Has extraterrestrial life been discovered? What do the bacteria and organic matter found in asteroid samples signify?

In recent years, scientists have made significant strides in understanding the processes that led to the emergence of life on our planet. The results have sparked renewed interest in the search for extraterrestrial life. For instance, the rover Perseverance is exploring Mars, while the Europa Clipper mission has already departed to investigate Jupiter's moons.

Amidst this, the media has begun to feature sensational headlines about the discovery of the first extraterrestrial "organisms," often accompanied by classic conspiracy theories about "aliens in the backyard." It’s no surprise that readers who aren’t closely following the topic might find all of this quite confusing.

"The Telegraph" aims to provide some clarity.

"First Contact," but not necessarily

If we disregard the sensationalism and look at serious sources, we may come across the recent discovery of microorganisms in samples from the asteroid Ryugu.

The Japanese mission "Hayabusa-2" was launched in 2014 to collect soil samples from this relatively nearby asteroid. In 2020, these samples were successfully returned to Earth in a sealed container and were opened in a sterile lab under a nitrogen atmosphere.

And, of course, the last thing anyone expected to find in these conditions was living microbes. However, more detailed investigations revealed that common terrestrial bacilli had settled on a dust particle measuring 1 x 0.8 mm. Specifically, bacteria from the genus Bacillus.

These microorganisms are known for their resilience to extreme conditions and can survive even in outer space. For instance, the Japanese program Tanpopo demonstrated that even three years in microgravity outside the ISS did not kill their spores. Moreover, the conditions in which the Ryugu samples were kept certainly did not deter these bacteria.

Later, the sources of contamination were identified—human hair and fibers from laboratory wipes.

To be fair, it should be noted that the samples from the asteroid did indeed contain organic compounds, including the amino acid uracil, which is one of the "building blocks" for life.

Moreover, scientists realized that the bacteria preferred to accumulate on surfaces where organic matter was present. This suggests that the extraterrestrial origin of the material posed no problem for terrestrial microorganisms, which found a source of energy in it.

(Here, a joke about "aliens" being consumed by bacteria, as predicted by science fiction pioneer H.G. Wells in his classic book "The War of the Worlds," should have been made.)

There is still hope

News about the discovery of (terrestrial) life in samples from Ryugu spread through the media at the end of November 2024, and by January 2025, information emerged that organic material (not life!) was also found in samples from the asteroid Bennu. The variety of organic compounds discovered there turned out to be much richer than those from Ryugu: 14 out of 20 common amino acids on Earth, aldehydes, and carboxylic acids.

Notably, adenine, guanine, cytosine, thymine, and uracil were found there. These compounds are known as nitrogenous or nucleotide bases and together form RNA and DNA.

It is important to emphasize that all five necessary nucleotide bases for forming DNA and RNA were found on a single asteroid. Such a discovery is unique in itself and prompts us to reconsider where life could theoretically originate. It should be noted that a number of indicators (the ratio of nitrogen isotopes, molecular composition, the ratio of D- and L-forms of amino acids, etc.) clearly indicate that the organic material from Bennu indeed formed on the asteroid.

The high levels of ammonia and nitrogen suggested to scientists that the asteroid originated from the outer part of the Solar System. Additionally, there is compelling evidence that the precursors for the emergence of life could have been synthesized in space. It is possible that they ultimately made their way to Earth from there.

Interestingly, it was previously thought that a planet with an atmosphere was necessary for the formation of "life molecules." However, the new findings suggest that potential locations for the emergence of life in the universe could be far more numerous.

So what's the deal with aliens?

And here we return to the main question: have scientists found extraterrestrial life? The short answer is no.

Decades of marketing efforts and the fact that chemistry is rarely a favorite subject in school often lead to the misconception that the word "organic" is synonymous with "life." This is not entirely accurate.

Organic compounds are essentially all compounds that contain carbon (yes, including plastic). Carbon makes up about 0.5% of all matter in the universe, making it the fourth most abundant element after hydrogen, helium, and oxygen. The unique chemical properties of carbon allow it to form long polymer chains, enabling the creation of very complex molecules like proteins and amino acids. This is why all known life consists of this element from the periodic table.

In simpler terms—all life is organic, but not all organic matter is life.

In the quasi-scientific community, ideas about the emergence of life based on silicon, nitrogen, or sulfur are being discussed; however, this would require truly extreme conditions such as extremely high temperatures or immense pressure. Furthermore, the lack of chemical flexibility in these elements leads further discussions on this topic into the realm of science fiction. So, sorry, silicon-based beings, but we're talking about more serious matters here.

Carbon, in turn, is found even in outer space in the form of carbon monoxide (CO), methane (CH4), and carbon dioxide (CO2). As mentioned earlier, due to its properties, it can begin to form complex amino acids under the influence of external factors (such as ultraviolet light).

For example, in a study from November 2024, scientists explained how gamma radiation can "break" methane molecules, leading to the onset of more complex reactions. Ultimately, they managed to transform methane into the amino acid glycine, although not without intermediate steps.

In another experiment, glycine was able to form from simple compounds even in a vacuum at a temperature of -260 degrees Celsius and without external radiation. At that time, scientists suggested that organic compounds in space could have existed even before the first stars ignited.

Glycine, in turn, is a sort of "precursor" for more complex amino acids. And, of course, we have evidence of their synthesis in space—for example, more than 90 amino acids were found in the Murchison meteorite, some of which are even not utilized in terrestrial biochemistry.

Thus, the presence of complex organic compounds anywhere in space does not provide us with direct evidence of life there. However, if humans do find extraterrestrial life somewhere, it will likely be based on already existing organic compounds.

Colonizers

The study of contaminated samples from Ryugu mainly demonstrates that even the brightest minds of humanity can also be careless. But on the other hand, it leads to a rather intriguing conclusion—terrestrial bacteria can exist in soil samples from asteroids.

After all, they not only survived in "sterile" laboratory conditions but also attempted to consume extraterrestrial organic matter. Despite the harsh conditions, the availability of energy allowed them to reproduce every 5.2 days.

This raises the question: could they have ventured into space at some point during Earth's existence?

The probability of this is far from zero. For instance, they could have been ejected into space after asteroid impacts on Earth, or perhaps even more realistically, they traveled aboard human spacecraft.

After the Surveyor 3 (1967) and Apollo 12 (1969) missions, scientists found bacteria that were able to survive a trip to the Moon and successfully return to Earth—although contamination after their return cannot be ruled out. Additionally, a 2023 study demonstrated the possibility of bacteria reproducing in Martian soil (they just need some water).

Now we know that bacteria are far more resilient than previously thought, and NASA is already seriously concerned about the possibility of them reaching Mars. While there is currently no indication that they can independently adapt to Martian conditions, scientists want to ensure that the precious samples brought back from there will contain hypothetical "native Martians" rather than "newcomer" bacilli.

After all, distinguishing between them may be more challenging than we think. But that is a whole different story.