Planet Pailly

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:

H.A.V.O.C.

Given a choice between colonizing Venus or Mars, I might actually choose Venus. Yes, surface conditions on Venus are hellish instant death. Like, literally hellish. It’s even got the sulfur. But a Venusian colony would not be built on the planet’s surface.

Atmospheric conditions at an altitude of about 50 km are actually quite pleasant. The temperature and pressure are about the same as on Earth. So is the gravity. And you wouldn’t need hydrogen or helium to keep your floating cities aloft; on Venus, oxygen is lighter than air.

Life in a Venusian floating city, drifting around right above the Venusian clouds, sounds almost—dare I say it?—heavenly. There’d be plenty of sunlight (solar panels would soak up plenty of energy), and Venus would provide some natural protection from solar and cosmic radiation (at least, more protection than you’d get on Mars).

And thanks to the weird chemical mix in Venus’s atmosphere, you’d be able to collect almost all the natural resources you’d need. Well, aside from water (Mars has got Venus beat there).

I know this sounds crazy, but the more you read about it, the more Venus colonization makes sense. Venus may not get the kind of attention (or funding) that Mars gets, but NASA and other space agencies do take this seriously. NASA has even given the idea a name: the High Altitude Venus Operational Concept, or H.A.V.O.C.

So I’m ready to sign up for a mission to colonize Venus. Who’s with me?

Things have been a bit hectic lately, so welcome to a rare Saturday edition of Sciency Words.

Every Friday (normally), we take a closer look at an interesting science or science-related term to help us all expand our scientific vocabularies together. Today’s term is:

PHOTOLYSIS

Last year, when I did my special Mission to the Solar System, I fell in love with one planet in particular: Venus. I guess I’ve always had a soft spot for sciency girls, and Venus is about as sciency as they get. She’s really, really into chemistry.

Photolysis (also known as photo-dissociation) is one of Venus’s favorite chemistry tools. Photolysis occurs when high-energy photons ram into chemical bonds, causing those bonds to break.

By high-energy photons, of course, I mean light. Specifically ultraviolet light, X-rays, and gamma rays. On Venus, UV rays from the Sun cause the photolysis of sulfur compounds, contributing to the sulfur cycle that causes Venus’s infamous sulfuric acid rain.

The same process breaks apart oxygen molecules in Earth’s stratosphere, allowing them to recombine as ozone, thus generating the ozone layer. Photolysis is also probably responsible for the chemical changes on Jupiter that make the Great Red Spot look red (or sometimes other colors).

And speaking as an artist, photolysis is something I have to guard against. Paints are just a mix of chemicals, and the photolytic break down of those chemicals can, over time, cause paints and other pigments to fade or change color.

Photolysis by any other name…

The term photolysis is sometimes used as a blanket term for similar kinds of chemical bond breaking. For example, very little sunlight reaches the surface of Venus, but sulfur compounds still vigorously break apart and recombine due to the intense heat.

Some academic sources I’ve read still call that photolysis, though I prefer the term thermal dissociation. Calling a chemical reaction that occurs in a near pitch-black environment “photolysis” feels awkward.

Just my opinion.

Photolysis here, photolysis there, photolysis everywhere…

When I first learned about photolysis, I didn’t fully appreciate its significance. I understood only that it (and also thermal dissociation) played key roles in Venus’s extra special chemistry projects.

Then I encountered the word again while researching other planets. And then it popped up in an art textbook I was reading. I’ve gradually come to understand that it is a fundamental concept in science, or at least in chemistry.

Next week, I’ll be revisiting Saturn’s largest and orangest moon: Titan. I have a sneaking suspicion that we will once again see photolysis in action.

Links

Photolysis of Sulphuric Acid as the Source of Sulphur Oxides in the Mesosphere of Venus from Nature Geoscience.

The Sulfur Cycle on Venus: New Insights from Venus Express from the 2009 Lunar and Planetary Science Conference.