by johnnydeep » Sun Aug 25, 2024 5:36 pm
JimB wrote: ↑Sun Aug 25, 2024 8:41 am
As Enceladus is spewing out water containing organics, shouldn't those surface features be a sort of mucky brown colour?
Like Sagan's "
tholins" (from Gk ϴὸλος, muddy; but also ϴoλòς, vault or dome), I suppose. But how and why their color might vary depending on particular composition and environment, I have no idea. See
https://www.planetary.org/articles/0722 ... re-tholins
Although informative, the definition given in the Nature article is not particularly easy to repeat when people ask, “what is tholin?” I have been studying tholin for almost a decade and in my experience the most frequently used synonyms for tholin are “gunk”, “brown gunk”, and “complex organic gunk”. Tholin is also often described as a “tar-like” substance. Words like tar, kerogen, bitumen, petroleum, asphalt, etc. all describe substances that are potentially similar to tholin in some ways. However, these materials all result from life; they are “biotic”.
Since 1979, the definition of tholin has expanded and now often includes organic solids produced from irradiation of cosmically abundant ices (rather than gases), and tholin experiments now routinely include other gases like N2, CO2, or CO. So what do scientists mean whey they say tholin? In general, we mean an abiotic complex organic solid that formed by chemistry from energy input into simple, cosmically relevant gases or solids. Shorter still, “abiotic complex organic gunk” works for me. You can see, perhaps, why Sagan and Khare felt the need to make up a word to capture this idea.
[quote=JimB post_id=340942 time=1724575269 user_id=147260]
As Enceladus is spewing out water containing organics, shouldn't those surface features be a sort of mucky brown colour?
[/quote]
Like Sagan's "[b][i]tholins[/i][/b]" (from Gk ϴὸλος, muddy; but also ϴoλòς, vault or dome), I suppose. But how and why their color might vary depending on particular composition and environment, I have no idea. See https://www.planetary.org/articles/0722-what-in-the-worlds-are-tholins
[quote]Although informative, the definition given in the Nature article is not particularly easy to repeat when people ask, “what is tholin?” I have been studying tholin for almost a decade and in my experience [b][color=#800040]the most frequently used synonyms for tholin are “gunk”, “brown gunk”, and “complex organic gunk”. Tholin is also often described as a “tar-like” substance.[/color][/b] Words like tar, kerogen, bitumen, petroleum, asphalt, etc. all describe substances that are potentially similar to tholin in some ways. However, these materials all result from life; they are “biotic”.
Since 1979, the definition of tholin has expanded and now often includes organic solids produced from irradiation of cosmically abundant ices (rather than gases), and tholin experiments now routinely include other gases like N2, CO2, or CO. So what do scientists mean whey they say tholin? In general, we mean an abiotic complex organic solid that formed by chemistry from energy input into simple, cosmically relevant gases or solids. Shorter still, “abiotic complex organic gunk” works for me. You can see, perhaps, why Sagan and Khare felt the need to make up a word to capture this idea.[/quote]