For years, earthlings have wondered about the potential for life on Mars. Little did we know that clues about the Red Planet could actually be tied to what’s here on our blue marble.

A recent discovery of organic matter on Mars led to the detection of a compound, thiophene, that is also native to Earth. Scientists have been studying the Martian compound to learn more about life there and to uncover any further connections with Earth.

It’s just another breakthrough on a long list of space discoveries over the past half-century that give us a better understanding of our solar system, and how the 7.6 billion people of Earth fit in with the inestimable pieces of matter in the universe.

Clues That Offer Hints About Martian Life

While making observations on the surface of Mars in 2018, NASA’s Curiosity rover found “tough” organic molecules in 3-billion-year-old mudstone — a fine-grained sedimentary rock — in the planet’s Gale Crater. Mars’ inhospitable surface couldn’t sustain life today, but the data collected from the molecules showed that a water lake inside Gale Crater had the necessary ingredients for chemical building blocks and an energy source, enough to kick-start some form of life.

As NASA noted at the time of the rover’s discovery, although organic molecules hold carbon and hydrogen — or oxygen, nitrogen and other elements — the molecules from the mudstone don’t necessarily suggest there was ever life on the planet. Organic molecules can also be formed by non-biological processes, NASA added.

Still, a study of those observations back here on Earth has recently captured attention because of what’s been found in the organic matter on Mars: the heterocyclic compound thiophene. (A heterocyclic compound has atoms of at least two different elements.) Astrobiologists Dirk Schulze‑Makuch of Washington State University and Jacob Heinz of Technische Universität in Berlin believe the presence of thiophenes could point to the presence of early life on Mars.

As they outlined this year in the peer-reviewed journal Astrobiology, Schulze‑Makuch and Heinz’s study of the organic matter suggests that a biological process that probably involved bacteria might have played a hand in the compound’s existence on Mars.

“We identified several biological pathways for thiophenes that seem more likely than chemical ones, but we still need proof,” Schulze‑Makuch told the Insider of Washington State University. “If you find thiophenes on Earth, then you would think they are biological, but on Mars, of course, the bar to prove that has to be quite a bit higher.”

Coal, crude oil and even white truffles that are found on Earth contain thiophenes. As the Insider notes, thiophene molecules hold four carbon atoms and a sulfur atom arranged in a ring. Although carbon and sulfur are bio‑essential elements, Schulze‑Makuch and Heinz couldn’t definitively rule out any non‑biological processes creating the compounds on Mars.

One such possibility is that a meteor crashing into Mars created a non-biological condition for the organic compound to develop. Another possibility is a process known as thermochemical sulfate reduction, in which a set of compounds is heated to 248 degrees Fahrenheit or higher.

Yet, the astrobiologists also don’t preclude the idea that when Mars was warmer and wetter more than 3 billion years ago, the groundwork for a biological kind of sulfate reduction process could have formed thiophenes.

Opportunities for More Space Discoveries

Further studies of Mars will hopefully discover more elements of the planet that could reveal even more about what formed its landscape and what conditions unfolded to possibly create and sustain life there. And as the astrobiologists’ study shows, there may be more connections between Earth and Mars. Still, scientists that they are, Schulze‑Makuch and Heinz urge holding back on speculation until Mars can be studied up close by humans.

“As Carl Sagan said ‘extraordinary claims require extraordinary evidence,'” Schulze‑Makuch told the Insider. “I think the proof will really require that we actually send people there, and an astronaut looks through a microscope and sees a moving microbe.”