April Mini Post 3: Mars rover Perseverance has MOXIE

Making something out of the red planet's atmosphere

Ahoy hoy! Welcome to April’s third and final mini post. This one was so hard to keep short! You can find the first post about Roman-era wall building escapades here, and the second post about the retiring metal kilogram here. Big thanks to the readers who have reached out with feedback about the shorter format and those who have jumped into the comments with ideas of their own. I love hearing from you, and I especially enjoy reading what you think about all these ideas we talk about! Keep it coming!

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This week I’ve been playing some samba-style riffs on the guitar and watching Formula 1: Drive to Survive on Netflix. I can’t say I’m particularly interested in racing, but two glowing reviews from respected sources (hi Art! hi Talia!) bumped it to the top of the queue following a Mandalorian rewatch. Michelle and I blew through all three seasons in a matter of a week or so. It’s character-driven and full of intrigue from all sides, and, crucially, viewers don’t have to be literate in F1 racing to enjoy it. You learn everything you need to know along the way. We were glued to our seats almost immediately. No spoilers, but there are a few episodes that included some of the most affecting documentary storytelling I’ve seen in ages. Highly recommend.

I’ve also been eagerly awaiting the arrival of a book in the mail - namely futurologist Rose Eveleth’s debut Flash Forward: An Illustrated Guide to Possible (and Not So Possible) Tomorrows based on their acclaimed podcast Flash Forward. I wrote about Eveleth’s influence on my own scientific philosophy a few weeks ago in a piece about the connection between thinking about the past and conceiving of the future.

Something else that seems futuristic but is very much here (how’s that for a segue) is the exploration that’s happening right now on the surface of Mars. A news item from last week has been rattling around in my head for a few days - the Mars rover Perseverance successfully performed an experiment in which it produced oxygen from the carbon dioxide-rich Martian atmosphere.

Let’s explore what this contraption does and what it could mean for future human visits to Mars.


The rover Perseverance as been operational since its touchdown on the surface of Mars on February 18th, 2021. Percy, as it’s nicknamed, carried a host of different instruments 205 million kilometres from home to do environmental testing and exploration ahead of potential human voyages anticipated to begin in the 2030s. One such instrument is called MOXIE, the Mars Oxygen In-Situ Resource Utilization Experiment.

MOXIE represents a pretty significant achievement. The car battery-sized unit is able to convert the ~96% carbon dioxide atmosphere into oxygen using a process called solid oxide electrolysis. On a basic level, the conversion works by exposing the carbon dioxide (CO₂) to a temperature of 800 ℃ and compressing it using a HEPA filter and a selection of certain ceramic materials that are known to oxidize (that means take the electrons away from) other materials.

Oxidization is sort of what happens when things rust - oxygen is an oxidizing agent! Over time, exposure to oxygen causes things to break down (like the way silver and iron tend to rust, for example), which is a chemical reaction where the material loses electrons and hydrogen molecules. The oxidization process leaves a new material behind as a product of the reaction.

So! Since solid oxide electrolysis makes it possible to to filter, sort, and selectively combine elements already found in the atmosphere, MOXIE is also able to functionally create new materials using a single process. For this unit, there is a set of known outcomes based on what ingredients are taken in by the unit, what those materials are combined with, and what byproducts are available at the end.

Some materials MOXIE can make using this method, briefly:

  • Breathable oxygen that can be stored and used over time for human life support in communal living spaces and in mobile applications.

  • Oxygen (liquid) to fuel ascent vehicle propulsion. This is key for the people headed to Mars to be able to return, since it’s unlikely that any spacecraft could carry enough fuel for the initial voyage and the return trip.

  • Carbon monoxide is suitable for use as a low-grade fuel and is a byproduct of the process. It can also be reacted with water to create methane, good for use as a primary fuel source.

  • Oxygen can also be combined with hydrogen to make water.

Last week was MOXIE’s first of ten trial runs. It will do nine more to test the unit’s function under different temperature and atmospheric conditions, as well as during dust storms to find its limitations. Once it’s proven to be reliable, the technology can be scaled up to accommodate the needs of crewed missions.

Making breathable air out of another planet’s atmosphere? Creating water where it hasn’t been for millennia? Makes me think that there’s some potential for MOXIE technology to help the greenhouse gas situation here on Earth, but that’s a post for another time.

Welcome to the future.