Here’s a summary of the VERITAS VEM instrument

VEM [7] covers >80% of the surface in six NIR bands located within five atmospheric windows sensi-tive to Fe mineralogy, plus eight atmospheric bands for calibration and water vapor measurements, all with significantly enhanced SNR relative to the VIRTIS instrument on the European Space Agency (ESA) Venus Express mission.

And the DAVINCI+

A multi-band imaging system that includes UV, Near IR (1 um), and an engi-neering wide-field mode, has been incorporated onto the Lockheed-Martin carrier/telecom/orbiter space-craft, with opportunities to acquire first-ever vantage points on Venus in the UV (where the mystery absorb-er is lurking) as well as in night-side 1 m emissivity.

So the VEMS is a more capable spectrometer but lacks UV VERITAS also will be in a circular orbit and I suspect DAVINCI+ will be in an elliptical orbit

Good breakdown, Van.

The VEM approach is even more evolved and specific than a spectrometer in general. I won't pretend to have absorbed all of the details, but the design is based on analyses of Venus spectra and how the atmosphere absorbs different IR wavelengths so that new imagery in five specific IR windows can be processed to cancel out the noise from the atmosphere and provide a meaningful six-band spectrum of the entire surface at what would effectively be ~50km/pixel. That's much worse than our radar imagery, but if you picture a 12 inch/30 cm globe of Venus, those pixels are just 2 mm, which is quite nice. The six bands should be sufficient to distinguish different surface compositions (both the origin of the rock and its chemical weathering are relevant). The resulting map of Venus' surface, for the first time, in "color", will be practically a new planet compared to any data we have previously received. (VIRTIS data allowed a bit of this analysis, but with fewer spectral bands; it, however, provided the data that allowed for the design of the VEM approach.)

I think a decent analogy is that it will do for Venus was MGS' TES instrument did for Mars. It won't have the spatial resolution that VIMS had at Titan, but comparable spectral resolution. It would likely identify for us any recent lava flows on Venus and possibly their ages, as well as a compositional map of the whole surface. It is simply unlike any data we currently have and probably could not be improved upon without airships operating below the clouds.

Could do, maybe, if it gets selected and if the massive complication of removing atmospheric signature actually works.

But perhaps I'm biased.

In the previous discovery competition, proposers in phase a could suggest enhancements that NASA could decide to fund it not. For example, jpl was going to propose the Cupid atmospheric robe for the previous VERITAS proposal. (I have no idea if this is true for this round). I wonder if DAVINCI+ might propose VEMS (it would be DLR supplied), and VERITAS the CUVE UV spectrometer ( it’s only 1-2 U in size)

Skepticism noted, Mike! Certainly the VEM instrument's success is subject to the yet-unknown realities of Venus itself, not only the atmosphere, but also the surface. It is exploration.

Is there any detail public yet about the nature of the DAVINCI imaging? I suppose one simple question I can't shake is whether it would all be down-looking or if there would be any side-looking panoramas made after or near touchdown.

Van, interesting thoughts about add-ons. It seems like DAVINCI has added a lot from the last time. I also would note that VERITAS, in utilizing a near-circular orbit, might therefore be pushing mass margins, but it would use aerobraking to achieve that orbit. Adding mass would make that more challenging, but the devil is in the details.

There are a variety of public papers and LPSC abstracts about the 2016 incarnation of DAVINCI from which inferences can be made. I'm not free to say anything about what might have changed, sorry.

I thought that was the likely response, but you can't blame a Venus fanatic for trying!

I can't find the link, but the previous DAVINCI imager would have built up overlapping images that would have allowed photogrammetric point matching to create 3D surfaces from the images. The presentation I remember showed that at high resolution. I don't know if it could have been done from higher elevations over wider areas.

From the one DAVINCI+ abstract available, it looks like they are supplementing the visible imager with a near infrared imager to relate finer scale composition to what would be seen from orbit.

If NASA (Congress) decides they are VERY interested in a out-of-cycle flagship or new frontiers class mission to Venus by middle of this decade to look at the... chemistry... of its atmosphere - do they collect new proposals, revisit the New Frontiers class missions that were turned down in 2019, or look at upscaling the current 2 Discovery class contenders?

I imagine that any proposed mission that wants to take a close look at the atmosphere's... composition... will want to include a sample return capsule or a balloon with an extensive chemistry lab on board. ISRO may be rethinking their decision not to include the atmospheric balloon on its payload as well.

NASA and Congress follow the priorities set in the Decadal Surveys. Unless the new survey prioritizes a Flagship Venus mission, it almost certainly won't happen. The one exception to this rule I can think of was former Congressman Culberson's insertion of the Europa Clipper mission into law (and the budget) along with a follow on Europa lander. The Clipper mission was the Decadal Survey's #2 flagship priority, so he was supporting the Decadal Survey's priorities there. The lander was not a Decadal priority, and while excellent mission definition work continues, Congress isn't providing the funding to take it to development anytime soon.

However, Culberson was an exception, probably unique in both his strong interest and his powerful position that allowed him to push Clipper through. Usually when someone in Congress backs a NASA mission ardently, it is because it brings a lot of $s and jobs to their state or district (such as Senator Shelby's strong support for the SLS).

All that said, the next Decadal Survey may continue to prioritize a Venus mission in the New Frontiers line, and good missions can fit into the Discovery line (a number of Venus atmospheric missions have been proposed for the Discovery program). And don't count out the SIMPLEx program. There are some exciting cubesat-scale atmospheric instruments in development to study Venus' atmosphere.

If either or both current proposals for Discovery missions to Venus succeed, then that would certainly change the balance sheet of outstanding scientific questions regarding Venus. They would also almost certainly raise new questions regarding Venus' surface and reorder the list of Venus priorities in ways that are difficult to foresee. Record of ancient sea floors? Active volcanoes? Something pertaining to the commonality of the origins of Earth's and Venus' respective atmospheres? I think it's likely that any Discovery mission would give us new information that would take time to gestate and would push any possible Venus flagship mission further into the future.

Given that Venus is already trending on Twitter (and it is not entirely about tennis), I expect public interest would definitely play a role in whether a major mission will be funded, "changing the balance sheet" as you put it.
I do wonder how a sample return from the atmosphere could be affected. Possibly even trickier then Mars sample return. An airship or balloon with a solid stage to carry a capsule to orbit for rendezvous and Earth return?

Multiple options for Venus atmospheric sample return are discussed here.

The DAVINCI+ Discovery proposal would measure Venus' atmospheric composition in situ with unprecedented accuracy. Until we know what that might find, we can't say if it would address many of the questions regarding Venus' atmospheric composition or if it would raise new ones.

Also note that an in situ measurement from the lower atmosphere could answer some questions better than a sample return from the upper atmosphere at certainly less cost.

https://www.hou.usra.edu/meetings/V2050/pdf/8164.pdf

Well - its officially released now. Phosphine gas has been found at the mid-latitudes (but not the poles) of the Venusian atmosphere by two different telescopes (very definitively by the ALMA array). There are no *known* abiotic processes to produce the concentrations found (up to 20 parts per billion).

So I imagine that the immediate focus from a space robotics perspective will be on the private Rocketlab and Indian missions which are both slated for launch in 2023, to see if they could get a more specific data on phosphine concentration at different altitudes and latitudes, and its chemical precursors.

Phosphine has been detected in the atmospheres of Jupiter and Saturn without exciting much comment I'm aware of. https://ui.adsabs.harvard.edu/abs/2009Icar......543F/abstract

The paper is paywalled, but section 4.3 of this 2019 paper on phosphine discusses that the pressures found at Jupiter and Saturn can produce this abiotically - but these conditions are not found on terrestrial sized planets (not even Venus) according to the discussion within the paper:

Theformation of PH3 on temperate, rocky planets is thermodynamically disfavored, even in high-reducing environments, unlike the fermentative
production of methane or hydrogen sulfide. In thermodynamic equilibrium,phosphorus can be conservatively expected to be found in the form of PH3
only at T > 800K, and at P > 0.1 bar (Visscher et al. 2006), which is why PH3 has been detected in Jupiter and Saturn, where these extreme temperatures
occur (in the deep layers of the atmosphere). We also note that the critical temperature of water is 647 K so there are no surface conditions that favor
both PH3 production and allow for the presence of liquid water

This chemistry was discussed in their press briefing just now as well.

RAS briefing here is still going:
https://www.youtube.com/watch?v=y1u-jlf_Olo

Phosphine gas in the cloud decks of Venus

So putting aside the out-of-forum scope questions... are their instruments planned on the upcoming Indian mission to Venus - or the two Discovery candidates (DAVINCI+, VERITAS) that are capable of detecting phosphine gas in the atmosphere? If not, are any suitable with modification? Or will this require instruments designed from the ground-up - or even a dedicated in-atmosphere mission - to better answer this question?

The team mentioned during the press conference they were working with RocketLab's 2023 Venus team - so presumably it will carry *something* that can help confirm the result, and further refine where phosphine is in the atmosphere.

It will be an interesting moderator challenge to figure out how, or even if, this discussion can occur in light of rule 1.3.

The phosphine news release led me to write some, I assure you, very funny and snarky comments that I won't post because of board rules, but in the realm of the safe-to-say: Venus has conditions well different from Earth's and undoubtedly, some interesting chemistry different than the chemistry here.

We still await a mission that performs Venus in situ surface science as thorough as Viking provided at Mars and the old conundrum one can't ignore is that temperatures require a viable strategy for survivability; there is a set of distinct strategies for making that work; as far as I know, there's no doubt that more than one of the strategies is viable, but nothing is going to come to fruition until a mission picks one of them and gets funded.

IMO, making a virtue of necessity, a mission architecture that seems promising for surface analysis is an aerobot that makes very short stays on the surface to grab samples, then inflates a helium balloon, ascends to cooler and survivable temperatures, performs analysis, and transmits results back to Earth while floating near cloud level. Winds at the cloud level could transport the craft almost unlimited distances downwind for touching down on and analyzing a second, etc. location. This would be in many ways analogous to Dragonfly at Titan, but with much greater capability for horizontal transport. One mission could conceivably visit all of the major terrain types on Venus – plains, tesserae, recently active volcanic surface, radar-reflective high altitude regions. With any other architecture, we would hope to drop two or more stationary landers and begin to understand the surface chemistry.

For a "Venus Insight" mission that includes a seismometer, I think it's a lot more hopeful that robust electronics could operate a surface station for long durations.

We are about a year away from learning if Venus scores one or two Discovery missions that would be preliminary to whatever next-generation surface mission.

It seems to me that phosphine at Venus is analogous to methane and other phenomena at Mars: We can make spectacular leaps in hypothesizing, but we're at an early point in the understanding and there's no doubt that we'd all like to understand the origin of methane at Mars and phosphine at Venus. How spectacular or mundane reality turns out to be is a matter that we don't control.

I'm not believing that this technology will be practical any time soon. See https://www.hou.usra.edu/meetings/exoplanet...ons/Gilmore.pdf for the current thinking of what could be done with a flagship budget, which has a goal of a lander that lasts 4-8 hours and a 30-day minimum lifetime balloon.

I noticed that someone asked about this at the RAS briefing. The reason if I understood correctly is different conditions at Jupiter and Saturn: Lots of hydrogen and much higher pressure where the phosphine forms.

As JRehling said, history shows we can civilly talk about the elephant in the room (methane spikes), you just can't argue about whether the elephant is biogenic. That's fine by me.

A fully anorganic approach I could offer is a release of PH3 by the reaction of a phosphide mineral with sulfuric acid similar to iron phosphide:
"Iron phosphide reacts with moisture and acids producing phosphine (PH3), a toxic and pyrophoric gas."

I'd consider Schreibersite one of the more plausible candidates.

mindat.org says: Schreibersite ((Fe,Ni)3P): "The mineral is estimated to stand for 1-10% of the total crustal phosphorus during the Hadean."
So, it might exist in Venus' subsurface, as well. Or it is added by meteorite impacts.
"Phosphide minerals are common accessory phases in meteorites and, to a lesser extent, in lunar rocks, interplanetary dust particles and comets."

All we need is a mechanism to get the presumed phosphide mineral in contact with the droplets of sulfuric acid in Venus' clouds.
Three mechanisms might be conceivable:
- meteorite impacts,
- dust / regolith stroms, or
- volcanic activity.

I might have overlooked a discussion of these phosphide mineral - acid reaction paths in the paper or in the supplementary material (p.11 ff.). I think, that the authors implicitely discarded this option due to the oxidizing environment of the atmosphere. But I'm not sure whether one can make such a simple assumption, especially for freshly exposed material.
Fresh exposure of (reduced) phosphide minerals would at least sound more plausible than a highly complex organic chemistry, which would require to sustain reduced compounds in an oxidizing environment, too.

Might there not be data in the VEX SPICAV archive that could help?

These observations were made at wavelengths of around 1mm, much longer than any remote-sensing instrument that's been flown to Venus AFAIK (SPICAV only goes to 4.3 um). You need to penetrate down to the 50-km level, and you probably can't do that at shorter wavelengths. Which puts in situ measurement at a distinct advantage.

Will the BepiColombo flyby coming up in a month be able to confirm this observation? Here is a quote from an ESA release:

Yeon Joo Lee, said: “The opportunity to use all these instruments simultaneously will give us access to multiple wavelengths to probe different altitudes of the atmosphere and to distinguish the different gases present. Simultaneous observations from a close-up to a global view mean that we can study physical processes on the planet at a variety of scales, from convection across a few tens of kilometres to global circulation patterns. The different viewing angles and distances of all the spacecraft and telescopes involved will enable us to see what’s happening on the dayside and the nightside of the planet and how processes evolve over time, which can be missed by just one mission.”

They talked about Earth-based observations to support the flyby, but I don't know if they will happen now with Covid-19.

There was a very analogous media tizzy a little over a decade ago about altitude variation of hydrogen on Titan. There are two challenges in this sort of situation, detection and attribution.

First, detection - is this really phosphine on Venus (and not some non-Doppler-shifted deuterated terrestrial phosphine line - Zahnle attributed one of the Mars methane detactions to this effect) or some other measurement artifact. The history of planetary science is replete with spectroscopic detections that turned out to be spurious. Radio/millimeter seems to be a bit better in this respect than the near-IR

Then (qv Sagan 'extraordinary claims require extraordinary evidence') is the signature exclusively attributable to a biotic process? This is a high bar. e,g, one can attribute methane on Mars to (abiotic) serpentinization reactions of water with hot rock. How much is at a level that requires a biogenic source? When one starts to look at these things quantitatively, the life/non-life boundary becomes very fuzzy. The paper makes an attempt to consider some alternative formation mechanisms, but it is difficult to know that you have addressed 'unknown unknowns' adequately.

Funding agencies and institutions like the press. The journals like the attention. The media reporting on the journal article like the buzz and the advertising $$. All the incentives are to talk up observations like this (and to ignore whatever caveats the authors expressed in their original discussion). So, while I dont deny Venus can use some more attention, some skepticism on the interpretations in this report is in order.

Seems pretty unlikely. The longest wavelength it can observe is the thermal infrared to about 14 um. I haven't been able to find what the spectrum of phosphine looks like at visible to thermal IR wavelengths, but this would require there to be windows at the appropriate wavelengths for general atmospheric scattering and absorption, and enough SNR to be able to detect absorption lines.

Not yet mentioned on this site - but private rocket/satellite company Rocketlab has committed to running a privately funded mission to Venus on its Electron rocket using its Photon satellite platform during the 2023 launch window. Budget is in the 10's of millions, and they are claiming that they can deliver a payload of 37 kg to Venus orbit - part of which will be an atmospheric drop probe. In other interviews they mention the drop probe having an IR spectrometer or onboard gas analyzer.

It's very unclear to me what "committed" means, and I see a lot of naive talk about how easy it would be to pull something like this off. But if you like that sort of discussion, I suggest https://forum.nasaspaceflight.com/ as a better venue.

The most intense vibrational absorption bands seem to be centered to wave numbers 2321.1314 cm^-1 and 2326.8766 cm^-1, see table 1, page 7020 in "The stretching vibrational overtone spectra of PH3: Local mode vibrational analysis, dipole moment surfaces from density functional theory and band intensities".
If I calculated correctly, this should correspond to a wavelength of about 4.3 um.
I didn't find longer vibrational wavelengths, and I didn't make an attempt to understand the rotational transitions.

There's a huge CO2 absorption right there, so that doesn't seem viable. See Figure 5 in https://arxiv.org/abs/2003.00228

But I'm no expert. I'm sure all of the orbital datasets will be getting a close look in the months ahead and people will be considering what types of remote sensing would be best suited (if any.)

re: Phosphine on Venus as biogenic:

If someone familiar only with Europe looked at the Moon through a telescope, they might conclude that it was covered with volcanoes, because big, circular holes in the ground in Europe always mean volcanoes.

In fact, that's exactly what European astronomers did conclude of the Moon. And it was wrong. It's just not a valid form of reasoning to conclude that.

Now, there are volcanic craters on the Moon, and there are impact craters on Earth. If you see one crater on the Moon, "volcano" is a fine hypothesis to put on the list. But that's where it stops before you acquire more evidence.

I'm not following the point you're trying to make at all. The paper attempts to show why non-biogenic origins are not possible under Venusian conditions. You can take issue with how complete this attempt was, but they certainly made it.

That's a valid point but I'm not sure why you make it here? In fairness to the authors of the paper they haven't concluded there is life the Venusian clouds, they only advance it as one hypothesis of several that might fit this data. They attempt to rule out some others, and happily admit there's a huge slew of known unknowns and unknown unknowns surrounding the detection and origin of this phosphine, when asked.

Even if we could rule out a biogenic origin right this instant, the presence of phosphine adds another mystery to the Venusian chemical environment - which is already known to be a complex, ever changing, environment with lots of mysteries already, and direct relevance to our efforts to better understand Earth and it's history. So I'll admit to being excited at the thought it might start to receive more attention.

ADMIN NOTE: Everybody play nice...which is another reason for the existence of rule 1.3.

The analogies and arguments about how much skepticism is warranted should be avoided. The latest xkcd tries to cover the bases there. (Think of the xkcd as 9 squares of strawmen being built up to get torn down, so... don't do it.)

I struggle to understand what this observation was, exactly, so I think the discussion of what other assets might replicate it the most interesting and on topic here.

What might be most informative is... why hasn't anything else seen it before? Or has it been seen before, just not noted?

Aha. This layman had been wondering about SOFIA, and this reddit thread (where you are free to go argue about whether other people are more or less excited than they should be), his this tidbit:

Nicely pullquoted from a NG article that I didn't read because I didn't want their spam:
https://www.nationalgeographic.com/science/...-phosphine-gas/

The UMSF moderating team has been discussing the recent Venus news in the context of rule 1.3 (which I assume everyone here is familiar with ;-).

The result is that it has been decided to relax rule 1.3 a bit in this thread, at least temporarily. This means that discussion of instrumentation and methods is entirely appropriate, and of course the purpose of some of the instruments would be to detect biosignatures (this means that it is perfectly OK to mention biosignatures in the discussion).

We need to emphasize the following, though:

1. Anybody claiming the discovery of life will be booted (no "unsung basement genius" bullshit).

2. Organic chemistry in the context of signatures is okay, but not extrapolation based on findings since that can get stupid quickly. This includes linking to the inevitable torrent of imaginative 'life in the clouds of Venus' nonsense articles that will shortly pop up all over.

3. Discussions that veer into sheer speculation (or even crackpot theories) will be shut down immediately.

Now let's have fun discussing possible future Venus missions etc. which suddenly have become a whole lot more exciting! (and even before this I found many of them interesting, e.g. DAVINCI+, VERITAS and EnVision).

How about this?

Phil

Click to view attachment

Wondering about whether VEX could have picked up signatures, I noticed this in an article in Forbes - could VEX's VIRTIS have collected evidence of Phosphine's presence already?

Phosphine has an absorption band in the infrared spectrum at roughly 3.05 microns, Julie Castillo, a planetary scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, told me. So, one should check the observations of the VIRTIS instrument on Venus Express for the possible presence of that phosphine in its VIRTIS observations, she says.

It has been well noted that the SO2 composition of Venus' atmosphere has varied dramatically over the duration of observations. It remains possible that the phosphine detected on Venus in 2017 wasn't present when Venus Express ended in 2014. (I'm not sure when VIRTIS last took measurements, so the EOM in 2014 may not be the relevant start of the window between last Venus Express measurement and the phosphine detection.

The Sousa-Silver paper notes that "phosphite can disproportionate to phosphine at T > 323K and acidic pH." If a volcanic event on Venus liberated phosphorus-bearing minerals in the last few years, the detection of phosphine could record a very temporary event.

In fact, I wonder if Venus provides a loophole here that hasn't been discussed (Sousa-Silver, et al were talking about exoplanets in general, not Venus), that a non-volcanic mass movement event on Venus (earthquakes, landslides) could introduce subsurface minerals to surface conditions and begin chemical reactions at the time of the event. The "acidic pH" condition might be met at the surface, but not in the subsurface. No volcano required. No inherent paradox that a gas that should be destroyed quickly in Venus' atmosphere is present now.

From my armchair (I am literally sitting in an armchair right now), VERITAS would likely provide better insight as to the rate and recency of mass movement events on Venus, while DAVINCI+ obviously provides different opportunities to investigate the phosphine result.

H₃PO₃ is thermally decomposed ("disproportionated") into PH₃ and H₃PO₄ near 200°C.
If there would exist some catalytic process in the presence of H₂SO₄ and CO₂ to recover the H₃PO₃ from H₃PO₄, we would get a closed cycle, depending a bit on the oxidation products of PH₃, and less supply from exogenic sources would be required.
Just to get rid of that one easy-looking O is probably the point where some "new chemistry" is needed. At least I wasn't able to find a paper describing or providing at least a hint how to track this way back.

To detect something in absorption, you have to 1) know where the absorption is, and then 2) you have to have a light source that would normally have a lot of energy at that wavelength (either reflected sunlight or thermal emission, depending on wavelength) and 3) it can't be absorbed or scattered by the other stuff between the instrument and the target, and 4) the instrument has to have enough SNR and spectral/spatial resolution to detect the absorption.

1 depends on the behavior of the substance under venusian conditions (if that's known; phosphine is horrifically toxic so people may not have enthusiastically studied it in the lab, I sure wouldn't); 2 and 3 depend on the complex properties of the atmosphere above (and for emission, below) the clouds; 4 is usually something the instrument designers know.

As I said upthread, I'm sure this will be gone over carefully for every dataset there is, and we'll see what happens.

We might not need to wait that long for new atmospheric data: Bepicolombo has two flybys coming up (this October and next August), and the MERTIS instrument does have the spectral range to attempt observations. The main hurdle is resolution; the August flyby is more likely to make any phosphine detection as it is only going to be 500 km away vs 10,000 for the first flyby (see this article)

It occurred to me yesterday that the phosphine is the second mystery of Venus that (may) relate to potassium, or at least to elemental composition in the same part of the periodic table.

Venus has an extremely high ratio of 36Ar/40Ar compared to that on Earth, reflecting a somewhat lower amount of 40Ar but a much higher amount of 36Ar. 40Ar is produced by the radioactive decay of 40K, so this seems to indicate that the Venusian atmosphere has had less interchange with any reservoir containing 40K.

That said, this doesn't point in the same direction as any excess of potassium, and even if it did, 40K is a very small fraction of terrestrial potassium anyway. This is also a comment on nuclear chemistry, not the chemistry that produces/sustains phosphine. What it does say is that the elemental composition of the Venusian atmosphere and crust is not like Earth's in some striking ways. If 36Ar can be superabundant on Venus, could 39K (related in no causal way that I see) also be superabundant? And if so, that could help boost the signal that we're seeing here.

Venera 8 and Venera 13 both reported high levels of K in the surface, while the other five sites tested reported low K. It seems to me like we need more and better understanding of venusian crustal composition and landing on one or two new sites isn't going to resolve the issue. Perhaps emissivity maps from Veritas could use the Soviet data to ground truth maps of surface composition. Failing that, we would need more surface probes or, as I suggested before, one with great mobility.

Isn't this a straightforward consequence of the much higher mass of the atmosphere (including Ar-36) of Venus compared to that of Earth, with composition (especially Ar-36 ratio of the atmosphere and bulk K-40 ratio in the planet), and planet mass and density otherwise assumed to be initially almost the same? Both planets would then produce the same amount of Ar-40 and release it to atmospheres of very different mass, especially of Ar-36.