In November 2022, Matthew Genge was peering through a scanning electron microscope at a millimeter-sized speck on the asteroid Ryugu when he noticed something amiss. Small but unmistakable tendrils of organic rod-like material clung to the surface. “I thought, ‘That’s strange,'” Genge recalls. “Then we found one after another.”
For a while, he and his colleagues may have made the most groundbreaking discovery in human history: the discovery of extraterrestrial life brought to Earth as a few grams of material recovered from a space rock. I thought. The Japan Aerospace Exploration Agency (JAXA)’s Hayabusa2 mission captured the sample in 2019 and delivered it in an airtight capsule to a remote touchdown site in Australia the following year. JAXA scientists then cataloged the individual particles using sterile tools in a state-of-the-art clean room and shipped them in airtight containers filled with nitrogen to researchers around the world, including Genge’s group. did.
But if these tiny threads were aliens, they would look and act much like hungry microorganisms on Earth, gorging themselves on the nutrients in Ryugu’s tiny specks. The species increased tenfold, and then became extinct due to the impact of scanning electron microscopy measurements from Earth. Curious scientists. While observing boom-bust cycles, Genge and his colleagues believe that the rods are almost certainly invaders from Earth, and that, despite researchers’ careful attention, they have somehow colonized small extraterrestrial samples. I realized that it had become. Humbly, they dutifully wrote up their findings and published them last month. “It’s a bit embarrassing,” says Genge, a planetary scientist at Imperial College London. “But as scientists, we have to tell the truth. It’s important to report these things.”
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Cases that require careful curation
That grains from Ryugu provided rich nutrients to terrestrial microorganisms is no surprise to scientists who study such primitive asteroids, which are usually packed with carbon-rich organic molecules. Rather, this incident is a reminder that even the most stringent protocols cannot always eliminate contamination of the planet. “I don’t think this is a failure of the team, but an unavoidable consequence of doing business on Earth in an environment where sterility cannot be ensured,” said a director at Carnegie Science’s Astrobiology Institute, who was not involved in the new research. says scholar Andrew Steele. Space agencies and scientists working with the samples make every effort to avoid contamination, and it is only through advanced technology and rigorous screening methods that such intruders can be detected even on the tiniest granules. It’s proof. “But ultimately, we live on a planet dominated by microbes, and chance events do happen,” Steele says. As such, this episode “gives us new avenues to research and learn.”
One lesson is that changing the way specimens are handled comes with risks. When Genge and his team first tested the grain in October 2022, no signs of bacteria were present. This suggests that the contamination may not have been due to some mistake in JAXA’s rigorous processes, but rather occurred during necessary preparatory steps in the Natural History Museum’s laboratory. In London, researchers removed the grain from the container to polish it for analysis. “We were very cautious, and no one was as careful as JAXA, because we don’t have the equipment,” Genge said. “All it takes is one bacterial cell on a specimen to contaminate it.”
This example “highlights the importance of curation and the value of making significant efforts to maintain these high standards during mission development,” the authors say of sample curation for the Hayabusa2 mission. says Toru Yada of JAXA, who has directed and published papers on meticulous sample curation. process. These precautions also apply to the construction, launch, and recovery of spacecraft, and while the likelihood of contamination within space agency facilities is extremely low, scientists around the world who do not have similar infrastructure have access to samples. It is inevitable that the risk will increase when a person is sent. “And[scientists around the world]make discoveries,” Genge said. “If you mistakenly think that contaminants are part of the sample, that becomes dangerous. You start to contaminate science with false assumptions.”
Genge’s best guess is that the rod-shaped fibers in Ryugu grains originate from microorganisms of the genus Ryugu. Bacillus. These hardy bacteria are known for their ability to rapidly inhabit new and extreme environments. However, no attempt was made to definitively identify it through DNA testing. Because the putative microorganisms were effectively trapped under the carbon coating applied for analysis. Several experiments on meteorites have shown that extraterrestrial material contains rich organic matter that could support life as we know it, sometimes for years. However, because microorganisms can survive in very small amounts, they usually do not alter the bulk composition of rocks in a way that scientists can easily detect, unless they achieve exceptionally large populations. The microfossils they leave behind can be valuable tracers of their presence, but distinguishing between genuine microfossils and abiotic processes that can imitate them is no easy task, and this has sparked a heated debate.
“If you find a microfossil (insert your favorite world), it could be a potential indicator of life,” says Manasvi Lingam, an astrobiologist at the Florida Institute of Technology. He was not involved in this research. However, the case of Ryugu sample contamination shows that “if we find these structures, we need to be careful that they were not somehow introduced by humans.”
Just a decade ago, scientists discovered that clean room etiquette allowed bacteria commonly found in nasal phlegm to enter NASA’s Surveyor 3 spacecraft, which sailed to the moon in the 1960s and whose parts returned to Earth. It was blamed on the bad behavior of the government. Since then, technology and protocols have advanced significantly to keep both cleanrooms and otherworldly exploration as natural as possible. Still, scientists continue to wrestle with similar difficult questions as they search for signs of extraterrestrial life in samples brought back from the Moon, Mars, and perhaps someday the intriguing icy moons of the outer solar system’s giant planets. no doubt.
For example, if NASA’s challenging Mars Sample Return (MSR) mission is successful, scientists hope to scrutinize carefully selected fragments of the world to understand their potential for life. “We are not only expecting organic-rich samples, but also preparing potential biosignatures,” the MSR team said in a statement. scientific american. “In addition to enhanced cleaning protocols, comprehensive sterilization of equipment and tools will therefore be required. This is part of our ongoing research and development efforts with our (European Space Agency) partners. ”
Microbial contamination is not a big concern for scientists working with Apollo-era lunar samples, because the Moon, which is close to Earth, has nothing that most living organisms can use for energy. With efforts like NASA’s, that could change in the future. Artemis III Lunar harvesting missions bring back material from areas that are a little more hospitable, such as ice-filled craters at the moon’s south pole. All such samples will be kept in their natural environment and loaned to institutionally accredited scientists who will be subject to security requirements. “NASA has taken special care of the Apollo samples,” says Darby Dyer, a geologist at Mount Holyoke College who is analyzing some of the pristine samples left behind by Apollo.
Similarly, as JAXA prepares for the 2026 launch of the Mars Moon Exploration (MMX) mission to bring back samples from the Martian moon Phobos, JAXA has begun monitoring the environment in which the spacecraft is being built. , Yada said, is developing protocols to deal with spacecraft exploration. I returned the sample. “We are publishing these curation procedures to share them with the global community… so that researchers receiving samples can have confidence in how their samples have been treated. “This is essential for interpreting scientific results,” he says.
Neither agency mandates specific infrastructure or procedures for institutions lending extraterrestrial samples, including to address microbial contamination. “Microbes are everywhere,” Dyer says of microbes. “From a scientific standpoint, you just do the best you can.” Thanks to advances in technology and screening tools, scientists are now able to understand the complex nuances of both biological and non-biological chemistry as much as they did just a decade ago. Now we can conduct research with a sensitivity that was unimaginable. Still, could we be fooled into mistaking ordinary old microbes and their lifeless remains on Earth for strange extraterrestrial life forms?
“This is something we in the Mars community have been working on for a long time,” Steele said. “The short answer is no, unless extraterrestrial life closely resembles terrestrial life.”
