After a tantalizing discovery at Venus, what could an astrobiology mission look like?

[Admin]

Suddenly, a mission to investigate whether Venus might be hospitable to life after all doesn't seem quite so outlandish.

After a tantalizing discovery at Venus, what could an astrobiology mission look like? : Read more

 

[Chris Crawford]

Jeez, people sure are getting carried away by this discovery. There are plenty of ways that phosphine can be made abiologically. The hypothesis that this phosphine is generated by living systems is less plausible than the hypothesis that it is generated by chemical processes lower in the atmosphere and transported up to where we see it.

More important, we must always ask "What is the ESSENCE of the problem?" and the essence of life is negentropy. Life cannot exist without a big supply of negentropy. So what could be the source of negentropy on Venus? Sunlight is the primary source of negentropy, but sunlight doesn't penetrate very far into the Venusian atmosphere, so it is an unlikely source. It is possible that big thermal gradients could supply a small amount of negentropy; that's how the creatures around black smokers deep in our oceans survive. But surface temperatures on Venus are already very high, so there's not much delta-T possible. And of course, big delta-Ts in a gas lead only to convection, not life. It's also possible that some chemical negentropy could be available. We know that some extremophiles on earth survive on chemical negentropy. But this form of life is rare and is unlikely to have evolved directly.

 

[Jasper]

A very convenient ‘finding’ then?

 

[joover]

You cite NASA, MIT and others in the US, but not a word about Professor Jane Greaves of Cardiff University, the team leader who made the discovery!

 

[just_some_dude]

Jeez, people sure are getting carried away by this discovery. There are plenty of ways that phosphine can be made abiologically. The hypothesis that this phosphine is generated by living systems is less plausible than the hypothesis that it is generated by chemical processes lower in the atmosphere and transported up to where we see it.

IMHO, if people "getting carried away" leads to funding for more probes to investigate the hypotheses, then it's a good thing.

I'm not sure what you mean by negentropy in this context , but it has been suggested that UV from the sun could be an energy source for atmospheric life. I'm not in a position to argue either way, but I'm glad to hear people are getting excited.

 

[Chris Crawford]

Wouldn't it be better if precious funding for space projects was given to the investigations that held the greatest promise of interesting results? If this phosphine hypothesis be false, as seems likely, then we'd be wasting money following up on it. There are so many worthy investigations that can't get funding, we really need to be careful about how we spend our money.

UV from the sun is not a primary source of negentropy; most of the negentropy is in the visible spectrum. Negentropy is a concept from thermodynamics. It's a confusing concept for most people, but in fact, it is the essence of life. All living systems, here or elsewhere, must be negentropy harvesting machines.

 

[just_some_dude]

Sure, but what's more promising than Venus at the moment, not already being investigated, and within technological reach? Also, people "getting carried away" can lead to MORE funding for space projects.

Regarding negentropy, the only source I really found on that was this line from Wikipedia: "In his book, Schrödinger originally stated that life feeds on negative entropy, or negentropy as it is sometimes called, but in a later edition corrected himself in response to complaints and stated that the true source is free energy. "

 

[Chris Crawford]

Yes, Venus is a tantalizing target. It's also a very difficult target, because of the extremely high temperatures. The probes we have sent down to the surface all lasted a few minutes before failing. Sure, we can make metals that can handle those temperatures, but how do we build electronics capable of functioning at those temperatures? So far, the best we can do is get something that can operate for a few minutes longer before failing. Perhaps something with extremely low thermal conductivity (think of the tiles on the bottom of the Space Shuttle) enclosing the electronics could keep it from frying for a little while. But how do the sensors work? To sense the environment, they have to BE in the environment. Nasty, nasty problem. This is why we know so little about the surface of Venus.

More promising would be studies of its atmosphere, which is not so hellishly hot. Indeed, there have been a number of proposals for balloons that float high in the Venusian atmosphere. It's crucial, however, to understand the vertical structure of the atmosphere, and that requires a balloon that can move vertically, dipping down into lower, hotter regions. Moreover, any such system would be vulnerable to high wind velocities.

Yes, Schrodinger's 1944 lecture is considered to be one of the landmarks. You can download the PDF here. You can also search the web for phrases like "negentropy and life" or "entropy and life". I warn you, this is heavy stuff; you'll have to knuckle down and read carefully.

 

[mbee1]

Jeez, people sure are getting carried away by this discovery. There are plenty of ways that phosphine can be made abiologically. The hypothesis that this phosphine is generated by living systems is less plausible than the hypothesis that it is generated by chemical processes lower in the atmosphere and transported up to where we see it.

More important, we must always ask "What is the ESSENCE of the problem?" and the essence of life is negentropy. Life cannot exist without a big supply of negentropy. So what could be the source of negentropy on Venus? Sunlight is the primary source of negentropy, but sunlight doesn't penetrate very far into the Venusian atmosphere, so it is an unlikely source. It is possible that big thermal gradients could supply a small amount of negentropy; that's how the creatures around black smokers deep in our oceans survive. But surface temperatures on Venus are already very high, so there's not much delta-T possible. And of course, big delta-Ts in a gas lead only to convection, not life. It's also possible that some chemical negentropy could be available. We know that some extremophiles on earth survive on chemical negentropy. But this form of life is rare and is unlikely to have evolved directly.

Sunlight does not penetrate into very far into the atmosphere? That is simply not true. The russian probes took pictures of the surface when they landed so sunlight is there. The problem is not sunlight it is the lack of water and the heat which might be solved if the life was floating around in the clouds which of course does not tell us how it got there.

 

[Chris Crawford]

Um, have you considered the fact that we cannot see the surface of Venus from earth? If little light from the surface gets OUT, then how much do you think gets IN? Yes, sunlight gets through -- but it's nowhere near as much sunlight as reaches the surface of the earth, even though we're further away. Look at some of the photos from the surface. Yes, there's light, but there's almost nothing in the way of shadows. The light is greatly diffused, which in turn reduces its negentropy.

Moreover, the delta-T on Venus is smaller than on earth. With surface temperatures of about 750ºK (as opposed to 300ºK on the surface of the earth), there's less negentropy to harvest. Lastly,

The absence of water is irrelevant; theoretically, you can have plenty of life without any water at all. Earth's life is based on chemical reactions taking place in water, but there are many other ways to harvest negentropy.

It would be extremely difficult for living systems to form in a gas. Not impossible, but you'd need a LOT of negentropy to drive that process.

 

[just_some_dude]

It would be extremely difficult for living systems to form in a gas.

Maybe they didn't originally form where they are today? https://www.space.com/venus-life-earth-grazing-asteroid

 

[Chris Crawford]

Yes, most extremophiles appear to have evolved from conventionally developed life. However, this merely begs the question of where the life originated. It's possible that Venus may have had radically different surface conditions some billions of years ago, permitting the development of living creatures on the surface, which then took to the atmosphere as the planet evolved. This scenario requires a lot of pieces to fit into the puzzle at the right moments. I don't consider it likely, but we can't rule out the possibility. We need to learn more about the evolution of the Venusian atmosphere before we can seriously consider that hypothesis, and the best way to do that is a combination of an atmospheric survey probe followed, after we have digested the information from that probe, by a short-lived surface probe that quickly searches for some key indicators.