{"id":2305,"date":"2015-01-27T09:24:52","date_gmt":"2015-01-27T09:24:52","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=2305"},"modified":"2015-01-27T09:27:36","modified_gmt":"2015-01-27T09:27:36","slug":"rosetta-watches-comet-shed-its-dusty-coat","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/rosetta-watches-comet-shed-its-dusty-coat\/","title":{"rendered":"Rosetta watches comet shed its dusty coat"},"content":{"rendered":"
\n
\"Fluffy<\/a>
Fluffy dust grains<\/figcaption><\/figure>\n

ESA\u2019s Rosetta mission is providing unique insight into the life cycle of a comet\u2019s dusty surface, watching 67P\/Churyumov\u2013Gerasimenko as it sheds the dusty coat it has accumulated over the past four years.<\/span><\/p>\n

The COmetary Secondary Ion Mass Analyser, or COSIMA, is one of Rosetta\u2019s three dust analysis experiments. It started collecting, imaging and measuring the composition of dust particles shortly after the spacecraft arrived at the comet in August 2014.\u00a0<\/span><\/p>\n

Results from the first analysis of its data are reported today in the journal\u00a0Nature<\/i>. The study covers August to October, when the comet moved along its orbit between about 535 million kilometres to 450 million kilometres from the Sun. Rosetta spent the most of this time orbiting the comet at distances of 30 km or less.<\/span><\/p>\n

The scientists looked at the way that many large dust grains broke apart when they were collected on the instrument\u2019s target plate, typically at low speeds of 1\u201310 m\/s. The grains, which were originally at least 0.05 mm across, fragmented or shattered upon collection.<\/span><\/p>\n

\"Comet<\/a>
Comet on 12 January 2015 \u2013 NavCam<\/figcaption><\/figure>\n

The fact that they broke apart so easily means that the individual parts were not well bound together. Moreover, if they had contained ice, they would not have shattered. Instead, the icy component would have evaporated off the grain shortly after touching the collecting plate, leaving voids in what remained.<\/span><\/p>\n<\/div>\n

\n
<\/div>\n

By comparison, if a pure water-ice grain had struck the detector, then only a dark patch would have been seen.<\/span><\/p>\n

The dust particles were found to be rich in sodium, sharing the characteristics of \u2018interplanetary dust particles\u2019. These are found in meteor streams originating from comets, including the annual Perseids from Comet 109P\/Swift\u2013Tuttle and the Leonids from 55P\/Tempel\u2013Tuttle.<\/span><\/p>\n

\u201cWe found that the dust particles released first when the comet started to become active again are \u2018fluffy\u2019. They don\u2019t contain ice, but they do contain a lot of sodium. We have found the parent material of interplanetary dust particles,\u201d says lead author Rita Schulz of ESA\u2019s Scientific Support Office.<\/span><\/p>\n

The scientists believe that the grains detected were stranded on the comet\u2019s surface after its last perihelion passage, when the flow of gas away from the surface had subsided and was no longer sufficient to lift dust grains from the surface.<\/span><\/p>\n

While the dust was confined to the surface, the gas continued evaporating at a very low level, coming from ever deeper below the surface during the years that the comet travelled furthest from the Sun. Effectively, the comet nucleus was \u2018drying out\u2019 on the surface and just below it.<\/span><\/p>\n<\/div>\n

\n
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\u201cWe believe that these \u2018fluffy\u2019 grains collected by Rosetta originated from the dusty layer built up on the comet\u2019s surface since its last close approach to the Sun,\u201d explains Martin Hilchenbach, COSIMA principal investigator at the Max-Planck Institute for Solar System research in Germany.<\/span><\/p>\n

\u201cThis layer is being removed as the activity of the comet is increasing again. We see this layer being removed, and we expect it to evolve into a more ice-rich phase in the coming months.\u201d<\/span><\/p>\n

The comet is on a 6.5-year circuit around the Sun, and is moving towards its closest approach in August of this year. At that point, Rosetta and the comet will be 186 million kilometres from the Sun, between the orbits of Earth and Mars.<\/span><\/p>\n

As the comet warms, the outflow of gases is increasing and the grains making up the dry surface layers are being lifted into the inner atmosphere, or coma. Eventually, the incoming solar energy will be high enough to remove all of this old dust, leaving fresher material exposed at the surface.<\/span><\/p>\n

\u201cIn fact, much of the comet\u2019s dust mantle should actually be lost by now, and we will soon be looking at grains with very different properties,\u201d says Rita.<\/span><\/p>\n

\u201cRosetta\u2019s dust observations close to the comet nucleus are crucial in helping us to link together what is happening at the very small scale with what we see at much larger scales, as dust is lost into the comet\u2019s coma and tail,\u201d says Matt Taylor, ESA\u2019s Rosetta project scientist.<\/span><\/p>\n

\u201cFor these observations, it really is a case of \u00a0\u201cwatch this space\u201d as we continue to watch in real time how the comet evolves as it approaches the Sun along its orbit over the coming months.\u201d<\/span><\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

ESA\u2019s Rosetta mission is providing unique insight into the life cycle of a comet\u2019s dusty surface, watching 67P\/Churyumov\u2013Gerasimenko as it sheds the dusty coat it has accumulated over the past four years. The COmetary Secondary Ion Mass Analyser, or COSIMA, is one of Rosetta\u2019s three dust analysis experiments. It started collecting, imaging and measuring the […]<\/p>\n","protected":false},"author":6,"featured_media":2307,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-2305","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium-300x300.jpg",300,300,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",65,65,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",305,305,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",96,96,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/01\/Comet_on_12_January_2015_NavCam_medium.jpg",150,150,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"News<\/a>","tag_info":"News","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/2305","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=2305"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/2305\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/2307"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=2305"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=2305"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=2305"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}