If you pick up In Ascension by Martin MacInnes, don’t expect a typical sci-fi romp with lasers and aliens jumping out of shadows. It’s not that kind of book. Honestly, it’s more of a mood—a slow-burn, slightly trippy exploration of where we came from and why we’re so obsessed with leaving.
The story follows Leigh, a marine microbiologist. She’s obsessed with algae. Sounds thrilling, right? But Leigh’s obsession takes her from a terrifyingly deep Atlantic trench to the literal edge of the solar system. The book is huge, clocking in at around 500 pages, and it’s been polarizing as hell. People either think it’s a masterpiece—it was longlisted for the 2023 Booker Prize and won the Arthur C. Clarke Award in 2024—or they find it a total slog.
The Weird Science of Leigh’s World
Leigh didn't have a great childhood. She grew up in Rotterdam, a city basically fighting a losing war against the ocean. Her dad was a hydraulic engineer who took his stress out on the family. You get the sense that Leigh’s move into deep-sea biology was less about a career choice and more about getting as far away from "home" as humanly possible.
The plot kicks off when Leigh joins a research vessel investigating a new thermal vent. This isn't just a hole in the ground; it’s an anomaly that seems to be 36 kilometers deep. For context, the Mariana Trench is about 11 kilometers deep. This thing shouldn't exist. When Leigh and her fellow divers get close to it, they don't just find new life—they start having hallucinations and physical meltdowns.
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Why Algae Matters (Seriously)
Eventually, Leigh gets recruited by a shadowy, NASA-like agency in the Mojave Desert. They aren't interested in her diving skills; they want her algae. Why? Because they’ve developed a new propulsion system that can hit 30 million miles per hour. They need a self-sustaining food source for long-haul space travel, and Leigh’s specialized "archaea-infused" algae is the key.
- The Propulsion: It’s called the "acceleration equation," and nobody quite knows how it was invented. The scientists who "discovered" it basically saw it in their dreams.
- The Mission: To intercept a mysterious object called Datura near the Oort Cloud.
- The Cost: Leigh has to basically abandon her dying mother and her sister, Helena, to go.
It’s a brutal choice. MacInnes spends a lot of time on the "Earth-loss" phenomenon—the psychological break that happens when you can no longer see your home planet. It’s not just homesickness. It’s a fundamental biological collapse.
That Ending: What Actually Happened?
Look, if you haven't finished In Ascension, skip this part. But if you have, you’re probably scratching your head.
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The mission to the Oort Cloud goes sideways. The crew loses contact with Earth. They realize the stars don't look right anymore. They haven't just traveled across space; they’ve slipped through time. The book ends with Leigh back on Earth, but it’s not her Earth. It’s a world entirely covered in water, billions of years in the past.
The Cycle:
- Leigh’s crew crashes into the primordial ocean.
- The genetically modified algae in their life-support systems leaks out.
- This algae becomes the "first life" that Leigh was studying at the start of the book.
It’s a closed loop. Humanity created itself by trying to leave. It’s a bit of a brain-melter, but it ties the "micro" (cellular biology) to the "macro" (the cosmos) in a way that feels incredibly earned, even if it's depressing as all get-out.
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Why Some Readers Hate It
Not everyone is a fan. The middle 200 pages are basically a manual on how to grow space-algae and the logistics of ship maintenance. Some critics have called it "ponderous" or "over-written." If you want Star Wars, you’re going to be miserable.
There’s also the issue of the "bad science." Some Reddit threads have been tearing into the 30-million-mph propulsion system, calling it pure fantasy disguised as hard sci-fi. But honestly? I think that misses the point. MacInnes isn't trying to write a textbook. He’s writing about the feeling of being a tiny, porous biological entity in a universe that is way too big for us.
Actionable Insights for Readers
If you're thinking about picking up In Ascension Martin MacInnes, here is how to actually enjoy it:
- Don't rush. This is a "slow cinema" version of a book. Let the atmosphere sink in.
- Pay attention to the sister. The section from Helena's perspective is vital. It challenges everything Leigh tells us and makes you wonder if our protagonist is actually a reliable narrator.
- Think about the "Earth-loss." The book is a massive metaphor for climate change. We are obsessed with finding a "new home" because we’ve broken the one we have.
If you’ve already read it and need something similar but maybe a bit more "grounded," check out The Overstory by Richard Powers or The Ministry for the Future by Kim Stanley Robinson. They hit those same "interconnectedness" notes without the time-traveling algae loops.
To get the most out of the experience, try reading the first section—the "Rotterdam" chapters—and the final "Epilogue" back-to-back. You'll see the linguistic mirrors MacInnes planted everywhere, from the way water is described to the specific chemical scents Leigh identifies. It makes the "cycle" ending feel much more intentional and less like a sudden twist.