But from Earth.
Scientists examining material from asteroid Ryugu, located over 200 million miles away, stumbled upon an unexpected discovery: Earth-based microbes thriving on the sample’s surface. This surprising finding underscores the resilience of life on our planet and raises critical questions about contamination during space exploration.
How Earth’s Microbes Invaded an Alien Rock
In 2020, Japan’s Hayabusa2 spacecraft brought back 5.4 grams of asteroid Ryugu material in an effort to study the building blocks of life. Extreme precautions were taken to prevent contamination. Once the spacecraft returned, the sample was carefully handled in a vacuum chamber inside a sterile room and stored under pressurized nitrogen. It was then shipped in sealed, nitrogen-filled containers to research labs worldwide.
As Live Science explains, despite these efforts, contamination wasn’t entirely avoided. When a sample was embedded in resin for analysis at Imperial College London, researchers discovered filamentous microorganisms—Earth-based bacteria—spreading across its surface. Their findings, published in Meteorics and Planetary Science, revealed that Earth microbes had somehow infiltrated the sample, even under stringent precautions.
Initially, X-ray scans showed no signs of contamination. However, after a few weeks in resin, researchers used a scanning electron microscope (SEM) and found organic filaments crisscrossing the sample. The bacteria’s sudden appearance, rapid growth, and structure matched terrestrial microbes, confirming contamination occurred after the sample left its pristine state.
What This Means for Space Exploration
Although this contamination complicates efforts to study Ryugu’s true composition, it offers valuable lessons about microbial resilience and the challenges of handling extraterrestrial materials. The study highlights the incredible adaptability of Earth’s microbes, which seem capable of thriving in nearly any environment, even those designed to exclude them.
The researchers explained: “Microorganisms are the world’s greatest colonizers, adept at circumventing contamination controls.” This discovery underscores the need for even stricter decontamination measures in future space missions, especially as humanity pushes further into the cosmos.
While the contaminated sample cannot provide clear answers about Ryugu’s original surface, the mission wasn’t a complete loss. Some uncontaminated portions of the sample revealed traces of amino acids and uracil—key components of organic life—bolstering the theory that life’s building blocks may come from space.
This discovery reignites the age-old question: Did life originate on Earth, or did it come from the stars? While Ryugu’s sample raises more questions than it answers, it reinforces the importance of vigilance in the search for extraterrestrial life. The next time we retrieve material from space, scientists will be even better prepared to protect it from Earth’s tenacious microbes.
