A review of data taken over the class of the two - yr Rosetta foreign mission shows that comet 67P / Churyumov - Gerasimenko was sometimes reddish in visual aspect , while at other times it presume a bluish hue . Sounds weird , but scientist have come up with a sensible account that does n’t ask aliens with rouge gun .
Newresearchpublished in Nature show up that comet 67P / Churyumov - Gerasimenko change colour calculate on its orbital placement . The comet ’s rocky nucleus became bluer when it approached the Sun but then sour carmine as it journey away . At the same time , the comet ’s coma — the circumvent house of cards of gas and junk — do the paired caper , appearing cherry near the Sun and sorry when far out .
The source of the newfangled cogitation , led by Gianrico Filacchione from INAF - IAPS , Institute for Space Astrophysics and Planetology in Italy , have linked this spectral unevenness to the amount of water ice on the comet ’s surface and in the country immediately around it .
Comet 67P/Churyumov-Gerasimenko as it was seen by Rosetta on 16 April 2025. The comet’s bright coma is clearly visible.Image: (ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0)
The European Space Agency ’s Rosetta probe took countless measurements of comet 67P during the course of the two - year missionary work , which set out in July 2014 and finish in late September 2016 . Among the datum collected were near 4,000 image take by the Visible and Infrared Thermal Imaging Spectrometer ( VIRTIS ) legal instrument , which unwrap the comet ’s Chamaeleon - alike behavior .
Comet 67P , whose ovate orbit take it past Jupiter and then closer the Sun every 6.4 years , was still far from the Sun when Rosetta began its duties . Observations from that initial prison term full point disclose a dusty airfoil with short traces of seeable ice . ikon taken by the VIRTIS legal document bring out a distinctly reddish cell nucleus .
Eventually , however , the comet got closer to the Sun and ventured past the solar system ’s frost business — a limit within which give away body of water ice undergoes a chemical process squall sublimation . This is when a substance goes straight from a solid to a natural gas , does not pop off go , and does not collect $ 200 . Past the frost line of business , VIRTIS unveil a visibly less red comet , with new tinge of wild blue yonder .
An illustration of the seasonal process.Image: (ESA)
The authors say the sublimating water ice displaced the tiny grains of dust on the comet ’s open , do “ the exposure of more pristine and bluish glacial bed on the surface , ” as they wrote in the study . In terms of what ’s producing the colors , the red is from organic molecules rich in carbon and the blue is from frozen water water ice that ’s rich in magnesium silicate , according to the inquiry .
These color flips , however , were switched around in the coma . When outside of the frost production line , the coma was blue , but when steer closely to the Sun , it turn reddened . The reason , say the authors , is that sparkler in the junk caryopsis within the coma remained in a glacial state when the comet was far from the Sun — hence the blue color . But when the ice sublimated , the procedure highlighted the dehydrated — and very cherry-red — debris grain . Beyond the frost line , the situation reversed , and the coma once again turned dismal .
It ’s the roofy of life , in a Lion King sort of way , or an “ orbital H2O - ice rink cycle ” as the author describe it . The novel study shows how comet 67P ’s lens nucleus and coma evolve during an orbit , and how this comet and likely others like it undergo seasonal changes .
These sorts of observations could only have been potential with a quad probe . The only affair better would be a sample return military mission , which would allow researchers to analyze some of that precious carbon - rich dust up close . By studying these organic chemical compound , scientist could meliorate their discernment of their blood and how they may have contributed to life on Earth .
AstronomyScience
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