This appears to be what the report is referring to. Saw another article where they found phosphine in the atmosphere and are using that as a potential biosignature.
Imagine it’s just a matter of time and exploration before we find a Martian equivalent of possible monocellular life.
7.
Baud
A gas on Earth has also been detected in the atmosphere of Venus.
While it may not signify the presence of life, the “entirely surprising” discovery of phosphine could hint at unknown processes occurring on Earth’s “twin.”
On Earth, phosphine is a flammable, foul, toxic gas produced by bacteria that doesn’t require oxygen — like those in swamps, wetlands, sludge or even animal guts. Its odor has been likened to decaying fish or garlic. It can also occur when organic matter breaks down.
At least they’re not bringing it back here, this year. Which would have been a total 2020 thing to do.
11.
catclub
@Baud:
I still remember James Lovelock’s argument in Gaia
that IF there is life, then it should be obvious in an atmosphere that is WAY out of thermodynamic equilibrium. And conversely, if the atmosphere is in thermodynamic equilibrium == no life.
The people looking for life on Mars did not really want to listen to that argument.
Researchers detected a distinctive signature of the gas—phosphine—in the venusian atmosphere in June 2017 using a ground-based telescope. The observation was later confirmed in March 2019 with another such telescope. The instruments showed a faint reduction in the light at a wavelength only known to be absorbed by the gas, Jane Greaves, an astronomer at Cardiff University, and her colleagues report today in Nature Astronomy. The absorption levels suggest phosphine is present at concentrations of up to 20 parts per billion at altitudes above 53 kilometers, Greaves says.
Although 20 parts per billion sounds like a trifling amount, there shouldn’t even be that much. Phosphine is relatively unstable and in the harsh, superacidic conditions found high in the venusian atmosphere, the average lifetime of a molecule is a mere 16 minutes or so. To counteract ongoing destruction of the gas, there must be a steady—and prodigious—source of it.
[…]
On Earth, a variety of microbes that thrive in low-oxygen environments produce phosphine. And those organisms would only need to pump out 10% of the phosphine they do here to explain the levels seen on Venus, the team notes. At altitudes between 53 and 61 kilometers above the venusian surface, temperatures are a balmy 30°C. That’s certainly more microbe-friendly than the hellish, lead-melting temperatures of about 900°C down at ground level. However, life as we know it would have a tough time in the hyperacidic, dehydrating conditions of Venus’s atmosphere regardless of the temperature.
The presence of phosphine isn’t a sure sign of life, says study co-author Sukrit Ranjan, a planetary scientist at the Massachusetts Institute of Technology. The chemistry of phosphine isn’t well known, and it’s possible that the gas could persist more readily at the lower, temperate layers of the venusian atmosphere, which could be shielded from sunlight that drives phosphine-destroying photochemical reactions.
[…]
Neato.
Cheers,
Scott.
13.
NobodySpecial
I know that they were talking about Earth normal temps about 50k above the surface of Venus, with a mostly carbon dioxide atmosphere, leading people to discuss the idea of aerostats on Venus. Cloud life would not surprise me.
@catclub: From my reading, “thermodynamic equilibrium” sounds a whole lot like a description of absolute zero. Are you suggesting Mars’ atmosphere is such?
A gas on Earth has also been detected in the atmosphere of Venus.
OK, who farted?
17.
scav
Selfishly — or perhaps idiosyncratically — I’m really enjoying learning this while staring out at my personal patch of errant wildfire smoke. Plus, sustained logic!
18.
germy
Venus community right now: "We TOLD you Venus is interesting!!!"
[If we've spent all this time looking for life on Mars and it turns out it's been on Venus this whole time…lolsob!]
One scientist said he was skeptical that phosphine gas on Venus is being produced by something living, but added, "I don’t have a better explanation for what it is." https://t.co/JDRY7TwvXU
@Just Chuck:
actually, no. Another Scott’s comment/quote at 12 is exactly what I was referring to:
The absorption levels suggest phosphine is present at concentrations of up to 20 parts per billion at altitudes above 53 kilometers, Greaves says.
Although 20 parts per billion sounds like a trifling amount, there shouldn’t even be that much. Phosphine is relatively unstable and in the harsh, superacidic conditions found high in the venusian atmosphere, the average lifetime of a molecule is a mere 16 minutes or so.
The protomolecule better hurry up and get the ring gate open, we don’t have a lot of time here.
25.
Chyron HR
Trump: “I did this.”
26.
Martin
So, a few things on this:
It’ll be interesting to see how this is verified by other planetary scientists.
After 2 decades of focus on Mars, it should be interesting to see how we look at further exploration of Venus. From what I understand a probe that floats in the atmosphere for an extended period of time is not out of the question.
I wonder if planetary scientists have learned to embrace the much faster cadence that SpaceX is demonstrating, or whether a new Venus probe is still going to take two decades to launch.
27.
oldster
“Venus, planet of love, was destroyed by global warming/
Did its people want too much, too? Did its people want too much?”
Dave is trying to class the joint up with his “scientific” theories…
There’s your problem.
29.
Delk
A goddess on a mountaintop?
30.
Subsole
So if they DO find life there, what does that imply for settlement, or even just further exploration?
I mean, North America was devastated by European colonists – and not just their microbes. Hell, the pigs were almost as bad as the pox in some places. More recently, kuzu damn near ate the south when we imported it.
And that is just competing earth biologies.
It seems like this would spur more exploration, but also curtail the scope of it for fear of cross contamination…
In the ’60s through the ’80s when NASA was directing most of its planetary exploration towards Mars, the Soviets were concentrating on Venus. Their various Venera and Vega missions sent a variety of landers, orbiters and two atmospheric balloons. The balloons each lasted a couple of days while drifting along at about the same altitude as the phosphine has been detected. I wonder if there is anything in that old balloon data that needs revisiting.
33.
Kelly
Oregon Fires Refugee Update:
Yesterday Mrs Kelly found a hotel on the coast accepts cats, Clarion Surfrider across 101 from Fogarty Creek State Park. We’re heading over this morning to get some fresh air. Due to caution about the plague we haven’t had our usual couple of coast trips this year and homeowners insurance should reimburse us.
34.
Immanentize
So do we expect to find the coronavirus vaccine in the clouds of venus?
35.
laura
@?BillinGlendaleCA: I’m struggling to figure out where the He Who Smelt It Dealt It theorem fits into this….
36.
Woodrow/asim
@Martin: I wonder if planetary scientists have learned to embrace the much faster cadence that SpaceX is demonstrating, or whether a new Venus probe is still going to take two decades to launch.
Hunh? Launch cadance isn’t just about how many rockets we can throw at a situation.
Launch windows that can take advantage of spacial, esp. gravatational, alignments matter. And, of course, we aren’t building probes from Off The Shelf parts quite yet.
@Subsole: I imagine any colony of ours on Venus will have to be hermetically sealed. It shouldn’t be hard to sterilise its outer surfaces and make sure none of our microbes escape. I’m imagining it floating in the upper atmosphere where the temperature is tolerable for us. If it crashes to the ground the temperature there will kill all Earth organisms pretty quickly.
No one is going to explore the surface of Venus in person, and the landers sent by the Soviets failed soon after landing.
Also, I’m not aware of anyone proposing a sample/return mission to Venus, but if one such was contemplated, finding microbial life in Venus’s clouds will rule that right out. It would be galactically stupid to risk bringing such an organism back to earth.
IIRC, the anaerobes on Very Young Earth had oxygen as their waste product, which eventually led to an oxygenated atmosphere. Throw in a few (quite a few) water-bearing comets, and Venus could become a more welcoming environment for more complex organisms in, oh…. a billion years or so.
50.
Martin
@Woodrow/asim: No, my point is that one of the problems that existing craft are discovering (Europa Clipper, for example) is that the launch platforms are evolving dramatically faster than the missions are being built.
Clipper is mandated by Congress to fly on an SLS, a launcher that currently doesn’t exist. There are concerns now that SLS will have too much vibration for Clipper. It could fly on a Falcon Heavy, a launcher that hadn’t even been conceived when Clipper was first funded.
Part of the problem here is that we design billion dollar probes to go on billion dollar rockets because rockets used to cost a billion dollars. But they don’t now – even big ones are much cheaper, but they also iterate much faster, and payload designers need to learn to also build much faster. They can also justify multiple smaller/cheaper missions due to the lower launch costs.
The launch industry has changed radically. The payload industry is also changing, but the scientific payload industry has not.
@Just Chuck: In this case the chemical equilibrium is more important; as long as the Sun shines none of the planets are going to be in thermodynamic equilibrium.
The idea is that certain chemicals, among them molecular oxygen, are highly reactive. If you find them in a planet’s atmosphere, something must be generating them faster than they can break down or combine with other chemicals. Life is a good candidate for the “something”.
53.
Uncle Cosmo
@joel hanes: It would be galactically stupid to risk bringing such an organism back to earth.
“Galactically stupid” better describes a scientifically ignorant comment like this.
If there is anything living in the Cytherean clouds, it exists under conditions nowhere close to any found anywhere on Earth and would have zero chance of surviving here for more than a few seconds.
We should be much more concerned with messing up their environment with our probes rather than terrified they’d take over ours. But we should still send probes – if for no other reason than to determine if there is life in those clouds & if so, what (if any) relationship it has to the terrestrial version.
Panspermia or independent evolution? My guess would be the former – a fair amount of material has been blasted off the surfaces of any given inner planet by meteorites over the last few billion years, & some likely found its way to another, perhaps to survive & prosper – but the latter would be a truly earth-shattering discovery.
That seems reasonable. I recall reading that at certain altitudes, breathable air acts like a lift gas on Venus. So maybe a massive dirigible, with a ceramic coating if some sort as acid-proofing?
Certainly would be easier than working at Marianas Trench pressures, blast furnace temperatures, and in a corrosive fog!
I think the Soviet probes lasted a little under 30 minutes before they failed…
56.
Ceci n est pas mon nym
@Just Chuck: It just means as much energy going out as coming in. A cup of room temperature water on your table is in thermodynamic equilibrium with the room.
True. I was honestly more worried about our experiments contaminating Venus.
Though from what I understand Venus would actually make a good transit hub if we ever start exploring out past the belt. Something about the orbital mechanics creating shorter trips. So maybe orbital stations or satellites if nothing else.
58.
MattF
@Ceci n est pas mon nym: Well, no. You can have a steady-state system with equal fluxes of energy going in and out that is far from equilibrium.
I’m with you on a probable common origin for Venerian atmospheric organisms and Earth life, and on the probability that impact eject can seed life within a planetary system.
60.
PenAndKey
Between the news of this short-lived biomarker gas and the previous reports of UV absorbing clouds composed of 1-15 micrometer sized particles (ie, bacterial sized) at the same 50km level I’m cautiously optimistic that this will turn out to be more than an unexplained geologic source. I’d absolutely love to see the biochemical pathways and potential nutrient sources that something absorbing UV energy, suspended in a sulfur acid cloud environment with phosphine waste byproducts, would need to employ.
Other than the acid levels of the clouds, the sea level-like pressure and just above room temperature environment is ideal for stable a hydrogen sulfide terminating anoxygenic photosythesis, which is a trait we see here on earth in species like green sulfur bacteria. I don’t know enough about Venus to know if it has any appreciably unexplained hydrogen sulfide levels, but it’s definitely something I’m sure someone’s looked at since this story broke. It’s puzzles like that, that make me happy I went to school for microbiology. Life is freaking weird.
I wouldn’t be at all surprised if someone figures out a non-organic mechanism to produce this molecule. We went through a similar excitement some time back with the Mars meteorites that supposedly had signatures of bacteria in them.
63.
Anonymous At Work
@Subsole: Arthur C Clarke already went there in 3001. Terraforming using ice-bearing asteroids to introduce oxygen, atmospheric gases and cool things off. Much easier, in theory, to develop a thick atmosphere over Venus than create strong magnetic fields over Mars.
64.
Ken
@PenAndKey: I’d absolutely love to see the biochemical pathways and potential nutrient sources that something absorbing UV energy, suspended in a sulfur acid cloud environment with phosphine waste byproducts, would need to employ.
Obviously it’s absorbing the sulfur-32 and splitting off a proton to create phosporus-31. The proton is probably used to drive a proton pump similar to the ones that generate ATP in Earth life. Of course the nuclear reaction is endothermic so the energy must be coming from the UV light.
it could go either way. I think i remember hearing about phosphine being detected in the atmospheres of Jupiter and Saturn.
66.
PenAndKey
@Ken: ah, my eternal failing, physics. There’s a reason I went into the biological sciences. I leave gold egg laying geese and alchemic bacteria to Asimov.
67.
Robert Sneddon
@Anonymous At Work: Raving libertarian SF writer L. Neil Smith had a simpler solution to getting some use out of Venus in his novel “The Venus Belt”. He astroformed Venus by lithobraking the asteroid Ceres into it to turn the planet into an asteroid belt.
Skip-aerobraking odd rocks into the upper atmosphere of Venus has been proposed as a method of thinning its atmosphere to the point of being tolerable for modified humans — since it’s mostly CO2 what remains after the bombardment stops can be reformed into a mainly oxygen atmosphere using bacteria and time (nitrogen is more of a problem). Another more ecological solution is to use robot tankers to scoop up Venusian CO2 from in-and-out dips through the upper atmosphere and dump it on Mars where it would be more welcome.
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Doug R
WHAAAAAAT?
Ceci n est pas mon nym
Well heck then. If life can survive on Venus where temperatures are hot enough to melt lead, why worry about global warming? We’ll adapt, amirite?
northlander
I, for one, welcome our new Venusian anaerobic microbial overlords.
Baud
A life sustaining planet with no Trump. Where do I sign up?
p.a.
Mars pouts.
Gravenstone
This appears to be what the report is referring to. Saw another article where they found phosphine in the atmosphere and are using that as a potential biosignature.
Imagine it’s just a matter of time and exploration before we find a Martian equivalent of possible monocellular life.
Baud
https://www.cnn.com/2020/09/14/world/venus-phosphine-gas-clouds-scn/index.html
Ramiah Ariya
October surprise!
germy
“As you are, we were. As we are, you will be.”
evinfuilt
At least they’re not bringing it back here, this year. Which would have been a total 2020 thing to do.
catclub
@Baud:
I still remember James Lovelock’s argument in Gaia
that IF there is life, then it should be obvious in an atmosphere that is WAY out of thermodynamic equilibrium. And conversely, if the atmosphere is in thermodynamic equilibrium == no life.
The people looking for life on Mars did not really want to listen to that argument.
Another Scott
https://www.sciencemag.org/news/2020/09/curious-and-unexplained-gas-spotted-venus-s-atmosphere-also-spewed-microbes-earth
Neato.
Cheers,
Scott.
NobodySpecial
I know that they were talking about Earth normal temps about 50k above the surface of Venus, with a mostly carbon dioxide atmosphere, leading people to discuss the idea of aerostats on Venus. Cloud life would not surprise me.
RobertDSC-Work
@Baud:
Same.
Just Chuck
@catclub: From my reading, “thermodynamic equilibrium” sounds a whole lot like a description of absolute zero. Are you suggesting Mars’ atmosphere is such?
?BillinGlendaleCA
@Baud:
OK, who farted?
scav
Selfishly — or perhaps idiosyncratically — I’m really enjoying learning this while staring out at my personal patch of errant wildfire smoke. Plus, sustained logic!
germy
MisterForkbeard
@Ceci n est pas mon nym:
Obviously the problem is that all life on Venus will have lead poisoning.
West of the Rockies
@Ceci n est pas mon nym:
I, for two, welcome our new microbial overlords!
germy
catclub
@Just Chuck:
actually, no. Another Scott’s comment/quote at 12 is exactly what I was referring to:
West of the Rockies
@?BillinGlendaleCA:
You had to go there…
Dave is trying to class the joint up with his “scientific” theories, and you bring up transdimensional space toots.
BruceFromOhio
The protomolecule better hurry up and get the ring gate open, we don’t have a lot of time here.
Chyron HR
Trump: “I did this.”
Martin
So, a few things on this:
oldster
“Venus, planet of love, was destroyed by global warming/
Did its people want too much, too? Did its people want too much?”
Mitski, “Nobody”
https://www.youtube.com/watch?v=qooWnw5rEcI
?BillinGlendaleCA
@West of the Rockies:
There’s your problem.
Delk
A goddess on a mountaintop?
Subsole
So if they DO find life there, what does that imply for settlement, or even just further exploration?
I mean, North America was devastated by European colonists – and not just their microbes. Hell, the pigs were almost as bad as the pox in some places. More recently, kuzu damn near ate the south when we imported it.
And that is just competing earth biologies.
It seems like this would spur more exploration, but also curtail the scope of it for fear of cross contamination…
Subsole
@MisterForkbeard:
So you’re saying we Earthlings will fit right in?
cope
In the ’60s through the ’80s when NASA was directing most of its planetary exploration towards Mars, the Soviets were concentrating on Venus. Their various Venera and Vega missions sent a variety of landers, orbiters and two atmospheric balloons. The balloons each lasted a couple of days while drifting along at about the same altitude as the phosphine has been detected. I wonder if there is anything in that old balloon data that needs revisiting.
Kelly
Oregon Fires Refugee Update:
Yesterday Mrs Kelly found a hotel on the coast accepts cats, Clarion Surfrider across 101 from Fogarty Creek State Park. We’re heading over this morning to get some fresh air. Due to caution about the plague we haven’t had our usual couple of coast trips this year and homeowners insurance should reimburse us.
Immanentize
So do we expect to find the coronavirus vaccine in the clouds of venus?
laura
@?BillinGlendaleCA: I’m struggling to figure out where the He Who Smelt It Dealt It theorem fits into this….
Woodrow/asim
Hunh? Launch cadance isn’t just about how many rockets we can throw at a situation.
Launch windows that can take advantage of spacial, esp. gravatational, alignments matter. And, of course, we aren’t building probes from Off The Shelf parts quite yet.
That said, there are proposed missions a-plenty to choose from.
David Evans
@Subsole: I imagine any colony of ours on Venus will have to be hermetically sealed. It shouldn’t be hard to sterilise its outer surfaces and make sure none of our microbes escape. I’m imagining it floating in the upper atmosphere where the temperature is tolerable for us. If it crashes to the ground the temperature there will kill all Earth organisms pretty quickly.
germy
https://trailers.apple.com/trailers/independent/the-blech-effect/
Baud
@germy:
An OzarkHillbilly documentary?
It’s about time.
?BillinGlendaleCA
@germy:
The Ozark Hillbilly Story.
?BillinGlendaleCA
@Baud: I’m getting slow in my old age.
RandomMonster
@?BillinGlendaleCA: He who smelt it, dealt it.
oatler.
Venusians are nasty customers. They want to steal our jobs and our women.
Doug R
@Subsole:
Pig almost caused a war between the USA and Britain/Canada:
https://en.wikipedia.org/wiki/Pig_War_(1859)
joel hanes
Phil Plait is good on this
joel hanes
take
joel hanes
@Subsole:
No one is going to explore the surface of Venus in person, and the landers sent by the Soviets failed soon after landing.
Also, I’m not aware of anyone proposing a sample/return mission to Venus, but if one such was contemplated, finding microbial life in Venus’s clouds will rule that right out. It would be galactically stupid to risk bringing such an organism back to earth.
joel hanes
@oatler.:
Calves like interplanetary cantaloupes
CaseyL
IIRC, the anaerobes on Very Young Earth had oxygen as their waste product, which eventually led to an oxygenated atmosphere. Throw in a few (quite a few) water-bearing comets, and Venus could become a more welcoming environment for more complex organisms in, oh…. a billion years or so.
Martin
@Woodrow/asim: No, my point is that one of the problems that existing craft are discovering (Europa Clipper, for example) is that the launch platforms are evolving dramatically faster than the missions are being built.
Clipper is mandated by Congress to fly on an SLS, a launcher that currently doesn’t exist. There are concerns now that SLS will have too much vibration for Clipper. It could fly on a Falcon Heavy, a launcher that hadn’t even been conceived when Clipper was first funded.
Part of the problem here is that we design billion dollar probes to go on billion dollar rockets because rockets used to cost a billion dollars. But they don’t now – even big ones are much cheaper, but they also iterate much faster, and payload designers need to learn to also build much faster. They can also justify multiple smaller/cheaper missions due to the lower launch costs.
The launch industry has changed radically. The payload industry is also changing, but the scientific payload industry has not.
MattF
Alexandra Petri wins.
Ken
@Just Chuck: In this case the chemical equilibrium is more important; as long as the Sun shines none of the planets are going to be in thermodynamic equilibrium.
The idea is that certain chemicals, among them molecular oxygen, are highly reactive. If you find them in a planet’s atmosphere, something must be generating them faster than they can break down or combine with other chemicals. Life is a good candidate for the “something”.
Uncle Cosmo
“Galactically stupid” better describes a scientifically ignorant comment like this.
If there is anything living in the Cytherean clouds, it exists under conditions nowhere close to any found anywhere on Earth and would have zero chance of surviving here for more than a few seconds.
We should be much more concerned with messing up their environment with our probes rather than terrified they’d take over ours. But we should still send probes – if for no other reason than to determine if there is life in those clouds & if so, what (if any) relationship it has to the terrestrial version.
Panspermia or independent evolution? My guess would be the former – a fair amount of material has been blasted off the surfaces of any given inner planet by meteorites over the last few billion years, & some likely found its way to another, perhaps to survive & prosper – but the latter would be a truly earth-shattering discovery.
schrodingers_cat
OT is any BJer in the Sri Preston Kulkarni’s district in TX?
Thanks.
Subsole
@David Evans:
That seems reasonable. I recall reading that at certain altitudes, breathable air acts like a lift gas on Venus. So maybe a massive dirigible, with a ceramic coating if some sort as acid-proofing?
Certainly would be easier than working at Marianas Trench pressures, blast furnace temperatures, and in a corrosive fog!
I think the Soviet probes lasted a little under 30 minutes before they failed…
Ceci n est pas mon nym
@Just Chuck: It just means as much energy going out as coming in. A cup of room temperature water on your table is in thermodynamic equilibrium with the room.
Subsole
@joel hanes:
True. I was honestly more worried about our experiments contaminating Venus.
Though from what I understand Venus would actually make a good transit hub if we ever start exploring out past the belt. Something about the orbital mechanics creating shorter trips. So maybe orbital stations or satellites if nothing else.
MattF
@Ceci n est pas mon nym: Well, no. You can have a steady-state system with equal fluxes of energy going in and out that is far from equilibrium.
joel hanes
@Uncle Cosmo:
I’m with you on a probable common origin for Venerian atmospheric organisms and Earth life, and on the probability that impact eject can seed life within a planetary system.
PenAndKey
Between the news of this short-lived biomarker gas and the previous reports of UV absorbing clouds composed of 1-15 micrometer sized particles (ie, bacterial sized) at the same 50km level I’m cautiously optimistic that this will turn out to be more than an unexplained geologic source. I’d absolutely love to see the biochemical pathways and potential nutrient sources that something absorbing UV energy, suspended in a sulfur acid cloud environment with phosphine waste byproducts, would need to employ.
Other than the acid levels of the clouds, the sea level-like pressure and just above room temperature environment is ideal for stable a hydrogen sulfide terminating anoxygenic photosythesis, which is a trait we see here on earth in species like green sulfur bacteria. I don’t know enough about Venus to know if it has any appreciably unexplained hydrogen sulfide levels, but it’s definitely something I’m sure someone’s looked at since this story broke. It’s puzzles like that, that make me happy I went to school for microbiology. Life is freaking weird.
Noskilz
@Baud: “life…but not as we know it”
Lee Hartmann
I wouldn’t be at all surprised if someone figures out a non-organic mechanism to produce this molecule. We went through a similar excitement some time back with the Mars meteorites that supposedly had signatures of bacteria in them.
Anonymous At Work
@Subsole: Arthur C Clarke already went there in 3001. Terraforming using ice-bearing asteroids to introduce oxygen, atmospheric gases and cool things off. Much easier, in theory, to develop a thick atmosphere over Venus than create strong magnetic fields over Mars.
Ken
Obviously it’s absorbing the sulfur-32 and splitting off a proton to create phosporus-31. The proton is probably used to drive a proton pump similar to the ones that generate ATP in Earth life. Of course the nuclear reaction is endothermic so the energy must be coming from the UV light.
I believe there was a report of a similar bio-nuclear reaction in an Earth organism back in the 1950s.
HarlequinGnoll
it could go either way. I think i remember hearing about phosphine being detected in the atmospheres of Jupiter and Saturn.
PenAndKey
@Ken: ah, my eternal failing, physics. There’s a reason I went into the biological sciences. I leave gold egg laying geese and alchemic bacteria to Asimov.
Robert Sneddon
@Anonymous At Work: Raving libertarian SF writer L. Neil Smith had a simpler solution to getting some use out of Venus in his novel “The Venus Belt”. He astroformed Venus by lithobraking the asteroid Ceres into it to turn the planet into an asteroid belt.
Skip-aerobraking odd rocks into the upper atmosphere of Venus has been proposed as a method of thinning its atmosphere to the point of being tolerable for modified humans — since it’s mostly CO2 what remains after the bombardment stops can be reformed into a mainly oxygen atmosphere using bacteria and time (nitrogen is more of a problem). Another more ecological solution is to use robot tankers to scoop up Venusian CO2 from in-and-out dips through the upper atmosphere and dump it on Mars where it would be more welcome.