Tag Archives: comets

Amateur finds moon orbiting comet in Rosetta archive

In mining the Rosetta archive of images of Comet 67P/C-G, an amateur astronomer has discovered a twelve-foot-diameter chunk of material that had broken from the comet and was in orbit around it.

Modelling of the Rosetta images indicates that this object spent the first 12 hours after its ejection in an orbital path around 67P/C-G at a distance of between 2.4 and 3.9 km from the comet’s centre. Afterwards, the chunk crossed a portion of the coma, which appears very bright in the images, making it difficult to follow its path precisely; however, later observations on the opposite side of the coma confirm a detection consistent with the orbit of the chunk, providing an indication of its motion around the comet until 23 October 2015.

While it is not really unusual for their to be small objects in the coma of the the comet, orbiting it, this is apparently the largest so far found. That they missed it initially is also not surprising, considering the amount of data they were gathering in such a short time.

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China announces plans for asteroid/comet sample return mission

The new colonial movement: China today announced plans to fly an ambitious mission to both an asteroid and comet, which would also bring back a sample from the asteroid.

The current plan, which is still under discussion, calls for a probe to visit and collect samples from the small near-Earth asteroid 2016 HO3 (also known as Kamo’oalewa). “Then, the probe will fly back to the proximity of Earth, and a return capsule will be released to bring the samples back to Earth,” Xinhua reported today (April 18), citing a China National Space Administration official. “After that, the probe will continue its journey. With the assistance of the gravity of Earth and Mars, it will finally arrive at the main asteroid belt and orbit the Comet 133P to explore it.”

Both objects are unusual. The asteroid is in a strange solar orbit that almost makes it a moon of the Earth, while the comet appears to be a main-belt asteroid with comet-like activity.

The mission is not finalized yet, so expect some revisions.

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All high resolution images from Rosetta now available

The Rosetta science team has now made available to the public all 70,000 images taken by the spacecraft’s high resolution camera.

Between 2014 and 2016, the scientific camera system OSIRIS onboard ESA’s Rosetta spacecraft captured almost 70000 images of comet 67P/Churyumov-Gerasimenko. They not only document the most extensive and demanding comet mission to date, but also show the duck-shaped body in all its facets. In a joint project with the Department of Information and Communication at Flensburg University of Applied Sciences, the Max Planck Institute for Solar System Research (MPS), head of the OSIRIS team, has now published all of these images. The OSIRIS Image Viewer is suited to the needs of both laymen and expert and offers quick and easy access to one of the greatest scientific treasures of recent years.

The Rosetta archive can be found here.

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Tess captures comet, variable stars, asteroids, and Martian light

During its testing period prior to beginning science operations this month, the exoplanet space telescope TESS spotted in one series of images a comet, a host of variable stars, some asteroids, and even the faint hint of some reflected light from Mars.

Over the course of these tests, TESS took images of C/2018 N1, a comet discovered by NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) satellite on June 29. The comet, located about 29 million miles (48 million kilometers) from Earth in the southern constellation Piscis Austrinus, is seen to move across the frame from right to left as it orbits the Sun. The comet’s tail, which consists of gases carried away from the comet by an outflow from the Sun called the solar wind, extends to the top of the frame and gradually pivots as the comet glides across the field of view.

In addition to the comet, the images reveal a treasure trove of other astronomical activity. The stars appear to shift between white and black as a result of image processing. The shift also highlights variable stars — which change brightness either as a result of pulsation, rapid rotation, or by eclipsing binary neighbors. Asteroids in our solar system appear as small white dots moving across the field of view. Towards the end of the video, one can see a faint broad arc of light moving across the middle section of the frame from left to right. This is stray light from Mars, which is located outside the frame. The images were taken when Mars was at its brightest near opposition, or its closest distance, to Earth.

The video that was compiled from these images is embedded below the fold.
» Read more

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Pluto formed from a billion comets?

Scientists have come up with a new theory for the origin of Pluto, based on data from New Horizons and Rosetta, that suggests the planets formed from the accretion of a billion comets or Kuiper Belt objects.

“We’ve developed what we call ‘the giant comet’ cosmochemical model of Pluto formation,” said Dr. Christopher Glein of SwRI’s Space Science and Engineering Division. The research is described in a paper published online today in Icarus. At the heart of the research is the nitrogen-rich ice in Sputnik Planitia, a large glacier that forms the left lobe of the bright Tombaugh Regio feature on Pluto’s surface. “We found an intriguing consistency between the estimated amount of nitrogen inside the glacier and the amount that would be expected if Pluto was formed by the agglomeration of roughly a billion comets or other Kuiper Belt objects similar in chemical composition to 67P, the comet explored by Rosetta.”

This is only a hypothesis, but it is intriguing. It suggests that Pluto’s make-up came only from the outer parts of the solar system, thus constraining how much mixing between the solar system’s inner and outer regions occurred. For scientists trying to understand the formation of the entire solar system, this lack of mixing would be significant. It means that the gas giants, while migrating inward, never migrated outward.

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Why jets formed on Comet 67P/C-G

Scientists analyzing the data produced by Rosetta while it was flying in formation with Comet 67P/C-G have determined that the comet’s complex topology acted almost like nozzles to encourage evaporating material to form jets.

The new study shows for the first time that mainly the unusual shape and jagged topography of the comet are responsible for this phenomenon. The researchers analyzed images at different observation geometries of the Hapi region located on the “neck” of the comet, the narrow part connecting its two lobes. In computer simulations, they were able to reproduce these images thus gaining a better understanding of the driving processes.

In particular, two effects proved to be decisive. Some regions on the surface are located at lower altitudes or in the shade. The first rays of sunlight reach them later. In contrast, the frost evaporates particularly efficiently from the early and strongly illuminated regions. In addition, pits and other concave structures virtually concentrate gas and dust emissions – much like an optical lens.

This means that predicting the evaporation patterns on other comets will require first obtaining a detailed map of the surface, showing both its topography and make-up. This also means that any future explorers will first have to send a robot scouting mission so that they can plan a safe arrival during active periods.

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Star’s close approach 70,000 years ago pinned to cometary orbits

Astronomers now think they have pinned the orbits of about 340 comets to another star’s close approach to our solar system 70,000 years ago.

About 70,000 years ago, when the human species was already on Earth, a small reddish star approached our solar system and gravitationally disturbed comets and asteroids. Astronomers from the Complutense University of Madrid and the University of Cambridge have verified that the movement of some of these objects is still marked by that stellar encounter. At a time when modern humans were beginning to leave Africa and the Neanderthals were living on our planet, Scholz’s star – named after the German astronomer who discovered it – approached less than a light-year from the Sun. Nowadays it is almost 20 light-years away, but 70,000 years ago it entered the Oort cloud, a reservoir of trans-Neptunian objects located at the confines of the solar system.

This discovery was made public in 2015 by a team of astronomers led by Professor Eric Mamajek of the University of Rochester (USA). The details of that stellar flyby, the closest documented so far, were presented in The Astrophysical Journal Letters.

Now two astronomers from the Complutense University of Madrid, the brothers Carlos and Raúl de la Fuente Marcos, together with the researcher Sverre J. Aarseth of the University of Cambridge (United Kingdom), have analyzed for the first time the nearly 340 objects of the solar system with hyperbolic orbits (very open V-shaped, not the typical elliptical), and in doing so they have detected that the trajectory of some of them is influenced by the passage of Scholz´s star.

It is likely that the close approach influenced a lot more objects, many of which might not have yet arrived in the inner solar system. Moreover, their computer models suggest that the star might have come closer to the Sun than 0.6 light years.

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The organic dust of Comet 67P/C-G

A study of the dust released by Comet 67P/C-G and captured by Rosetta shows that carbon molecules appear to comprise the comet’s largest component, and that this material is found in the form of very large macromolecules.

As the study shows, organic molecules are among those ingredients at the top of the list. These account for about 45 percent of the weight of the solid cometary material. “Rosetta’s comet thus belongs to the most carbon-rich bodies we know in the solar system,” says MPS scientist and COSIMA team member Dr. Oliver Stenzel. The other part of the total weight, about 55 percent, is provided by mineral substances, mainly silicates. It is striking that they are almost exclusively non-hydrated minerals i.e. missing water compounds. “Of course, Rosetta’s comet contains water like any other comet, too,” says Hilchenbach. “But because comets have spent most of their time at the icy rim of the solar system, it has almost always been frozen and could not react with the minerals.” The researchers therefore regard the lack of hydrated minerals in the comet’s dust as an indication that 67P contains very pristine material.

…The current findings also touch on our ideas of how life on Earth came about. In a previous publication, the COSIMA team was able to show that the carbon found in Rosetta’s comet is mainly in the form of large, organic macromolecules. Together with the current study, it becomes clear that these compounds make up a large part of the cometary material. Thus, if comets indeed supplied the early Earth with organic matter, as many researchers assume, it would probably have been mainly in the form of such macromolecules.

Organic here does not mean life, but is instead used as chemists use it, to mean the molecule includes the element carbon. The results do suggest however that the early solar system had a lot of carbon available, and that much of it was in a relatively pure form available to interact with other elements.

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Rosetta’s capture of a dust jet from Comet 67P/C-G

Dust jet on Comet 67P/C-G

Cool image time! The Rosetta science team has released images and data gathered in July 2016 when the spacecraft successfully observed a dust outburst erupting from Comet 67P/C-G’s surface. The image on the right, slightly reduced in resolution, shows that outburst.

When the Sun rose over the Imhotep region of Rosetta’s comet on July 3, 2016, everything was just right: As the surface warmed and began to emit dust into space, Rosetta’s trajectory led the probe right through the cloud. At the same time, the view of the scientific camera system OSIRIS coincidentally focused precisely on the surface region of the comet from which the fountain originated. A total of five instruments on board the probe were able to document the outburst in the following hours.

As should be expected, the results did not match the models or predictions. The jet, instigated by water-ice just below the surface turning into gas when heated by the Sun, was much dustier than predicted. They have theories as to why, but it appears that no one likes these theories that much.

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Hubble spots most distance active comet yet

Comet C/2017 K2

Using the Hubble Space Telescope astronomers have imaged a comet that is sublimating material at a distance from the Sun farther than any previously known comet, out beyond Saturn.

“K2 is so far from the Sun and so cold, we know for sure that the activity — all the fuzzy stuff making it look like a comet — is not produced, as in other comets, by the evaporation of water ice,” said lead researcher David Jewitt of the University of California, Los Angeles. “Instead, we think the activity is due to the sublimation [a solid changing directly into a gas] of super-volatiles as K2 makes its maiden entry into the solar system’s planetary zone. That’s why it’s special. This comet is so far away and so incredibly cold that water ice there is frozen like a rock.”

Based on the Hubble observations of K2’s coma, Jewitt suggests that sunlight is heating frozen volatile gases – such as oxygen, nitrogen, carbon dioxide, and carbon monoxide – that coat the comet’s frigid surface. These icy volatiles lift off from the comet and release dust, forming the coma. Past studies of the composition of comets near the Sun have revealed the same mixture of volatile ices.

The significance here is that by studying the comet’s activity scientists will be able to identify some of these volatile gases, which in turn will tell them something about the make-up of the outermost fringes of the solar system.

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One last image from Rosetta

Rosetta's last image

Engineers reviewing the last bits of telemetry that was transmitted back to Earth by Rosetta just before it crashed on Comet 67P/C-G have discovered one last image of the comet’s surface.

That image is on the right. It is slightly blurred because of the limitations of Rosetta’s camera at this short range, and the incompleteness of the data received.

The image covers an area about a meter across, with a resolution of about two millimeters per pixel.

I imagine this surface is relatively soft, since the gravity holding the comet together is so slight. If you wanted to dig down, you would find it easy digging.

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Hubble finds binary asteroid that also acts like a comet

Worlds without end: Astronomers using the Hubble Space Telescope have identified a strange new object in the asteroid belt, two asteroids closely orbiting each other while also acting like a comet.

The images of 288P, which is located in the asteroid belt between Mars and Jupiter, revealed that it was actually not a single object, but two asteroids of almost the same mass and size, orbiting each other at a distance of about 100 kilometres. That discovery was in itself an important find; because they orbit each other, the masses of the objects in such systems can be measured.

But the observations also revealed ongoing activity in the binary system. “We detected strong indications of the sublimation of water ice due to the increased solar heating — similar to how the tail of a comet is created,” explains Jessica Agarwal (Max Planck Institute for Solar System Research, Germany), the team leader and main author of the research paper. This makes 288P the first known binary asteroid that is also classified as a main-belt comet.

The data also suggests that this binary has only existed as such for a few thousand years, and probably broke into two pieces because of its rotation. When this happened, it exposed water ice buried below the surface, which having been exposed to sunlight is sublimating away and producing the binary’s cometlike of a tail and coma.

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Astronomers find unexpected comets in outer reaches of solar system

Using data from the WISE space telescope, astronomers have found that there are more comets lurking in the far reaches of the solar system than they had predicted.

Scientists found that there are about seven times more long-period comets measuring at least 0.6 miles (1 kilometer) across than had been predicted previously. They also found that long-period comets are on average up to twice as large as “Jupiter family comets,” whose orbits are shaped by Jupiter’s gravity and have periods of less than 20 years. Researchers also observed that in eight months, three to five times as many long-period comets passed by the Sun than had been predicted.

These are comets whose orbits never allow them to come close to the inner solar system, which allows them to remain puffy and large.

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Astronomers confirm that comet caused Wow! signal, not aliens

Astronomers have confirmed that the Wow! signal, thought to be the most promising detection by SETI of alien life, was actually caused by a comet.

Last year, a group of researchers from the Center of Planetary Science proposed a new hypothesis that argued a comet might be the culprit. The frequency could be caused by the hydrogen cloud they carry, and the fact that they move accounts for why it seemingly disappeared. Two comets, named 266/P Christensen and P/2008 Y2 (Gibbs), happened to be transiting through that region of space when the Wow! signal was detected, but they weren’t discovered until after 2006.

To test the hypothesis, the team made 200 radio spectrum observations between November 2016 and February 2017. Sure enough, 266/P Christensen was found to emit radio waves at a frequency of 1,420 MHz, and to double check, the researchers moved their radio telescope by one degree. As expected, the signal vanished, and only returned when the telescope was trained back on the comet.

This story demonstrates once again why, in science, it is very dangerous to jump to any conclusions. The data we receive is a mystery. We must keep an open mind to solve that mystery.

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The changes seen by Rosetta on Comet 67P/C-G

A new study released today describes in detail the many changes seen by scientists in the data collected by Rosetta during its two years in close proximity to Comet 67P/C-G.

“We saw a massive cliff collapse and a large crack in the neck of the comet get bigger and bigger,” said El-Maarry. “And we discovered that boulders the size of a large truck could be moved across the comet’s surface a distance as long as one-and-a-half football fields.”

In the case of the boulder, Rosetta’s cameras observed a 282-million-pound (130-million-kilogram), 100-feet-wide (30-meter) space rock to have moved 150 yards (460 feet, or 140 meters) from its original position on the comet’s nucleus. The massive space rock probably moved as a result of several outburst events that were detected close to its original position.

The warming of 67P also caused the comet’s rotation rate to speed up. The comet’s increasing spin rate in the lead-up to perihelion is thought to be responsible for a 1,600-foot-long (500-meters) fracture spotted in August 2014 that runs through the comet’s neck. The fracture, which originally extended a bit longer than the Empire State Building is high, was found to have increased in width by about 100 feet (30 meters) by December 2014. Furthermore, in images taken in June 2016, a new 500- to 1,000-foot-long (150 to 300 meters) fracture was identified parallel to the original fracture.

“The large crack was in the ‘neck’ of the comet — a small central part that connects the two lobes,” said El-Maarry. “The crack was extending–indicating that the comet may split up one day.”

It is almost a shame that Rosetta did not see that break-up. The images would have been breath-taking, and the science learned priceless.

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Asteroid breaks in two, each piece develops a tail

Astronomers have discovered a main belt asteroid that six years ago broke in two, after which both pieces developed tails resembling comets.

“The results derived from the evolution of the orbit show that the asteroid fragmented approximately six years ago, which makes it the youngest known asteroid pair in the Solar System to date,” says Fernando Moreno, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC), in charge of the project.

P/2016 J1 presents another important peculiarity, which makes it very unusual. “Both fragments are activated, i.e., they display dust structures similar to comets. This is the first time we observe an asteroid pair with simultaneous activity,” says Fernando Moreno (IAA-CSIC).

Analyses revealed that the asteroids were activated near their perihelion – the point on the orbit nearest to de Sun – between the end of 2015 and the beginning of 2016, and that they remained for a period of between six and nine months. The span of time between the moment of fragmentation and their bout of activity implies that the two events are not related. In fact, the data suggests that the fragmentation also happened near the perihelion but during the previous orbit (it takes P/2016 J1 5.65 years to spin around the Sun). “In all likelihood, the dust emission is due to the sublimation of ice that was left exposed after the fragmentation,” says Moreno (IAA-CSIC).

I suspect that the more we learn about asteroids and comets the more we will blur the line that separates them.

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A comet breaks apart

On February 12 members of the amateur astronomy organization Slooh actually viewed the break-up of Comet 73P/Schwassmann-Wachmann into two large fragments.

On the night of February 12th, Slooh members using the company’s telescopes in Chile were able to view the comet as it broke into two pieces. This seems to be the continuation of a process that was first witnessed in 1995, then again in 2006.

Slooh members were among the first to confirm that the nucleus of comet 73P/Schwassmann-Wachmann had split into at least two large pieces. “They immediately pointed Slooh’s telescopes to capture the event,” says Slooh Astronomer, Paul Cox. “Members will continue to monitor the comet live over the coming weeks – assuming the comet survives that long.”

They have created an animation from their images, but it appears that they only started taking images after the actual breakup, so the animation shows the two fragments, but not the moment they broke apart.

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Rosetta’s last image

Rosetta's last image

The Rosetta mission has ended. The spacecraft worked up until it landed on the comet’s surface. The image on the right was the last image, taken from about 167 feet away with a resolution capable of seeing objects less than a quarter of an inch across.

You can see a nice collection of approach images here.

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The interior of Comet 67P/C-G

The Rosetta science team has released a summary of what they have learned about the interior of Comet 67P/C-G.

Essentially, they have found that the comet’s interior has a rather uniform and soft and fluffy interior, with few voids or dense pockets. They also found that the comet’s two lobes almost certainly came from two different objects that somehow made contact and stuck to each other. And finally, it appears that the upper few feet of the surface of the smaller lobe where Philae landed is different than its interior, a difference likely caused by the surface’s exposure to the Sun.

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Watching Rosetta’s finale

The Rosetta team has released a step-by-step outline on what will happen this week as Rosetta is sent crashing into Comet 67P/C-G, including details on how the public can watch.

More information here. Coverage will begin at 6:30 am (Eastern) on September 30 and end a little over an hour later.

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The outbursts on Comet 67P/C-G

The Rosetta science team has released a detailed analysis of the jets and outbursts that they observed coming from Comet 67P/C-G during the comet’s close approach to the Sun.

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.

They have also released a new image taken by the navigation camera of Rosetta’s September 30th landing zone.

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Rosetta’s last days

The Rosetta team has released a detailed description of what will be happening in the last two weeks of the spacecraft’s mission, leading up to its landing on the comet’s surface on September 30.

Their description of the difficulty of planning maneuvers based on the complex asymmetrical gravitational field of the two-lobed comet nucleus is especially interesting.

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Hubble captures on-going comet break-up

animation of comet debris

Cool image time! The animation to the right, taken over three days by the Hubble Space Telescope, cropped and reduced to fit here, shows the debris flying away from Comet 332P/Ikeya-Murakami. It also shows a new piece of debris close to the comet on the lower left.

The research team calculated that the comet probably shed material over several months, between October and December 2015. Jewitt suggests that even some of the ejected pieces have themselves fallen to bits in a kind of cascading fragmentation. “Our analysis shows that the smaller fragments are not as abundant as one might expect based on the number of bigger chunks,” he said. “This is suggestive that they’re being depleted even in the few months since they were launched from the primary body. We think these little guys have a short lifetime.”

Hubble’s sharp vision also spied a chunk of material close to the comet, which may be the first salvo of another outburst. The remnant from still another flare-up, which may have occurred in 2012, is also visible. The fragment may be as large as Comet 332P, suggesting the comet split in two. But the icy remnant wasn’t spotted until Dec. 31, 2015, by the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) telescope in Hawaii, in work supported by the Near-Earth Object Observations program in NASA’s Planetary Defense Coordination Office. That discovery prompted Jewitt and colleagues to request Hubble time to look at the comet in detail. Around the same time, astronomers around the world began to notice a cloudy patch of material near the comet – which Hubble later resolved into the 25 pieces.

The scientists think they actually “may be seeing a comet fragmenting itself into oblivion.”

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Rosetta’s final descent to Comet 67P/C-G

The Rosetta science team today posted two stories, describing details about the planned final descent of the spacecraft to the surface of Comet 67P/C-G on September 30, ending the mission.

The spacecraft will land in a region dubbed Ma’at that contains several active pits more than 300 feet across and 150 feet deep. This is also where several of the comets dust jets originate.

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Rosetta finds carbon molecules in comet dust

The Rosetta science team has announced that they have detected very complex carbon molecules in solid dust particles that were released from Comet 67P/C-G.

“Our analysis reveals carbon in a far more complex form than expected,” remarked Hervé Cottin, one of the authors of the paper reporting the result that is published in Nature today. “It is so complex, we can’t give it a proper formula or a name!” The organic signatures of seven particles are presented in the paper, which the COSIMA team say are representative of the two hundred plus grains analysed so far.

The carbon is found to be mixed with other previously reported elements such as sodium, magnesium, aluminium, silicon, calcium and iron. It is bound in very large macromolecular compounds similar to the insoluble organic matter found in carbonaceous chondrite meteorites that have fallen to Earth, but with a major difference: there is much more hydrogen found in the comet’s samples than in meteorites.

But as this kind of meteorite is associated with reasonably well-processed parent bodies such as asteroids, it is reasonable to assume that they lost their hydrogen due to heating. By contrast, comets must have avoided such significant heating to retain their hydrogen, and therefore must contain more primitive material.

Because of the use of the term organics here for these carbon-based molecules, expect a lot of news reports to misreport this discovery and incorrectly announce with great excitement that Rosetta has “discovered life” on Comet 67P/C-G! Among scientists, any carbon molecule is referred to as organic, even if it is entirely inanimate. In this case these molecules are not the result of life, but of carbon’s atomic structure, allowing it to form an infinite variety of molecules with almost any other element.

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Philae found!

Philae!

Less than a month before Rosetta’s mission ends the spacecraft’s high resolution camera has finally located Philae in its final resting spot on the surface of Comet 67P/C-G.

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.

The image on the right clearly shows the lander on its side with one leg sticking up, as theorized by the Rosetta engineers based on the small amount of data they had received before Philae went dead. Furthermore, the wide image at the link above shows that the lander landed exactly as predicted by data, up against a wall — in this case a large boulder — which placed it in shadow most of the time.

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Changes on Comet 67P/C-G

Cool image time! Below the fold are two images taken by Rosetta of the smooth boulder-strewn area on Comet 67P/C-G called Imhotep, which has been featured many times by the Rosetta science team. The image on the left was taken October 26, 2014 soon after the spacecraft’s arrival at the comet. The image on the right was taken August 17, 2016, almost two years later after it had completed its close approach to the Sun. With both images I have cropped them and reduced their resolution to fit here. With the more recent image I have also stretched it horizontally to better match it to the older image.

The point? The giant boulders on this smooth region act as markers so that we can more easily compare the region and see how it has changed with time. The newer image clearly shows a loss of material from the surface, with the depressions in the smooth areas having grown much larger and in some areas much deeper. At the same time, there has been a softening in some of the edges between the lower and higher areas, especially in the middle of the smooth region.

What will happen here in the future? It appears that the smooth area is actually pond of dust that is slowly evaporating away with each close approach to the Sun, leaving behind the solid bedrock pinnacles within it that only appear as boulders because they are mostly buried. Eventually, when the dust is gone, some of those pinnacles will break away as well.
» Read more

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Rosetta photographs outburst on Comet 67P/C-G

The Rosetta science team today released data and images of a February 19, 2016 outburst on Comet 67P/C-G that the spacecraft was able to photograph, as it happened.

A strong brightening of the comet’s dusty coma was seen by the OSIRIS wide-angle camera at 09:40 GMT, developing in a region of the comet that was initially in shadow. Over the next two hours, Rosetta recorded outburst signatures that exceeded background levels in some instruments by factors of up to a hundred. For example, between about 10:00–11:00 GMT, ALICE saw the ultraviolet brightness of the sunlight reflected by the nucleus and the emitted dust increase by a factor of six, while ROSINA and RPC detected a significant increase in gas and plasma, respectively, around the spacecraft, by a factor of 1.5–2.5.

In addition, MIRO recorded a 30ºC rise in temperature of the surrounding gas. Shortly after, Rosetta was blasted by dust: GIADA recorded a maximum hit count at around 11:15 GMT. Almost 200 particles were detected in the following three hours, compared with a typical rate of 3–10 collected on other days in the same month.

Be sure an look at the animated gif at the link.

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A fine collection of Rosetta images

Comet 67P/C-G

Many cool images! The Rosetta team has released a bunch of very nice images taken of Comet 67P/C-G during August when the spacecraft was flying in close. The image on the right, cropped and reduced in resolution to post here, shows the comet’s large lobe, with the narrow neck to the left. Make sure you check out the full resolution image. It was taken on August 10, 2016 from about 8 miles away, and has a resolution of less than four feet per pixel. If a person was standing there you could just see them!

What I find most fascinating is the incredible curvature of the comet’s surface. The smooth area on the left, dubbed Imhotep (images of which have been posted here previously), has several big boulders on its flat surface. If you stood there, the ground would be down and horizontal. Walk only a short distance and you quickly reach the curving horizon and that flat area would look like a steep slope dropping down behind you. Yet, the boulders do not roll down hill! Walk a short distance more and you begin to enter the neck region, with giant walls rising above you, until you start to walk up them and they become the floor!

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