Svensmark on Venus: Mystery of the Unknown UV Absorber Solved?

Guest post by John Tillman

Disulfur Dioxide, the Solar Cycle and Cosmic Rays in the Venusian Atmosphere

In 1928, Yerkes Observatory astronomer and physicist Frank Ross published a journal paper, “Photographs of Venus”.  It reported finding in the Venusian atmosphere a strong absorption between 320 and 400 nm, ie in the near-UV, just overlapping light visible to humans.  The observation of dark patches has since been repeatedly confirmed both from Earth and space.

The identity of the UV-absorber remained incognito for 90 years, and the now leading candidate is still not universally accepted.

Among the hypotheses seeking to explain the absorber is ET atmospheric microbes, probably first suggested by the astonomical Dr. Carl Sagan and biophysicist Harold Morowitz in their 1967 Nature article “Life in the Clouds of Venus?”.  (The previous year, then Lynne Sagan had proposed that mitochondria are endosymbiotic bacteria.  This was a young couple welcoming academic notoriety.)

After 50 more years of observations by short-lived landers and long-orbiting probes, three researchers from the University of Copenhagen (home town of GCR-proponent Henrik Svensmark) and Cal Tech proposed a more conventional, chemical solution to the enigma.  Their 2016 study positing isomers of disulfur dioxide as the mystery absorber is not pay-walled:

Identification of OSSO as a near‐UV absorber in the Venusian atmosphere

“The planet Venus exhibits atmospheric absorption in the 320–400 nm wavelength range produced by unknown chemistry. We investigate electronic transitions in molecules that may exist in the atmosphere of Venus. We identify two different S2O2 isomers, cis‐OSSO and trans‐OSSO, which are formed in significant amounts and are removed predominantly by near‐UV photolysis. We estimate the rate of photolysis of cis‐ and trans‐OSSO in the Venusian atmosphere and find that they are good candidates to explain the enigmatic 320–400 nm near‐UV absorption. Between 58 and 70 km, the calculated OSSO concentrations are similar to those of sulfur monoxide (SO), generally thought to be the second most abundant sulfur oxide on Venus.”

This hypothesis soon enjoyed confirmation: 

The near-UV absorber OSSO and its isomers.

“Disulfur dioxide, OSSO, has been proposed as the enigmatic “near-UV absorber” in the yellowish atmosphere of Venus. However, the fundamentally important spectroscopic properties and photochemistry of OSSO are scarcely documented. By either condensing gaseous SO or 266 laser photolysis of an S2O2 complex in Ar or N2 at 15 K, syn-OSSO, anti-OSSO, and cyclic OS([double bond, length as m-dash]O)S were identified by IR and UV/Vis spectroscopy for the first time. The observed absorptions (λmax) for OSSO at 517 and 390 nm coincide with the near-UV absorption (320-400 nm) found in the Venus clouds by photometric measurements with the Pioneer Venus orbiter. Subsequent UV light irradiation (365 nm) depletes syn-OSSO and anti-OSSO and yields a fourth isomer, syn-OSOS, with concomitant dissociation into SO2 and elemental sulfur.”

Not everyone is convinced, however.  There are still holdouts for cloud-dwelling organisms, as argued for in other recent studies.  At the very least, the ET life hypothesis might help sell space missions to explore the dense, sulfuric acidic Venusian atmosphere.

However, an August 2019 Astronomical Journal paper by Lee, et al., notes that the (possibly still) unknown absorber shows a marked correlation with the solar cycle and cosmic ray flux modulated thereby.  The University of Wisconsin=Madison (Yerkes’ state) press report on the paper below is surprisingly good:

Here is the paper itself, again blessedly open-access:

Long-term Variations of Venus’s 365 nm Albedo Observed by Venus

Express, Akatsuki, MESSENGER, and the Hubble Space Telescope

“An unknown absorber near the cloud-top level of Venus generates a broad absorption feature from the ultraviolet (UV) to visible, peaking around 360 nm, and therefore plays a critical role in the solar energy absorption. We present a quantitative study of the variability of the cloud albedo at 365 nm and its impact on Venus’s solar heating rates based on an analysis of Venus Express and Akatsuki UV images and Hubble Space Telescope and MESSENGER UV spectral data; in this analysis, the calibration correction factor of the UV images of Venus Express (Venus Monitoring Camera) is updated relative to the Hubble and MESSENGER albedo measurements. Our results indicate that the 365 nm albedo varied by a factor of 2 from 2006 to 2017 over the entire planet, producing a 25%–40% change in the low-latitude solar heating rate according to our radiative transfer calculations. Thus, the cloud-top level atmosphere should have experienced considerable solar heating variations over this period. Our global circulation model calculations show that this variable solar heating rate may explain the observed variations of zonal wind from 2006 to 2017. Overlaps in the timescale of the long-term UV albedo and the solar activity variations make it plausible that solar extreme UV intensity and cosmic-ray variations influenced the observed albedo trends. The albedo variations might also be linked with temporal variations of the upper cloud SO2 gas abundance, which affects the H2SO4–H2O aerosol formation.”

While the hypothesis that GCRs affect cloud formation, weather and climate, modulated by the solar cycle, is heretical to consensus “climate science” for planet Earth, apparently it’s respectable for Venus.

Study co-author, UWM planetary scientist Sanjay Limaye, notes, “The difference between Earth and Venus is that on Earth most of the energy from the sun is absorbed at ground level while on Venus most of the heat is deposited in the clouds”. 

So, while Venus’ hellish heat has generally been attributed to an ancient runaway greenhouse effect, the GHE no longer works on Venus as it allegedly does on Earth.  Due to high albedo and absorption in the dense, cloudy atmosphere, very little light makes it to the surface.  In in any case, the ground is so hot that it doesn’t even radiate in the peak wavelength bands of CO2.If I can find the time and am permitted to do so, I’d like to discuss an alternative scenario for the history of our planet’s fraternal twin when Venus was young.  The consensus is that for up to two billion years, Venus had liquid water on its surface, as some evidence suggests.  But it’s possible that the planet was always too hot for seas to form, even presuming initially high atmospheric pressure.  The RGHE hypothesis is based upon evaporating or even boiling water (as per Jim Hansen), not CO2.  The alternate hypothesis supposes loss of hot atmospheric water vapor rather than liquid from the surface.

Both hypotheses remain speculative until more probes and especially landers can explore our evil twin’s world.  Characterized as straight out of a “steam-punk” fantasy, NASA is designing a tough, back-to-the-future analog, tracked rover with a mechanical computer capable of surviving the hostile Venusian land conditions.

A Clockwork Rover for Venus

An airship craft to search for ET extremophiles in the clouds might be less challenging for space engineers.

100 thoughts on “Svensmark on Venus: Mystery of the Unknown UV Absorber Solved?

  1. “In in any case, the ground is so hot that it doesn’t even radiate in the peak wavelength bands of CO2”

    I don’t think you meant that. Higher temperatures mean increased radiance at every wavelength, but the fractional (relative) emittance shifts to lower wavelengths with increased temperature.

    • Yes, that’s what I meant, but didn’t want to write “peak” twice in the same sentence. Could have worded it better.

    • How do we know that the ground is so hot at the night side? Has the night side surface temperature even been measured?

      • I don’t know if a lander ever transmitted from the night side, but orbiters have been able to observe IR radiation from the surface.

          • The Venus atmosphere has a few atmospheric window bands in the near IR around 1 micron. They’re not completely clear, but the optical depth is low enough you can see the emission from the surface.
            –and, yes, two Russian landers landed on the night side (Vega-1 and Vega-2).

          • Geoff:
            Radiation beyond 1 micron…like 1.5 to 1.7 micron comes through from below the cloud tops, but not directly from the surface. I particular, some very weak Carbon dioxide overtone & combination absorption bands have been measured and rotational temperature determined ~ 350K. When I worked at NASA-Ames spectroscopy lab I made laboratory intensity measurements of the weakest band of the (3 0 1) – (0 0 0) tetrad which had been observed in Venus’ spectrum (~ 1.6 microns).

        • The longest any lander has ever lasted (operated) on the Venusian surface is 110 minutes.

          • Geoffrey and RocketScientist,

            Thanks for the information.

            Almost two hours is pretty good for 20th century technology, IMO. I hope we can do better now. We’ll have to do so, in order to answer key questions, such as, “Is there granite”, and “Of what does its core consist, besides presumably nickel and iron?”

        • My recollection is only microwave radiation (3 to 10 cm wavelength) can radiate directly from Venus’ surface to space. Thermal IR measurements (~10 microns) made with the 200 inch Palomar telescope in the early 1960s and subsequently by Mariner 2 measured brightness temperatures about 240K, the effective temperature, at the cloud tops, with no measurable difference dark side or bright side.

      • Thanks for asking, BTW.

        Akatsuki recently confirmed prior observations:

        The Japanese orbiter has experienced quite an adventurous saga. On arrival, it misfired and went into solar orbit. Japanese mission controllers were able to get it into Venusian orbit using maneuvering thrusters. But the orbit is highly elliptical, so it has made far fewer observations than hoped.

        • Vega 1 made a nighttime landing, so took no pictures. Dunno if there were other descents to the surface during the 58-day long darkness.

        • This work reconstructs the surface temperature from a single 1.01 μm channel data. It feels more bold than trustworthy.

          • That was the least noisyt of three channels. As noted, it confirms previous observations from the surface and orbit.

            Venus would be unlikely to get warmer than Mercury if it cooled off during its almost two-month-long night, as does its neighbor. While there is lithospheric conduction and volcanism, the main reason for the equanimity, if that’s the right term for a hellscape, is its atmosphere.

            Even Earth’s much thinner atmosphere serves to warm up the night, although our relative chilly average temperature owes both to distance from the Sun and far more rapid rotation.

          • I am unaware of previous observations. Vega 1 not only took no pictures, but apparently no temperature readings. The craft seems to have been mostly destroyed in a descent through a hurricane.

            As the main post speculates about a mystery of an unknown UV absorber, I assume that there may be unknown IR absorbers. The question is, are IR readings from a single channel, noisy or not, a better temperature proxy than tree rings?

          • Yes, measuring IR is better than using tree rings as a proxy treemometer. Rings are a better indicator of water than T.

            Vega 2 did return nighttime T data.

        • Thanks much for posting this, John. There’s much to digest here and in the links. I was Carl Sagan’s first grad student research assistant in 1961-1962 when he was a postdoc at UC Berkeley. At that time radio telescope observations were finding microwave (~ 10 cm) brightness temperature about 600K, and Carl deduced this was indeed the surface temperature, and a lot of atmospheric opacity was required to keep the surface this hot. This was prior to finding the atmosphere was mostly carbon dioxide and nearly 100 atmosphere surface pressure.
          The Russian landings and photographs on Venus’ surface show that some sunlight does reach the surface, although not much. Most is reflected by the bright clouds, and much of what penetrates the clouds absorbed in the atmosphere by the many overtone and combination and pressure-induced carbon dioxide bands, some of which I measured in the spectroscopy lab at NASA-Ames. I have long wondered if enough solar radiation (in watts/sq. meter) was left to be absorbed at the surface to maintain the high surface temperature. You have concluded NO, something else is required? But can a minimum amount of solar radiation needed to maintain the surface temperature by the greenhouse mechanism be determined? I’ve long pondered how that could be done.
          ……………(Former) Mayor of Venus (served 1961-1962 term)

          • Thanks!

            IMO Venus is hotter than Mercury despite less irradiance at the surface because 1) Venus rotates even more slowly than Mercury, 2) its thick atmosphere and high winds keep the night side hot, 3) as too do volcanism and lithospheric convection, 4) it’s hot atmosphere means less loss of surface heat, and 5) possibly some radiative GHE as understood on Earth, despite present lack of water vapor. Furthermore, as Tty notes, CO2 is supercritical near the surface and peak radiation from the hot ground lies outside gaseous CO2’s absorption peaks, although close to its 4300 nm peak.

            I’d like to investigate and speculate about the early Venusian atmosphere and assess the odds of a liquid ocean on Archean Eon and Paleoproterozoic Era Venus, perhaps misapplying terrestrial geological terms. “Zoic” ought not apply if life never developed there, as per your mentor’s hypothesis.

            I’m probably missing some factors, which is why a new post is indicated.

  2. The “science is settled” CAGW proponents long ago assured us that the high atmospheric concentration of CO2 on Venus was the cause of its very high surface temperatures . . . setting it up as a possible future fate of Earth . . . you know the runaway greenhouse effect.

    I guess they didn’t think it was important to mention the fact that there was a mysterious, unknown near-UV absorber present in the Venusian atmosphere, recognized in the science community for the last 90 years.

    I guess they’ll now be calling for a sulfur tax, sulfur credits and a sulfur-free economy by 2025.

    • They also fail to mention that if there indeed were a runaway GHE on Venus, it was due to water vapor, not CO2. But it’s not clear if there ever were oceans of liquid water on our planet’s evil twin. There may well have been for two billion years, but we need landers, ideally rovers, to find out. But they’ll have to be resistant to heat, pressure and corrosion.

      The high CO2 content is probably not primordial but thanks to billions of years of volcanism and lack of chemical or biological removal from the air.

      • John,
        On Gordon’s point regarding the alleged runaway greenhouse effect on Venus, Chapter 10 of James Hansen’s “ Storms of my Grandchildren” is titled “The Venus Syndrome”.
        In December 2008, he gave the Bjerknes lecture at the AGU conference in San Francisco entitled “Climate Threat to the Planet.”
        He commenced with the “Goldilocks slide” comparing Mars (-50C), Earth (+15C) and Venus (+450C).
        He stated: “Venus and Earth having commenced from the same interstellar gas during the formation of the solar system, must have begun with similar atmospheric conditions.
        So the early Venus atmosphere, contained lots of water vapour.The sun was 30% dimmer at that time so Venus was probably cool enough to have oceans on its surface. But they did not last long.As the sun brightened, the surface of Venus became hotter, water evaporated and the strong greenhouse effect of water amplified the warming.
        Eventually a runaway greenhouse effect occurred, with the ocean boiling and evaporating into the atmosphere…
        ….So Venus had a runaway Greenhouse effect.Could Earth? Of course we know that it could.The question is, rather, how much must CO2 ( or some other climate forcing) increase before a runaway effect occurs.”
        One wonders whether Hansen still adheres to this claim.
        I recall Sir John Houghton dismissed the Venus Syndrome in his book, “Climate change:The Complete briefing”.
        Also I recall a link to an IPCC ruling rejecting the likelihood of such a Venus runaway greenhouse effect on earth ( probably on a post here on WUWT).

        • While alarmists sometimes try to make a case for a possible RGHE on Earth, most of even the most ardent CACA adherents admit that it simply isn’t possible in our present climate system.

          In the future, ie 500 million to five billion years from now, when the Sun is five percent more powerful, or has gone red giant, then, yes, Earth is liable to lose its water.

          Jim “Venus Express” Hansen has always been wrong about both planets. He wrote his PhD thesis on a dust model for Venus’ heat, although even in 1967 he must have known that dust wasn’t the explanation. Then he argued that SO2 explained Venusian heat, until forced to admit that SO2 actually cools the surface by blocking incoming radiation.

          CO2 is not why Venus is hot, nor could humans ever release enough of it to produce a runaway GHE.

        • It takes more than just evaporating the water on Venus’ hypothesized oceans. The water vapor needs to be dissociated and the hydrogen atoms escape to space. The normal hydrogen atoms would more easily escape compared to deuterium, leaving a higher ratio of deuterium to normal hydrogen on Venus today compared to earth. There have been measurements claiming this is indeed the case, but I don’t recall if these measurements are considered reliable.

          • Yes. Venus has a high deuterium ratio. But the issue is whether the split water molecules had been in a liquid ocean or always in the hot atmosphere.

    • I’m old enough to remember breathing sulfur dioxide pollution in Chicago, but that air problem has pretty much disappeared in the US, between scrubber technology and offshoring of heavy manufacturing, so there’s not enough left to tax, I’m afraid.

  3. Interesting. If we destroy our ozone layer with our refrigerators/air-conditioners (sarc), we could pump disulfur dioxide into the upper atmosphere to absorb UV instead. It could be done with 20-mile tall stacks from unscrubbed high-sulfur coal plants. 😉

    • “we could pump disulfur dioxide into the upper atmosphere to absorb UV instead” Don’t give them any more stupid ideas, AOC’s GND is already out there.

  4. “The difference between Earth and Venus is that on Earth most of the energy from the sun is absorbed at ground level while on Venus most of the heat is deposited in the clouds”.

    I am convinced that Earth’s mostly deep-water covered surface is the primary reason it is neither like Venus, nor Mars.
    This is the water planet, and the atmosphere is much more controlled by the oceans than the antithetic theory claims.

    • Yup. Surface on Earth means 71% ocean and 29% land. Also, in present configuration, 81% water in SH and 61% NH, which matters.

      There was more water and lower average land elevation at the end of the Cretaceous, which contributed to a warmer world as well. The Cenozoic has seen a lot of mountain-building.

  5. Interesting that sulfur is entirely depleted from Earth’s atmosphere, and CO2 nearly depleted as well…

    • Earth enjoys physical, chemical and biological processes which remove CO2 and SO2 from our air with some rapidity. Methane even more so.

      I hope to find time to write a post in part speculating about the atmospheric histories of the twin planets.

      • I look forward to it. Most of us know the CO2 removal process, from the biological prospective, although that seems to be forgotten by the media. Or even energy companies, for that matter. When I see a TV commercial that shows a tree hugging a house for being carbon efficient, I want to smack someone. Aside from the climate considerations, the speculation of the planetary histories, I find to be fascinating, and would also love to see more “exploration” occur in the future.

        • Thanks!

          Encouragement helps. The speculation isn’t totally idle, since there is some slim evidence on which to go. Venus’ high deuterium ratio shows that it was wetter in the past. The issue is, was the water all gas in the air, or was there some liquid on the surface, as well.

          The physical hint of surface water, rather than just wishful thinking by Jim “Boiling Oceans” Hansen and his GISS colleagues (or co-conspirators) came from IR returns interpreted as granite on so-called “continents”, one in each hemisphere, ie highlands above the planet’s generally flat plains.

          A more recent analysis however found no sign of granite from a structure adjacent to a highland.

          However, if Venus did once have an ocean, it probably would have been too hot for terrestrial biochemistry. If the planet’s atmospheric N2 be primordial or mostly so, then its early air was dense, maybe four bar or more at a minimum. In that case, the boiling point of water there and then would have been 143.6 degrees C. Maybe at some depth in the shallow seas life could have developed, but thermoextremophiles on Earth can’t survive much above 120 degrees C.

          Presumably Venus’ and Earth’s original atmospheric mass and composition would have been similar, despite the probably violent birth of the Moon. But the two airs soon went their separate ways. Water definitely condensed out of our atmosphere, and has stayed on the surface, though at times as ice.

        • A tree is an especially egregious choice, since they are C3 plants par excellence. Maybe a cactus for the ad. Although its embrace wouldn’t be all that huggy.

  6. This from the Kirkby CERN CLOUD Experiment :
    Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation

    Numerous references can be found here and elsewhere on the unknown aerosol effect of sulfur here on Earth.

    Looks like Venus sheds light in this darkness.

    • Yup. IMO missions to Venus are worth the cost. Although I don’t pay much in federal tax, so I would say that.

  7. Float a “mother ship” blimp (filled w/hydrogen) high in the atmosphere w/a number of small, drop-able high-temp-resistant robots to analyze the lower atmosphere & then surface for whatever time they can survive.

    • Don’t need H. In the Venusian air, Earth air would be a lifting gas. The airship crew could get high on their own supply of N/O mixture, or at least breathe.

  8. While the hypothesis that GCRs affect cloud formation, weather and climate, modulated by the solar cycle, is heretical to consensus “climate science” for planet Earth, apparently it’s respectable for Venus.

    As it should be. Cosmoclimatology/the Svensmark Effect is a misattribution.

    The ocean produces the low clouds Svensmark claims for his cosmic ray theory, during increasing MEI/decreasing Central Pacific OLR conditions, as observed here using figure 10 from his latest paper.

    The strong OLR-cloud relationship is plotted here and here.

    Cosmic rays exhibit almost no correlation with ISCCP clouds

    It’s no coincidence that cosmic rays and clouds follow the solar cycle, but to claim cosmic rays cause the clouds is a misattribution, like misattributing temperature rise to increasing CO2, wherein both theories implicitly ignore the primary role of the sun’s TSI in warming/cooling the ocean.

    It’a not surprising Venus also shows a very real solar cycle influence. Nice article John Tillman.

    • Glad you liked it. You’re welcome.

      IMO there are instances of GCR-generated cloud condensation nuclei seeding clouds where otherwise they might not have formed. Oceans of course are a major source of CCNs. There’s an hypothesis that tropical Cretaceous seas were too hot to produce enough biological CCNs, thus contributing the warmth of the period, particularly its middle.

  9. Instead of a mechanical computer, we might be able to make workable electronics out of diamond or SiC substrates that would work at >450C. Couple that with molten-salt batteries which can operate at 450C, or a RTG like Curiosity has, and you could make a probe that could operate at the ambient temps on Venus.

    Still, it’d be a huge development effort to make something as simple as an 8080 or 6800 microprocessor work reliably at those temps, in addition to all the other components needed.

    • Good suggestions. Send NASA a helpful note. Definitely a challenge, but probably not insurmountable. If engineers went the solid state digital route, then the insulation and cooling would have to be ingenious.

      The rover might also have to be heavy, with a pressure hull like a submersible capable of diving to 3000 feet. Maybe Space Age materials could help solve the pressure and corrosion problems, as well as heat.

      Must admit to fondness for the steam punk angle, though. Artemus Gordon goes to Venus. Or Doc in BTTF, Part III.

    • RTG s won’t work very well on Venus because they require a cold sink for their thermocouples. Venus is not much of a cold sink.

  10. John,

    I always enjoy reading your contributions. Here is one other factor in Venus’s hellish surface that I have never seen anyone discuss. If one were standing upon the surface, the upward hemispherical view contains a lot of the surface of Venus. The density gradient in the atmosphere causes a superior mirage. Radiation leaving the surface upward has a fraction, perhaps a large fraction striking the surface again. The window of radiant transport upward is more like a porthole.

    Now, it might be that scattering in the atmosphere completely dominates the process, but it is interesting to think about.

    • Thanks!

      I read conflicting data or estimations as to how much light reaches the surface, and by what routes.

      Some say under ten percent, of which less than three percent directly, and the rest scattered. You raise a very good point about back scatter, which is different from back radiation on Venus, to the extent that it even happens, given how much sunlight is reflected and absorbed by the air.

      Should I ever find time to consider the consensus runaway greenhouse effect as thoroughly as possible, your excellent comment must figure in the conjectures. Unfortunately, we just don’t yet have the needed observations to conclude whether Venus had an ocean or not. Life could probably not have developed in the air there, although it’s not completely out of the question, given a wet enough atmosphere for long enough.

      But, in any case, the enigmatic UV absorber now looks to be chemical rather than biological.

    • Another complication is that the pressure on Venus is so high that the CO2 in the lower atmosphere is in a supercritical state with uncertain effects on climate. For example the thermal conductivity is high, which might have bearing on the high night temperatures.

      • Yes. Venus’ atmosphere smacks a little of an ocean. Weird chemistry and physics going on, by terrestrial standards.

        So similar, and yet so not. Unlike twins raised apart. More like normal siblings, or fraternal twins.

      • Indeed, for those who argue that the ideal gas law predicts surface temperatures on all the planets have to abandon that idea on Venus and use the “real gas law” instead.

        • Kevin, if supercritical, then no longer gas phase. But we understand and use such CO2 in processing eg as a solvent. Not affecting atmosphere above the critical zone of course.
          Surface T, now that could be interesting. Forgetting the radiative dead end of cagw and sticking with KE and convection works still above the phase change, an ocean surface. Brett

      • True, but there must be quite a lot of NIR and IR, and by “view” I would mean such radiation as actually leaves the surface on upward paths.

      • With sun overhead, it’s supposed to look like a cloudy day. How overcast, I don’t know, not having computed likely brightness.

  11. “So if Venus’s atmosphere is being lit, heated and driven electrically, where are the “wires” feeding current into it? Probes have discovered that the planet has no significant magnetic field and no magnetosphere. But it has an ionosphere laced with “Birkeland current ropes” of electric current from the solar “wind” and a plasma tail composed of Birkeland currents (“stringy things” in the jargon of astrophysics). As Nobel Laureate Hannes Alfvén has described, Birkeland currents act as “power cables,” transmitting electrical energy over vast distances. From an Electric Universe point of view, the galactic circuit that powers the sun generates a “leakage current” across Venus. The planet and its atmosphere act as a load in the circuit, converting some of the energy into heat, light and motion.”

    • I know of nothing observed on Venus contradicting the fact of gravity. But then there’s a lot I don’t know.

      Nobody knows much about the core of Venus, except that it doesn’t produce a strong internal magnetosphere, as does Earth. Venus’ induced magnetosphere has been studied in some detail, by contrast. To learn more about the planetary core, we’ll have to send landers.

      Solar and planetary gravitational effects may explain the slow rotations of Mercury and Venus, their tiny axial tilt, and possibly the former’s highly elliptical and the latter’s retrograde orbit. But collisions early in their histories, as posited for the formation of the Moon, have also been suggested.

  12. If there ever was liquid water on Venus, the presence of high concentrations of sulfur oxides in the atmosphere would have resulted in formation of sulfuric acid and/or oleum, which have higher boiling points than water. This could remain liquid at high temperatures, but would be inhospitable to life.

    Earth is a favorable location for liquid water, due to both its gravity and distance from the sun. Water can be evaporated under strong sunlight, but the upper atmosphere is cold enough to condense or freeze out water before it can escape the atmosphere, forming clouds and resulting in rain or snow.

    Venus has similar gravity to Earth, but receives about 2.7 times the solar radiation as Earth, so that water vapor (with its low molecular weight of 18) rises through the heavier atmosphere (CO2 = 44 MW, SO2 = 64 MW) without condensing, and may escape Venus’ gravity.

    The Moon receives about the same solar radiation as Earth, but has about 1/6 of the Earth’s gravity, so that all gases can escape the Moon’s gravity on the sunlit side, which remains sunlit for 14 Earth days at a time.

    • Good points.

      Solar irradiance at the top of Venus’ atmosphere is 2601.3 W/m^2; at Earth’s 1361.0 W/m^2, so about twice as much for our twin, as to be expected by the inverse square law and average distance from the Sun. Venus’ orbit is even more nearly circular than ours.

      The difference between day and night sides of Mercury and the Moon show what an atmosphere does for diurnal temperature variation, if that’s the right adjective for a 59-Earth day Mercurial (?) day.

      • But the albedo of Venus is 0.76 whereas that of Earth is 0.31 so Venus actually receives slightly less energy than Earth.

        • When you factor in greater absorption in the Venusian atmosphere, it’s even less. Under a tenth of incident irradiance reaches the surface. But Earth rotates 243 times faster than Venus, which also has practically no tilt.

    • So, any life arising on Venus would need to be at least triple extremophile, setting aside radiation from the angry young Sun’s flares when throwing a tantrum: heat-, acid- and probably salt-loving, as the presumably shallow seas would be extra ionic, thanks to runoff from high rainfall and weathering from fast winds.

  13. “The difference between Earth and Venus is that on Earth most of the energy from the sun is absorbed at ground level while on Venus most of the heat is deposited in the clouds”.

    Some solar energy on earth is lost by back-radiation to space before reaching the ground.

    • For sure.

      Earth’s present Bond albedo has been measured at 0.33; Venus’ at 0.76.

      But besides that which is reflected, some incoming sunlight is also absorbed by both atmospheres, although more in our twin’s case. Absorption in Earth’s atmosphere isn’t insignificant, however. The most energetic wavelengths of UV, for instance, don’t reach the ground because they’re absorbed making and breaking ozone high in the atmosphere.

  14. Nikolov and Zeller showed that atmospheric temperatures on all solar system planets with atmospheres are predictable based on pressure and distance from the sun alone:

    Atmospheric composition is not a factor.

    Figure 4 of this paper makes the highly testable prediction that the atmosphere of Jupiter’s moon Titan will be found to have either a higher surface temperature or a lower atmospheric pressure, than currently thought. We shall see.

    • For the gas and ice giants, it’s hard to say where the surface is, or of what it consists.

      But ya gotta like an hypothesis which makes a testable prediction, even if that’s so early 20th century!

    • Phil:
      Titan is the largest moon of Saturn, not Jupiter. Jupiter’s 4 major moons (Io, Europa, Ganymede, and Callisto) all have no significant atmosphere. Since Saturn is nearly twice the distance from the Sun as Jupiter, sunlight at Saturn and Titan is only slightly more than 25% that at Jupiter and its moons. This might be a major factor why Titan has a substantial atmosphere, while the similar sized moons of Jupiter do not.
      …………(Former) Mayor of Venus, also served as Ambassador to Jupiter.

  15. For detection of gasses in Venus’ atmosphere, here’s another idea for NASA.
    Create robust probes shaped to free-fall like bombs, sampling gas as they go.
    Each probe would detect a single gas only, so quite a number would be needed.
    The detectors should be as simple, robust, thermally resistant and passive as possible.
    If the probe detected it’s assigned gas, then it would emit a powerful radio signal at a specific frequency, powered by a chemical explosion. In the process the probe would self-destruct.
    Thus pulses of radio waves from a firing probe would signal the detection of the corresponding gas.
    The atmosphere of Venus would be “bombed” with several dozen or hundred of these devices, and the resulting signal bursts would give information of what gasses are detected and possibly, at what height.
    Some nearby orbiter(s) could detect and establish the position the signalling probes.
    Fun speculation anyway 🙂

    • We have a pretty good idea of the composition of the atmosphere. From radar imagery, we also know roughly what the surface looks like and its temperature. The problem is the chemical and mineral composition of the crust and estimates of the mantel and core. That calls for long-endurance rovers, which have told us so much about Mars, such as its apparently watery past.

      CACA proponents might not want to risk finding out that there were never oceans on Venus, to be lost to a runaway GHE. But I’d like to know. Could be simple. If landers find granite, then there was liquid water. Case closed/

      • It would be very good, I think, to run the granite theme by us in detail .
        I may be wrong, but I heard granite is crust formed by the older anaerobic biosphere ocean, before photosynthesis, and heated by mantle processes.
        That would mean an active oceanic biosphere, but also an active mantle…

        • Granite formation requires liquid water, as do plate tectonics. Venus has a mantle, but apparently presently lacks plate tectonics.

          It seems that most of its surface was overturned 300 to 500 Ma, as an alternative to plate movements driven by mantle superplumes.

        • PS: Seawater alone can form granite. No life, anaerobic or aerobic, is needed in the recipe. Granite has continued to form since the rise of aerobic organisms. Indeed, granite outcrops have been found as young as 10 million to 800,000 years old.

          Granite is now thought to require long-lasting oceans and plate tectonics to drag seawater, trapped in seafloor minerals, into the lower crust and mantle. So far, Earth is the only planet known for sure to feature granite rocks and continents.

          That’s why discovering granite on Venus would indicate ancient oceans. Suggestions of granite on Venus made over a decade ago have so far not been confirmed, as in a study this year:

          Ovda Fluctus, the Festoon Lava Flow on Ovda Regio, Venus: Not Silica‐Rich

          Mars probably had liquid water, but possibly never plate tectonics. Hints of granite were found there in 2013, but I haven’t followed up on whether that was confirmed:

          • I think any granite formation on this planet involves the biosphere, anaerobic or otherwise – is there any place here without it? Anaerobic stuff continues here, as a background chorus.

            I presume the high radioactivity counts of granite is because of mantle subduction. That raises the issue of its source. In other words any granite exploration should involve. let’s say simply, a Geiger counter?

            Anyway a great subject, indeed.

          • Yes, Earth still has lots of anaerobic life.

            Verifying granite on Venus will require landing on its surface, by whatever means. Or at least getting very close to it.

  16. (The previous year, then Lynne Sagan had proposed that mitochondria are endosymbiotic bacteria. This was a young couple welcoming academic notoriety.)

    Lynn was already divorced from Carl by then and married Thomas Margulis in ’67. Her hypothesis wasn’t accepted for about another ten years, hence her fame is as Lynn Margulis.
    The CO2 absorption bands are hugely broadened compared with the Earth’s atmosphere.
    At the surface temperature of ~462ºC the peak emission will be ~4µm so there will be strong absorption by the CO2 4.3µm and 2.7µm bands. Also as mentioned above the lower atmosphere is composed of supercritical CO2.

    • She published her endosymbiosis paper under the name of Lynn Sagan in 1966, although she had indeed divorced Carl the year before. She didn’t marry Margulis until the next year.

      Peak radiation from the surface of Venus lies just outside the 4.3 µm peak CO2 absorption band. CO2 has three peaks, at 2.7, 4.3 and 15 µM. Peak radiation for 462 degrees C is 3.94174372577 µM, so close to 4.3, but no cigar.

      • Indeed, her first paper on the subject was submitted to about 15 journals before being accepted for publication and it took about another 10 years for the theory to be accepted. I believe that she once received a response to a proposal that her research “was crap”. Interestingly the symbiotic event that gave rise to chloroplasts has been shown to have occurred at least three times yielding different versions.

        Peak radiation from the surface of Venus lies just outside the 4.3 µm peak CO2 absorption band. CO2 has three peaks, at 2.7, 4.3 and 15 µM. Peak radiation for 462 degrees C is 3.94174372577 µM, so close to 4.3, but no cigar.

        Yes but the radiation has a broad peak also the absorption is not a narrow peak either, at 90 atms and a temperature of 462ºC the broadening is substantial. The absorption near the maximum emission by CO2 near the surface will be total.

        • Thanks!

          Yes, I think that Lynn and Carl were still married when she first tried to get her heretical paper accepted.

          Even with some absorption by CO2, the traditional GHE hardly matters on Venus, with such a hot atmosphere from absorbing sunlight on the way in, and succh an already hot surface.

          The issue of water vapor GHE in the past however IMO needs assessment.

        • As of now, it looks as if chloroplast endosymbiosis happened only twice:

          Early photosynthetic eukaryotes inhabited low-salinity habitats

          “Although it is widely accepted that the chrloroplasts in photosynthetic eukaryotes can be traced back to a single cyanobacterial ancestor, the nature of that ancestor remains debated. Chloroplasts have been proposed to derive from either early- or late-branching cyanobacterial lineages, and similarly, the timing and ecological setting of this event remain uncertain. Phylogenomic and Bayesian relaxed molecular clock analyses show that the chloroplast lineage branched deep within the cyanobacterial tree of life ∼2.1 billion y ago, and ancestral trait reconstruction places this event in low-salinity environments. The chloroplast took another 200 My to become established, with most extant groups originating much later. Our analyses help to illuminate the little known evolutionary history of early life on land.”

          Separately, somewhere around 500 Ma, it happened again, in the line leading to the modern amoeboid Paulinella chromatophora.

  17. Well, I clearly remember watching Carl Sagan on TV scoffing at Velikovsky’s prediction that Venus’ atmosphere would be very very hot. That was before the first probe landed, and Sagan quickly changed his tune. Of course, E.V. never got credit. Ditto for his Jupiter prediction.

    For those who haven’t heard about the first ever international academic boycott of a publisher and its target. The book was “Worlds in Collision”, and it suggested that Venus was a comet that had often had near brushes with both Mars and Earth before settling into it’s present orbit, and that its heat was brought with it when it was ejected from Jupiter.

    • By the time of his 1980 TV show “Cosmos”, Sagan and other astronomers knew how hot Venus’ atmosphere was.

      • I never watched any of Sagan’s shows. What I saw was a newscast, and Sagan dismissed the idea of a hot Venus saying that the heavy clouds would keep it cold. IIRC, he also derided I.V.’s prediction that the atmosphere would be heavy with hydrocarbons.

        Be thankful he’s not around now. My guess is he’d be right up there waving the climate change flag, and making good money at it. Velikovsky, OTOH, was a classical amateur in the best sense.

        • I missed that interview.

          You’re right that the astronomical Dr. would be waving the CACA-stained flag.

    • “Billions and billions!”, his astronomical catch phrase, was accurate. His advocacy of “Nuclear Winter”, not so much.

  18. The latest interpretation of the Juno spacecraft data is that a proto-planet 10 times the mass of earth had a direct hit on Jupiter’s core 4.5 Billion years in ago. That sounds just like something Velikovsky wrote about as the mechanism for his theory of Venus being ejected from Jupiter.

  19. Honest questions:
    1) If Venus had water or oceans, then where did the hydrogen go? Is there hydrogen in the atmosphere of Venus (or in another chemical compound)? We understand O2 can be converted into CO2, but that would leave four H’s unaccounted for.
    2) My understanding of ‘albedo’ is that is the term used for ‘reflection’ (as in mirror) from the surface of a planet. Is ‘albedo’ possibly a combination of ‘surface reflection’ plus ‘atmospheric absorption’?
    3) When I measure the temperature of the ocean far offshore on one of my sailing adventures, why do I see a difference in sea temperature between the in hull thermometer and my thermal sensor pointed over the side at the water? The thermometer in the hull says temp is 25 deg C, but the temp gun says 22 deg C. Satellite in sky says water temp is 25 deg C. Why discrepancy?

    Thank you in advance for any insight.

    • 1) Please see below.
      2) Albedo is the proportion of incident irradiance reflected by a surface, in this case, the atmosphere of a planet or moon, back out to space. Absorption in the air and by the ground and sea, if any, are parts of the energy budget of such a body.
      3) I’m sorry, I could only speculate.

  20. 1) If Venus had water or oceans, then where did the hydrogen go? Is there hydrogen in the atmosphere of Venus (or in another chemical compound)? We understand O2 can be converted into CO2, but that would leave four H’s unaccounted for.

    Hydrogen has an escape velocity on Earth and Venus and over time will leave the atmosphere for space.

    • Yup. Water is broken down and recombined into H molecules, which escape due to their lightness. DH is heavier by a neutron, so with mass half again as much as H2, thus less of it escapes, yielding Venus’ high D ratio. The thick Venusian atmosphere now contains only about 20 ppm of water, equivalent to some 1860 on Earth, much less than over the moist tropics, at around 40,000 ppm, but a lot more than over the arid, cold polar regions. But there are also trace amounts of hydrogen chloride and flouride, plus clouds of sulfuric acid (H2SO4).

  21. Thank you. Good answers.
    Regarding my question #3: I speculate the thermal gun is ‘seeing’ below the surface and reporting back a ‘composite’ of warmer surface and cooler deeper water. Similar to the way a satellite looking for total outgoing radiation sees a ‘composite’ of warmer surface temps and colder atmospheric temps.
    BTW – I know the thermal gun is accurate, because when it looks at the bronze seawater inlet inside the aluminum hull it gets the temperature exactly right.
    I’m curious about this, and welcome any thoughts.

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