Comet surface changes before Rosetta's eyes

Comet surface changes before Rosetta’s eyes
Sequence of ten images showing changes in the Imhotep region on Comet 67P/Chruymov-Gerasimenko. The images were taken with the OSIRIS narrow-angle camera on Rosetta between 24 May and 11 July 2015. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

In the months leading to the perihelion of Comet 67P/Churyumov-Gerasimenko, Rosetta scientists have been witnessing dramatic and rapid surface changes on the Imhotep region, as reported in a paper to be published in Astronomy & Astrophysics

Since arriving at Comet 67P/C-G in August 2014, Rosetta has been witnessing an increase in the activity of the comet, warmed by the ever-closer Sun. A general increase in the outflow of gas and dust has been punctuated by the emergence of jets and dramatic rapid outbursts in the weeks around perihelion, the closest point to the Sun on the comet's orbit, which occurred on 13 August 2015.

But in June 2015, just two months before perihelion, Rosetta scientists started noticing important changes on the surface of the nucleus itself. These very significant alterations have been seen in Imhotep, a region containing smooth terrains covered by fine-grained material as well as large boulders, located on 67P/C-G's large lobe.

"We had been closely monitoring the Imhotep region since August 2014, and as late as May 2015, we had detected no changes down to scales of a tenth of a metre," comments Olivier Groussin, an astronomer at the Laboratoire d'Astrophysique de Marseille, France, OSIRIS Co-Investigator and lead author of the study.

"Then one morning we noticed that something new had happened: the surface of Imhotep had started to change dramatically. The changes kept going on for quite a while."

First evidence for a new, roughly round feature in Imhotep was seen in an image taken with Rosetta's OSIRIS narrow-angle camera on 3 June. Subsequent images later in June showed this feature growing in size, and being joined by a second round feature. By 2 July, they had reached diameters of roughly 220 m and 140 m, respectively, and another new feature began to appear.

Comet surface changes before Rosetta’s eyes
Annotated version of the sequence of ten images showing changes in the Imhotep region on Comet 67P/Chruymov-Gerasimenko. The images were taken with the OSIRIS narrow-angle camera on Rosetta between 24 May and 11 July 2015. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

By the time of the last image used in this study, taken on 11 July, these three features had merged into one larger region and yet another two features had appeared.

"These spectacular changes are proceeding extremely rapidly, with the rims of the features expanding by a few tens of centimetres per hour. This highlights the complexity of the physical processes involved," adds Olivier.

Comet surface changes before Rosetta’s eyes
The Imhotep region on Comet 67P/C-G on 3 June 2015. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The sublimation of volatile species is clearly an important factor, as colour images of this region reveal the signature of exposed ice on some of the rims of the newly-formed surface features. The rapid rate of expansion is unexpected, however: models of sunlight-driven sublimation would predict erosion rates of just a few centimetres per hour, and thus the scientists believe that additional mechanisms are required to explain the observations.

Comet surface changes before Rosetta’s eyes
The Imhotep region on Comet 67P/C-G on 24 May 2015. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

A simple possibility is that the surface material is very weak, allowing for more rapid erosion, but it is also possible that the crystallisation of amorphous ice or the destabilisation of so-called 'clathrates' (a lattice of one kind of molecule containing other molecules) could liberate energy and thus drive the expansion of the features at faster speeds.

The erosion could be accompanied by increased rates of gas outflow, including H2O, CO2, or CO. The scientists also searched in OSIRIS images for evidence of increased dust rising from Imhotep as the surface morphology evolved, but did not find any.

Comet surface changes before Rosetta’s eyes
Colour images of the Imhotep region on Comet 67P/C-G, taken with the OSIRIS narrow-angle camera on Rosetta on 18 June (upper row), 2 July (middle row) and 11 July 2015 (lower row). The first column shows images taken in the orange filter (649 nanometres); the second column shows the ratio between images taken with the blue filter (481 nanometres) and the orange filter for the 18 June and 2 July images, and the ratio between images taken with the blue and the red (701 nanometres) filters for the 11 July image; the third column shows a composite obtained by combining the images in the previous two columns. The yellow arrows indicate some of the new features that were detected on Imhotep. These colour images show that some patches on the surface of the comet reflect orange/red light less effectively and blue light more effectively than their surroundings. They appear as white in the central column, where the colour ratio is shown. This indicates the presence of frozen water ice at or just below the surface of these patches. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

While it is unlikely that many small (micron-sized) dust particles were released as the features formed and expanded, it is possible that the same amount of mass was released in a smaller number of larger (millimetre-sized) particles, which would produce less reflected light and thus be harder to detect with OSIRIS.

In addition, a significant fraction of the dust released may have immediately fallen back to the , accumulating at the base of the expanding rims.

Comet surface changes before Rosetta’s eyes
Activity seen above the Imhotep region with the OSIRIS narrow-angle camera on Rosetta on 23 May 2015 (left), before significant morphological changes were seen in this region, and on 23 June 2015 (right), after the changes had begun to appear. (Times are in UT.) The positions of the first two new features that were seen in Imhotep are marked with A and B. The white arrows indicate the direction along which an increase of activity would have been seen in the case of jets lifting from the newly arisen features. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Although the scientists were initially surprised to see such significant changes taking place on smooth terrains such as those seen in Imhotep, the location of this region close to the comet's equator guarantees that it receives large amounts of sunlight.

"We are looking forward to combining our OSIRIS observations with data from other instruments on Rosetta, to piece together the origin of these curious features," concludes Olivier.

Comet surface changes before Rosetta’s eyes
The Imhotep region on Comet 67P/C-G on 5 June 2015. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Explore further

Image: Increasingly active Comet 67P

More information: "Temporal morphological changes in the Imhotep region of comet 67P/Churyumov-Gerasimenko," A&A, Received: 21 July 2015 / Accepted: 08 September 2015 DOI: dx.doi.org/10.1051/0004-6361/201527020
Journal information: Astronomy & Astrophysics

Citation: Comet surface changes before Rosetta's eyes (2015, September 22) retrieved 18 October 2019 from https://phys.org/news/2015-09-comet-surface-rosetta-eyes.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Sep 22, 2015
There is a process that can explain this phenomena, EDM.

https://www.thund...5/18083/

Sep 22, 2015
I knew at least one eu nutter would comment on this story.

Sep 22, 2015
Stalker troll alert! Vietkiller is off his dementia meds again...

Sep 22, 2015
There is a process that can explain this phenomena, EDM.

https://www.thund...5/18083/

That looks cool. Although modern art really doesn't attract me.

I really enjoyed the artistic work made by them over the decades:
https://en.wikipe...26_Magic

Where I can see the images of the giant spikes and plates that shape the worlds through electric discharges?
I already know what a meteorite or volcano is. No reference needed for these.

Sep 23, 2015
Rosetta is in a shady place at the moment. Is there any probability that the shaded area will be illuminated by Sun once the asteroid completes the revolution around sun and starts it's journey away from Sun ?

Sep 23, 2015
There is a process that can explain this phenomena, EDM.

https://www.thund...5/18083/

Surely a link everyone will find useful.

Sep 23, 2015
There is a process that can explain this phenomena, EDM.

https://www.thund...5/18083/

Surely a link everyone will find useful.


The link is broken.

Sep 23, 2015
Rosetta is in a shady place at the moment. Is there any probability that the shaded area will be illuminated by Sun once the asteroid completes the revolution around sun and starts it's journey away from Sun ?

You must be talking about Philae. It receives enough energy to power up and execute some tasks but there seems to be some technical issues with it. Here is the last report on it: http://blogs.esa....ae-team/ You should also know that, at the moment, Rosetta is too far to communicate with it; the comet is to active to get in close proximity.

Sep 23, 2015
There is a process that can explain this phenomena, EDM.

https://www.thund...5/18083/

Surely a link everyone will find useful.


The link is broken.

like that dudes head

Sep 23, 2015
Where I can see the images of the giant spikes and plates that shape the worlds through electric discharges?


Lightning is created in the lab using various equipment, and oddly when lightning occurs in nature such equipment is not present.

Sep 23, 2015
Lightning is created in the lab using various equipment, and oddly when lightning occurs in nature such equipment is not present.

That's not odd, you need things like an atmosphere and clouds, not equipment.
Are these pics of Mars, Mercury and Callisto? Electrical storms in such places?
Cool, where I can see some of that? Where can I see how lighting creates such features?

I saw a "discharge experiment", compared with "Devil's Tower". It was made with a plate, it's not? What's the point of that?
Nice art, really. And more "refined" that this guy who tried it using mashed potatoes:
https://www.youtu...JLI-GRuU

Where can I see how EDM caused any of this?

Sep 23, 2015
Of course, all of this EDM nonsense being proposed fails to take into account that electric discharges will show up as hard x-rays. Satellites with the ability to detect such x-rays have looked at comets for some years. They have never seen these hard x-rays. Just the soft x-rays associated with charge exchange between the solar wind and the cometary coma. And that goes for Thorhill's idiotic claims of a pre-impact flash at Tempel 1. Nope. Not seen by Chandra or SWIFT, just a 3 second delay, and then the soft x-rays from charge exchange with the excavated material. Doesn't stop them believing the cretin, though!

Sep 23, 2015
In addition to which, the temperature caused by this process would be extremely high. Temperature data have been measured at three comets; Tempel 1, Hartley 2 and 67P. Never seen anything anomalous. And that includes the highly active Hartley 2, which showed the region around this high activity to be slightly lower than the ambient temperature. None of the measured temps was higher than ~350K.

Sep 27, 2015
I think I can explain the anomalies occurring on Comet 67P. Capricorn One.

Sep 28, 2015
I think I can explain the anomalies occurring on Comet 67P. Capricorn One.


There are no anomalies on 67P! Only in the minds of the neo-Velikovskian eejits who expected some sort of electrical display by now! Ain't going to happen. They'll have to turn to Wal again, to spin the story, so that he can continue to sell his books and DVDs. Just like he did for the Deep Impact mission, which well and truly put this garbage in the grave that it belongs.

Oct 04, 2015
I think I can explain the anomalies occurring on Comet 67P. Capricorn One.


There are no anomalies on 67P! Only in the minds of the neo-Velikovskian eejits who expected some sort of electrical display by now! Ain't going to happen. They'll have to turn to Wal again, to spin the story, so that he can continue to sell his books and DVDs. Just like he did for the Deep Impact mission, which well and truly put this garbage in the grave that it belongs.

Nope, no anomalies. Totally expected.... That's why the article states;

"The rapid rate of expansion is unexpected, however: models of sunlight-driven sublimation would predict erosion rates of just a few centimetres per hour, and thus the scientists believe that additional mechanisms are required to explain the observations."

Your idiotic presumptions of what should be expected from EDM only highlights your profound ignorance of the processes.

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