As scientists gear up for a new era of lunar exploration, recent studies indicate that spacecraft may leave more than just footprints on the moon. Research shows that methane emitted by spacecraft exhaust can disperse across the lunar surface faster than expected, potentially contaminating critical areas that could hold ancient chemical evidence regarding the origins of life on Earth.
The findings reveal that if an astronaut lands near the moon’s south pole, methane molecules can quickly “hop” to the north pole in less than two lunar days. As governments, private firms, and NGOs prepare for upcoming moon missions, understanding the impact of exploration on future scientific discoveries is becoming increasingly vital, researchers say.
This research was published in Geophysical Research Journal: Planets, an AGU journal dedicated to planetary science.
“Our goal is to safeguard scientific integrity and investments in space,” stated Silvio Sinibaldi, planetary protection officer at the European Space Agency and lead author of the study. He noted that while the moon provides a unique opportunity to examine the early history of the solar system, paradoxically, “our activities might hinder scientific exploration.”
Ancient Lunar Ice: Key to Understanding Life
Near the moon’s poles lie craters that experience permanent shadow, creating cold environments that harbor ice possibly containing materials delivered by asteroids and comets billions of years ago.
Scientists suggest that these deposits may hold “prebiotic organic molecules,” the fundamental chemicals that ultimately formed life’s building blocks, such as DNA. Studying these molecules in their pristine state could offer groundbreaking insights into how life began on Earth.
“We know organic molecules exist in our solar system, particularly in asteroids,” said Sinibaldi. “However, understanding how they evolved to perform specific biological functions remains a knowledge gap we need to fill.”
As Earth’s surface continuously changes, much of the ancient evidence has been lost. In contrast, many areas on the moon have remained stable for billions of years, making them an invaluable archive of the early solar system’s history. Permanently shadowed regions are especially significant due to their frigid temperatures, which preserve molecules. However, these same cold traps could also trap organic compounds released by visiting spacecraft, obscuring primordial materials crucial for scientific study.
Modeling Methane Movement on the Lunar Surface
To explore this issue, Sinibaldi and lead author Francisca Paiva, a physicist at the Institute of High Technology, developed a sophisticated computer simulation focusing on ESA’s Argonaut mission as a case study.
The researchers modeled how methane, the primary organic compound released during the combustion of Argonaut’s propellant, would disperse after landing near the moon’s south pole. While previous studies have examined water molecule movement on the lunar surface, this marks the first simulation of organic molecules like methane, incorporating factors like solar wind and ultraviolet light effects.
“We aimed to simulate thousands of molecules, observing their movement, collisions, and interactions with surfaces,” Paiva shared, a master’s student at the University of Leuven and intern at the European Space Agency during the research. “This required substantial computing power, with simulations taking days or weeks to run.”
Rapid Dispersion of Methane Across the Moon
Simulation results indicated that methane could reach the moon’s North Pole in under two lunar days. Within seven lunar days (approximately seven Earth months), over half of the emitted methane became “cold-trapped” in the permanently cold polar regions, with 42% accumulating in the South Pole and 12% in the North Pole.
“That finding was the biggest surprise,” Sinibaldi noted. “Within a week, the molecules could be distributed from the South Pole to the North Pole.”
Due to the moon’s lack of atmosphere, dispersal occurs rapidly. The absence of air molecules allows methane to move freely under gravity, bouncing off surfaces energized by sunlight or slowed down by cooler temperatures.
“Their motion is effectively ballistic,” Paiva explained. “They’re simply hopping from one point to another.”
This means there may not be a completely safe landing site. “Our study showed that molecules can travel all over the moon, suggesting that no matter where you land, contamination is likely,” Paiva added.
Ensuring the Integrity of Lunar Science
Researchers emphasize that contamination does not have to be an inevitable outcome. Paiva noted that if a landing site is cold, exhaust molecules might remain more localized compared to warmer regions. Sinibaldi also aims to explore whether exhaust molecules only affect the surface ice, leaving deeper material intact and suitable for scientific investigation.
Both researchers stressed the need for future lunar missions to validate their computer simulations through additional modeling and direct measurements.
“I want this discussion to reach the mission teams. Ultimately, this isn’t merely theoretical—it’s the reality of our exploration,” stated Sinibaldi. “Failing to incorporate the necessary validation equipment onboard means missing a significant opportunity.”
Paiva also plans to research whether other substances, such as compounds released by spacecraft components like paint or rubber, could pollute the scientifically significant lunar surface.
“We have regulations to prevent pollution in global environments such as Antarctica and national parks,” she emphasized. “I believe the moon deserves the same level of protection.”
This research appears in Geophysical Research Journal: Planets, an AGU journal.
Source: www.sciencedaily.com