Category Archives: Rosetta

It’s Called Churymoon

It’s a fun moniker, “Churymoon” – a REAL chip off the old comet. Couldn’t resist. Very pleased to see Rosetta in the news again!

Image:  ESA/Rosetta/MPS/OSIRIS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/J. Roger (CC BY-SA 4.0)

ESA: Last week marked five years since ESA’s Rosetta probe arrived at its target, a comet named 67P/Churyumov-Gerasimenko (or 67P/C-G). Tomorrow, 13 August, it will be four years since the comet, escorted by Rosetta, reached its perihelion – the closest point to the Sun along its orbit. This image, gathered by Rosetta a couple of months after perihelion, when the comet activity was still very intense, depicts the nucleus of the comet with an unusual companion: a chunk of orbiting debris (circled).

Comet 67P/C-G is a dusty object. As it neared its closest approach to the Sun in late July and August 2015, instruments on Rosetta recorded a huge amount of dust enshrouding the comet. This is tied to the comet’s proximity to our parent star, its heat causing the comet’s nucleus to release gases into space, lifting the dust along. Spectacular jets were also observed, blasting more dust away from the comet. This disturbed, ejected material forms the ‘coma’, the gaseous envelope encasing the comet’s nucleus, and can create a beautiful and distinctive tail.

A single image from Rosetta’s OSIRIS instrument can contain hundreds of dust particles and grains surrounding the 4 km-wide comet nucleus. Sometimes, even larger chunks of material left the surface of 67P/C-G – as shown here.

The sizeable chunk in this view was spotted a few months ago by astrophotographer Jacint Roger from Spain, who mined the Rosetta archive, processed some of the data, and posted the finished images on Twitter as an animated GIF. He spotted the orbiting object in a sequence of images taken by Rosetta’s OSIRIS narrow-angle camera on 21 October 2015. At that time, the spacecraft was at over 400 km away from 67P/C-G’s centre. The animated sequence is available for download here.

Scientists at ESA and in the OSIRIS instrument team are now looking into this large piece of cometary debris in greater detail. Dubbed a ‘Churymoon’ by researcher Julia Marín-Yaseli de la Parra, the chunk appears to span just under 4 m in diameter.

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.

Scientists have been studying and tracking debris around 67P/C-G since Rosetta’s arrival in 2014. The object pictured in this view is likely the largest chunk detected around the comet, and will be subject to further investigations.

Comet 67P/C-G is currently in the outer Solar System, between the orbits of Mars and Jupiter, and will have its next perihelion in late 2021.

The Horizon of Comet 67P/C-G

This image from the Rosetta spacecraft shows the horizon over Churyumov-Gerasimenko.  The image was taken on 06 August 2014 so this is a sort of anniversary image.  I always marvel at the boulders – gravity is pretty cool.

Here’s ESA’s caption:

On 6 August of 2014, after a decade of travelling through interplanetary space, ESA’s Rosetta spacecraft arrived at its final target: Comet 67P/Churyumov-Gerasimenko (67P/C-G). The mission was the first to successfully land on a comet when it sent the lander Philae down to the surface a few months later, while the orbiter studied 67P/C-G in detail before the mission’s end on 30 September 2016.

Over its lifetime Rosetta extensively mapped the comet’s surface, which has since been divided into 26 geological regions named after Ancient Egyptian deities. The entire comet has been likened to a duck in shape, with a small ‘head’ attached to a larger ‘body’.

This image shows a section of 67P/C-G as viewed by Rosetta’s high-resolution camera OSIRIS on 10 February 2016. Amateur astronomer Stuart Atkinson, from the UK, selected and processed this view from the OSIRIS image archive. It is a crop of a larger image that shows a slightly wider view of the comet’s ‘Bes’ region on body of the comet, which takes its name from the protective deity of households, children and mothers.

It shows the uneven, shadowed surface of the comet in detail; particularly prominent just to the right of centre is an upright feature surrounded by scattered depressions, rocky outcrops and debris.

Explore the full mission image archive yourself at https://imagearchives.esac.esa.int and let us know what hidden treasures you find via @esascience.

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA – CC BY SA 4.0; Acknowledgement: S Atkinson.

Rosetta’s Final Images

ESA put together this compilation of the final images from the epic Rosetta mission. The images were taken by Rosetta’s high resolution OSIRIS camera during the mission’s final hours at Comet 67P/Churyumov-Gerasimenko.

Rosetta Continues

We all know the end of a spacecraft doesn’t necessarily mean an end to the process of scientific discovery and learning.

Scientists are meeting to discuss the Rosetta mission and the findings so far.

Comet Storm

If you were cruising along next to a comet and looked out your window you might see this scene. Reminds me of driving in a snowstorm except more random. This particular comet storm was outside of Rosetta during its journey with comet 67P/Churyumov–Gerasimenko.

ESA’s caption: Perhaps you live in a part of the world where you regularly experience snow storms or even dust storms. But for many of us, the weather forms a natural part of everyday conversation – more so when it is somewhat extreme, like a sudden blizzard that renders transport useless or makes you feel highly disoriented as you struggle to fix your sights on recognisable landmarks.

ESA’s Rosetta mission had a similar experience, for more than two years, as it flew alongside Comet 67P/Churyumov–Gerasimenko between 2014 and 2016. It endured the endless impacts of dust grains launched by gaseous outpourings as the comet’s surface ices were warmed by the heat of the Sun, evaporating into space and dragging the dust along.

This image was taken two years ago, on 21 January 2016, when Rosetta was flying 79 km from the comet. At this time Rosetta was moving closer following perihelion in the previous August, when the comet was nearer to the Sun and as such at its most active, meaning that Rosetta had to operate from a greater distance for safety.

As can be seen from the image, the comet environment was still extremely chaotic with dust even five months later. The streaks reveal the dust grains as they passed in front of Rosetta’s camera, captured in the 146 second exposure.

Excessive dust in Rosetta’s field of view presented a continual risk for navigation: the craft’s startrackers used a star pattern recognition function to know its orientation with respect to the Sun and Earth. On some occasions flying much closer to the comet, and therefore through denser regions of outflowing gas and dust, the startrackers locked on to dust grains instead of stars, creating pointing errors and in some cases putting the spacecraft in a temporary safe mode.

Despite its dangers, the dust was of high scientific interest: three of Rosetta’s instruments studied tens of thousands of grains between them, collectively analysing their composition, their mass, momentum and velocity, and profiling their 3D structure. Studying the smallest and the most pristine grains ejected is helping scientists to understand the building blocks of comets.

Two years before the image was taken, 20 January 2014, Rosetta was only just waking up from 31 months of deep-space hibernation. It arrived at its destination after 10 years in space  in August 2014, and released the lander Philae three months later. Rosetta made unique scientific observations of the comet until reaching its grand finale on 30 September 2016 by descending to the comet’s surface. By the end of the mission, more than a hundred thousand images had been taken by the high-resolution OSIRIS camera (including the one shown here) and the navigation camera, the majority of which are available to browse in the Archive Image Browser.

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

A Big Surprise from Rosetta


ESA – Scientists analysing the final telemetry sent by Rosetta immediately before it shut down on the surface of the comet last year have reconstructed one last image of its touchdown site.After more than 12 years in space, and two years following Comet 67P/Churyumov–Gerasimenko as they orbited the Sun, Rosetta’s historic mission concluded on 30 September with the spacecraft descending onto the comet in a region hosting several ancient pits.

It returned a wealth of detailed images and scientific data on the comet’s gas, dust and plasma as it drew closer to the surface.

But there was one last surprise in store for the camera team, who managed to reconstruct the final telemetry packets into a sharp image.

“The last complete image transmitted from Rosetta was the final one that we saw arriving back on Earth in one piece moments before the touchdown at Sais,” says Holger Sierks, principal investigator for the OSIRIS camera at the Max Planck Institute for Solar System Research in Göttingen, Germany.

“Later, we found a few telemetry packets on our server and thought, wow, that could be another image.”

During operations, images were split into telemetry packets aboard Rosetta before they were transmitted to Earth. In the case of the last images taken before touchdown, the image data, corresponding to 23 048 bytes per image, were split into six packets.

For the very last image the transmission was interrupted after three full packets were received, with 12 228 bytes received in total, or just over half of a complete image. This was not recognised as an image by the automatic processing software, but the engineers in Göttingen could make sense of these data fragments to reconstruct the image.

Rosetta’s Legacy

Rosetta was an epic mission no doubt about it. For some looking at all the data from the mission is the best part; something akin to looking through a treasure chest, you never know what you might find.

Video

Moving a Boulder on a Comet

Take a look at these images of a boulder that moved on Comet 67P/Churyumov-Gerasimenko as seen by the Rosetta spacecraft.  Fascinating stuff.  The boulder clearly moved.  But how?

Here’s ESA’s caption (via NASA):
A 100 foot-wide (30 meter), 28-million-pound (12.8-million-kilogram) boulder, was found to have moved 460 feet (140 meters) on comet 67P/Churyumov-Gerasimenko in the lead up to perihelion in August 2015, when the comet’s activity was at its highest. In both images, an arrow points to the boulder; in the right-hand image, the dotted circle outlines the original location of the boulder for reference.

The movement could have been triggered in one of two ways: either the material on which it was sitting eroded away, allowing it to roll downslope, or a sufficiently forceful outburst could have directly lifted it to the new location. Indeed, several outburst events were detected close to the original position of the boulder during perihelion.

The images were taken by Rosetta’s OSIRIS camera on May 2, 2015 (left) and Feb. 7, 2016 (right), with resolutions of 7.5 feet (2.3 meters) per pixel and 2.6 feet (0.8 meters) per pixel, respectively.

Rosetta is a European Space Agency mission with contributions from its member states and NASA. Rosetta’s Philae lander is provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; French National Space Agency, Paris; and the Italian Space Agency, Rome. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the U.S. participation in the Rosetta mission for NASA’s Science Mission Directorate in Washington.

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So first I’m siding with the erosion idea by way of off gassing or jets. It seems that a jet strong enough to directly lift a “12.8 million-kg” boulder would lift more material than just the boulder and if it did the boulder would likely show more of an impact mark as the soil looks sand-like. True the same forces could erase those marks but you’d think there would be some physical sign of such a powerful event. Still there are no “boulder-tracks” and again off-gassing might erase the tracks.

The other thing that isn’t explained is this: Is the 12.8 million-kg / 28 million-lb boulder a true 67P weight or is that what it would weigh here on Earth?  OR is this a measure of mass but not stated as such? This is a case where knowing the mass would be helpful. Like I said – fascinating stuff!

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

Rosetta Archive

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The last of the NAVCAM images are now archived. The images in the latest  archive release are from the Rosetta’s last month of activity during the fantastic mission around Comet 67P/Churyumov-Gerasimenko.

This and other images can be found with the ESA Archive Image Browser

ESA’s description of the image above, one of the last five from Rosetta’s NAVCAM taken on 30 September 2016:

Single frame enhanced NavCam image taken on 29 September 2016 at 23:25 GMT, when Rosetta was 19.4 km from the centre of the nucleus of Comet 67P/Churyumov-Gerasimenko. The scale at the surface is about 1.7 m/pixel and the image measures about 1.7 km across.

Image (and description): ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0