{"id":8354,"date":"2016-04-08T07:21:11","date_gmt":"2016-04-08T07:21:11","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=8354"},"modified":"2016-04-08T07:21:11","modified_gmt":"2016-04-08T07:21:11","slug":"the-colou","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/the-colou\/","title":{"rendered":"The colour changing comet"},"content":{"rendered":"
\n
\"The<\/a>
The colour-changing comet<\/figcaption><\/figure>\n

Rosetta\u2019s comet has been seen changing colour and brightness in front of the ESA orbiter\u2019s eyes, as the Sun\u2019s heat strips away the older surface to reveal fresher material.<\/span><\/p>\n

Rosetta\u2019s Visible and InfraRed Thermal Imaging Spectrometer, VIRTIS, began to detect these changes in the sunlit parts of Comet 67P\/Churyumov\u2013Gerasimenko \u2013 mostly the northern hemisphere and equatorial regions \u2013 in the months immediately following the spacecraft\u2019s arrival in August 2014.<\/span><\/p>\n<\/div>\n

\n

A new paper, published in the journal\u00a0Icarus<\/i>, reports on the early findings of this study, up to November 2014, during which time Rosetta was operating between 100 km to within 10 km of the comet nucleus. At the same time, the comet itself moved along its orbit closer to the Sun, from about 542 million km to 438 million km.<\/span><\/p>\n

\"Comet<\/a>
Comet on 19 September 2014 \u2013 NavCam<\/figcaption><\/figure>\n

VIRTIS monitored the changes in light reflected from the surface over a wide range of visible and infrared wavelengths, as an indicator of subtle changes in the composition of the comet\u2019s outermost layer.\u00a0<\/span><\/p>\n<\/div>\n

\n

When it arrived, Rosetta found an extremely dark body, reflecting about 6% of the visible light falling on it. This is because the majority of the surface is covered with a layer of dark, dry, dust made out of mixture of minerals and organics.<\/span><\/p>\n

Some surfaces are slightly brighter, some slightly darker, indicating differences in composition. Most of the surface is slightly reddened by organic-rich material, while the occasional ice-rich material shows up as somewhat bluer.<\/span><\/p>\n

Even when Rosetta first rendezvoused with the comet far from the Sun, ices hidden below the surface were being gently warmed, sublimating into gas, and escaping, lifting some of the surface dust away and contributing to the comet\u2019s coma and tail.<\/span><\/p>\n

VIRTIS shows that as the \u2018old\u2019 dust layers were slowly ejected, fresher material was gradually exposed. This new surface was both more reflective, making the comet brighter, and richer in ice, resulting in bluer measurements.<\/span><\/p>\n<\/div>\n

\n

On average, the comet\u2019s brightness changed by about 34%. In the Imhotep region, it increased from 6.4% to 9.7% over the three months of observations.<\/span><\/p>\n

\"Imhotep<\/a>
Imhotep mosaic<\/figcaption><\/figure>\n

\u201cThe overall trend seems to be that there is an increasing water-ice abundance in the comet\u2019s surface layers that results in a change in the observed spectral signatures. In that respect, it\u2019s like the comet is changing colour in front of our eyes,\u201d says Gianrico Filacchione, lead author of the study.<\/span><\/p>\n

\u201cThis evolution is a direct consequence of the activity occurring on and immediately beneath the comet\u2019s surface. The partial removal of the dust layer caused by the start of gaseous activity is the probable cause of the increasing abundance of water ice at the surface.\u201d<\/span><\/p>\n

\u201cThe surface properties are really dynamic, changing with the distance from the Sun and with the levels of comet activity,\u201d adds Fabrizio Capaccioni, VIRTIS principal investigator.<\/span><\/p>\n

\u201cWe\u2019ve started analysing the subsequent datasets and can already see that the trend continues in the observations made beyond November 2014.\u201d<\/span><\/p>\n

\u201cThe evolution of surface properties with activity has never been observed by a cometary mission before and is a major science objective of the Rosetta mission,\u201d says Matt Taylor, ESA\u2019s Rosetta Project Scientist.<\/span><\/p>\n

\u201cIt is great to see science papers being published directly addressing this topic and we\u2019re looking forward to seeing how things have changed over the entire mission.\u201d<\/span><\/p>\n

\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Rosetta\u2019s comet has been seen changing colour and brightness in front of the ESA orbiter\u2019s eyes, as the Sun\u2019s heat strips away the older surface to reveal fresher material.<\/p>\n","protected":false},"author":6,"featured_media":8355,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[20],"tags":[],"class_list":["post-8354","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-space-news"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",625,391,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large-300x187.jpg",300,187,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",625,391,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",625,391,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",625,391,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",625,391,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",625,391,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",625,391,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",600,375,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",600,375,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",625,391,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",550,344,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",95,59,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",625,391,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",96,60,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/04\/The_colour-changing_comet_large.jpg",150,94,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Space\/ AstroPhysics<\/a>","tag_info":"Space\/ AstroPhysics","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/8354","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=8354"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/8354\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/8355"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=8354"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=8354"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=8354"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}