In 2025, scientists found 'strongest hints yet' of life on Mars and K2-18b—but, a survey of hundreds of astrobiologists say we still haven’t found aliens

In 2025, two discoveries gave fresh momentum to the search for alien life. Scientists detected possible chemical signs linked to biological activity on the distant exoplanet K2-18b, while NASA’s Perseverance rover found unusual mineral features in a Martian rock known as Cheyava Falls that could potentially be a biosignature.

The findings quickly sparked headlines suggesting humanity might be closer than ever to answering one of its biggest questions: have we finally found evidence of life beyond Earth?

But when hundreds of astrobiologists were asked what they actually thought, the answer was far more cautious.


Only 6.6% believed the K2-18b evidence probably indicated extraterrestrial life, while 15.1% reached the same conclusion about the Martian discovery. Most scientists either disagreed or said the evidence was still too uncertain to make such a claim.

The survey, discussed by The Conversation and published in Nature Astronomy, notes an important distinction between finding a possible sign of life and proving that life is actually responsible for it.

K2-18b created enormous excitement

K2-18b became a major talking point in April 2025 after researchers reported possible detections of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) in the planet's atmosphere.

The molecules are interesting because biological activity on Earth can produce them. That does not mean their presence automatically proves life exists on K2-18b.

Detecting a potentially biological molecule on a planet more than 100 light-years away is very different from finding an organism or independently confirming that the molecule was produced by living things.

Still, the announcement quickly became one of the most widely discussed developments in the search for extraterrestrial life. The Conversation noted that coverage frequently portrayed the finding as a major step towards answering one of science's biggest questions.

But when researchers asked astrobiologists how convinced they actually were, the response was far less enthusiastic.

Researchers surveyed members of the international astrobiology community shortly after the announcements.

For K2-18b, just 6.6% of respondents agreed that scientists had probably found extraterrestrial life.Nearly two-thirds disagreed, while 28% remained neutral.

That is an important distinction.

The survey was not asking whether life on K2-18b was possible. It was asking whether scientists had probably found evidence of it.

The answer from most respondents was essentially: not yet.

The cautious response also reflects a broader problem in the search for alien life. A molecule that can be produced by organisms on Earth is interesting, but scientists need to establish that it cannot reasonably be produced by non-biological processes under the conditions found elsewhere.

Then came the mysterious rock on Mars

Several months later, something new caught news headlines - a distant exoplanet to a rock sitting on the surface of Mars.

NASA scientists studying a sample known as Cheyava Falls identified unusual mineral formations sometimes described as “leopard spots.” Similar features on Earth can be associated with chemical reactions involving microbial activity.

NASA described the finding as a potentially significant biosignature.

The discovery was exciting because, unlike K2-18b, Mars is close enough for spacecraft to examine its rocks directly. The Perseverance rover can study the geological setting in which the feature formed, collect samples and gather additional information about its chemical composition.

Even so, a potentially biological-looking feature is not the same thing as a fossil or living organism.

As the The Conversation analysis pointed out, scientists also have to consider the possibility that geological and chemical processes could produce features that resemble those created by life.

The survey produced a somewhat different response to the Cheyava Falls claim.

About 15.1% of surveyed astrobiologists agreed that scientists had probably found extraterrestrial life in the Martian material. That was more than twice the proportion who reached that conclusion for K2-18b.

But the majority still stopped short of accepting the discovery as proof. Around 44.6% disagreed, while 40.3% were neutral.

The peer-reviewed study found that astrobiologists were therefore more persuaded by the Martian evidence than by the K2-18b claim, although confidence remained far from overwhelming.

Why scientists are more cautious than the headlines

Part of the difference comes down to the nature of the evidence.

K2-18b is an extremely distant world. Scientists cannot visit it or directly collect samples. Instead, they analyse the light passing through its atmosphere and attempt to determine which molecules may be present.

That process involves complicated measurements and interpretation.

Mars presents a different opportunity. Spacecraft can examine rocks on the surface and potentially return samples to Earth for much more detailed laboratory analysis. Yet even on Mars, scientists have to rule out non-biological explanations.

This is one of the fundamental difficulties in astrobiology: life can create distinctive chemical and geological signatures, but nature can sometimes create similar signatures without life.

Scientists did not simply move from ‘no’ to ‘yes’

One of the most interesting findings from the survey was not simply how many scientists supported the claims, but how their level of confidence changed between the two cases.

For the K2-18b claim, 35.1% strongly disagreed that extraterrestrial life had probably been found. For Cheyava Falls, that figure dropped to 11.1%.

At first glance, that might look like a dramatic shift towards believing in alien life. But the researchers say the picture is more nuanced.

Much of the movement was towards uncertainty rather than outright acceptance. Scientists appeared more willing to say that the evidence deserved serious consideration without concluding that life had been discovered.

That distinction matters because scientific opinion is rarely as simple as a “yes” or “no.”

FAQ about alien life

Have scientists found alien life?

No. Most astrobiologists surveyed do not believe that extraterrestrial life has been confirmed.

What did scientists say about K2-18b?

Only 6.6% of surveyed astrobiologists said scientists had probably found extraterrestrial life on K2-18b. Most remained unconvinced or uncertain about the evidence.

What did scientists think about the Mars discovery?

Scientists were somewhat more open to the possibility of life on Mars. About 15.1% said the evidence from the Cheyava Falls rock probably indicated extraterrestrial life, but the majority still did not reach that conclusion.

Does K2-18b have signs of alien life?

K2-18b has shown possible chemical signatures that are associated with biological activity on Earth. However, scientists have not established that these molecules could only have been produced by life.

Could the strange features on Mars have been created without life?

Yes. Although the “leopard spots” on the Cheyava Falls rock could be associated with microbial activity, non-biological geological and chemical processes may also produce similar features.

Why haven't scientists confirmed alien life yet?
Researchers need stronger evidence that rules out non-biological explanations and can be independently verified. At present, both the K2-18b and Mars findings remain promising clues rather than proof of extraterrestrial life.

Does this mean scientists think alien life does not exist?

No. The survey shows caution about specific discoveries, not a rejection of the possibility of life beyond Earth. Scientists continue to search for evidence of extraterrestrial life on Mars, exoplanets and elsewhere.