The surprisingly dark and organic surface of Comet 67P/C-G
Link here.
The first surprising result emerging from VIRTIS’s study of Comet 67P/Churyumov-Gerasimenko is the measurement of its albedo, or how much sunlight is reflected by the surface of the nucleus. With an albedo of only 6%, about half as much as the Moon’s, 67P/C-G is one of the darkest objects in the Solar System. Such a low reflecting power indicates that the surface of the comet contains minerals such as, for example, iron sulfides, but also carbon-based compounds. The low albedo also indicates that there is little or no water ice on the outermost layers of the surface of the nucleus.
“This clearly doesn’t mean that the comet is not rich in water, but only that there is no water ice in the outermost shell, just over one millimetre thick,” explains Fabrizio Capaccioni, VIRTIS Principal Investigator from INAF-IAPS in Rome, Italy. “The reason for this is rooted in the recent history of the comet’s evolution, since repeated passes in the vicinity of the Sun cause surface ice to sublimate.”
This result, combined with other Rosetta data, also suggests that during each pass the dust that did not escape along the comet’s tail settled back down to coat the surface and hide the lower layers of water ice.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Link here.
The first surprising result emerging from VIRTIS’s study of Comet 67P/Churyumov-Gerasimenko is the measurement of its albedo, or how much sunlight is reflected by the surface of the nucleus. With an albedo of only 6%, about half as much as the Moon’s, 67P/C-G is one of the darkest objects in the Solar System. Such a low reflecting power indicates that the surface of the comet contains minerals such as, for example, iron sulfides, but also carbon-based compounds. The low albedo also indicates that there is little or no water ice on the outermost layers of the surface of the nucleus.
“This clearly doesn’t mean that the comet is not rich in water, but only that there is no water ice in the outermost shell, just over one millimetre thick,” explains Fabrizio Capaccioni, VIRTIS Principal Investigator from INAF-IAPS in Rome, Italy. “The reason for this is rooted in the recent history of the comet’s evolution, since repeated passes in the vicinity of the Sun cause surface ice to sublimate.”
This result, combined with other Rosetta data, also suggests that during each pass the dust that did not escape along the comet’s tail settled back down to coat the surface and hide the lower layers of water ice.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
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