What is the aphrodiocentric theory? It’s something I made up. It comes from aphrodio-, the scientific prefix meaning Venus, and centric, meaning center, as in center of the universe. We’ve had a geocentric theory and a heliocentric theory, but sadly, there was never an aphrodiocentric theory.

In 1610, Galileo began observing Venus through his telescope. At certain times, Venus appeared as a full circle, just like any other planet. But at other times, Venus appeared as a crescent shape or half-circle shape or some other not-quite-a-circle shape.

In other words, Venus as observed from Earth had phases, just like the Moon. After puzzling over these observations, Galileo soon concluded that Venus must orbit the Sun. It’s not much of a leap from there to realize that all the planets, including Earth, orbit the Sun.

If you remember nothing else about Venus, remember this: right from the start, Venus has been teaching us about our own planet. It taught us the folly of our geocentrism, it taught us the dangers of greenhouse gases, and no doubt it will continue to teach us in the future.

This is the final post in my series on Venus. Clearly there is a lot more to say about such a mysterious and chemically active planet, but it is time for us to move on. The 2015 Mission to the Solar System will continue on Friday as we begin our exploration of Earth.

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Every Friday, we take a look at a new and interesting scientific term to help us all expand our scientific vocabularies together. Today’s word is:

VENUS SYNDROME

On Thursday, we talked about what it would take to terraform Venus. Turning Venus into another Earth is, in short, difficult. So instead, how about we turn Earth into another Venus?

In the worst-case scenario for climate change, accumulating greenhouse gases in Earth’s atmosphere trigger a runaway greenhouse effect analogous to what happened long ago on Venus. Hence the name “Venus syndrome.”

Here’s how Venus became the charming hellhole we know today:

• Venus had oceans: Early Venus probably had oceans of liquid water. As the early Sun grew brighter, these oceans warmed up, releasing water vapor. Water vapor, believe it or not, is a greenhouse gas. It’s transparent, so light energy passes straight through; but it traps heat, so once light energy becomes heat energy, it can’t escape.
• The oceans boiled: The initial temperature change would have been relatively minor, but it created a positive feedback loop. More water vapor trapped more heat, which evaporated more water, which trapped more heat, until the oceans boiled away completely. Then things got worse.
• The rocks sublimated: The temperature rose to the point that certain carbon-containing rocks sublimated (turned from solids directly into gases). Carbon dioxide took over for water vapor as Venus’s principle greenhouse gas. More CO₂ caused more rocks to sublimate, generating more CO₂, and… well, you get the idea.
• The sulfur cycle began: The now ludicrous temperatures also released sulfur compounds into the planet’s atmosphere, providing the key ingredient for Venus’s infamous sulfuric acid clouds.

So could this happen on Earth? Could manmade greenhouse gases initiate a runaway greenhouse effect, ultimately boiling our oceans and sublimating the carbon and sulfur in Earth’s crust?

According to the U.N.’s International Panel on Climate Change, human activities have “virtually no chance” of causing Venus syndrome. They’re predicting less dramatic consequences: rising sea levels, mass extinctions, etc. So that’s reassuring, I guess.

The problem is we don’t know the point at which slight changes to Venus’s environment began spiraling out of control. This makes Venus the subject of rather urgent research by both climatologists and planetary scientists.

Venus syndrome is a worst-case scenario, meaning it’s the greatest extreme on a spectrum of possibilities. But that doesn’t mean we can ignore it. The story of humanity’s exodus from a Venus-like Earth needs to be told, perhaps as science fiction, before it has the chance to become science fact.

Links

2009 Assessment Report from the International Panel on Climate Change.

Venus and Mars Hold Priceless Climate-Change Warnings for Earth from The Daily Galaxy.

Could Greenhouse Gases Turn Earth into Venus? (Yes, But Not Anytime Soon) from Mother Jones.

Venus wants to kill you.

With its sulfuric acid clouds, dangerously high atmospheric pressure, absurdly high surface temperature, et cetera, et cetera, Venus has more options for killing humans than any other planet in the Solar System. But maybe we can fix that. Maybe we can make Venus more like Earth.

To terraform Venus (or any other planet) we must do two things:

• Add stuff that we need to survive, like water and oxygen.
• Remove or mitigate conditions that would harm us.

Most discussions on terraforming seem to overlook that second part, perhaps because the biggest threats to life-as-we-know-it are not always immediately obvious.

Turning Venus into Earth

Converting Venus’s noxious atmosphere of CO₂ and sulfuric acid into a friendly oxygen/nitrogen mix will require some creativity. Since I’ve never personally terraformed a planet (yet), I can only guess about the tools required; but my educated guess is that some sort of bioengineered algae would work best.

We’d need something that converts carbon dioxide into oxygen. Algae already do this. We’d need something that can endure prolonged exposure to sulfuric acid and solar radiation. Some species of bacteria can do that. We’d also need something that can survive, at least at first, in a high temperature environment where water is scarce. Again, life on Earth has already shown that this is possible. We just have to design a new species that puts all of these qualities together.

Once our bioengineered algae start gobbling up Venus’s CO₂, removing Venus’s primary greenhouse gas, a process of global cooling should begin. Cooler temperatures would disrupt the sulfur cycle, so the sulfuric acid clouds would start disappearing on their own, and traces of water vapor in the upper atmosphere would be able to condense into liquid water.

Admittedly, this liquid water would only result in a few puddles, so we’d still have to transport in more water. Also, I’m not sure how to deal with the atmospheric pressure. But still, we’re off to an amazing start. Unfortunately, Venus has other plans.

Turning Venus Back into Venus

I sometimes joke that I want to live on Venus because I’d have so many more hours in my day to get stuff done. From sunrise to sunset, a day on Venus is over 2,800 hours long.

Venus has an abnormally slow rotation. In fact, compared to the rest of the Solar System, Venus is rotating backwards (the only planet weirder than Venus in this regard is Uranus, which rotates sideways).

2,800 hours of daylight can have some peculiar effects on a planet, especially an Earth-like planet. The oceans that our algae worked so hard to create would soon boil. Water vapor would act as a greenhouse gas. The planet’s carbon cycle would come to a grinding halt, allowing CO₂ to accumulate in the atmosphere once again, and the rising temperatures would kick start a brand new sulfur cycle.

Without constant efforts by us to maintain cool temperatures on Venus, the planet would rapidly turn back into its old self. In the end, Venus kills you.

I normally end these posts with links to some of my sources, but today, I want to end with a book recommendation: Venus Revealed by David Grinspoon. Without getting into too much technical detail, Grinspoon covers many key topics related to Venus, including a brief but illuminating section on terraforming. The book is a wealth of knowledge not only on Venus but concerning planetary science in general (although the bits about exoplanets are now out of date).

UPDATE: The length of a day on Venus has been corrected in this post.  According to this article from Universe Today, the time from sunrise to sunset equals 116.75 Earth days (which comes out to 2,802 hours).  I apologize for my previous mistakes, in which I stated a figure of 1,400 hours and, before that, a mere 60 hours.

No place in the Solar System (except Earth) is exactly welcoming to human life, but Venus’s anti-human hostility reaches a whole other level. Venus will try to kill you eight different ways before you even touch the ground. You’ll never have to worry about the lack of water or oxygen because you’ll already be dead.

And yet, there is serious discussion about colonizing Venus. The trick, it turns out, is to not bother trying to land. Instead, Venusian colonists would live in cities suspended in the upper atmosphere. The oxygen/nitrogen air that we breathe would have sufficient lifting force on Venus to keep our floating cities aloft, so we don’t even need helium or hydrogen balloons.

NASA has even produced this video showing what our first manned mission to Venus might look like. Get ready for space blimps!

The magic number is 55. At an altitude of 55 kilometers above the Venusian surface, the temperature is about the same as a warm summer’s day on Earth, with 90% Earth gravity and atmospheric pressure only a hair above Earth normal. The environment actually sounds pleasant—aside from the hurricane force winds and sulfuric acid clouds.

So could we colonize Venus? Sure. It’s definitely possible, and there may be good scientific reasons for doing it. Just so long as I’m not the one who has to go.

Links

Colonization of Venus, a proposal by Geoffrey A. Landis.

Acid Clouds and Lightning from ESA.

Super-Hurricane-Force Winds on Venus are Getting Stronger from ESA.

If you want to land on Mars, the United States can help. The U.S. has a pretty good track record for successfully landing space probes on Mars. But if you’d rather land on Venus, talk to the Russians. They’ll tell you how it’s done.

In fact, I’d say Russia’s special relationship with Venus began in 1761 when Russian astronomer Mikhail Lomonosov discovered that Venus has its own atmosphere.

In more recent history, Russia’s Venus-related accomplishments include:

• Venera 1: First spacecraft ever sent to Venus, or any other planet for that matter. Sadly, radio contact was lost before Venera 1 reached its destination.
• Kosmos 27: Failed in Earth orbit.
• Zond-1: Failed on route to Venus.
• Venera 3: First spacecraft to land on Venus. Well, crash land.

Okay, a lot of these missions didn’t go so well, but the Soviet space program can teach us all the value of persistence. And eventually, Russian persistence paid off.

• Venera 4: Successfully transmitted data from inside Venus’s atmosphere.
• Venera 7: First successful landing on Venus. Plenty of data transmitted back to Earth.
• Venera 11 and 12: Observed thunderstorms on Venus.
• Venera 13: First color photos from the surface of Venus.
• Vega 1 and 2: First weather balloons deployed to study Venus’s atmosphere.

As an interesting side note, Russia’s Venera 4 entered Venus’s atmosphere at almost the same time that the U.S.’s Mariner 5 was passing by. Despite the tensions of the Cold War, this was just too good an opportunity to pass up. The sharing of data from the two spacecraft was one of the earliest examples of international cooperation in space exploration.

Russia’s next mission to Venus won’t be for a while. The launch of the Venera-D space probe is currently scheduled for 2024.

Links

Russia’s Unmanned Missions to Venus from Russian Space Web.

When the Veneras Challenged Venus’s Hellish Atmosphere from Discovery News.

Soviet Balloon Probes May Have Seen Rain on Venus from Wired.com.