Update on Mars' atmosphere, Media briefing on NASA Jan 15th |
Update on Mars' atmosphere, Media briefing on NASA Jan 15th |
Jan 12 2009, 06:01 PM
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The Poet Dude Group: Moderator Posts: 5551 Joined: 15-March 04 From: Kendal, Cumbria, UK Member No.: 60 |
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Jan 19 2009, 10:27 PM
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Newbie Group: Members Posts: 14 Joined: 26-October 08 From: Portugal Member No.: 4466 |
Sorry for this question from someone that does not understand these things very well.
When they say "parts per billion", what billions are they talking about, other atmosphere components? Considering the thinness of Mars atmosphere, how would that translate to Earth's atmosphere? Thanks in advance. |
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Jan 19 2009, 11:26 PM
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
That is an EXCELLENT question.
It would imply one gram of stuff (methane) in a billion grams of other stuff (air). Here is a more detailed article: http://en.wikipedia.org/wiki/Parts_per_notation My favorite quote: "it is not formally part of the International System of Units (SI).[2] Consequently, according to IUPAP, 'a continued source of annoyance to unit purists has been the continued use of percent, ppm, ppb, and ppt.'" [I count myself among the 'annoyed': for most drug-like molecules, ppm is directly proportional to units molar (M). But if you are comparing with especially heavy or light molecules in the mix, this can throw off the relationship.] -Mike -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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