We were trying to terraform Mars but instead we saved the sea snails

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We were trying to terraform Mars but instead we saved the sea snails<br>A story about scientific creativity and halogenase enzymes

Erika Alden DeBenedictis<br>May 19, 2026

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The best way I’ve found to get a room full of scientists to think creatively is to tell them we’re going to terraform Mars.<br>Scientific progress is famously dependent on luck, which makes attempts to “go faster” hard. One reliable way to tilt the odds is to begin with a familiar problem and impose genuinely new constraints. Doing that has a way of stripping away the comfortable defaults, and forcing you to ask different questions than you have before. In that vein, my former academic lab set out with an extremely nonstandard constraint—the goal of terraforming Mars —and, in trying to make that goal concrete, we ran into a technical blocker that pushed us into a new approach to enzyme engineering. The result was a paper on engineering halogenase enzymes and their application to making therapeutics, now out in Nature Communications. The toolchain we created turned out to be useful for nearer-term applications on Earth, a small but vivid example of how “weird” constraints can produce practical innovations.<br>Thanks for reading Erika’s Newsletter! Subscribe for free to receive new posts and support my work.

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The idea

To terraform Mars, the fundamental challenge is to heat the planet up enough that liquid surface water doesn’t immediately freeze or evaporate. Despite what Elon says, you need to do much more than simply liberate the CO2 in Mars’s Northern ice cap1. One proposal is to use a mixture of super greenhouse gases that would be sufficient to keep Mars warm. This could work… if it were possible to manufacture such gases at scale. This leads us to a problem statement: can we interact with super-greenhouse gases — produce and degrade them — at scale with biology?<br>When I started my academic lab in 2022, I created a program called ‘Focus Areas’ that guided students all the way through the process of learning about a completely new topic area to pitching actionable projects over a period of four weeks2. A group of four people in my lab went from never having thought about the intersection of greenhouse gases and biology to pitching projects on the topic!<br>What did we learn? Powerful greenhouse gases often have exotic atoms in them like Fluorine, Chlorine, and Bromine, which are from the second-to-the-right-most column of the period table and are all referred to as “halogens ”. You may have heard of CFCs, or chloro-fluoro-carbons (meaning they contain both chlorine and fluorine), the classic uber-greenhouse gas that is 10,000x more powerful than CO2 per weight. CFCs were common in spray aerosols because they are stable, nontoxic, and nonflammable, but they were banned and phased out in the 70’s and 80’s after it was discovered they deplete ozone. Enzymes that can move around the chemical bonds attached to a halogen atom are called “halogenases” and are the type of enzyme that would be needed to produce or degrade these compounds.

What are halogenases? They are enzymes that can interact with chemical bonds on halogen atoms.<br>What is it about halogenated compounds that causes them to have such unusual properties? A key moment I remember during brainstorming was when Osaid Ather, a practicing physician who worked part-time in my lab on therapeutics manufacturing with synthetic biology, realized that half the drugs he prescribes are halogenated. Halogen-carbon bonds are extremely stable, which makes the resulting molecules less reactive and thus difficult to degrade in your body! Indeed, nature does create halogenated compounds, but rarely, and mostly as toxins, which makes sense: toxins also benefit from being hard to degrade, just like therapeutics. In general, there’s a very wide variety of useful halogenated compounds we interact with in everyday life including pharmaceuticals, pigments, and coatings, and today they’re manufactured chemically with expensive processes that often involve toxic byproducts. Creating halogenated compounds using low-cost, non-toxic biomanufacturing methods could be hugely beneficial for lots of applications, and not just terraforming!<br>So why don’t we already manufacture halogenated compounds with biology? Unfortunately, the existing known natural halogenases don’t work very well . They are low-activity, sensitive to temperature, and very insoluble, which makes them tough to work with in an industrial setting. Before you can get to assembling large pathways to make useful specific halogenated compounds, you just need better enzymes. Where do you look for them, and how do you measure them? We don’t even have good biosensors for detecting whether or not halogenase enzymes are working in cells! These were some of the key bottlenecks we came up with.

Action shot: going from gauging interest in a...