Finding the right conditions for life off the Earth justifiably drives many a researcher's work, but nailing down just what might make the environment beneath an icy moon's surface benign isn't easy. The recent wave of speculation about Enceladus revolves around the discovery of phosphorus, a key ingredient for the kind of life we are familiar with. But Alex Tolley speculates in the essay below that we really don't have a handle on what this discovery means. There's a long way between 'habitable' and 'inhabited,' and many data points remain to be analyzed, most of which we have yet to collect. Can we gain the knowledge we need from a future Enceladus plume mission? by Alex Tolley  There has been abundant speculation about the possibility of life in the subsurface oceans of icy moons. Europa’s oceans with possible hydrothermal vents mimicking Earth’s abyssal oceans and the probable site of the origin of life, caught our attention now that Mars has no extant surface life. Arthur C...

Did Carl Sagan play a role in the famous Arecibo message transmitted toward the Hercules Cluster in 1974? I’ve always assumed so, given Sagan’s connection with Frank Drake, who was then at Cornell University, where Sagan spent most of his career. But opinion seems to vary. Artist/scientist Joe Davis, who now has affiliations with both MIT’s Laboratory of Molecular Structure and Harvard Medical School, noted in an email this morning that Sagan’s widow, Ann Druyan, supports the connection, but according to Davis, Drake himself denied Sagan’s role in the composition or transmission of the message. I mention all this because of Tuesday’s post on the simulated SETI signal being sent via ESO’s Mars ExoMars Trace Gas Orbiter, as a kind of work of art in its own right as well as a test case in building public involvement in the decoding of an unusual message. The idea of doing that irresistibly recalled Joe Davis because in 1988 Davis performed his own act of scientific art involving SETI,...

Now and again scientists think of interesting ways to use our space missions in contexts for which they were not designed. I’m thinking, for example, of the ‘pale blue dot’ image snapped by Voyager 1 in 1990, an iconic view that forcibly speaks to the immensity of the universe and the smallness of the place we inhabit. Voyager’s cameras, we might recall, were added only after a debate among mission designers, some of whom argued that the mission could proceed without any cameras aboard. Fortunately, the camera advocates won, with results we’re all familiar with. Now we have a project out of The SETI Institute that would use a European Space Agency mission in a novel way, one that also challenges our thinking about our place in the cosmos. Daniela de Paulis, who serves as artist in residence at the institute, is working across numerous disciplines with researchers involved in SETI and astronautics to create A Sign in Space, the creation of an ‘extraterrestrial’ message. This is not a...

With landers on places like Enceladus conceivable in the not distant future, how we might recognize extraterrestrial life if and when we run into it is no small matter. But maybe we can draw conclusions by addressing the complexity of an object, calculating what it would take to produce it. Don Wilkins considers this approach in today's essay as he lays out the background of Assembly Theory. A retired aerospace engineer with thirty-five years experience in designing, developing, testing, manufacturing and deploying avionics, Don tells me he has been an avid supporter of space flight and exploration all the way back to the days of Project Mercury. Based in St. Louis, where he is an adjunct instructor of electronics at Washington University, Don holds twelve patents and is involved with the university’s efforts at increasing participation in science, technology, engineering, and math. Have a look at how we might deploy AT methods not only in our system but around other stars. by Don...

The old trope about signals from Earth reaching other civilizations receives an interesting twist when you ponder just what those signals might be. In his novel Contact, Carl Sagan has researchers led by Ellie Arroway discover an encrypted TV signal showing images from the Berlin Olympics in 1936. Thus returned, the signal announces contact (in a rather uncomfortable way). More comfortable is the old reference to aliens watching “I Love Lucy” episodes in their expanding cone of flight that began in 1951. How such signals could be detected is another matter. I’m reminded of a good friend whose passion for classical music has caused him to amass a collection of recordings that rival the holdings of a major archive. John likes to compare different versions of various pieces of music. How did Beecham handle Delius’ “A Walk in the Paradise Garden” as opposed to Leonard Slatkin? Collectors find fascination in such things. And one day John called me with a question. He was collecting the...

The enigmatic ‘Oumuamua continues to stir controversy. Last week we looked at a new paper from Jennifer Bergner (UC-Berkeley) and Darryl Seligman (Cornell University), discussing a mechanism for the interstellar object’s unusual non-gravitational acceleration. The researchers explored the possibility that ice impacted by high-energy particles like cosmic rays would dissociate water in a comet to create molecular hydrogen within the ice. Was the warming of this hydrogen, all but undetectable according to the authors, the cause of outgassing and the anomalous acceleration? Image: This very deep combined image shows the interstellar object ‘Oumuamua at the center of the image. It is surrounded by the trails of faint stars that are smeared as the telescopes tracked the moving comet. Credit: ESO/K. Meech et al. Answering the question in a paper just submitted to the arXiv site is Harvard’s Avi Loeb, working with Thiem Hoang (Korea University of Science and Technology), who home in on...

Alex Tolley follows up his analysis of agriculture on Mars with a closer look at the Interstellar Research Group’s MaRMIE project – the Martian Regolith Microbiome Inoculation Experiment. Growing out of discussions on methods beyond hydroponics to make the Red Planet fertile, the project is developing an experimental framework, as described below, to test our assumptions about Martian regolith here on Earth. A path forward through simulation and experiment could help us narrow the options for what may be possible for future colonists. Fertile regolith, achieved through perchlorate removal, would open up possibilities far beyond what is achievable through hydroponics. by Alex Tolley Successful settlement of distant locations requires living off the land, which requires resourcing food. Failure can lead to disaster, as experienced by some of the early American colonies. While near Earth space settlements could be supplied with packaged food, this would be too costly for an expanding...

Robert Gray was something of an outsider in the community of SETI scientists, spending most of his career in the world of big data, calculating mortgage lending patterns and examining issues in urban planning from his office in Chicago. As an independent consultant specializing in data analysis, his talents were widely deployed. But SETI was a passion more than a hobby for Gray, and he became highly regarded by scientists he worked with, many of whom were both surprised to hear of his death on December 6, 2021. It was Jim Benford who gave me the news just recently, and it humbles me to think that a Centauri Dreams post I worked with Gray to publish (How Far Can Civilization Go?) appeared just months before he died. Gray’s independent status accounts for the lack of publicity about his death in our community, but I’m still startled that I’m only now learning about it. His name certainly has resonance on this site, particularly his book The Elusive Wow: Searching for Extraterrestrial...

The idea that life on Earth came from somewhere else has intrigued me since I first ran into it in Fred Hoyle's work back in the 1980s. I already knew of Hoyle because, if memory serves, his novel The Black Cloud (William Heinemann Ltd, 1957) was the first science fiction novel I ever read. Someone brought it to my grade school and we passed the copy around to the point where by the time I got it, the paperback was battered though intact. Its cover remains a fine memory. I remember being ingenious about appearing to be reading an arithmetic text in class while actually reading the Hoyle novel. In the book, the approach of a cloud of dust and gas in the Solar System occasions alarm, with projections of the end of photosynthesis as the Sun's light is blocked. Even more alarming are the unexpected movements of the cloud once it arrives, which suggest that it is no inanimate object but a kind of organism. I've been meaning to re-read The Black Cloud for years and this post energizes me...

Walking along dark streets this morning, as autumn leaves gusted past under a deepening lunar eclipse, I realized that there was a reason for my recent foray into what I called ‘Stapledon thinking.’ The reason: Landscape by moonlight. What these early walks remind me of is the beginning of Olaf Stapledon’s 1937 novel Star Maker, in which the narrator takes a similar walk in the darkness, musing on his personal relationships as well as his place in the larger structure of the cosmos (I’m using the word ‘structure’ there deliberately, as we’ll see later). The narrator walks to a hill overlooking houses below, somewhere near the sea. There is a lighthouse. He sits down on the heather. And now ‘the hawk-flight of imagination,’ in Stapledon’s lovely phrase, takes over. An astral journey begins: Imagination was now stimulated to a new, strange mode of perception. Looking from star to star, I saw the heaven no longer as a jeweled ceiling and floor, but as depth beyond flashing depth of...

How unusual that the study of an interstellar object should receive a boost from the United States Space Command, which is responsible for US military operations off-planet. But that’s part of the story of CNEOS 2014-01-08, which is described in its discovery paper as “a meteor of interstellar origin.” The 2019 finding came from Harvard’s Avi Loeb, working with then undergraduate student Amir Siraj. Loeb had been examining a catalog containing data on meteors over the last three decades in terms of the strength of their fireball, prompted by a 2018 fireball off the Kamchatka peninsula. The Kamchatka meteor produced a blast with ten times the energy of the Hiroshima bomb, leading Loeb to put Siraj to work on calculating the past trajectories of the fastest meteors in the CNEOS catalog – CNEOS is NASA’s Center for Near Earth Object Studies. In an email yesterday morning, Loeb explained that numerous factors went into the study. Siraj was able to work with the position and velocity of...

Just how likely is it that the galaxy is filled with technological civilizations? Kelvin F Long takes a look at the question using diffusion equations to probe the possible interactions among interstellar civilizations. Kelvin is an aerospace engineer, physicist and author of

Our recent focus on life detection on nearby worlds concludes with a follow-up to Alex Tolley's June essay on Venus Life Finder. What would the sequence of missions look like that resulted in an unambiguous detection of life in the clouds of Venus? To answer that question, Alex takes the missions in reverse order, starting with a final, successful detection, and working back to show what the precursor mission to each step would have needed to accomplish to justify continuing the effort. If the privately funded VLF succeeds, it will be in the unusual position of making an astrobiological breakthrough before the large space organizations could achieve it, but there are a lot of steps along the way that we have to get right. by Alex Tolley In my previous essay, Venus Life Finder: Scooping Big Science, I introduced the near-term, privately financed plan to send a series of dedicated life-finding probes to Venus' clouds. The first was a tiny atmosphere entry vehicle with a dedicated...

My prediction that we're going to find evidence for exo-life around another star before we find it in our own Solar System is being challenged from several directions. Alex Tolley recently looked at the Venus Life Finder mission, a low-cost and near-term way to examine the clouds of the nearest planet for evidence of biology (see Venus Life Finder: Scooping Big Science). Now we learn of advances in a ten-year old project at the University of Hawai'i at Manoa, where Anupam Misra and team have been working on remote sensing instruments to detect minute biomarkers. This one looks made to order for Mars, but it also by extension speaks to future rovers on a variety of worlds. Image: This artist's impression shows how Mars may have looked about four billion years ago. The young planet Mars would have had enough water to cover its entire surface in a liquid layer about 140 m deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars's...

We've looked before at the growing interest in exploring near-Earth space for evidence of probes from other civilizations that may have been sent in the distant past to monitor and report home on the progression of life in our Solar System. If extraterrestrial civilizations exist, the idea that one of them might have explored our system and left behind what Jim Benford calls a 'lurker' probe is sensible enough. We send probes to places we want to learn more about, and we would certainly have probes around the nearest stars if we had the means. Breakthrough Starshot is an example of such interest. A century from now, human probes to other stars may be commonplace. Various places to search for lurker probes have been suggested, from Lagrange points - where objects placed there tend to stay put, with minimal need for fuel consumption - to barely studied Earth co-orbitals to the surface of the Moon. But what about Earth orbit? Surveillance of the Earth could involve probes in long-term...

I've maintained for years that the first discovery of life beyond Earth, assuming we make one, will be in an extrasolar planetary system, through close and eventually unambiguous analysis of an exoplanet's atmosphere. But Alex Tolley has other thoughts. In the essay below, he looks at a privately funded plan to send multiple probes into the clouds of Venus in search of organisms that can survive the dire conditions there. And while missions this close to home don't usually occupy us because of Centauri Dreams' deep space focus, Venus is emerging as a prominent exception, given recent findings about anomalous chemistry in its atmosphere. Are the clouds of Venus concealing an ecosystem this close to home? by Alex Tolley Introduction The discovery of phosphine (PH3), an almost unambiguous biosignature on Earth, in the clouds of Venus in 2021 increased interest in reinvestigating the planet's clouds for life, a scientific goal that had been on hiatus since the last atmospheric entry and...

What can we say about the possible appearance and spread of civilizations in the Milky Way? There are many ways of approaching the question, but in today’s essay, Dave Moore focuses on a recent paper from Robin Hanson and colleagues, one that has broad implications for SETI. A regular contributor to Centauri Dreams, Dave was born and raised in New Zealand, spent time in Australia, and now runs a small business in Klamath Falls, Oregon. He adds: “As a child, I was fascinated by the exploration of space and science fiction. Arthur C. Clarke, who embodied both, was one of my childhood heroes. But growing up in New Zealand in the ‘60s, such things had little relevance to life, although they did lead me to get a degree in biology and chemistry.” Discovering like-minded people in California, he expanded his interest in SETI and began attending conferences on the subject. In 2011, he published a paper in JBIS, which you can read about in Lost in Time and Lost in Space. by Dave Moore I...

I often think of Dyson structures around stars as surprisingly benign places, probably motivated by encountering Larry Niven's wonderful Ringworld when it was first published by Ballantine in 1970. I was reading it in an old house in Iowa on a windy night and thought to start with a chapter or two, but found myself so enthralled that it wasn't until several hours later that I re-surfaced, wishing I didn't have so much to do the next day that I had to put the book aside and sleep. I hope I'm not stretching the definition of a Dyson construct too far when I assign the name to Niven's ring. It is, after all, a structure built by technological means that runs completely around its star at an orbit allowing a temperate climate for all concerned, a vast extension of real estate in addition to whatever other purposes its creators may have intended. That a technological artifact around a star should be benign is a function of its temperature, which makes things possible for biological...

We haven't found any technosignatures among the stars, but the field is young and our observational tools are improving steadily. It's worth asking how likely an advanced civilization will be to produce the kind of technosignature we usually discuss. A Dyson swarm should produce evidence for its existence in the infrared, but not all advanced technologies involve megastructures. Even today we can see the movement of human attention into cyberspace. Would a civilization living primarily within virtual worlds produce a detectable signature, or would it more or less wink out of observability? In 2020, Valentin Ivanov (ESO Paranal) and colleagues proposed a modification to the Kardashev scale based on how a civilization integrates with its environment (citation below). The authors offered a set of classes. Class 0 is a civilization that uses the environment without substantially changing it. Class 1 modifies its environment to fit its needs, while Class 2 modifies itself to fit its...