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Go to CuriosityStream.com/Space to learn more. [ intro ]. Venus is sometimes referred to as Earth's sister planet.

It's close by, and pretty similar in size. It's thought to have been fairly Earth-like early in its history. Once upon a time, it may even have had lots of nice, shallow seas -- a great place to form life.

But it's not so nice to visit any more. A runaway greenhouse effect caused Venus to undergo massive, rapid climate change, boiling off the seas and transforming it from what may have been a pleasant, beachy planet into a desolate nightmare complete with sulfuric acid rain. Earth's got a bit of a greenhouse effect problem too.

So it seems like studying Venus could help us understand both our past and our future. Too bad -- because Venus is so awful, sending missions there just isn't worth it. So, we know Venus is hellish, but how bad is it, really?

Well, the average surface temperature is 471°C. Mercury is closer to the Sun, but it tops out in the neighborhood of 430°C. Venus is hotter thanks to its atmosphere.

That atmosphere is made mostly of carbon dioxide, so it traps tons and tons of heat. And the clouds are made of sulfuric acid. And those clouds do indeed rain!

Meanwhile, the atmosphere is so thick that the surface pressure is a whole 90 times greater than Earth's. Which would feel like being almost a kilometer beneath the ocean, if that was something human beings could experience and survive to make the comparison. We could try to engineer something akin to a deep-sea submersible to keep astronauts alive under the pressure of Venus' atmosphere, but that would still fall somewhere between very risky and /certain death/.

Astronauts are brave, and they're also very smart. Smart enough that there's not a lot of motivation for a human mission to Venus. But what about robots?

They don't need to breathe! The USSR actually sent not one or two, but 16 robots to Venus. This was the Venera project, in which a whole bunch of probes were sent to Venus in the 70s and 80s.

They did send some good data back. But the absolute toughest of the landers, Venera 13, lasted a whole 127 minutes. That was longer than its predicted lifespan of half an hour, but still shorter than the shortest Harry Potter film.

Which is Deathly Hallows, part 2. We checked. At that time, it was really impressive that humans were able to build something that could survive the conditions on Venus for longer than 30 minutes.

It's still impressive today. And that's because machines have their limits too. If we think of a rover or lander as a set of instruments contained in a single package, we don't just need the packaging to survive, but those instruments too.

It's kind of like building a spacecraft for humans, actually: the outside needs to be strong enough to withstand the environment, and the inside needs to be hospitable to its inhabitants. Hypothetically, we could build a lander or rover out of something that is primarily carbon, which has a melting point of 3550 °C. But that's just the body, the casing.

Inside that casing, we need to create the pressure and temperature conditions necessary for computers and scientific instruments to function. And while we've made lots of advances in high temperature computing, like innovating new heat-resistant materials for circuitry, we're not ready to put a computer on Venus for a long mission just yet. Essentially, we'd have to radically rethink and re-engineer everything we know about space rovers in order to send one to Venus.

And the time, money, and energy it would take to do that is just … not worth the results, and not really in line with NASA's current goals. Right now, we're big into astrobiology. We really want to unravel the origins of life and probe its limits.

If Venus once had life on it, before its seas boiled and its air became poison, evidence of that life would be incredibly difficult to get to, if it exists at all. That evidence would have to have survived billions of years of... Venus, and if we can't get state-of-the-art technology to last longer than two-thirds of Avengers:.

Endgame, again we checked we don't have much chance of finding it in time. Space exploration is inherently risky, so exploration plans are very much about risk mitigation. And whatever interesting science might theoretically be on Venus, it's not worth investing huge amounts of energy on a mission so risky when there are other, much less risky targets for exploration.

Take Mars, for example. Mars is very hard to get to, but it won't immediately break your machines when you get there. And every time we go, we find new and exciting evidence for a once-habitable red planet, like dry lake beds and extinct hot springs.

And just past Mars is a field of more great targets: asteroids. There's a lot we want to look into there, from water to chemicals similar to ones used for life on Earth. And asteroids are comparatively easy to explore.

You can't have acid rain if you don't have an atmosphere. So, yes, Venus is metal as heck. But that's precisely why it's not a good target. t's too metal for us.

Or rather, we are not metal enough for it. Yet. By now, we're extended our search for life far beyond our solar system.

And if you enjoy learning about how we look for habitable worlds, you might enjoy Living Universe, a CuriosityStream original. Living Universe explores how we could identify and explore potentially habitable worlds in other star systems. And it's just one of the over 2,400 documentaries and non­fiction titles available on CuriosityStream.

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