The sample from the asteroid Ryugu was overrun with Earth-based life forms after they were brought to the planet, scientists have concluded in a study. The research, published in the journal Meteoritics & Planetary Science, explains how successful terrestrial microorganisms are at colonisation, even for extraterrestrial materials.

These samples have been collected by the Hayabusa2 spacecraft of the Japan Aerospace Exploration Agency (JAXA). It was launched in December 2014 and successfully rendezvoused with Ryugu in June 2018.

Later, it spent a year examining the asteroid having a diameter of roughly 3,000 feet (900 meters), before scooping out a sample, which returned to The Earth on December 6, 2020. Haybusa2 continued with its study of more asteroids. 

The sample was split and sent to different teams of scientists, including the one that conducted the latest research. Team leader Matthew Genge, who is from Imperial College London told Space.com that they have discovered microorganisms in the sample returned from the asteroid. 

“They appeared on the rock and spread with time before finally dying off,” Genge said.

The “change in the number of microorganisms” further confirmed these were living microbes. “However, it also suggested they only recently colonised the specimen just before our analyses and were terrestrial in origin,” Genge added.

The team observed filamentous microorganisms as the discovery took the form of filaments and rods of organic matter, Space.com reported.

However, the researcher noted the type of microorganisms was still unknown.

“Without studying their DNA, it is impossible to identify their exact type… However, they were most likely bacteria such as Bacillus since these are very common filamentous microorganisms, particularly in soil and rocks,” Genge noted.

The team has ruled out the possibility of these microorganisms being already there on Ryugu when the samples were gathered.

“Before we prepared the sample, we performed nano-X-ray computed tomography, and no microbes were seen,” Genge said, adding the change in population suggests they only appeared after the sample was exposed to the atmosphere upon its return to the Earth.