Reference : arXiv:2404.05356v1 [astro-ph.EP]. Published on 8 Apr 2024
https://arxiv.org/pdf/2404.05356This is obviously a riposte to the claim, several years ago now, of phosphine in the radio spectrum of Venus' atmosphere. Which has been disputed, the instrument readings disputed, the noise profile challenged ... all the usual suspects.
Just from the title, it sounds like a discussion of the (theoretical) requirements, and potentially their observability, rather than actual new observations.
Now, here's weird - in some of the Blogger Preview modes, ":hover" doesn't work. Or is there something else going on? It's a problem with their preview system. I hadn't noticed that before.
Sections
| Abstract |
| I. Introduction |
| II. LIFE CYCLE FOR VENUSIAN AERIAL MICROBES |
| III. REPLICATION RATES AND FALLOUT TIMES |
| IV. COSMIC RAY EFFECTS ON MICROBIAL LIFE |
| V. CONCLUSIONS |
| End of document |
I'm trying a different styling. Paragraphs with this "PowderBlue" background are direct quotes - WHY AM I NOT USING BLOCKQUOTE FOR THIS? while my thopughts are on a plain background. Really, semantically, I should be doing this with BLOCKQUOTE. Why am I re-inventing the Semantic Web?
OK, re-considered, I'll use BLOCKQUOTE. Which has a LightYellow background ON HOVER. Forget the PowderBlue.
Abstract
Millimeter-waveband spectra of Venus from both the James Clerk Maxwell Telescope (JCMT) and the Atacama Large Millimeter/submillimeter Array (ALMA) provide conclusive evidence (signal-to-noise ratio of about 15σ) of a phosphine absorption-line profile against the thermal background from deeper, hotter layers of the atmosphere. Phosphine is an important biomarker; e.g., the trace of phosphine in the Earth’s atmosphere is uniquivocally associated with anthropogenic activity and microbial life (which produces this highly reducing gas even in an overall oxidizing environment). Motivated by the JCMT and ALMA tantalizing observations we reexamine whether Venus could accommodate Earthly life. More concretly, we hypothesize that the microorganisms populating the venusian atmosphere are not free floating but confined to the liquid environment inside cloud aerosols or droplets. Armed with this hypothesis, we generalize a study of airborne germ transmission to constrain the maximum size of droplets that could be floating in the venusian atmosphere and estimate whether their Stokes fallout times to reach moderately high temperatures are pronouncedly larger than the microbe’s replication time. We also comment on the effect of cosmic ray showers on the evolution of aerial microbial life.
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So, one useful point - that airborne life is more likely in droplets, rather than actual free-floating microbes. Fair point. From which, settling velocities are an approachable topic, while the supply of minerals from the ground isn't so approachable - needs considerably more assumptions. The question of vertical mixing in the atmosphere should make an appearance too.
Back to List.
I. Introduction
Their citations for early discussion of Venus-life as cloud-life starts with "H. Morowitz and C. Sagan, Life in the clouds of Venus?, Nature 215, 1259 (1967) doi:10.1038/2151259a0" - which shouldn't really be a surprise. Sagan gets everywhere.
And they go straight into modelling a "sHigo" (spherical h(H)ydrogen gasbag isopyenic organism) and, with reasonably conservative assumptions get a minimum buoyant size of ~4cm (diameter). That's not insane for a multicellular organism, but a bit much from terrestrial experience of microbes. It also sort of (to me) implies an origin on the ground, getting lofted (evolving into buoyancy) as the environment went from Hadean era (with solar illumination ~20% down on today) to triggering the runaway greenhouse and boiling the oceans. But I'll leave that aside for the time being.RETURN TO THIS
Refereences [4] through [12] cover the controversy about the original detection claim, and raised concerns about the calibration and interpretation of the signals. Clearly these authors feel that the issues raised have bene answered, and the phosphine detection can be treated as valid.
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II. LIFE CYCLE FOR VENUSIAN AERIAL MICROBES
This seems to be a re-hash and expansion of :
[14] S.Seager, J.J.Petkowski, P.Gao, W.Bains, N.C.Bryan, S.Ranjan, and J.Greaves, "The venusian lower atmosphere haze as a depot for desiccated microbial life: A proposed cycle persistence of the venusian aerial biosphere." Astrobiology 21, 1206 (2021) doi:10.1089/ast.2020.2244 [arXiv: 2009.06474]
This modle life cycle is predicated on the atmosphere of Venus. Only two references are given, but the structure of the atmopshere has been probed by multiple landers and tested by various combinations of radar from Earth and from (Venus) orbit, so it's not much in dispute.
I'm in the habit of collecting such bits of data on the expectation that I'll need them again. So ... I'll do exactly that, and put the information below. Wait - what's this - from Wiki : Additionally, the clouds consist of approximately 1% ferric chloride.[61][62] Other possible constituents of the cloud particles are ferric sulfate, aluminium chloride and phosphoric anhydride.
Well, that's a thing I hadn't considered when making my "supply of minerals" comment above. Hmmm.
| Altitude (km) | Temperature (K) | Pressure (Pa) |
|---|---|---|
| 0 | 735.16 | 9332032.5 |
| 5 | 697.16 | 6753311.25 |
| 10 | 658.16 | 4801791.75 |
| 15 | 621.16 | 3347778 |
| 20 | 579.16 | 2281839 |
| 25 | 537.16 | 1512782.25 |
| 30 | 495.16 | 998152.575 |
| 35 | 453.16 | 599540.025 |
| 40 | 416.16 | 354738.825 |
| 45 | 383.16 | 200522.175 |
| 50 | 348.16 | 108012.45 |
| 55 | 300.16 | 53844.105 |
| 60 | 263.16 | 23882.3025 |
| 65 | 243.16 | 9894.38625 |
| 70 | 230.16 | 3738.8925 |
| 80 | 197.16 | 482.307 |
| 90 | 169.16 | 37.85502 |
| 100 | 161.16 | 2.695245 |
Well, let's find some pressure-temperature-altitude data. Ah, good, Wiki has done the searching for me. But ... it seems difficult to generate a chart (in LibreOffice) with multiple ranges for the X-axis, and a common factor for the Y axis. So - subterfuge. Including "tweaking" the drawing in Draw. Not perfect, but it'll do for the moment.
Clearly, I've forgotten the details of Blogger's floating of elements. I'm trying to put the data table beside the graph, but that's not working. I thought I'd figured that out a while ago, but I'll have to work on it again.
And I've got other things to do today.
I need to put some padding onto those rightward elements. Done that, but BLOCKQUOTE needs some attention.
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III. REPLICATION RATES AND FALLOUT TIMES
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IV. COSMIC RAY EFFECTS ON MICROBIAL LIFE
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V. CONCLUSIONS
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Tables
| Heading 1 | Hdg 2 | Heading 3 |
|---|---|---|
| Row 1 CS 1 ; CP 11 | R1 C2 CS 2; CP 3 | R1 C3 CS 5 ; CP4 |
| Row 2 CS 2 ; CP 12 … | R2 C2 CS 6; CP 6 | R2 C3 CS 7 ; CP 8 |
| Row 3 CS 3 ; CP 13 | R3 C3 CS 9 ; CP 16 | |
| Heading |
|---|
| a |
| b |
| c … |
- ul
- ul
- reversed Specifies that the list order should be reversed (9,8,7...)
- start number Specifies the start value of an ordered list
- type 1,A,a,I,i
- ol
- ol
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