Many mysteries remain unanswered, even in our solar system’s backyard. There are volcanic-looking formations on Venus, but it’s unclear if they’re active. The landscape of Mars shows that a large ocean previously existed, but how it vanished is unknown. Recent detections of chemical substances that could suggest the presence of biological activity on Mars and Venus, known as biosignatures, however, keep the quest for life beyond Earth alive. The answers may lay in examining the light that reaches us from these planets, as well as the “fingerprints” that the molecules leave in the light’s spectrum.
In a new study published in Atmosphere, researchers from the Instituto de Astrofsica e Ciências do Espaço (Faculty of Sciences at the University of Lisbon, Portugal) compared simulations obtained with the Planetary Spectrum Generator (PSG), a planetary spectrum simulator, with observations of infrared light from the planets Venus, Mars, and Jupiter.
The researchers were able to explain the results of several observations using PSG, created by NASA, and concluded that this simulator is an efficient instrument for analyzing the abundances of chemical compounds present at minute levels in planetary atmospheres.
Methane, one of the chemical molecules studied, may be produced by both biological and geological processes. That is why its elusive presence on Mars remains a mystery, despite discovery by the Mars Express probe and the absence of detection by the ExoMars TGO spacecraft.
By altering the parameters of our simulations and understanding the conditions and places in which they can occur. This is a key step toward elucidating the link between methane on Mars and the possibility of life, “Pedro Machado (IA & Ciências ULisboa), co-author of this work, explains.
“By varying the parameters of our simulations, we were able to explain this detection and non-detection of methane on Mars and understand the conditions and locations in which they can occur. This is an important step towards clarifying the association of methane on Mars with the possible existence of life,”
Pedro Machado (IA & Ciências ULisboa), co-author of this study.
“Knowing the ratio of two hydrogen isotopes, deuterium, and plain hydrogen, helps us comprehend the chronological development of water on Mars. Deuterium is a heavy hydrogen atom with one additional neutron in its nucleus, hence making water, H2O, composed of a deuterium atom and a hydrogen atom, HDO, is heavier and will have a more difficult time escaping into space. The ability to compare this ratio at a global and local level on Mars, made feasible by this study, provides us with significant knowledge regarding the fate of Martian water, “explains Joo Dias (IA & Ciências ULisboa), the study’s primary author.
This research also found that phosphine may be created spontaneously in high pressure and temperature conditions in the presence of phosphorus and hydrogen, the two chemical elements that make it up. “This is what happens on Jupiter, with phosphine being one of those responsible for the colorful bands in this gas giant’s atmosphere,” Pedro Machado adds, “but on a hard planet, like Earth, where these extreme conditions do not exist, its presence is related with biological activity.”
So, when a study discovered phosphine in the clouds of Venus in 2020, the scientific community focused on this planet. Further tests conducted under different settings revealed that phosphine may not be present at all or may be present in considerably lower proportions than initially reported, which we were also able to reproduce.
While still on Venus, “sulfur dioxide is critical for determining whether or not there is volcanic activity. As we have proven with PSG, we will be able to determine the origin of this molecule by carefully determining its quantity at different elevations, as we have proven with PSG, “Joo Dias adds.
“This work is very important for space missions that are currently being developed by the European Space Agency (ESA), such as EnVision, Ariel, and Mars Express, in which IA is involved, because it tells us the expected values for these chemical components and allows the instruments that are being designed for these missions to be optimized to detect within the range of expected values,” says Pedro Machado, a co-investigator on these missions.
“Missions like Ariel, which will investigate the atmospheres of planets orbiting stars other than the Sun, called exoplanets, benefit enormously from this type of solar system research, which can serve as a model for what we hope to observe outside the solar system,” Joo Dias says.
“This demonstration of the effectiveness of PSG is very important for the scientific community, and the IA is at the forefront of these studies by including specialists in both the study of the atmospheres of planets in the solar system and the detection and characterization of exoplanets in its Planetary Systems team,” says Pedro Machado.
