Climate collapse, Fermi paradox 

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I wonder if it's possible that an artificial satellite orbiting Venus would have remained invisible to this day. If it has a small enough radar cross-section and stable orbit...

I wish I would know more astronomy.

/cc @anne

This could make an awesome AND terrifying science-fiction story.

@uint8_t oh gosh we love this idea

one of the old ideas of scifi is that the sun is cooling down over time, and so Mars is the old dead world, Earth is the current one, and Venus is the infant to eventually take Earth's place.

and, welp, turns out that's backwards, the sun is *brightening* over time

but it would definitely be cool to see that trope reversed with nothing to do with the sun at all - now it's life that heats up planets.

Venus was then, Earth is now, Mars is next.

@diodelass What if we build giant spaceships which transfer the excess CO2 from Venus to Mars? We get 2 more habitable planets!

Make rocket fuel from CO2, water, and sunlight in floating cities on Venus. Fill solidified CO2 into reusable tanks, send them into low Venus orbit. Take the frozen CO2 out, send back the tanks, and use laser propulsion to send most of the CO2 ice to Mars.

@uint8_t @diodelass i think orbital rings make more sense than rockets.

Ditto for Saturn/Jupiter, but those are even more.. involved orbital rings. Skyhooks might also be possible..

orionsarm.com/ has a bunch of articles from Paul Birch about it orionsarm.com/fm_store/Paul%20 and of course the Lofstrom loop also has a whole article too.

I like OrionsArm, but tbh it lacks detail sometimes.

@diodelass @uint8_t I'm not sure there's any hope of Mars springing to life (alas) without intelligent intervention - there really isn't enough hydrogen to make oceans. This is a general problem throughout the inner solar system, where small bodies and high temperatures let water escape to space.

With intelligent intervention, well, we might learn to live in current Martian conditions, or we might drop comets on it for a (temporary but long) bunch of extra hydrogen.

@uint8_t I saw an article about a similar hypothesis, but on Earth, several million years ago during one of the mass extinction, as the period was hotter than today, and was following a rapid increase of CO2 in the atmosphere.

@Feufochmar But how much carbon is still in hydrocarbon and coal form on our planet? What if we burn everything? (if the atmosphere gets depleted, we can liberate oxygen from minerals, it's just a matter of energy)

@uint8_t pretty sure I’ve already read one like this but about Mars.

Also modern time JG Ballard has some corker post apocalyptic fiction like:

The Drowned World is a 1962 science fiction novel by British writer J. G. Ballard. The novel depicts a post-apocalyptic future in which global warming has caused the majority of the earth to become uninhabitable.

@uint8_t They have bounced some pretty serious radar off of Venus - like, transmitted with the 300m Arecibo dish. But it's a long way away, and artificial satellites can be small. How long they could last, well, many of our satellites will come down soon but that's because we put them up as low as wee can get away with. The ones that are high up are going to be there a very long time.

@uint8_t Venus is actually a pretty comfortable place, a reasonable temperature, reasonably clear sky, just a bit acidic, at the one-atmosphere altitude. The ground is just a long way below that. But breathable air is a lifting gas on Venus, so there's this idea that you could build floating cities at the 1 atmosphere depth on Venus.

@uint8_t It certainly is possible for runaway global warming to occur, and it is thought to have happened to Venus - the oceans would have boiled, and the water vapour would have added to the greenhouse effect until it escaped to interplanetary space. At that point the result is really irreversible. It seems like maybe we can't make it happen here:
royalsocietypublishing.org/doi

@uint8_t TIL: Venus has 100 times more deuterium mixed into its hydrogen than Earth. This is strong evidence for an ocean that boiled away, and it was measured by one of our probes before they died.

@kragen @anne Deuterium is an isotope of hydrogen. Heavy water (D2O) has a slightly higher boiling point, lower vapor pressure, and lower mean speed, so if you got an ocean with a H2O-D2O mixture, the concentration of D2O increases as you boil the water away. Our oceans have a higher D2O concentration than our rivers.

@kragen @anne @uint8_t because it is heavier, it's less distant from oxygen in a water molecule, and has a stronger bond.

Also any molecule it is on, it tends to make it heavier than the identical one with regular hydrogen, so it typically ends up lower in the atmosphere.

@jasper @anne @uint8_t Do we mean 100 times more deuterium in Venus's atmospheric hydrogen than in Earth's hydrogen, most of which is, I think, in its oceans? Is there a big difference between the deuterium fraction in Earth's atmosphere and in its oceans?

@kragen @jasper @uint8_t So the article describing the measurement is: ncbi.nlm.nih.gov/m/pubmed/1778
Terrestrial spectroscopy cast some doubt on the result but Venus Express seems to confirm it:
sci.esa.int/venus-express/5406

The deuterium enrichment is thought to have occurred because hydrogen is lost more easily to space; fortunately the Earth doesn't lose a lot of hydrogen because it's mostly in water and the "cold trap" keeps that too low for photodissociation.

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