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Future Venus Missions
Phil Stooke
post Jul 1 2005, 01:30 AM
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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


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vjkane
post Oct 16 2020, 08:55 AM
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Another team observing Venus in the thermal infrared has failed to detect phosphine, suggesting an upper limit on concentrations several times lower than that suggested by observations at millimeter wavelengths.

Press release link on SpaceRef

Following the announcement of the detection of phosphine (PH3) in the cloud deck of Venus at millimeter wavelengths, we have searched for other possible signatures of this molecule in the infrared range.

Since 2012, we have been observing Venus in the thermal infrared at various wavelengths to monitor the behavior of SO2 and H2O at the cloud top. We have identified a spectral interval recorded in March 2015 around 950 cm−1 where a PH3 transition is present.

From the absence of any feature at this frequency, we derive, on the disk-integrated spectrum, a 3-σ upper limit of 5 ppbv for the PH3 mixing ratio, assumed to be constant throughout the atmosphere. This limit is 4 times lower than the disk-integrated mixing ratio derived at millimeter wavelengths.

Our result brings a strong constraint on the maximum PH3 abundance at the cloud top and in the lower mesosphere of Venus.

T. Encrenaz (1), T. K. Greathouse (2), E. Marcq (3), T. Widemann (1), B. Bézard (1), T. Fouchet (1), R. Giles (2), H. Sagawa (4), J. Greaves (5), C. Sousa-Silva (6) ((1) LESIA, Observatoire de Paris, PSL Université, CNRS, Sorbonne Université, Université de Paris, (2) SwRI, (3) LATMOS/IPSL, UVSQ Université Paris-Saclay, Sorbonne Université, CNRS, (4) Kyoto Sanyo University, (5) School of Physics and Astronomy, Cardiff University, (6) Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology)

Comments: Astronomy & Astrophysics, in press
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2010.07817 [astro-ph.EP] (or arXiv:2010.07817v1 [astro-ph.EP] for this version)
Submission history
From: Bruno Bézard
[v1] Thu, 15 Oct 2020 15:11:37 UTC (805 KB)
https://arxiv.org/abs/2010.07817
Astrobiology, Astrochemistry,
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Xerxes
post Oct 16 2020, 05:34 PM
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The original paper attempted to pre-rebut this argument:
QUOTE
We caution that mid-infrared and far-infrared observations might not detect any phosphine in absorption, depending on the height where the quasi-continuum signal is generated in these wavebands; e.g. at high altitudes, the molecules are expected to be photo-destroyed.


This paper makes some arguments as to why the original signal would actually have to be at high altitude:
QUOTE
the core of millimeter line is very narrow (less than about 20 MHz). If the PH3 millimeter line was formed within the clouds, at a pressure level of 100 mbars or more, its HWHM would be at least 0.01 cm−1, i.e. 300 MHz. Such a broad line would not be observable by heterodyne spectroscopy. This implies that the millimeter line observed by Greaves et. al. (2020) must be formed relatively high in the mesosphere


I suppose one would need a great deal more expertise to know whose argument is stronger.
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rlorenz
post Oct 17 2020, 03:10 AM
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QUOTE (Xerxes @ Oct 16 2020, 12:34 PM) *
I suppose one would need a great deal more expertise to know whose argument is stronger.


Expertise, maybe. But as humans, we can also employ our heuristic tools of caricature, profiling and prejudice.

Therese Encrenaz has been in *planetary* spectroscopy a long time. I think (and my Planetary Climate book gives many examples) in planetary science there are many instances of spectroscopic detections being disproved by in-situ or other data, which make some people (like her) cautious. In stellar astronomy (which seems to be where the Cardiff group has more pedigree), I could imagine there are fewer disproved 'discoveries' just because there are fewer ways to confirm or refute initial announcements.

So, IMHO, if Therese says it isnt in her data, then it isnt in her data... (and knowing her, she wouldnt say it wasnt there on Venus, only that there wasnt evidence for it in her data).

It may be non-PC to consider such meta-factors, but at the hairy edge of detectability, one is obliged - Bayeswise - to weigh all the information.

There are sadly a lot of incentives in the journals and the media to talking up anything that could bear on life in the universe - indeed Nature Astronomy even had an editorial congratulating itself on how much press the paper had generated and how this was only possible because of their media embargo policy. Cui bono....

All this said, Venus deserved the attention.


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Posts in this topic
- Phil Stooke   Future Venus Missions   Jul 1 2005, 01:30 AM
- - vjkane   In the previous discovery competition, proposers i...   Feb 24 2020, 02:16 AM
- - dtolman   If NASA (Congress) decides they are VERY intereste...   Sep 13 2020, 01:00 PM
|- - vjkane   QUOTE (dtolman @ Sep 13 2020, 05:00 AM) I...   Sep 13 2020, 01:16 PM
|- - JRehling   If either or both current proposals for Discovery ...   Sep 13 2020, 09:41 PM
- - Explorer1   Given that Venus is already trending on Twitter (a...   Sep 14 2020, 01:44 AM
|- - JRehling   Multiple options for Venus atmospheric sample retu...   Sep 14 2020, 01:57 AM
- - dtolman   Well - its officially released now. Phosphine gas ...   Sep 14 2020, 03:28 PM
- - mcaplinger   Phosphine has been detected in the atmospheres of ...   Sep 14 2020, 03:35 PM
|- - dtolman   The paper is paywalled, but section 4.3 of this 20...   Sep 14 2020, 03:43 PM
|- - Bjorn Jonsson   QUOTE (mcaplinger @ Sep 14 2020, 03:35 PM...   Sep 14 2020, 05:43 PM
- - Explorer1   RAS briefing here is still going: https://www.yout...   Sep 14 2020, 03:45 PM
|- - JRehling   The phosphine news release led me to write some, I...   Sep 14 2020, 04:51 PM
|- - JRehling   It seems to me that phosphine at Venus is analogou...   Sep 14 2020, 05:13 PM
||- - rlorenz   QUOTE (JRehling @ Sep 14 2020, 12:13 PM) ...   Sep 15 2020, 04:17 AM
|- - mcaplinger   QUOTE (JRehling @ Sep 14 2020, 08:51 AM) ...   Sep 14 2020, 05:21 PM
- - centsworth_II   Phosphine gas in the cloud decks of Venus QUOTE E...   Sep 14 2020, 04:41 PM
- - dtolman   So putting aside the out-of-forum scope questions....   Sep 14 2020, 04:45 PM
- - mcaplinger   It will be an interesting moderator challenge to f...   Sep 14 2020, 04:46 PM
|- - stevesliva   QUOTE (mcaplinger @ Sep 14 2020, 11:46 AM...   Sep 14 2020, 06:44 PM
- - Gerald   A fully anorganic approach I could offer is a rele...   Sep 14 2020, 08:58 PM
- - ollopa   Might there not be data in the VEX SPICAV archive ...   Sep 14 2020, 09:06 PM
|- - mcaplinger   QUOTE (ollopa @ Sep 14 2020, 01:06 PM) Mi...   Sep 14 2020, 09:16 PM
- - Ron Hobbs   Will the BepiColombo flyby coming up in a month be...   Sep 15 2020, 03:38 AM
|- - mcaplinger   QUOTE (Ron Hobbs @ Sep 14 2020, 07:38 PM)...   Sep 15 2020, 05:53 PM
|- - Gerald   QUOTE (mcaplinger @ Sep 15 2020, 07:53 PM...   Sep 15 2020, 09:30 PM
|- - mcaplinger   QUOTE (Gerald @ Sep 15 2020, 01:30 PM) Th...   Sep 15 2020, 10:07 PM
|- - JRehling   re: Phosphine on Venus as biogenic: If someone fa...   Sep 15 2020, 11:20 PM
|- - mcaplinger   QUOTE (JRehling @ Sep 15 2020, 03:20 PM) ...   Sep 15 2020, 11:29 PM
|- - marsbug   QUOTE (JRehling @ Sep 16 2020, 12:20 AM) ...   Sep 16 2020, 01:00 AM
- - dtolman   Not yet mentioned on this site - but private rocke...   Sep 15 2020, 06:57 PM
|- - mcaplinger   QUOTE (dtolman @ Sep 15 2020, 10:57 AM) p...   Sep 15 2020, 07:13 PM
- - nprev   ADMIN NOTE: Everybody play nice...which is another...   Sep 16 2020, 02:47 AM
- - stevesliva   The analogies and arguments about how much skeptic...   Sep 16 2020, 02:49 AM
- - stevesliva   Aha. This layman had been wondering about SOFIA, ...   Sep 16 2020, 03:09 AM
- - Bjorn Jonsson   The UMSF moderating team has been discussing the r...   Sep 17 2020, 12:15 AM
- - Phil Stooke   How about this? Phil   Sep 17 2020, 07:49 AM
- - dtolman   Wondering about whether VEX could have picked up s...   Sep 17 2020, 12:09 PM
|- - JRehling   It has been well noted that the SO2 composition of...   Sep 17 2020, 03:55 PM
||- - Gerald   QUOTE (JRehling @ Sep 17 2020, 05:55 PM) ...   Sep 17 2020, 04:39 PM
|- - mcaplinger   QUOTE (dtolman @ Sep 17 2020, 04:09 AM) W...   Sep 17 2020, 05:27 PM
- - Explorer1   We might not need to wait that long for new atmosp...   Sep 18 2020, 01:24 AM
|- - JRehling   It occurred to me yesterday that the phosphine is ...   Sep 19 2020, 05:19 PM
|- - Gerald   QUOTE (JRehling @ Sep 19 2020, 07:19 PM) ...   Sep 19 2020, 10:37 PM
|- - JRehling   There's no consensus on why Venus shows the is...   Sep 20 2020, 03:35 PM
- - Phil Stooke   https://arxiv.org/abs/2009.12758 Maybe Phosphine...   Sep 30 2020, 12:17 AM
- - Gerald   ... obtained with the entirely different method of...   Sep 30 2020, 07:40 PM
- - vjkane   Another team observing Venus in the thermal infrar...   Oct 16 2020, 08:55 AM
|- - Xerxes   The original paper attempted to pre-rebut this arg...   Oct 16 2020, 05:34 PM
|- - JRehling   One also needs to know if "high" and ...   Oct 16 2020, 08:01 PM
|- - rlorenz   QUOTE (Xerxes @ Oct 16 2020, 12:34 PM) I ...   Oct 17 2020, 03:10 AM
- - Greenish   For what it's worth, this is new on the arxiv,...   Oct 27 2020, 11:35 PM
- - antipode   Here's a Venus mission concept I hadn't se...   Nov 23 2020, 03:24 AM
|- - vjkane   QUOTE (antipode @ Nov 22 2020, 07:24 PM) ...   Nov 23 2020, 02:29 PM
- - vjkane   Moderators: I obviously had problems editing my pr...   Nov 23 2020, 09:27 PM
|- - JRehling   As a non-mechanical engineer, I nonetheless share ...   Nov 23 2020, 10:07 PM
|- - mcaplinger   QUOTE (JRehling @ Nov 23 2020, 02:07 PM) ...   Nov 23 2020, 10:45 PM
- - Gerald   I was wondering whether any fiber is known to be s...   Nov 24 2020, 02:21 AM
|- - mcaplinger   QUOTE (Gerald @ Nov 23 2020, 06:21 PM) In...   Nov 24 2020, 04:15 AM
|- - JRehling   Reading the afore-linked reports, I think I've...   Nov 27 2020, 12:26 AM
- - antipode   Here's another Venus mission proposal from LPS...   Feb 17 2021, 08:36 AM
|- - stevesliva   That would be quite a lot of tether mass. It also...   Feb 17 2021, 01:55 PM
|- - vjkane   QUOTE (stevesliva @ Feb 17 2021, 05:55 AM...   Feb 17 2021, 03:39 PM
- - bobik   The EnVision Assessment Study Report is now out...   Feb 21 2021, 04:57 PM
|- - JRehling   I missed, until now, the announcement made in Octo...   Feb 21 2021, 05:24 PM
|- - vjkane   QUOTE (JRehling @ Feb 21 2021, 09:24 AM) ...   Feb 21 2021, 06:57 PM
|- - JRehling   Thanks for the updates, Van, although I quietly gr...   Feb 21 2021, 09:06 PM
|- - vjkane   QUOTE (JRehling @ Feb 21 2021, 01:06 PM) ...   Feb 21 2021, 09:11 PM
- - Phil Stooke   DAVINCI+ and Veritas, both selected - big times fo...   Jun 2 2021, 07:40 PM
|- - JRehling   I'm shivering in excitement. Congratulations t...   Jun 2 2021, 08:28 PM
|- - rlorenz   QUOTE (Phil Stooke @ Jun 2 2021, 03:40 PM...   Jun 3 2021, 02:18 AM
|- - JRehling   And in a sense, there were three Venus winners, be...   Jun 3 2021, 03:14 AM
- - Explorer1   Wonderful news! Press release here: https://...   Jun 2 2021, 08:14 PM
- - Holder of the Two Leashes   YYYYYEEEEEEEEEEESSSSS!   Jun 2 2021, 10:03 PM
- - TrappistPlanets   OH HECK YEAH!!   Jun 2 2021, 10:35 PM
- - Explorer1   The PIs of both missions will be speaking tomorrow...   Jun 2 2021, 11:22 PM
- - dtolman   Wow! Does both being selected mean that they a...   Jun 3 2021, 12:55 AM
- - Phil Stooke   They are totally different, they can't really ...   Jun 3 2021, 01:05 AM
- - Tom Tamlyn   From Scott Maxwell (@marsroverdriver) on twitter: ...   Jun 3 2021, 03:31 AM
- - dtolman   What will the descent probe's velocity be? Is ...   Jun 3 2021, 03:46 AM
- - Hungry4info   From here. QUOTE DAVINCI has no requirement to sur...   Jun 3 2021, 05:00 AM
- - antipode   That's excellent. Lets hope against hope for a...   Jun 3 2021, 08:03 AM
|- - JRehling   Reading up on the science of noble gas abundance i...   Jun 3 2021, 08:37 AM
|- - vjkane   QUOTE (antipode @ Jun 3 2021, 01:03 AM) T...   Jun 3 2021, 02:30 PM
|- - rlorenz   QUOTE (vjkane @ Jun 3 2021, 10:30 AM) D+...   Jun 3 2021, 03:02 PM
|- - vjkane   QUOTE (rlorenz @ Jun 3 2021, 08:02 AM) I ...   Jun 3 2021, 06:21 PM
|- - JRehling   I for one was just looking at MARDI descent imager...   Jun 3 2021, 06:31 PM
||- - vjkane   QUOTE (JRehling @ Jun 3 2021, 11:31 AM) A...   Jun 3 2021, 06:45 PM
|- - rlorenz   QUOTE (vjkane @ Jun 3 2021, 01:21 PM) Ral...   Jun 4 2021, 02:58 AM
- - vjkane   Perhaps the most valuable landed science simply wo...   Jun 3 2021, 06:52 PM
|- - JRehling   I believe that the noble gas analyses will be the ...   Jun 3 2021, 09:30 PM
- - Saturns Moon Titan   Rumor has it ESA will announce its M5 mission sele...   Jun 10 2021, 09:46 AM
- - Bjorn Jonsson   EnVision selected! Exciting times ahead for e...   Jun 10 2021, 10:41 AM
- - JRehling   Unbelievable! Venus sweeps three mission selec...   Jun 10 2021, 11:22 AM
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