Comments by "Kevin Street" (@Kevin_Street) on "" video.

  1. In this case the researchers have attempted to calculate how much phosphine could be generated by known non-living processes, and have concluded the amount they've observed is too large to be accounted for in that way. With a planet outside our Solar System, looking for these biosignatures would be more complicated because nothing could be directly observed except the spectra. But like Scott Manley says in the video, oxygen and methane together is a good bet, since they normally combine to form carbon dioxide.
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  2. Good point, E Cognitio.
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  3. This paper: https://arxiv.org/ftp/arxiv/papers/1910/1910.05224.pdf has a chart on page 4, but the results are given in nanograms per cubic meter. The results range from 0.1 to just over 1000 ng/m3 on Earth, but someone else will have to make the conversions. I tried but I'm pretty sure I got it wrong.
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  4. According to this: https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.files/fileid/14285 the formula is: Concentration (ppm) = 24.45 x concentration (mg/m3) รท molecular weight So to do the calculation one needs to - convert ng/m3 to mg/m3 - plug in the molecular weight of phosphine (PH3), which Google says is 33.99758 g/mol, and convert it to mg/mol, I guess If anyone wants to give it a go. The chart's value of 1000 ng/m3 would provide a nice outer bound for comparison to Venus's 20 ppb.
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  5. Thanks for putting out this video! It's certainly an interesting result that should be further investigated.
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