Youcef Sellam: A Ph.D. Student’s Journey to Uncover Clues About Life On Mars

When we imagine the search for life on Mars, we often picture high-tech rovers scanning dusty landscapes or orbiters analyzing strange rock formations from above. But what if the key to discovering ancient life isn’t in the vast Martian deserts – what if it’s hidden inside crystals?

That’s the question driving the research of Youcef Sellam, a doctoral student at the University of Bern. In a recent SETI Live, Sellam and communication specialist Beth Johnson discussed how microscopic fossils found in gypsum crystals from Algeria could offer vital clues about the potential for life on Mars.
 

A Childhood Spark Turns Scientific

Sometimes, big scientific discoveries begin in unexpected ways. For Sellam, the journey to astrobiology began with childhood curiosity. Growing up, he watched science documentaries with his father, asking endless questions that fueled a deep fascination with the unknown. That passion led him to study microbiology in Algeria, then earn two master’s degrees in France, where he discovered the field of paleontology and, subsequently, microfossils.

During an internship in Italy, Sellam and his colleagues made a remarkable discovery: the first microbial fossils ever found in Algerian gypsum. Now, as a Ph.D. student at the University of Bern, he’s taking that research even further.
 

What are Microfossils?

Microfossils are exactly what they sound like: microscopic remains of life. They could be bacteria, archaea, protists, or even tiny fragments of larger organisms. Studying them isn’t just about identifying ancient microbes—it’s about piecing together Earth’s environmental past.

Did you know that the older the fossil, the more it can reveal about how life began and evolved? For instance, cyanobacteria fossils (the oldest known fossils) can tell scientists whether a water body was shallow or deep based on how far the light could penetrate. By analyzing microfossils, researchers can reconstruct paleoenvironmental conditions, such as water depth and chemistry, at the time of the fossils’ formation.
 

Life Trapped in Gypsum

Sellam’s research focuses on gypsum, a mineral that forms rapidly and can trap microorganisms during its crystallization. His team discovered microbial fossils preserved within 5 to 5.5 million-year-old gypsum crystals from Algeria. These fossils were found in different forms, sometimes as carbon, sometimes as minerals, and sometimes as a mix of both.
 

Determining Biogenicity

Determining whether a structure is truly biological involves assessing its biogenicity (the origin or production of something by living organisms). This means looking for certain clues: 

• Does the structure resemble known microorganisms?
• Was it found in an environment capable of supporting life?
• Does it contain life-related elements such as carbon, hydrogen, nitrogen, sulfur, or biomolecules like amino acids or lipids? 

These multiple lines of evidence help researchers avoid mistaking non-biological formations for actual fossils.
 

The Power of LIMS

Sellam uses Laser Ionization Mass Spectrometry (LIMS) to analyze the microfossils, a technique that targets microscopic areas with a laser, vaporizing and ionizing the material. The resulting charged atoms are funneled through a mass analyzer to determine their composition. This system, developed at the University of Bern, is designed for automated and remote planetary operation, making it suitable for a Mars rover.

Using this technique, the team detected carbon and sulfur in the Algerian crystals, which are crucial for understanding biological processes that can provide evidence of past life forms.
 

A Bigger Picture

Scientists think that a long time ago, Mars had rivers, lakes, and even oceans that might have sustained life. Although Mars is very different today, some ancient rocks could contain minerals like gypsum, which may still hold clues about past life. This finding highlights how chemical analysis can reveal biological traces in minerals, and with each discovery, we get closer to answering the question of whether life ever existed on Mars.

Watch the video below or find Chasing Martian Microbes: A New Technique for Finding Microbial Fossils in Minerals on our YouTube channel.