I saw this today on Space.com – Rosetta’s ‘rubber ducky’ comet changed color as it neared the sun. Here’s why.: https://www.space.com/rosetta-comet-turned-bluer-near-sun.html. There’s an image of the color change between red to blue back to red.
A solar pass made Comet 67P/Churyumov-Gerasimenko much bluer.
The Rosetta spacecraft‘s rubber ducky comet has slowly changed color as it moved through space, from red to blueish and then red again.
According to a new paper published Feb. 5 in the journal Nature, the color change is a signal of a water cycle on the first comet ever visited by a human probe. As comet 67P/Churyumov–Gerasimenko (Rosetta’s comet’s full name) crossed a boundary in its orbit around the sun, known as the frost line, ice began to turn to gas on its surface, sublimating away into space. When that happened, an outer layer of dirty ice on the comet’s surface, full of reddish dust, blew away into the vacuum, revealing the bluer, cleaner ice underneath.
There were, in fact, two opposite cycles at work around the comet, the researchers wrote. Approaching the sun and crossing the frost line — about three times Earth‘s distance from the sun — exposed that more pristine, blue surface. But the coma, a hazy region around the solid nucleus made of dust and gas, got redder.
What caused that reddening? “Grains made of organic material and amorphous carbon in the coma” the researchers wrote.
In other words, all those microscopic grains of carbon-rich dust that melted off the comet’s surface stopped reddening the surface and started reddening the coma.
Once the comet moved away from the sun again, its solid core reddened again as dust once again settled on the surface of the nucleus
Previous Space Saturdays: https://upsdownsfamilyhistory.wordpress.com/tag/space-saturdays/