This is important, because water / ammonia mixtures have very low freezing points. I look forward to the journal article. Nice to see Wired.com is continuing to feature astronomy articles.
Antifreeze Could Keep Saturn Moon Wet
By Hadley Leggett July 22, 2009 | 1:39 pm | Categories: Space
http://www.wired.com/wiredscience/2009/ ... usammonia/
Ammonia, best known on Earth as a potent antifreeze, has been found on Enceladus, offering strong evidence that an ocean of liquid water might be lurking beneath the crust of Saturn’s icy moon.
Jets of ice from cracks near the south pole of Enceladus generate plumes of gas and particles, mostly made of water and carbon dioxide. Last October, using a special instrument on NASA’s Cassini probe, researchers detected traces of ammonia in the plumes, suggesting that the source of the gas might be liquid water beneath the ice shell.
“This is the first time Cassini has actually been able to ’smell’ ammonia,” said planetary scientist Jonathan Lunine of the University of Arizona, co-author of the study in Nature on Wednesday. “And because ammonia is an antifreeze, it probably ensures that there is liquid water in the interior of Enceladus.”
And where there’s water, there could be life. Scientific evidence for liquid water has been piling up in the past year. In June, another paper in Nature reported sodium salts found in Saturn’s outermost ring. Together, these two pieces of data offer a strong argument for liquid water, Lunine said.
“I’m pretty convinced,” Lunine said. “By itself, the findings we have are strong. But they’re made even stronger by the article in Nature last month that found, using a different instrument on Cassini, that there are sodium and ice particles on the E-ring.”
But not everyone is convinced the discovery of ammonia means liquid water on Enceladus. Space scientist Susan Kieffer of the University of Illinois has developed a model that doesn’t require liquid water for the creation of gas plumes, and the finding of ammonia hasn’t changed her skepticism.
“The argument in this paper hinges on an early announcement by NASA that temperatures in excess of 180 Kelvin have been reported,” Kieffer wrote in an e-mail. However, later measurements near the plume cracks reported temperatures closer to 167 Kelvin, she said.
“It sounds like a small difference, but it’s huge in terms of the ammonia-water system,” Kieffer wrote. If the temperature is above 173 Kelvin, there can be liquid water, but below there would likely be a system of frozen solids.
Despite the lower temperatures, Lunine says he stands by his group’s conclusions. Because the Cassini temperature instrument samples a fairly large region around the gas plumes, the temperature it reports is an average of hotter and colder regions of the moon.
“These temps are lower limit temperatures for what’s in the crack,” Lunine said. “Given fact that ammonia and water can melt at 176 Kelvin, we’re really in the range that liquid water could exist.”
“I’d love to have a situation where we actually dipped our toes into the water, although I’m not sure I’d want to do it barefoot,” Lunine said. “But we’re not going to be able to do that. Just the fact that we can sample the water — smell it if you will — by studying the gas in the plumes, is pretty great.”
Antifreeze Could Keep Saturn Moon Wet
By Hadley Leggett July 22, 2009 | 1:39 pm | Categories: Space
http://www.wired.com/wiredscience/2009/ ... usammonia/
Ammonia, best known on Earth as a potent antifreeze, has been found on Enceladus, offering strong evidence that an ocean of liquid water might be lurking beneath the crust of Saturn’s icy moon.
Jets of ice from cracks near the south pole of Enceladus generate plumes of gas and particles, mostly made of water and carbon dioxide. Last October, using a special instrument on NASA’s Cassini probe, researchers detected traces of ammonia in the plumes, suggesting that the source of the gas might be liquid water beneath the ice shell.
“This is the first time Cassini has actually been able to ’smell’ ammonia,” said planetary scientist Jonathan Lunine of the University of Arizona, co-author of the study in Nature on Wednesday. “And because ammonia is an antifreeze, it probably ensures that there is liquid water in the interior of Enceladus.”
And where there’s water, there could be life. Scientific evidence for liquid water has been piling up in the past year. In June, another paper in Nature reported sodium salts found in Saturn’s outermost ring. Together, these two pieces of data offer a strong argument for liquid water, Lunine said.
“I’m pretty convinced,” Lunine said. “By itself, the findings we have are strong. But they’re made even stronger by the article in Nature last month that found, using a different instrument on Cassini, that there are sodium and ice particles on the E-ring.”
But not everyone is convinced the discovery of ammonia means liquid water on Enceladus. Space scientist Susan Kieffer of the University of Illinois has developed a model that doesn’t require liquid water for the creation of gas plumes, and the finding of ammonia hasn’t changed her skepticism.
“The argument in this paper hinges on an early announcement by NASA that temperatures in excess of 180 Kelvin have been reported,” Kieffer wrote in an e-mail. However, later measurements near the plume cracks reported temperatures closer to 167 Kelvin, she said.
“It sounds like a small difference, but it’s huge in terms of the ammonia-water system,” Kieffer wrote. If the temperature is above 173 Kelvin, there can be liquid water, but below there would likely be a system of frozen solids.
Despite the lower temperatures, Lunine says he stands by his group’s conclusions. Because the Cassini temperature instrument samples a fairly large region around the gas plumes, the temperature it reports is an average of hotter and colder regions of the moon.
“These temps are lower limit temperatures for what’s in the crack,” Lunine said. “Given fact that ammonia and water can melt at 176 Kelvin, we’re really in the range that liquid water could exist.”
“I’d love to have a situation where we actually dipped our toes into the water, although I’m not sure I’d want to do it barefoot,” Lunine said. “But we’re not going to be able to do that. Just the fact that we can sample the water — smell it if you will — by studying the gas in the plumes, is pretty great.”
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