Researchers have created a model to understand the evolution of Mars’s atmosphere, offering a new perspective on the planet’s history.
Today, Mars is a cold and arid planet, but geological records indicate that it supported liquid water around 3 to 4 billion years ago. Water is often associated with life. To explore the critical question of whether life ever existed on Mars, scientists from Tohoku University have devised an in-depth model regarding the production of organic matter in Mars’s ancient atmosphere.
Organic matter encompasses the remnants of once-living organisms like plants and animals or the products of specific chemical processes. The stable carbon isotope ratio (13C/12C) in organic materials offers important insights into their formation, shedding light on Mars’s geological past. This has piqued the interest of Mars exploration missions. For instance, NASA’s Curiosity rover discovered that the organic material in Martian sediments from that era exhibits a significant depletion of 13C, with notable variations in carbon isotope ratios across samples. However, the cause of these differences remained unclear.
To delve deeper into these discoveries, a research team led by Shungo Koyama, Tatsuya Yoshida, and Naoki Terada from Tohoku University developed a Martian atmospheric evolution model that looked at formaldehyde (H2CO). This choice stems from their previous determination that formaldehyde could plausibly have formed in Mars’s ancient atmosphere. Formaldehyde is significant because it can create complex organic molecules like sugars, which are crucial for life. Thus, it might hold the key to understanding the unusual carbon isotope values observed by the Curiosity rover and possibly indicate past life.
This model paired a photochemical model with a climate model to analyze how the carbon isotope ratios for formaldehyde changed on Mars over the last 3 to 4 billion years. The results suggested that the 13C depletion in formaldehyde arises from the photodissociation of CO2 caused by solar ultraviolet radiation, leading to a preference for one stable isotope over the other. Additionally, they found that variations in carbon isotopes were influenced by factors including the atmospheric pressure on Mars at that time, the amount of light reflected by its surface, the CO to CO2 ratio, and volcanic activity’s release of hydrogen.
“This model offers a potential explanation for previously bizarre observations, including the mysterious depletion of 13C,” comments Koyama, a graduate student at Tohoku University.
This finding suggests that formaldehyde played a role in forming organic matter on ancient Mars, indicating the possible production of biologically significant molecules like sugars and ribose (a vital component of RNA found in all living organisms).
The research results were published in Scientific Reports on September 17, 2024.
