Did Mars Destroy Its Own Biosignatures? | GC-MS, Sterols & the Search for Life

🎤Megan Farrah (Tufts University)

What if Mars already had biosignatures… and destroyed them?

In this episode of Concentrating on Chromatography, host David Oliva sits down with Megan Farrah to explore how GC-MS is being used to reconstruct potential biosignatures under simulated Martian conditions.

Inside a Mars Simulation Chamber, Megan irradiates sterols and hopanes — two of NASA’s priority targets for life detection — in soil matrices containing oxychlorine salts similar to those detected by Mars missions.

Her goal? Determine whether chlorinated hydrocarbons detected by rover-based pyrolysis GC-MS were:

• Indigenous Martian organics
• Terrestrial contamination
• Or molecules altered by heat during analysis

We dive deep into:

🔬 SIM mode vs. full scan when you don’t know what you’re looking for
🧂 Why residual salts can destroy a GC column (and how ion chromatography prevents it)
🔥 The dangers of heating organics in the presence of perchlorates
🧪 Toluene/BHT extraction and preventing artificial oxidation
🧼 GC-MS contamination: septa, liners, plasticizers, detergents, and why her entire bench is glass
🚀 What Mars Sample Return would require from separation scientists

Megan explains why finding “organics” does not automatically mean finding life — and why Mars is far from geologically dead.

We also explore how she explains Mars chemistry to fifth graders using paper chromatography… and why separation science still feels like magic.

If you care about:

• GC-MS method development
• Column contamination control
• Environmental salt matrices
• Astrobiology
• Or the future of life detection

This is an episode you don’t want to miss.

Topics Covered

• Mars Simulation Chamber experiments
• Sterols and hopanes as biosignatures
• Oxidant-induced fragmentation
• Derivatization with BSTFA
• Ion chromatography salt cleanup
• Pyrolysis GC-MS on Mars rovers
• High-salt matrix challenges
• Sensitivity vs column lifetime

Video Transcription

Introducing Separation Science Through Paper Chromatography

Farrah begins by describing volunteer outreach activities at an elementary school chemistry club. One exercise involved simple paper chromatography, where students separated ink dyes into individual colors.

Although young students were not learning concepts such as partition coefficients or stationary phases, the experiment provided an intuitive introduction to separation science. Watching a single ink spot separate into multiple colors allowed children to understand the idea of a mixture being divided into its individual components. Farrah noted that the experience reinforced how chromatography can be explained through visual transformations rather than technical terminology.

She also draws a parallel between this classroom experiment and her own research. While children can directly observe colored compounds separating on chromatography paper, her laboratory work involves invisible molecules that require sophisticated analytical instruments to detect and identify.

Simulating Martian Chemistry in the Laboratory

A central component of Farrah’s research is the use of a Mars simulation chamber, where chemical compounds are exposed to conditions resembling the Martian environment.

In simplified terms, the process begins with a known chemical compound. The sample is then subjected to simulated Martian sunlight and chemically reactive salts. These conditions induce chemical transformations, generating complex mixtures of degradation products. The resulting mixtures are analogous to the separated colors observed during paper chromatography, except that the individual compounds must be detected through analytical instrumentation rather than visual observation.

The objective is not simply to identify compounds present in a sample, but rather to understand how organic molecules change after long-term exposure to Martian environmental conditions.

The Challenge of Unknown Degradation Products

Unlike many analytical projects where target analytes are known beforehand, Farrah’s work focuses on degradation products that cannot be predicted with certainty.

Biomolecules exposed to simulated Martian chemistry can fragment into hundreds of compounds, many of which may never have been observed previously. As a result, traditional targeted analytical methods are insufficient.

Instead, Farrah employs a broad exploratory strategy involving multiple analytical platforms:

• Gas chromatography–mass spectrometry (GC-MS)
• Liquid chromatography–mass spectrometry (LC-MS)
• Ion chromatography (IC)
• Nuclear magnetic resonance spectroscopy (NMR)

Samples are often analyzed using several complementary methods and instrument settings, including workflows optimized for lipids, oxidized sterols, and unknown compounds. Rather than searching for a specific molecule, the goal is to characterize the entire chemical landscape created by Martian degradation processes.

Martian Organics or Analytical Artifacts?

One of the most intriguing scientific questions discussed during the interview concerns organic compounds detected on Mars by NASA missions.

The Viking landers and the Curiosity rover’s Sample Analysis at Mars (SAM) instrument both utilized pyrolysis GC-MS. In these systems, samples are heated to very high temperatures—up to approximately 1000 °C—to volatilize compounds prior to analysis.

The complication arises because Martian soil contains abundant oxychlorine salts, including perchlorates. When organic molecules are heated in the presence of these salts, chlorinated compounds can be generated during the analytical process itself.

Consequently, compounds such as chloromethane and chlorobenzene may have several possible origins:

1. Indigenous Martian organic compounds altered naturally on Mars.
2. Terrestrial contaminants chlorinated during analysis.
3. Native Martian compounds transformed inside the analytical instrument.

Farrah’s research focuses on determining whether chlorination processes could have occurred naturally on Mars through long-term exposure to ultraviolet radiation and oxychlorine-rich environments, rather than being artifacts produced during pyrolysis analysis.

Misconceptions About Organic Molecules on Mars

Farrah identifies two common misconceptions surrounding Martian organic chemistry.

The first is the widespread assumption that the detection of organic compounds automatically implies the existence of life. She explains that organic molecules are not exclusive to biological systems. Carbon-containing compounds occur throughout the universe, including meteorites, comets, and interstellar dust clouds. Therefore, the presence of organic molecules on Mars alone does not constitute evidence of life.

The second misconception is that Mars is a completely inactive world. While often described as cold and dead, Mars continues to experience geological processes and once possessed liquid water and conditions potentially suitable for habitability over geologically significant timescales. According to Farrah, subsurface environments may still preserve evidence of ancient biological activity that has yet to be discovered.

Sample Preparation and Oxidation Control

Because oxidation plays a major role in Martian chemistry, preventing unwanted oxidation during laboratory handling is critical.

Farrah uses butylated hydroxytoluene (BHT) as an antioxidant during extraction procedures. BHT functions as an oxygen scavenger, protecting analytes from oxidation that could occur during sample preparation and extraction. This ensures that observed oxidation products originate from simulated Martian processes rather than laboratory artifacts.

Following liquid–liquid extraction, aqueous fractions are analyzed by LC-MS to investigate polar oxidation products. In studies involving cholesterol and related sterols, oxidation introduces functional groups such as:

• Hydroxyl groups
• Ketones
• Epoxides

These modifications increase molecular polarity and influence partitioning behavior during extraction, making LC-MS particularly useful for characterizing such products.

The Role of Ion Chromatography

Ion chromatography serves a critical quality-control function within the workflow.

Before samples are analyzed by GC-MS, Farrah uses ion chromatography (IC) to verify that residual salt concentrations remain below detection limits. This step is especially important because her samples intentionally contain large quantities of perchlorate and related salts.

Introducing salts into a GC system can have severe consequences:

• Accumulation at the column inlet
• Reduced chromatographic performance
• Contamination of volatile analyte regions
• Increased maintenance requirements
• Potential damage to the analytical system

Farrah describes ion chromatography as an “insurance policy” that helps ensure reliable GC-MS performance while preventing the accidental generation of unwanted oxidation or chlorination products during later processing steps.

Derivatization for GC-MS Analysis

Many oxidation products contain polar functional groups that are difficult to analyze directly by gas chromatography.

Compounds containing:

• Hydroxyl groups
• Carboxyl groups
• Long-chain acids

tend to form hydrogen bonds and exhibit poor volatility. To improve chromatographic behavior, Farrah performs derivatization using BSTFA (N,O-bis(trimethylsilyl)trifluoroacetamide).

This reagent replaces active hydrogen atoms with trimethylsilyl (TMS) groups, producing derivatives that:

• Vaporize more readily
• Travel through the GC column efficiently
• Generate sharper chromatographic peaks
• Improve analytical sensitivity and reproducibility

The resulting enhancement in peak shape significantly facilitates compound identification and quantification.

Contamination Control in GC-MS Laboratories

A substantial portion of the interview focuses on contamination management, which Farrah describes as one of the most important practical aspects of GC-MS analysis.

Major contamination sources include:

Salts

Residual salts can damage chromatographic systems and interfere with analyses.

Instrument Consumables

Components such as:

• Inlet liners
• Syringe needles
• Septa

gradually accumulate contaminants and require routine replacement to maintain clean baselines and reliable performance.

Plastic-Derived Contaminants

Siloxanes and plasticizers originating from:

• Pipette tips
• Vial caps
• Laboratory plastics

can contribute significant background contamination. To minimize these effects, Farrah uses predominantly glass and metal laboratory equipment and avoids unnecessary plastic contact whenever possible.

Detergent Residues

Common laboratory cleaning detergents represent another major contamination source. Instead of detergents, Farrah relies on solvent rinsing, nitric acid cleaning, and high-temperature baking procedures for glassware preparation.

Learning from Earth’s Extreme Environments

The discussion also highlights the value of terrestrial Mars analogues.

Researchers in Farrah’s laboratory investigate environments such as:

• The Atacama Desert
• Antarctica’s Dry Valleys

These locations are among the harshest environments on Earth and provide useful models for understanding potential Martian chemistry.

Analytical challenges encountered in these environments—including trace organic detection, salt removal, and extraction optimization—closely resemble those anticipated for future Mars sample-return missions. Techniques developed today using terrestrial analogues may therefore become directly applicable to extraterrestrial samples in the future.

Balancing Sensitivity and Instrument Longevity

Farrah concludes by discussing the trade-off between analytical sensitivity and instrument maintenance.

Because her research focuses on detecting extremely low-abundance degradation products, analytical sensitivity is prioritized. This sometimes involves:

• High injector temperatures
• Concentrated sample injections
• Splitless GC operation
• Aggressive chromatographic conditions

Although such approaches can accelerate column wear, relatively low sample throughput in academic research allows greater flexibility than is often possible in industrial laboratories. Nevertheless, careful method development and extensive sample cleanup remain essential for protecting instrument performance while maximizing analytical sensitivity.

This text has been automatically transcribed from a video presentation using AI technology. It may contain inaccuracies and is not guaranteed to be 100% correct.

Concentrating on Chromatography Podcast

Dive into the frontiers of chromatography, mass spectrometry, and sample preparation with host David Oliva. Each episode features candid conversations with leading researchers, industry innovators, and passionate scientists who are shaping the future of analytical chemistry. From decoding PFAS detection challenges to exploring the latest in AI-assisted liquid chromatography, this show uncovers practical workflows, sustainability breakthroughs, and the real-world impact of separation science. Whether you’re a chromatographer, lab professional, or researcher you'll discover inspiring content!

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