Future Venus Missions Options

[Phil Stooke]

Oh well, might as well start that new topic since it's already well advanced in the Juno area...

My perspective on landers is as follows. All the landers we've had so far were dropped blind onto an essentially unknown surface. Any future landers can be targeted for specific terrains. It really is not true that we have had representative landings. Even a descent image or two, a panoramic photo plus a bit of surface composition, from a simple Venera-class lander just updated a bit, would be useful if we could put several down at well chosen targets. My choices would be:

Examples of the main plains units (smooth, fractured, ridged)

tesserae

high elevation radar-bright tesserae

large fresh lava flow unit ('fluctus')

crater dark parabola

crater ejecta outflow unit

dunes area.

And I have always assumed, rightly or wrongly, that it would be relatively easy to put these down, so they ought to be fairly inexpensive as planetary landers go.

Phil

[Explorer1]

No, it's still happening. Not a paper (since it's a private mission), but there is a recent interview with Peter Beck here with a few more details (at 5:20 he mentions ~200 seconds in the atmosphere with a tunable laser spectrometer).

https://www.youtube.com/watch?v=U7iVs0Cq84M

[JRehling]

This round of missions will return most of its data in the timeframe of 2029-2034. Then the scientific priorities should define what comes next.

A long-life seismic station (or network) will certainly be a priority if and when it's feasible. In other respects, it's frankly hard to say what missions will make sense in the 2040s until we have results back from the three missions that were just approved.

A potential line of exploration will depend on whether or not the tesserae contain ancient surface from a distinct earlier epoch when Venus was fundamentally a different planet. That's what Curiosity and Perseverance are doing at Mars. But you can't plan that until you know that it's even there to explore. Maybe all the tesserae contain such terrain. Maybe 1% of them do and we have to hunt for that 1%. Maybe 0% do and it's just chaotic, broken-up versions of what is in the plains. Maybe spectroscopy helps us identify such terrain and maybe it doesn't. Maybe we would want to have an airplane below the clouds map visible+IR spectrometry during the daytime or IR emissivity at night.

Roughly speaking, this is like the state of Mars exploration in 1992. Nobody then could have known that twelve years later we'd be examining the layers of sedimentary rock on Mars. But for us to do that, the planet has to have sedimentary rock, and Venus is still an enigma.

[mcaplinger]

Roughly speaking, this is like the state of Mars exploration in 1992. Nobody then could have known that twelve years later we'd be examining the layers of sedimentary rock on Mars.

Let's say that Magellan global radar has a resolution of 75 m/pix (a little bit of oversimplification but not wildly unfair). VISAR https://www.hou.usra.edu/meetings/lpsc2020/pdf/1449.pdf claims 30 m/pixel resolution globally and 15 m/pix in small targeted regions. So that's a fair approximation of what Viking gave us for Mars. It took another 10x increase in resolution provided by MOC to yield the results John is talking about.

Viking orbital imagery was very evolutionary, not revolutionary, from Mariner 9. And at least as far as orbital radar is concerned, these missions will likely be evolutionary from Magellan if the Mars experience is applicable (which I admit it may not be.)

[JRehling]

Inarguable points, Mike, and I won't overly press the comparison between two situations. The spatial resolution is certainly in favor of Mars but I'll add that Venus exploration now is – possibly – matched with or beyond on Mars exploration in the Nineties in two ways. One, the emissivity data from the three upcoming missions will strive to accomplish what TES delivered for Mars, and this might be decisive in some way even if spatial resolution is lacking, but admittedly, this layers speculation on top of speculation: Perhaps emissivity will not tell us as much as we hope and we don't even know what we're looking for yet. Secondly, while the first three Mars landings were on flat, comparatively boring locations (and the fourth, incredibly flat, but not at all boring), the Venera and DAVINCI+ landing sites are pretty daring and even if they have been the equivalent of blindfolded dart throws, they've moved quickly towards the possible objectives of some of the more exciting terrain. It also occurs to me, for the first time, that the upcoming missions might place Venera surface data into much more meaningful context after the fact.

Venus is certainly more challenging than Mars on the whole, and it may not even be possible – ever – to achieve a knowledge of Venus comparable to our current knowledge of Mars, not only because of the obscuring clouds and harsh conditions but because its ancient surfaces may simply be obliterated. Beyond that, what we're even looking for remains speculative. I am being Mars-o-centric in speculating that we might eventually look on Venus for exactly what we're now exploring on Mars – the remaining traces of a more earth-like past. But who knows?

[vjkane]

Inarguable points, Mike, and I won't overly press the comparison between two situations. The spatial resolution is certainly in favor of Mars but I'll add that Venus exploration now is – possibly – matched with or beyond on Mars exploration in the Nineties in two ways. One, the emissivity data from the three upcoming missions will strive to accomplish what TES delivered for Mars, and this might be decisive in some way even if spatial resolution is lacking, but admittedly, this layers speculation on top of speculation: Perhaps emissivity will not tell us as much as we hope and we don't even know what we're looking for yet. Secondly, while the first three Mars landings were on flat, comparatively boring locations (and the fourth, incredibly flat, but not at all boring), the Venera and DAVINCI+ landing sites are pretty daring and even if they have been the equivalent of blindfolded dart throws, they've moved quickly towards the possible objectives of some of the more exciting terrain. It also occurs to me, for the first time, that the upcoming missions might place Venera surface data into much more meaningful context after the fact.

Venus is certainly more challenging than Mars on the whole, and it may not even be possible – ever – to achieve a knowledge of Venus comparable to our current knowledge of Mars, not only because of the obscuring clouds and harsh conditions but because its ancient surfaces may simply be obliterated. Beyond that, what we're even looking for remains speculative. I am being Mars-o-centric in speculating that we might eventually look on Venus for exactly what we're now exploring on Mars – the remaining traces of a more earth-like past. But who knows?

Venus exploration will always lag far behind Mars'. It is, if you will forgive the bad pun, a hellish place to study. MRO's context camera will outperform the radar instruments of both VERITAS and EnVision by an order of magnitude. The emissivity composition measurements will have a handful of spectra and 50 *km* resolution (although that may be improved with time by over sampling). We simply can't compare the two in terms of resolution - Mars will always be favored.

Rather, I think, we need to accept Venus for what it is. V and EnV will provide an order of magnitude improvement in resolution (Magellan resolutions are more typically quoted as ~300 m, with some limited areas at ~75 m). V will improve topographic resolution by at least one magnitude, perhaps two. Both V and EnV will be able to detect subtle changes in topography to look for activity.

Venus is one of four terrestrial planets, it's been overlooked (with BepiColombo, Mercury will be much better studied). The question, in my mind, isn't whether Mars, or the moon, or Mercury can be studied at higher resolution, but what can be done with Venus. These missions hugely move the goal posts.

[mcaplinger]

Magellan resolutions are more typically quoted as ~300 m, with some limited areas at ~75 m.

Having spent more than a small amount of time working with the full-res F-BIDR products and even the raws back when the mission was still running, anyone who would say global coverage from Magellan is only 300m is not trying hard enough, IMHO.

Doing a more modern job of reprocessing the Magellan data would probably have payoffs for those brave enough to try it.

[mcaplinger]

Doing a more modern job of reprocessing the Magellan data would probably have payoffs for those brave enough to try it.

In the decades since I last worked on Magellan, full-res map products ("FMAPs") at 75 m/pix have been produced. See https://pds-imaging.jpl.nasa.gov/volumes/ma...an.html#mgnFMAP

Per the documentation,

the present
series of maps contains all coverage (about 92% of the planet) obtained
with the left-looking nominal desired look angle profile (DLAP). Future
series may be created containing data obtained with the right-looking
constant incidence DLAP and left-looking stereo DLAP, increasing total
coverage to 96% with considerable redundancy.

[vjkane]

In the decades since I last worked on Magellan, full-res map products ("FMAPs") at 75 m/pix have been produced. See https://pds-imaging.jpl.nasa.gov/volumes/ma...an.html#mgnFMAP

Per the documentation,

I stand corrected