylene, ethane, methane and carbon monoxide.

    It may seem logical that short-period comets, with more passes close to the sun, would have fewer volatiles. But previous work shows no correlation between those molecules and number of orbits.

    So Della Russo and colleagues conclude that the comets were “built” with less of those chemicals in the first place – or were kept in conditions that enabled those molecules to react into different ones more easily.

    One of the next steps, the researchers suggest, is to check out levels of these “parent” and “daughter” molecules.

    See the full article here .

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  • richardmitnick 2:38 pm on September 30, 2016 Permalink | Reply
    Tags: , , ESA Rosetta, , The finale   

    From ESA: “ESA’s historic Rosetta mission has concluded as planned” 

    ESA Space For Europe Banner

    European Space Agency

    30 September 2016
    No writer credit

    ESA/Rosetta spacecraft
    ESA/Rosetta spacecraft

    ESA Rosetta Philae Lander
    ESA Rosetta Philae Lander

    1
    Comet landing site

    ESA’s historic Rosetta mission has concluded as planned, with the controlled impact onto the comet it had been investigating for more than two years.

    Confirmation of the end of the mission arrived at ESA’s control centre in Darmstadt, Germany at 11:19 GMT (13:19 CEST) with the loss of Rosetta’s signal upon impact.

    Rosetta carried out its final manoeuvre last night at 20:50 GMT (22:50 CEST), setting it on a collision course with the comet from an altitude of about 19 km. Rosetta had targeted a region on the small lobe of Comet 67P/Churyumov–Gerasimenko, close to a region of active pits in the Ma’at region.

    2
    Rosetta’s last image

    The descent gave Rosetta the opportunity to study the comet’s gas, dust and plasma environment very close to its surface, as well as take very high-resolution images.

    Pits are of particular interest because they play an important role in the comet’s activity. They also provide a unique window into its internal building blocks.

    The information collected on the descent to this fascinating region was returned to Earth before the impact. It is now no longer possible to communicate with the spacecraft.

    “Rosetta has entered the history books once again,” says Johann-Dietrich Wörner, ESA’s Director General. “Today we celebrate the success of a game-changing mission, one that has surpassed all our dreams and expectations, and one that continues ESA’s legacy of ‘firsts’ at comets.”

    “Thanks to a huge international, decades-long endeavour, we have achieved our mission to take a world-class science laboratory to a comet to study its evolution over time, something that no other comet-chasing mission has attempted,” notes Alvaro Giménez, ESA’s Director of Science.

    “Rosetta was on the drawing board even before ESA’s first deep-space mission, Giotto, had taken the first image of a comet nucleus as it flew past Halley in 1986.

    “The mission has spanned entire careers, and the data returned will keep generations of scientist busy for decades to come.”

    3
    Landing sites in context
    Released 23/09/2016
    Copyright CIVA: ESA/Rosetta/Philae/CIVA; NAVCAM: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0; OSIRIS: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; ROLIS: ESA/Rosetta/Philae/ROLIS/DLR

    Rosetta’s planned impact point in Ma’at shown in context with Philae’s first and final touchdown sites. All three sites are on the smaller of Comet 67P/Churyumov–Gerasimenko’s two lobes.

    Insets show close-up details of the three sites. Philae’s first touchdown in Agilkia was captured by the lander’s descent camera ROLIS; the image shown here was taken from a height of just 9 m above the surface on 12 November 2014, and has a resolution of 0.95 cm/pixel. The view at Philae’s final touchdown site, known as Abydos, was taken by the lander’s CIVA camera on 13 November 2014; the image shown here is a two-image mosaic, and includes one of the lander’s feet.

    Rosetta is destined to make a controlled impact into the Ma’at region of Comet 67P/Churyumov–Gerasimenko on 30 September 2016, targeting a point within a 700 x 500 m ellipse (a very approximate outline is marked on the image). The inset was taken with Rosetta’s Navigation Camera on 13 October 2014 from a distance of 16.8 km; the full frame original image can be found in the Archive Image Browser.

    “As well as being a scientific and technical triumph, the amazing journey of Rosetta and its lander Philae also captured the world’s imagination, engaging new audiences far beyond the science community. It has been exciting to have everyone along for the ride,” adds Mark McCaughrean, ESA’s senior science advisor.

    Since launch in 2004, Rosetta is now in its sixth orbit around the Sun. Its nearly 8 billion-kilometre journey included three Earth flybys and one at Mars, and two asteroid encounters.

    The craft endured 31 months in deep-space hibernation on the most distant leg of its journey, before waking up in January 2014 and finally arriving at the comet in August 2014.

    After becoming the first spacecraft to orbit a comet, and the first to deploy a lander, Philae, in November 2014, Rosetta continued to monitor the comet’s evolution during their closest approach to the Sun and beyond.

    “We’ve operated in the harsh environment of the comet for 786 days, made a number of dramatic flybys close to its surface, survived several unexpected outbursts from the comet, and recovered from two spacecraft ‘safe modes’,” says operations manager Sylvain Lodiot.

    “The operations in this final phase have challenged us more than ever before, but it’s a fitting end to Rosetta’s incredible adventure to follow its lander down to the comet.”

    The decision to end the mission on the surface is a result of Rosetta and the comet heading out beyond the orbit of Jupiter again. Further from the Sun than Rosetta has ever journeyed before, there would be little power to operate the craft.

    Mission operators were also faced with an imminent month-long period when the Sun is close to the line-of-sight between Earth and Rosetta, meaning communications with the craft would have become increasingly more difficult.

    “With the decision to take Rosetta down to the comet’s surface, we boosted the scientific return of the mission through this last, once-in-a-lifetime operation,” says mission manager Patrick Martin.

    Many surprising discoveries have already been made during the mission, not least the curious shape of the comet that became apparent during Rosetta’s approach in July and August 2014. Scientists now believe that the comet’s two lobes formed independently, joining in a low-speed collision in the early days of the Solar System.

    Long-term monitoring has also shown just how important the comet’s shape is in influencing its seasons, in moving dust across its surface, and in explaining the variations measured in the density and composition of the coma, the comet’s ‘atmosphere’.

    Some of the most unexpected and important results are linked to the gases streaming from the comet’s nucleus, including the discovery of molecular oxygen and nitrogen, and water with a different ‘flavour’ to that in Earth’s oceans.

    Together, these results point to the comet being born in a very cold region of the protoplanetary nebula when the Solar System was still forming more than 4.5 billion years ago.

    While it seems that the impact of comets like Rosetta’s may not have delivered as much of Earth’s water as previously thought, another much anticipated question was whether they could have brought ingredients regarded as crucial for the origin of life.

    Rosetta did not disappoint, detecting the amino acid glycine, which is commonly found in proteins, and phosphorus, a key component of DNA and cell membranes. Numerous organic compounds were also detected ¬by Rosetta from orbit, and also by Philae in situ on the surface.

    “It’s a bittersweet ending, but in the end the mechanics of the Solar System were simply against us: Rosetta’s destiny was set a long time ago. But its superb achievements will now remain for posterity and be used by the next generation of young scientists and engineers around the world.”

    While the operational side of the mission has finished today, the science analysis will continue for many years to come.

    Overall, the results delivered by Rosetta so far paint comets as ancient leftovers of early Solar System formation, rather than fragments of collisions between larger bodies later on, giving an unparalleled insight into what the building blocks of the planets may have looked like 4.6 billion years ago.

    “Just as the Rosetta Stone after which this mission was named was pivotal in understanding ancient language and history, the vast treasure trove of Rosetta spacecraft data is changing our view on how comets and the Solar System formed,” says project scientist Matt Taylor.

    “Inevitably, we now have new mysteries to solve. The comet hasn’t given up all of its secrets yet, and there are sure to be many surprises hidden in this incredible archive. So don’t go anywhere yet – we’re only just beginning.”

    Notes for Editors

    Rosetta was an ESA mission with contributions from its Member States and NASA. Rosetta’s Philae lander was provided by a consortium led by DLR, MPS, CNES and ASI. Rosetta was the first mission in history to rendezvous with a comet and escort it as they orbited the Sun together. It was also the first to deploy a lander to a comet’s surface, and later end its mission in a controlled impact on the comet.

    Comets are time capsules containing primitive material left over from the epoch when the Sun and its planets formed. By studying the gas, dust and structure of the nucleus and organic materials associated with the comet, via both remote and in situ observations, the Rosetta mission is a key to unlocking the history and evolution of our Solar System.

    See the full article here .

    Please help promote STEM in your local schools.

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 5:48 pm on July 28, 2016 Permalink | Reply
    Tags: , , ESA Rosetta,   

    From ESA: How Comets are Born 

    ESA Space For Europe Banner

    European Space Agency

    28 July 2016
    Markus Bauer








    ESA Science and Robotic Exploration Communication Officer









    Tel: +31 71 565 6799









    Mob: +31 61 594 3 954









    Email: markus.bauer@esa.int

    Bjorn Davidsson
    Email: bjorn.davidsson@jpl.nasa.gov

    Matt Taylor
    ESA Rosetta Project Scientist
    Email: matt.taylor@esa.int

    1
    Profile of a primordial comet

    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.

    2
    Rosetta navigation camera (NavCam) image taken on 22 March 2015 at 77.8 km from the centre of comet 67P/Churyumov-Gerasimenko. The image has been cropped and measures 6.0 km across; the resolution is about 6.6 m/pixel. Credit: European Space Agency

    A new study addressing this question led by Björn Davidsson of the Jet Propulsion Laboratory, California Institute of Technology in Pasadena (USA), has been published in Astronomy & Astrophysics.

    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.

    “Either way, comets have been witness to important Solar System evolution events, and this is why we have made these detailed measurements with Rosetta – along with observations of other comets – to find out which scenario is more likely,” says Matt Taylor, ESA’s Rosetta project scientist.

    During its two-year sojourn at Comet 67P/Churyumov–Gerasimenko, Rosetta has revealed a picture of the comet as a low-density, high-porosity, double-lobed body with extensive layering, suggesting that the lobes accumulated material over time before they merged.

    ESA/Rosetta spacecraft
    ESA/Rosetta spacecraft

    ESA Rosetta Philae Lander
    ESA Rosetta Philae Lander

    The unusually high porosity of the interior of the nucleus provides the first indication that this growth cannot have been via violent collisions, as these would have compacted the fragile material. Structures and features on different size scales observed by Rosetta’s cameras provide further information on how this growth may have taken place.

    Earlier work showed that the head and body were originally separate objects, but the collision that merged them must have been at low speed in order not to destroy both of them. The fact that both parts have similar layering also tells us that they must have undergone similar evolutionary histories and that survival rates against catastrophic collision must have been high for a significant period of time.

    Merging events may also have happened on smaller scales. For example, three spherical ‘caps’ have been identified in the Bastet region on the small comet lobe, and suggestions are that they are remnants of smaller cometesimals that are still partially preserved today.

    At even smaller scales of just a few metres across, there are the so-called ‘goosebumps’ and ‘clod’ features, rough textures observed in numerous pits and exposed cliff walls in various locations on the comet.

    While it is possible that this morphology might arise from fracturing alone, it is actually thought to represent an intrinsic ‘lumpiness’ of the comet’s constituents. That is, these ‘goosebumps’ could be showing the typical size of the smallest cometesimals that accumulated and merged to build up the comet, made visible again today through erosion due to sunlight.

    According to theory, the speeds at which cometesimals collide and merge change during the growth process, with a peak when the lumps have sizes of a few metres. For this reason, metre-sized structures are expected to be the most compact and resilient, and it is particularly interesting that the comet material appears lumpy on that particular size scale.

    Further lines of evidence include spectral analysis of the comet’s composition showing that the surface has experienced little or no in situ alteration by liquid water, and analysis of the gases ejected from sublimating ices buried deeper within the surface, which finds the comet to be rich in supervolatiles such as carbon monoxide, oxygen, nitrogen and argon.

    4
    How are comets born?

    These observations imply that comets formed in extremely cold conditions and did not experience significant thermal processing during most of their lifetimes. Instead, to explain the low temperatures, survival of certain ices and retention of supervolatiles, they must have accumulated slowly over a significant time period.

    “While larger TNOs in the outer reaches of the Solar System appear to have been heated by short-lived radioactive substances, comets don’t seem to show similar signs of thermal processing. We had to resolve this paradox by taking a detailed look at the time line of our current Solar System models, and consider new ideas,” says Björn.

    Björn and colleagues propose that the larger members of the TNO population formed rapidly within the first one million years of the solar nebula, aided by turbulent gas streams that rapidly accelerated their growth to sizes of up to 400 km.

    Around three million years into the Solar System’s history, gas had disappeared from the solar nebula, only leaving solid material behind. Then, over a much longer period of around 400 million years, the already massive TNOs slowly accreted further material and underwent compaction into layers, their ices melting and refreezing, for example. Some TNOs even grew into Pluto or Triton-sized objects.

    Comets took a different path. After the rapid initial growth phase of the TNOs, leftover grains and ‘pebbles’ of icy material in the cold, outer parts of the solar nebula started to come together at low velocity, yielding comets roughly 5 km in size by the time gas has disappeared from the solar nebula. The low speeds at which the material accumulated led to objects with fragile nuclei with high porosity and low density.

    This slow growth also allowed comets to preserve some of the oldest, volatile-rich material from the solar nebula, since they were able to release the energy generated by radioactive decay inside them without heating up too much.

    The larger TNOs played a further role in the evolution of comets. By ‘stirring’ the cometary orbits, additional material was accreted at somewhat higher speed over the next 25 million years, forming the outer layers of comets. The stirring also made it possible for the few kilometre-sized objects in size to bump gently into each other, leading to the bi-lobed nature of some observed comets.

    “Comets do not appear to display the characteristics expected for collisional rubble piles, which result from the smash-up of large objects like TNOs. Rather, we think they grew gently in the shadow of the TNOs, surviving essentially undamaged for 4.6 billion years,” concludes Björn.

    “Our new model explains what we see in Rosetta’s detailed observations of its comet, and what had been hinted at by previous comet flyby missions.”

    “Comets really are the treasure-troves of the Solar System,” adds Matt.

    “They give us unparalleled insight into the processes that were important in the planetary construction yard at these early times and how they relate to the Solar System architecture that we see today.”

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 7:00 am on May 28, 2016 Permalink | Reply
    Tags: , Building blocks of life spotted around comet for the first time, ESA Rosetta   

    From New Scientist: “Building blocks of life spotted around comet for the first time” 

    NewScientist

    New Scientist

    27 May 2016
    Conor Gearin

    1
    Cosmic chemistry. ESA / ATG medialab / Rosetta / Navcam

    A frosty comet could have delivered the ingredients for life to Earth. The European Space Agency’s Rosetta spacecraft has spotted an amino acid on the comet it orbits – confirming that a ball of ice and dust can hold a major building block of life.

    Amino acids are the building blocks of proteins, which control essential reactions in living cells. Astrobiologists have long wondered whether they could have been delivered to early Earth on the backs of comets or asteroids.

    In 2009, scientists reported that they had found the simplest amino acid, glycine, in comet dust brought back by NASA’s Stardust spacecraft, but it’s possible those samples were contaminated with dust from Earth.

    Now, Rosetta, which has been orbiting comet 67P Churyumov-Gerasimenko since 2014, has definitively seen glycine in the gas cloud surrounding the comet. The probe also picked up the scent of phosphorus, a component of DNA.

    Previously, the spacecraft had found alcohols, sugars and oxygen compounds, which are also needed for life and cellular structure. With the addition of glycine and phosphorous, all the major types of prebiotics have been found on the comet.

    “The beauty of it is that now we see all the ingredients which are needed for life in one place,” says Kathrin Altwegg of the University of Bern in Switzerland, who directs Rosetta’s chemical detector.

    The Rosetta mission hadn’t made finding glycine a goal because the scientists didn’t expect to find it, Altwegg says – not because they thought it wasn’t there, but because it would have been frozen on the comet and not in the cloud of gas that Rosetta can sample. “I was almost convinced we would not see it,” Altwegg says.

    “It’s very exciting,” says Susanna Widicus Weaver of Emory University, in Atlanta, Georgia. “There have been a lot of people looking for glycine in space for a very long time.”

    Trapped in ice

    It’s been a mystery how Earth got its prebiotic molecules, because the developing planet probably couldn’t support them. As the Earth formed 4.5 billion years ago, the surface was hot and violent, and probably evaporated organic molecules before they could combine to form the first cells, Weaver says. But once Earth’s atmosphere cooled down, comets with molecules trapped in ice could have delivered the necessary ingredients.

    Though comets are incredibly cold, they’re able to host the chemical reactions that form complex molecules, says Ralf Kaiser of the University of Hawaii at Manoa. As they rotate, radiation from the sun cooks simpler chemicals on the comet into prebiotic molecules. Once formed, these molecules get trapped in ice.

    Kaiser was not surprised to see glycine near 67P – lab simulations a decade ago showed how these reactions can happen. But he is pleased to see that such molecules can indeed form on comets. “It’s a really nice confirmation,” he says.

    Whether we can detect the even more complex components of DNA in space remains unclear. Astronomers recently saw the chemical signature of phosphorus-oxygen molecules in a star-forming region, suggesting that simple precursors of DNA float in the soup of new solar systems.

    But Kaiser says he hopes Rosetta might find nucleotides, the building blocks of DNA, on the comet. “That would be a major breakthrough.”

    Rosetta is now just 5 kilometres above the surface of the comet inside a denser cloud of molecules. Analysing data gathered from this low orbit could reveal new ingredients for life formed in space.

    Science paper: Science Advances, DOI: 10.1126/sciadv.1600285 http://advances.sciencemag.org/content/2/5/e1600285

    See the full article here .

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  • richardmitnick 7:06 am on March 29, 2016 Permalink | Reply
    Tags: , , , ESA Rosetta,   

    From Discovery: “Documentary 2015 Landing On A Comet Rosetta Mission 2014 New Details” 

    Discovery News
    Discovery News

    Published on Nov 13, 2014

    Documentary Landing On A Comet Rosetta Mission 2014 New

    Watch, enjoy, learn.

    See the full article here .

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  • richardmitnick 8:09 am on November 12, 2015 Permalink | Reply
    Tags: , , ESA Rosetta,   

    From ESA: “Rosetta and Philae: one year since landing on a comet” 

    ESASpaceForEuropeBanner
    European Space Agency

    12 November 2015
    Markus Bauer








    ESA Science and Robotic Exploration Communication Officer









    Tel: +31 71 565 6799









    Mob: +31 61 594 3 954









    Email: markus.bauer@esa.int

    Patrick Martin
    Rosetta Mission Manager
    Email: patrick.martin@esa.int

    Sylvain Lodiot
    Rosetta Spacecraft Operations Manager
    Email: sylvain.lodiot@esa.int

    Matt Taylor
    ESA Rosetta Project Scientist
    Email: matt.taylor@esa.int

    Koen Geurts
    Philae Lander Technical Manager, DLR
    Email: Koen.Geurts@dlr.de

    Stephan Ulamec
    Philae Lander Manager, DLR
    Email: Stephan.Ulamec@dlr.de


    Reconstructing Philae’s flight
    download mp4 video here.

    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.

    In the year since landing, a thorough analysis has also now been performed on why Philae bounced.

    1
    Agilkia mosaic, labelled

    There were three methods to secure it after landing: ice screws, harpoons and a small thruster. The ice screws were designed with relatively soft material in mind, but Agilkia turned out to be very hard and they did not penetrate the surface.

    The harpoons were capable of working in both softer and harder material. They were supposed to fire on contact and lock Philae to the surface, while a thruster on top of the lander was meant to push it down to counteract the recoil from the harpoon.

    Attempts to arm the thruster the night before failed: it is thought that a seal did not open, although a sensor failure cannot be excluded.

    Then, on landing, the harpoons themselves did not fire. “It seems that the problem was either with the four ‘bridge wires’ taking current to ignite the explosive that triggers the harpoons, or the explosive itself, which may have degraded over time,” explains Stephan Ulamec, Philae lander manager at the DLR German Aerospace Center.

    “In any case, if we can regain contact with Philae, we might consider an attempt to retry the firing.”

    The reason is scientific: the harpoons contain sensors that could measure the temperature below the surface.

    Despite the unplanned bouncing, Philae completed 80% of its planned first science sequence before falling into hibernation in the early hours of 15 November when the primary battery was exhausted. There was not enough sunlight in Philae’s final location at Abydos to charge the secondary batteries and continue science measurements.

    The hope was that as the comet moved nearer to the Sun, heading towards closest approach in August, there would be enough energy to reactivate Philae. Indeed, contact was made with the lander on 13 June but only eight intermittent contacts were made up to 9 July.

    The problem was that the increasing sunlight also led to increased activity on the comet, forcing Rosetta to retreat to several hundred kilometres for safety, well out of range with Philae.

    However, over the past few weeks, with the comet’s activity now subsiding, Rosetta has started to approach again. This week it reached 200 km, the limit for making good contact with Philae, and today it dips to within 170 km.


    Philae’s descent: The director’s cut
    download the mp4 video here.

    In the meantime, the lander teams have continued their analysis of the data returned during the contacts in June and July, hoping to understand the status of Philae when it first woke up from hibernation.

    “We had already determined that one of Philae’s two receivers and one of the two transmitters were likely no longer working,” says Koen Geurts, Philae’s technical manager at DLR’s Lander Control Centre in Cologne, Germany, “and it now seems that the other transmitter is suffering problems. Sometimes it did not switch on as expected, or it switched off too early, meaning that we likely missed possible contacts.”

    The team is taking this new information into account to determine the most promising strategy to regain regular contact.

    But it’s a race against time: with the comet now heading out beyond the orbit of Mars, temperatures are falling.

    “We think we have until the end of January before the lander’s internal temperature gets too cold to operate: it cannot work below –51ºC,” adds Koen.

    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.

    The solar-powered Rosetta will no longer receive enough sunlight to operate as the comet recedes from the Sun, out beyond the orbit of Jupiter on its 6.5-year circuit. It will travel even further out than during the previous 31 months of deep-space hibernation that ended in January 2014.

    In addition, as seen from Earth next September, Rosetta and the comet will look very close to the Sun, making the relay of both scientific data and operational commands very difficult.

    The Rosetta teams are now investigating the manoeuvres needed for operating close to the comet in the weeks leading up to the dramatic mission finale.

    “We are still discussing exactly what the final end of mission scenario will involve,” says Sylvain Lodiot, ESA’s Rosetta spacecraft operations manager. “It is very complex and challenging, even more so even than the lander delivery trajectory our flight dynamics teams had to plan for delivering Philae.

    “The schedule we’re looking at would first involve a move into highly elliptical orbits – perhaps as low as 1 km – in August, before moving out to a more distant point for a final approach that will set Rosetta on a slow collision course with the comet at the end of September.”

    It is expected that science observations would continue throughout and up to almost the end of mission, allowing Rosetta’s instruments to gather unique data at unprecedentedly close distances.

    “We’ll control Rosetta all the way down to the end, but once on the surface it will be highly improbable that we’ll be able to ‘speak’ to it anymore,” adds Sylvain.

    “Landing Rosetta on a comet will be a fitting ending to this incredible mission,” says Patrick Martin, ESA’s Rosetta mission manager.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 3:44 pm on October 28, 2015 Permalink | Reply
    Tags: , , , ESA Rosetta, O2   

    From ESA: “First detection of molecular oxygen at a comet” 

    ESASpaceForEuropeBanner
    European Space Agency

    28 October 2015
    Markus Bauer








    ESA Science and Robotic Exploration Communication Officer









    Tel: +31 71 565 6799









    Mob: +31 61 594 3 954









    Email: markus.bauer@esa.int

    Kathrin Altwegg

    Principal investigator for ROSINA

    University of Bern, Switzerland

    Email: kathrin.altwegg@space.unibe.ch

    Andre Bieler
    University of Michigan
    Email: abieler@umich.edu

    Ewine van Dishoeck
    Leiden Observatory, University of Leiden, the Netherlands
    Email: ewine@strw.leidenuniv.nl

    Matt Taylor
    ESA Rosetta Project Scientist
    Email: matt.taylor@esa.int

    1
    Rosetta’s detection of molecular oxygen Released 28/10/2015

    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.

    2
    Comet 67P/Churyumov–Gerasimenko

    ESA Rosetta spacecraft
    Rosetta

    4
    Rosetta’s Philae Lander

    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.

    “We weren’t really expecting to detect O2 at the comet – and in such high abundance – because it is so chemically reactive, so it was quite a surprise,” says Kathrin Altwegg of the University of Bern, and principal investigator of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis instrument, ROSINA.

    ESA Rosetta ROSINA
    ROSINA

    “It’s also unanticipated because there aren’t very many examples of the detection of interstellar O2. And thus, even though it must have been incorporated into the comet during its formation, this is not so easily explained by current Solar System formation models.”

    The team analysed more than 3000 samples collected around the comet between September 2014 and March 2015 to identify the O2. They determined an abundance of 1–10% relative to H2O, with an average value of 3.80 ± 0.85%, an order of magnitude higher than predicted by models describing the chemistry in molecular clouds.

    The amount of molecular oxygen detected showed a strong relationship to the amount of water measured at any given time, suggesting that their origin on the nucleus and release mechanism are linked. By contrast, the amount of O2 seen was poorly correlated with carbon monoxide and molecular nitrogen, even though they have a similar volatility to O2. In addition, no ozone was detected.

    Over the six-month study period, Rosetta was inbound towards the Sun along its orbit, and orbiting as close as 10–30 km from the nucleus. Despite the decreasing distance to the Sun, the O2/H2O ratio remained constant over time, and it also did not change with Rosetta’s longitude or latitude over the comet.

    In more detail, the O2/H2O ratio was seen to decrease for high H2O abundances, an observation that might be influenced by surface water ice produced in the observed daily sublimation–condensation process.

    The team explored the possibilities to explain the presence and consistently high abundance of O2 and its relationship to water, as well as the lack of ozone, by first considering photolysis and radiolysis of water ice over a range of timescales.

    In photolysis, photons break bonds between molecules, whereas radiolysis involves more energetic photons or fast electrons and ions depositing energy into ice and ionising molecules – a process observed on icy moons in the outer Solar System, and in Saturn’s rings. Either process can, in principle, lead to the formation and liberation of molecular oxygen.

    Radiolysis will have operated over the billions of years that the comet spent in the Kuiper Belt and led to the build-up of O2 to a few metres depth.

    5
    Known objects in the Kuiper belt beyond the orbit of Neptune. (Scale in AU; epoch as of January 2015.)

    But these top layers must all have been removed in the time since the comet moved into its inner Solar System orbit, ruling this out as the source of the O2 seen today.

    More recent generation of O2 via radiolysis and photolysis by solar wind particles and UV photons should only have occurred in the top few micrometres of the comet.

    “But if this was the primary source of the O2 then we would have expected to see a decrease in the O2/H2O ratio as this layer was removed during the six-month timespan of our observations,” says Andre Bieler of the University of Michigan and lead author of the paper describing the new results in the journal Nature this week.

    “The instantaneous generation of O2 also seems unlikely, as that should lead to variable O2 ratios under different illumination conditions. Instead, it seems more likely that primordial O2 was somehow incorporated into the comet’s ices during its formation, and is being released with the water vapour today.”

    In one scenario, gaseous O2 would first be incorporated into water ice in the early protosolar nebula stage of our Solar System. Chemical models of protoplanetary discs predict that high abundances of gaseous O2 could be available in the comet forming zone, but rapid cooling from temperatures above –173ºC to less than –243ºC would be required to form water ice with O2 trapped on dust grains. The grains would then have to be incorporated into the comet without being chemically altered.

    “Other possibilities include the Solar System being formed in an unusually warm part of a dense molecular cloud, at temperatures of 10–20ºC above the –263ºC or so typically expected for such clouds,” says Ewine van Dishoeck of Leiden Observatory in the Netherlands, co-author of the paper.

    “This is still consistent with estimates for the comet formation conditions in the outer solar nebula, and also with previous findings at Rosetta’s comet regarding the low abundance of N2.”

    Alternatively, radiolysis of icy dust grains could have taken place prior to the comet’s accretion into a larger body. In this case, the O2 would remain trapped in the voids of the water ice on the grains while the hydrogen diffused out, preventing the reformation of O2 to water, and resulting in an increased and stable level of O2 in the solid ice.

    Incorporation of such icy grains into the nucleus could explain the observed strong correlation with H2O observed at the comet today.

    “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.

    “This is an intriguing result for studies both within and beyond the comet community, with possible implications for our models of Solar System evolution,” says Matt Taylor, ESA’s Rosetta project scientist.

    Abundant molecular oxygen in the coma of 67P/Churyumov–Gerasimenko, by A. Bieler et al is published in the 29 October 2015 issue of the journal Nature.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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