HOPES of finding traces of alien life in the universe have been scuppered yet again.
And this time on asteroid Ryugu, a space rock with an orbit that passes between Earth and Mars.
The Japanese Space Agency’s (JAXA) Hayabusa2 spacecraft retrieved the samples from Ryugu in 2019.
Last year, stunned researchers found two organic compounds that are essential for living organisms in samples of the distant asteroid.
The discovery supported the theory that perhaps space rocks like asteroids and meteors carry seeds of alien life used colonise the galaxy.
But a team of researchers, led by Matthew Genge of Imperial College London, have since squashed that theory – at least in relation to asteroid Ryugu.
In a recent paper published in the journal Meteoritics & Planetary Science, researchers confirmed that while the samples did host evidence of microbial life – it was not from an unknown alien species.
The microorganisms, instead, originated a lot closer to home: on Earth.
The findings indicate that the samples got contaminated by human microorganisms – tiny, microscopic creatures like bacteria, fungi and viruses.
Trillions of microbes live in and on the human body, helping it to digest food and even fight against infection.
The discovery has branded these microorganisms the “world’s greatest colonisers” for their ability to spread even with the greatest precautions.
“The presence of terrestrial microorganism within a sample of Ryugu underlines that microorganisms are the world’s greatest colonisers and adept at circumventing contamination controls,” the paper reads.
“The presence of microorganisms within space-returned samples, even those subject to stringent contamination controls is, therefore, not necessarily evidence of an extraterrestrial origin.”
The “box of treasure”, as Nasa affectionately named the samples, were transported in hermetically sealed chambers, and opened in nitrogen filled clean rooms.
Each particle was picked with sterilised tools, which were stored under nitrogen in airtight containers.
“The discovery emphasizes that terrestrial biota can rapidly colonize extraterrestrial specimens even given contamination control precautions,” the team concluded.
Space samples may even provide an untouched breeding ground for Earth-based microorganisms.
Here's what you need to know, according to Nasa...
The Hayabusa2 spacecraft collected the samples in February 2019, and delivered them to Earth in December 2020.
The rocky grains were extracted in Japan in July 2021 and analysed at Nasa’s Goddard Space Flight Centre later that same year.
A small amount of sample – 30mg or roughly 0.001 ounce – was allocated for the international soluble organic analysis team.
The sample was extracted like tea, according to Nasa, in many different solvents in Japan and analysed in labs in Japan, Goddard, and Europe.
The Ryugu samples will be studied for years, alongside crumbles of asteroid Bennu that were collected by Nasa’s OSIRIS-REx mission.
Launched in 2016, the OSIRIS-REx mission’s target was Bennu, a “near-Earth” asteroid thought to have formed during the solar system’s first 10million years.
The Bennu samples were returned to Earth in 2023, and eventually opened in January 2024 after some struggle opening the container they were stored in.
