Sailing the Cloud Tops Over Hell

It's no secret that Elon Musk's ultimate goal for SpaceX is to colonize Mars and make humanity interplanetary; it's so ingrained in the company culture, literally the wall opposite the Hawthorne office mezzanine cafe is a massive mural of this terraformed Mars illustration. Of course Mars is the logical next step for humanity, the Red Planet has long been the apex of human aspiration and a subject of our science fiction for decades. Right???

 Terraformed Mars makes for excellent interior decor as I eat my free unlimited froyo every afternoon at the SpaceX office!

But what if I told you we might be mistakenly ignoring our other planetary neighbor, Venus? Most people would say that's absolute lunacy: while our sister planet is similar to Earth in size, Venus's brutal atmosphere of carbon dioxide and sulfuric acid generates surface temperatures of 870$^{\circ}$F and pressure of almost 100 Earth atmospheres at sea level, more than enough to crush anyone foolish enough to venture down there. The only probes ever to reach the surface, sent by the Soviet Union in the '70s and '80s and built to be as indestructible as possible, only lasted a few hours before being obliterated by the harsh environment. So if the Venusian surface is basically our solar system's closest incarnation of Biblical Hell, why would anyone want to go?

 Left: clearest image ever taken of the surface of Venus, by the Soviet Venera 13 in 1982 | Right: Artist's depiction of Venera 13 on Venus

That's precisely where it gets awesome. The idea isn't to live on the surface, but instead in enormous blimp-like habitats to form a suspended city in the clouds. Crazy? It's not as far-fetched as it may seem - in fact, the upper atmosphere of Venus is the most Earth-like place in the solar system! At an altitude of around 30 miles, the pressure is almost exactly 1 Earth atmosphere, while the temperature ranges between about 80 - 180$^{\circ}$F. Definitely steamy, but within our technological ability to adjust for with some solid A/C, and since the human body can survive less than 1 atmosphere, we could probably go up a little higher to bring the temperature down some. Amazingly, in this environment a human could venture outside wearing nothing more than an oxygen gas mask and a light suit to protect against sulfuric acid corrosion, unlike the full-on spacesuit an astronaut would need to survive the intense cold and borderline nonexistent atmosphere of Mars!

 Reminds me of Bespin from Star Wars, but instead of a galaxy far far away, it's our planetary neighbor!

But wait, sulfuric acid poses a major threat to human habitation and health doesn't it? Actually, the solution to dealing with extraterrestrial acid rain is probably sitting in your kitchen right now - Teflon! The synthetic polymer is completely resistant against sulfuric acid and was used by the Soviets on their 1985 Vega mission, which placed two balloons precisely in the upper Venusian atmosphere. A light coating on the exterior of any structure would probably be more than enough!

 Giving new meaning to the idiom, "I'm on Cloud Nine!"

Fine then, let's say I agree Venus's atmosphere isn't a horrendous place for humanity to set up shop. But wouldn't it take an absolutely inordinate amount of propulsive power to hoist a human colony into the sky? No army of helicopters or hot air balloons on Earth could ever suspend a city in the clouds! But ah, here's where Venus's nasty atmosphere actually does us a solid - the habitat obviously needs to be filled with nitrogen and oxygen to recreate the air we breathe on Earth. Turns out both gases are much lighter than Venus's carbon dioxide atmosphere, meaning a balloon filled with plain ol' air will naturally float on Venus, the same way helium balloons float on Earth! And because the pressure inside and outside the habitat is more or less equal, any tear in the structure would just be a slow leak that can be easily repaired, nothing like the explosive pop you might imagine from a punctured balloon

 Totally random, but a cloud city on Venus makes me think of Skyloft from The Legend of Zelda: Skyward Sword! Any Nintendo fans reading? :)

This artificial atmosphere can even be produced on site, sidestepping the impossible task of transporting massive quantities of air from Earth. Nitrogen is already present in Venus's atmosphere, and using electrolysis, the CO2 on Venus can be split into oxygen and carbon, while the sulfuric acid can be split into water, oxygen, and sulfur. Finally, Venus provides two additional advantages relative to Mars: better radiation protection due to its thicker atmosphere, and 90% Earth gravity instead of Mars's measly 37%, which will be crucial to preventing bone loss and other dangerous deep-space ailments

 As promising as it may sound, sadly we're still a long way off from colonizing Venus | Credit: Ralph Ewig

Sounds like paradise right? Let's go! Unfortunately, colonizing Venus still poses monumental challenges. Any manned mission to Venus would still require transporting massive amounts of hardware millions of miles away, a hefty ask given no one has left Earth orbit since the last Apollo mission in 1972. Furthermore, although Venus is closer than Mars, a one way trip still takes 5 months, while the return trip must also wait many more months until the planets realign. And finally, Mars has taken up the lion's share of scientific research efforts, meaning our understanding of Venus's environment is still woefully lacking. Still, the next time you hear a space fan say "Mars or bust," let them know that's not necessarily the case. We just might have two Plan(et) B's!