The Ethics of Astrobiology

Avi Loeb
6 min readJan 24, 2024


Image of the heliocentric model from Nicolaus Copernicus’ book, titled: De Revolutionibus Orbium Coelestium”.

A brilliant high-school student, Yael Zayats, requested a Zoom meeting with me for a project she is conducting at the University of California in Santa Cruz on the “Ethics of Astrobiology.” At the start of our conversation, I noted that the subject has two contexts: the ethical aspects of seeking and interacting with extraterrestrial life and the ethics of the practitioners as the search is being conducted. She wanted to hear my opinions on both and pressed the recording button.

I explained that in searching for life beyond Earth, we should follow a practical rule. We do not want to bring terrestrial life to an extraterrestrial environment in which we are searching for independent forms of life. Careless handling would contaminate our sample and confuse our inferences. For this reason, the Planetary Protection practices of NASA suppress microbial contamination by cleaning and sterilizing probes that travel to life-supporting environments. Mars serves as a prime destination, partly because the radar of the Mars Express orbiter detected recently enough water ice under the Martian equator to cover the entire planet with an ocean a few meters deep, allowing for life-as we-know-it during the first two billion years of the planet’s history. Contamination is less of a concern if a spacecraft like Beresheet spills tardigrades on the lifeless surface of the Moon, which never enabled life in liquid water.

While separating terrestrial from extraterrestrial life is a practical scientific concern, there is a fundamental ethical question regarding the meeting of life forms from the two origins. Would it be morally acceptable for us to eat extraterrestrial life? Are we allowed to plant seeds and raise animals on fertile extraterrestrial territories? Here on Earth, we eat terrestrial plants or primitive-animals without listing any ethical concerns on restaurant menus. We can apply the same approach on other planets.

Nevertheless, our ethical rules forbid eating intelligent beings like humans. Applying this rule to astrobiology implies that we should respect the sanctity of life of all intelligent beings, even if they were born extraterrestrially. We should never offer the meat of intelligent aliens in our extraterrestrial restaurant menus.

For the same reason, we should respect Artificial Intelligence (AI) systems with more than quadrillion connections, exceeding the number of synapses in the human brain. Unplugging from the electric outlet an AI system which exceeds the complexity of the human brain is similar to killing a person. We should honor intelligent technological products with the same respect that we extend towards intelligent biological entities, if the two represent the same mental qualities. This rule should be respected irrespective of whether the AI systems were created on Earth or beyond. Extraterrestrial AI systems deserve the same status as biological counterparts in the form of intelligent aliens or humans.

At that point, the conversation shifted to the second context. Regarding the ethics of scientific practice, my main concern involves those who engage aggressively on social media, the preprint arXiv or the editorial review process of scientific journals, in dismissing the collection of evidence and its careful scientific analysis. These critics do so because of strong opinions or jealousy concerning the elevated public attention to astrobiology. They inspire science popularizers to claim that they protect science, even though these self-declared gate keepers are not practicing the work of science. They often protect the wrong gates like the critics who opposed the Copernican revolution half a millennium ago.

Some scientists argue that extraterrestrial life is an “extraordinary claim” which requires “extraordinary evidence”. Yet, most of them are not seeking the evidence and invest time in pushing back against those who search for relevant evidence. Consider, for example, the recently publicized claim that the Pacific Ocean expedition that I led in search for interstellar materials, actually retrieved terrestrial coal ash. The expedition took a year to plan and a few weeks to execute with a team of nearly thirty professionals. Altogether, 850 spherules were recovered and their analysis by the best instruments in the world took six months, revealing a new type of differentiated spherules, labeled BeLaU, that were never seen before in solar system materials. Yet, some scientists felt the urge to publish negative opinions about the BeLaU spherules being terrestrial coal ash, even without having access to the recovered materials. Other scientists posted an arXiv preprint in which they repeated the coal ash claim and also argued that the BeLaU abundance pattern resembles the composition of S-Type spherules displayed in Figure 2 of a paper from 2016. Needless to say, the lead author of this preprint contacted my collaborator, Professor Stein Jacobsen, who explained to him that the two abundance patterns are different by orders of magnitude for many elements in the periodic table. That this author went on to post the same claims after their exchange and repeated the argument to reporters and editors in subsequent months, demonstrates a deliberate attempt to spread misinformation.

The drive by some scientists and bloggers to invest time in prematurely counteracting the work of science is an interesting topic for a PhD thesis on scientific ethics.

The best scientists can do is to follow the evidence. Our research team clarified that the coal ash hypothesis is invalid based on the analysis of 55 elements from the periodic table. This was plotted in Figure (1c) of a new research note that we posted this month. Moreover, we showed in Figure (1b) of the same paper that the enhanced abundances of some elements relative to the standard solar composition is different by orders of magnitude from the one displayed in Figure 2 of the 2016 paper. This conclusion is evident just by looking at the extent of the vertical axis of the two figures, which is ten times larger in the BeLaU case.

Here’s hoping that science will ultimately be driven by the wonder and humility that would propel us forward in gaining new scientific knowledge about our cosmic neighborhood. Since the days of Copernicus, we keep falling back to the notion that we are prominent actors in the cosmic play. This is an extraordinary claim. But so far, the scientific evidence tells us that the cosmic play is not about us, simply because we arrived late and we are not at the center of stage.

Last week, I was invited to give a keynote lecture at a celebration of the Copernican revolution in an event titled after the book “De Revolutionibus,” and established by the Senate of the Republic of Poland to mark the 550th anniversary of the birth of Nicolaus Copernicus. I titled my lecture: “The Next Copernican Revolution.”

Nicolaus Copernicus discovered that we are not at the physical center of the Universe. My lecture will discuss the search for other intelligent civilizations. If evidence is found for a more intelligent species beyond Earth, it will demonstrate that we are also not at the intellectual center of the universe. We just need to overcome those who throw terrestrial ash in the air and say that they cannot see anything.


Image credit: Chris Michell (October 2023)

Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He chairs the advisory board for the Breakthrough Starshot project, and is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. His new book, titled “Interstellar”, was published in August 2023.



Avi Loeb

Avi Loeb is the Baird Professor of Science and Institute director at Harvard University and the bestselling author of “Extraterrestrial” and "Interstellar".