COSIMA catches cosmic dust

While many of us spend time trying to eliminate dust, Rosetta’s COSIMA team have a different attitude – they are actively attempting to catch it.  Today we heard that they succeeded and have the picture to prove it!

At the European Planetary Science Congress (EPSC) held in Lisbon, Portugal, the COSIMA team presented an image of the first dust grains collected by the COSIMA instrument when Rosetta was at a distance of less than 100 km from the nucleus of comet 67P/Churyumov-Gerasimenko.

COSIMA studies dust in situ by capturing grains on small (1 cm by 1 cm) target plates, first imaging these with an optical microscope and then analysing the composition of selected grains using a secondary ion mass spectrometer. The instrument is designed to investigate dust grains larger than about 10 microns.

The COSIMA instrument on Rosetta imaged cometary dust grains on 24 August 2014 when the spacecraft was at a distance of less than 100 km from the comet nucleus and more than 500 million km from the Sun. These are among the first dust grains collected from beyond the Solar System’s snow line, the distance from the Sun at which ice grains can form.  Left: an image of the target plate (measuring 1cm by 1 cm) on which the grains were collected; right: a section of the plate showing the state on 17 August (top) when no dust grains were visible and 24 August (bottom) when some large dust grains were detected. The plate is illuminated from the right by LEDs and the length of the shadows is proportional to the height of the dust grains. The resolution of the image is 14 microns per pixel. Credit: ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/ BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S

COSIMA catches first dust grains. Left: an image of the target plate (measuring 1 cm by 1 cm) on which the grains were collected; right: a section of the plate showing the state on 17 August (top) when no dust grains were visible and 24 August (bottom) when some large dust grains were detected. The plate is illuminated from the right by LEDs and the length of the shadows is proportional to the height of the dust grains. The resolution of the image is 14 microns per pixel.
Credit: ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/
BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S

Early in the morning of 11 August, the first of COSIMA’s 24 target plates was exposed to space. As the team mentioned in a previous blog post, models of 67P/C-G’s coma suggest that at the present low level of activity, it should be comparable to a high-quality cleanroom – in other words, there should not be many dust particles. They therefore decided to expose this plate for at least one month and to check back periodically to see if they had been lucky and something had been picked up at this early stage.

On 24 August, when the COSIMA team looked at the image of the plate they saw a number of large dust grains from the comet on a target that had been pristine when examined one week before. A first examination of the plate indicates that the largest two grains are about 50 microns and 70 microns in width, comparable to the width of a human hair.

Scientists from the COSIMA team are now examining the image of the target plate in detail to determine the locations of the dust grains. Some will be selected for further analysis: the target plate will be moved to place each chosen grain under an ion gun which will then ablate the grain layer by layer. The material is then analysed in a secondary ion mass spectrometer to determine its composition.

The results of these investigations are eagerly awaited since these are among the first dust grains to have been collected from beyond the Solar System’s snow line – the distance from the Sun at which ice grains can form.

COSIMA is one of three instruments on Rosetta that will study cometary dust, the other two being GIADA and MIDAS. In mid August, the GIADA team reported the detection of four dust grains, ranging in width from a few tens of microns up to a few hundreds of microns, collected when Rosetta was between 814 and 179 km from the comet.

Comments

10 Comments

  • Errol Coder says:

    What is this "dust" mainly composed of? When I imagine dust, I picture minerals and other material common to Earth "dust". But, this posts seems to reference ice. Does that mean even they the term dust was used to describe the "dust plume" captured in the 8/31 images, may also be composed of out-gassing ice verses just what we would typically think of "dust"? Is there anyway to determine the composition of the out-gassing of these couple plumes from the surface we are seeing, and to see how much of it is either actual gas, verses, ice, versus minterals?

    • Errol Coder says:

      After reading the GIADA thread, it answered my question. The dust is a combination of the silicates etc and the ice it is encased in when released due to sublimation. I guess my question is whether or not other forms of gas has been monitored to be released from the ice other then water vapor, of which will be answered from any of the spectroscopy results.

    • Peon says:

      The reason it's more like dust, is it's not a ball of dirty ice. The Comet is an electrically charged rock, that occasionally has to discharge in the form of plasma. The surface is dark and dusty due to electric charring, and it's double lobed because of it's formation.

  • Dave says:

    Errol,
    Do you still think that ice is there? It seems unlikely, none of the previous comets that we have seen close have ice at the surface.
    The dirty snowball theory was made a long time ago before we could get this close, so what seemed reasonable from the available data in the 50s & 60s is unlikely correct now that we can see a comet close up.
    The theory that Ice is under thesurface is just because people are not looking beyond a very old theory.
    There are enough exposed carved escarpments on this comet for us to see Ice if it was really under the surface.
    The only evidense for water is the OH ions in the coma, but what if these were not produced from sublimating water ice?
    We should then look at what other chemical reactions can produce the coma. We might then get to an up to date theory.
    Hopefully this new theory may shed light on how the solar system was formed, so there is exiting science to come. (Even as a boy at school the model for the formation of our solar system seemed very unlikely) lets just sit back and wait for the data and hope the lander manages to get down to the comet safetly.

  • Erka says:

    Our solar system is a giant junkyard full of stuff and at tiny fraction of it is this comet from wich a tiny orbiting dust grain was collected and this grain analyzed on molecular and atomic level. Whatever it contains should be no surprise. If it is a surprise then the next grain is not and so on.
    What i mean is that there is no other place in our solarsystem that is more complicated and full of secrets then right here on earth. This mission is a great adventure but we vill not find any revolutionary secrets due to it. All the instruments in its backpack are not more then a desperat wish to find something we did not know before. In a year when all is done what remains of it is the knowledge that we could do this journey and return a few nice pictures for our albums. Im not saying the money is wasted as we waste a lot more money on a private journey to a romantic iland and return with not more then a few memories and pictures for the album. Then we plan for the next adventure, save some money and hope that this time we find something we never had before. Maybe a walk in the forest on a warm and sunny day would bring a lot more then to do spectral analysis of billion years old booring dust.

  • Dertutenix says:

    The places this comet has been is all in a hard environment where cosmic radiation is forming its evolution from an original stardust cloud lumping up to an oddly shaped body with lots of scars. Its low density is the only thing that is a surprise for me telling that this never was a part of a planet and compressed to a ten times higher density due to a thousend fold higher gravity field, all of it is extreme porous piled up dust in vacuum. Its composition of minerals and ice and gasses will be no additional great news.

  • Erka says:

    This comet is not of the original matter our solar
    system was created of. It is a composition of the leftover remnant of the creation of our solar system. All of it is a more than third hand recycling process dirt bag material. Not even solid or pure but just very old ashes.

  • Jjrogers says:

    What an amazing journey, so far. When the two lobes disjoin, what images will be captured...that is when we might see the inner materials and structures.

  • Steve Kasian says:

    Why is it that the "smartest" people posting in these threads have no understanding of basic grammar, can't spell, and don't understand the difference between the words "then" and "than"? If you didn't pay attention in school, please don't bother trying to act like you know what you're talking about here by commenting about how ignorant scientists are, or how they are wrong about everything they've ever published about comets. Your own lack of scientific knowledge is really quite obvious when you don't even understand the proper use of commas, how to spell (or even how to acknowledge automatically flagged misspelled words), or proper use of the most rudimentary of English words. Thanks.

  • Joe says:

    The dust coming off the surface contains Sodium and Magnesium, which are common on earth as soluble salts in the oceans as well as deserts like Atacama.

    I would expect to find heavy metal ores and transitional metals, Lanthanides and Actinides in the core, as comets are presumably similar to the proto planet material generated by the matter element-genesis in stellar thermonuclear activity throughout the Universe.

    It's a pity it is not possible to get to study the actual core of the comet on this mission, but then is blasting a comet open justified ? Still I'm following this great project with great interest - I think ESA is doing a great job ! Well Done!

Comments are closed.