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Janusz J. Petkowski, William Bains, Sara Seager | Life | (2020)
Primary Link Archive Pubmed DOI Openalex Full text (OA)

Key Takeaways

Plain English Takeaway

Silicon, even though it's similar to carbon, can't really replace carbon as the main ingredient for life, especially in water. But in some harsh places like sulfuric acid, silicon might play a bigger role in life’s chemistry.

Study Aim

The paper aims to systematically review and assess whether silicon could serve as a main building block for life, similar to carbon. The authors investigate silicon’s chemical properties, its potential for forming diverse and reactive molecules, and its suitability in different planetary solvents such as water, cryosolvents (very cold, non-water liquids), and sulfuric acid. They seek to clarify if silicon-based life is plausible under any known or modeled conditions. Simply put: The study asks if silicon could ever take carbon’s place as the main ingredient for life.

Study Design

The authors conduct a comprehensive literature review and theoretical analysis of silicon chemistry, comparing it to carbon. They examine experimental data, modeled chemical spaces, and thermodynamic calculations. The study evaluates silicon’s chemical diversity, stability, and reactivity in various solvents, including water, ammonia, sulfuric acid, and cryosolvents. They also analyze the structural and functional diversity of silicon compounds and polymers, and assess their potential roles in hypothetical biochemistries. Simply put: The researchers compared silicon and carbon chemistry in different liquids to see if silicon could work for life.

Findings

The research demonstrates that silicon cannot serve as the main scaffold (core structure) for life in water-rich environments because it quickly forms unreactive silica (SiO2), limiting its chemical diversity. In water, silicon can only act as a rare, specialized atom in a few molecules. In cryosolvents, all molecules—including those with silicon—have extremely low solubility, making life unlikely. However, the study reveals that sulfuric acid can support a much wider range of stable silicon compounds than water, suggesting that silicon could play a significant role as a common functional atom in hypothetical sulfuric-acid-based life. The authors recommend focusing on silicon as a contributor to biochemistry in specific environments, rather than as a universal building block for life. Simply put: Silicon can’t replace carbon for life in water, but it might be useful for life in places with lots of sulfuric acid.

Abstract

Despite more than one hundred years of work on organosilicon chemistry, the basis for the plausibility of silicon-based life has never been systematically addressed nor objectively reviewed. We provide a comprehensive assessment of the possibility of silicon-based biochemistry, based on a review of what is known and what has been modeled, even including speculative work. We assess whether or not silicon chemistry meets the requirements for chemical diversity and reactivity as compared to carbon. To expand the possibility of plausible silicon biochemistry, we explore silicon’s chemical complexity in diverse solvents found in planetary environments, including water, cryosolvents, and sulfuric acid. In no environment is a life based primarily around silicon chemistry a plausible option. We find that in a water-rich environment silicon’s chemical capacity is highly limited due to ubiquitous silica formation; silicon can likely only be used as a rare and specialized heteroatom. Cryosolvents (e.g., liquid N2) provide extremely low solubility of all molecules, including organosilicons. Sulfuric acid, surprisingly, appears to be able to support a much larger diversity of organosilicon chemistry than water.

Referenced In

StarTalk

Season 17, Episode 27: Could There Be Silicon-Based Life?

Hey StarTalkians! In season 17, episode 27, Neil and Chuck sat down with astrobiologist and bacteriology professor Betül Kaçar to talk about the origins of life and astrobiology. Towards the end of the interview, they discuss a topic that will be familiar to any sci-fi fans: the possibility silicon-based life.

How Did Life Begin? with Betül Kaçar - StarTalk Radio

(from 52:57)

One of the most memorable examples in fiction are the rock creatures from Star Trek’s “The Devil in the Dark”, but is such a thing really possible? Dr. Kaçar implied it was, but they didn’t have time to go into much detail, so here’s the whole story.

Why Silicon?

As explained on the podcast, the main reason people take the idea of silicon-based life seriously is because of its similarity with carbon. It’s in the same group of the periodic table, which means it has the same valency as carbon. As Neil explains, this is basically saying it has the same outer electron configuration.

This means – theoretically – it could produce a similar range of compounds, with silicon taking carbon’s place as a “scaffold” for complex chemical structures. A 2020 paper goes into this in detail.

The Problems with Silicon

Many discussions of this topic breeze past a few substantial issues for the sake of the Trek­-style thought experiment. Firstly, and most importantly for “life as we know it,” silicon-based compounds are often vulnerable to hydrolysis, so they can’t survive for long in water.

The argument about valency also misses some detail. Yes, silicon can make the same number of covalent bonds as carbon, but a fully-bonded carbon atom has a full outer electron orbital, while silicon doesn’t. Silicon bonds are also more strongly polarized than carbon bonds, and these factors combined leads to some different behavior.

Silicon-Based Molecules Can Work

As Dr. Kaçar describes, scientists have had some success in making silicon-based organic molecules using enzymes, and other researchers have incorporated silicon-carbon bonding into amino acids. This is why the theory still seems solid, despite some issues.

Life, But Not as We Know It

Shockingly, silicon-based molecules tend to be more stable in sulfuric acid than in water, and could have an advantage over carbon in hot environments. So while Earth-like environments aren’t ideal, silicon-based life could be found on a Venus-like world we’d consider uninhabitable.  

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May 27, 2026 11:59 AM

I actually re-watched the Horta Star Trek episode recently. A classic! The Petkowski paper seems cool. Read the tldr, which says silicon life would be more possible in a sulfuric acid rich environment. Interestingly, the Horta uses some sort of corrosive acid to bore through rock (and people). Perhaps a serendipitous feature by the series writers!