The hunt for extraterrestrial life has long been one of the most fascinating endeavors in science. As space exploration progresses and our understanding of the universe deepens, tantalizing headlines often emerge suggesting that “we are close” to discovering alien life. From news stories affirming that the detection of extraterrestrial life is “just a matter of time” to optimistic headlines such as “We’re probably not close” or “Nobody knows,” the portrayal of the scientific community’s beliefs is often framed in a positive light. But how much agreement is there among scientists, and what do they really believe about the likelihood of alien life in the universe?
In September 2023, we were told that the discovery of extraterrestrial life might be just around the corner, fueling speculation and excitement about the next big breakthrough. A year later, in September 2024, we were again assured that we are on the cusp of this discovery. But if we dig deeper into the actual opinions of scientists in the field, we find a more nuanced picture. Are scientists across the board as optimistic as these headlines suggest? Is there a consensus among experts in astrobiology, and are those not in the field equally optimistic?
In our recently published paper in Nature Astronomy, we sought to address these questions by surveying a wide range of scientists about their views on extraterrestrial life. Over a period from February to June 2024, we conducted four comprehensive surveys, asking scientists about the potential existence of basic, complex, and intelligent extraterrestrial life. The results shed light on the degree of agreement, disagreements, and even the deeper context behind the answers provided by the expert community.
The Survey: Methods and Participants
We surveyed two main groups of scientists: 521 astrobiologists—those specializing in the study of life beyond Earth—and 534 scientists from other fields, including physicists, biologists, and geologists, who might have less direct involvement in astrobiology but are still well-versed in scientific methods and concepts.
The survey specifically asked respondents for their opinions about the likelihood that extraterrestrial life, both simple and advanced, exists in the universe. In total, 86.6% of the astrobiologists surveyed expressed agreement or strong agreement with the statement that extraterrestrial life of at least a basic form exists somewhere in the universe. Remarkably, less than 2% of astrobiologists disagreed with this claim, and 12% remained neutral. These results suggest a broad consensus in the astrobiological community that the existence of extraterrestrial life is highly likely.
Interestingly, scientists from other fields, although not specializing in astrobiology, overwhelmingly concurred, with an 88.4% agreement rate. This finding is significant, as it suggests that the belief in the existence of life elsewhere in the universe extends beyond the specialty of astrobiology, raising the possibility that scientists from diverse backgrounds share similar assumptions about the universe’s ability to harbor life.
A Complex Picture: Complex Life and Intelligence
While nearly all scientists seem to agree that simple forms of extraterrestrial life likely exist, the question of more complex or intelligent life yields more mixed responses. For the possibility of “complex” extraterrestrial life, 67.4% of astrobiologists agreed, and for “intelligent” extraterrestrial life, 58.2% expressed agreement. Though these numbers still indicate a solid degree of optimism, the sharp drop in agreement compared to basic life suggests that scientists are more cautious about the chances of complex or intelligent life beyond Earth.
The results from other scientists were in alignment with those of astrobiologists: a total of 58.4% agreed with the possibility of complex life, while 47.6% agreed with the likelihood of intelligent alien civilizations. Disagreement on these questions remained low, with only 10.2% of astrobiologists expressing doubt about the existence of intelligent extraterrestrial life.
Are Scientists Just Speculating?
Given that we have no direct empirical evidence of extraterrestrial life at this time, one might wonder: are scientists merely speculating in their answers? After all, making conclusions without clear evidence is not a hallmark of good science. To address this concern, we included a “neutral” option in the survey, allowing respondents to acknowledge the uncertainty surrounding the question while avoiding speculation. Remarkably, only 12% of respondents—across both groups of astrobiologists and other scientists—chose the “neutral” answer, which suggests that most scientists are not uncomfortable with the idea of life beyond Earth.
So what justifies this optimism, considering the lack of concrete proof? Much of it rests on “indirect” or “theoretical” evidence that suggests the universe is teeming with environments where life could potentially arise. For example, we now know that habitable environments are relatively common across the universe. Within our own solar system, we find compelling examples on moons such as Europa and Enceladus, both of which harbor subsurface oceans capable of supporting microbial life. Mars, too, was once home to flowing rivers and lakes, further adding to the possibility that life could have existed or might still exist in some form there.
Moreover, scientists now recognize that life can arise from non-life—a process known as abiogenesis. Though the origin of the first life on Earth is still not fully understood, there is no compelling reason to believe that life requires extraordinarily rare conditions to emerge. Even in the most conservative scenario, the sheer number of potentially habitable environments suggests that life is not an improbability but a likelihood, albeit an uncertain one.
Interpreting the Survey Results
If we break down the survey results with this context in mind, we may see that the degree of agreement among scientists is not actually that surprising—it’s perhaps even weak relative to the vastness of the universe. For instance, even with very pessimistic assumptions about the likelihood of life starting on any given habitable world, optimists and pessimists would still likely agree that extraterrestrial life exists. The sheer number of potentially habitable worlds across the universe, estimated in the trillions, makes the case for life elsewhere quite compelling, even for those who hold more conservative views on the origin of life.
For example, if one assumes that only one in a billion billion habitable worlds in the universe could support life, that still yields an astronomically high number of worlds likely to harbor life. Thus, whether optimistic or pessimistic, most scientists would agree that extraterrestrial life exists. This viewpoint highlights how large-scale calculations, even when made with highly conservative estimates, are enough to drive a strong belief in the likelihood of alien life.
Discounting Neutral Responses: A Higher Agreement Score
Interestingly, if we disregard the 60 “neutral” responses from our survey, which represent scientists who felt uncomfortable speculating on such a significant matter, the agreement rate among those who took a stance (either for or against) climbs to 97.8%. This means that, when focusing only on the respondents willing to express a view, an overwhelming majority—over 97%—agrees that extraterrestrial life likely exists.
While disregarding neutral responses may seem controversial at first glance, it is not entirely without merit. In research, when faced with uncertainties, scientists often opt for the “safe” option of neutrality, as the risk of being wrong is eliminated. This tendency to “satisfice,” or choose the least risky option, is well-established in scientific practice. In this context, neutral responses likely reflect a reluctance to speculate, not a true absence of belief in the possibility of extraterrestrial life.
Conclusion: A Balanced View
The results of our surveys reveal a fascinating picture of scientific consensus on the existence of extraterrestrial life. While the lack of direct evidence makes definitive conclusions difficult, the overwhelming majority of scientists—both astrobiologists and those from other fields—believe that life, at least in some basic form, likely exists somewhere in the universe. The gap in agreement between the possibility of simple life and more complex or intelligent life shows a more nuanced view, one that acknowledges both optimism and caution.
Ultimately, the question of extraterrestrial life is far from settled, but these results demonstrate that there is a strong scientific belief in the plausibility of its existence. Whether we choose to present the agreement rate with or without neutral responses, both perspectives reveal valuable insights into the thinking of scientists on this profound topic. What is clear is that, as we continue to explore the universe, the discovery of extraterrestrial life remains not just a possibility, but a highly probable outcome.
Source: The Conversation
More information: Vickers, P., Gardiner, E., Gillen, C. et al. Surveys of the scientific community on the existence of extraterrestrial life. Nature Astronomy (2025). doi.org/10.1038/s41550-024-02451-0 , www.nature.com/articles/s41550-024-02451-0