Editor's Note: This article by the distinguished astronomer Jennifer Wiseman first appeared in the September/October 2011 issue of Books & Culture.

Will we, as Earthlings, ever find extraterrestrial life, and what will it mean if we do or don't? Those are the provocative questions explored by Jeffrey Bennett in Beyond UFOs: The Search for Extraterrestrial Life and Its Astonishing Implications for Our Future. While the title evokes visions of flying saucers and E.T., the book could perhaps be further subtitled "When Real Science Confronts Science Fiction" or "What Life Out There Are We Actually Likely To Detect?" Despite Bennett's hopes that alien civilizations exist, he makes very cogent arguments for why it is illogical that any such beings would dash in and out of our sights in the manner popularly attributed to UFOs.

What Bennett does present is actually much more exciting: the new science of astrobiology, seeking to determine what conditions both on and beyond Earth are conducive to sustaining life. We live in the most fertile time in history for discoveries regarding the universe, especially the burgeoning detections of extrasolar planets—planets orbiting stars other than our Sun. While just 20 years ago only a handful of extrasolar planets had been detected, the technology and techniques for finding these small bodies has dramatically progressed to the point where hundreds of extrasolar planets, mostly the large gaseous Jupiter-type, have been found, with a continuing focused goal of finding planets more and more like Earth. And this year, NASA's Kepler space telescope scientists announced over a thousand more candidate stars that are possibly hosting extrasolar planetary systems, the evidence seen from the periodic slight dimming of the star as an orbiting planet passes in front. From the Kepler mission's initial findings, it looks like at least a third of all stars have planets. Thus in the span of two decades we have moved from hypothetical extrasolar planets to real entities suitable for scientific study. We have even progressed from simply "finding" them to actually characterizing them, that is, determining simple descriptors like mass, radius, orbit, and the presence of an atmosphere.

Could any of these planets host life? Could we detect simple life forms as well as advanced life? Is Earth unique, or are planets like Earth common? These are the big questions now coming into the scientific viewfinder. The quest weaves together several branches of science. Starting with ancient Greek views of the natural world and then moving through Ptolemy, Copernicus, Kepler, and Galileo, Bennett first presents what "science" really is and how we now arrive at scientific conclusions. Then he turns to the basic biological questions: what exactly IS life, and how would we recognize it? The familiar schoolbook answers are no longer adequate. Even on our own planet, we are finding weird life forms—extremophiles—living under conditions that ought to kill everything; at the same time, we find "non-life" acting in some sense like life—reproducing, for example. Bennett concludes that life must share at least three properties: it creates order out of chaos; it makes copies of itself, but not quite perfectly (so variations can allow the natural selection of traits adaptive to changing environments); and it evolves through time.

And what does it take for a planet to be habitable for life? The simplest test is whether it is in the "Goldilocks" zone relative to its parent star, such that it is neither too hot nor too cold for liquid water (currently seen as one common need for all life) to be present. But Bennett describes how complicated the situation really is, with a planet's atmosphere, geology, radiation, history, oceans, and even feedback from life itself all contributing to environmental conditions that may support or extinguish sustained life, once it has begun.

Some of the environmental features increasingly understood as required for life to thrive can also, in certain settings, be catastrophic for life. Consider this: plate tectonics, responsible for horrific earthquakes, devastating countless lives, are now considered essential for recycling the atmosphere and regulating the temperature of "living" planets like Earth. Oceans "lubricate" the system, allowing surface plates to slide. Carbon dioxide from the atmosphere gets deposited to the ground by rain and dissolves into rocks and minerals that are carried to the sea, ending up in the sediments on the sea floor. As plates move, one plate can get subducted under another, carrying the sea floor sediments deep into the hot mantle of the continent. The hot material is eventually vented out into the atmosphere through volcanoes, completing the cycle. Without oceans, rain, and the motions of plate tectonics, the atmosphere would get overburdened with carbon dioxide. This is why Venus, it is posited, is an unbearably hot greenhouse planet, overburdened with thick atmosphere and unsuitable for life, even though it is also in the "habitable zone" around our Sun, as Earth is. Venus, however, has not had the benefits of oceans and plate tectonics to the extent that Earth has. In short, Earth life has needed plate tectonics, the same dynamics that also spawn the earthquakes that cause so much suffering.

How does life get started in the first place? Though this is a question still unanswered by science, Bennett gives a good description of the basic natural conditions that might be conducive for first life. Beyond UFOs is not a theological book, but Bennett does pause early on to address the question, "Where does God fit into this picture?" He points out the devout Christian faith of foundational scientists like Kepler. And, while denouncing Intelligent Design approaches as non-scientific, he states clearly and refreshingly that science, when correctly understood, can be completely compatible with faith in God, pointing out the fallacies that occur when either scientific understanding or biblical interpretation is stretched beyond its proper bounds. "Indeed," Bennett emphasizes, "the lack of conflict between science and religion seems to me so self-evident that I'm flabbergasted at the fact that not everyone else sees it the same way. Can everyone just calm down, and realize that science and religion do not pose threats to one another?"

But what about the actual detection of life beyond Earth? Is Christian belief broad enough to encompass extraterrestrials? Bennett does not delve into such issues. But others have, and with gusto. The Vatican, through its Pontifical Academy of Sciences, held its first major conference on astrobiology in November 2009. "Why is the Vatican involved in astrobiology?" Father Jose Funes, Director of the Vatican Observatory, asked rhetorically in The Washington Post (November 2009). "Although astrobiology is an emerging field and still a developing subject, the questions of life's origins and of whether life exists elsewhere in the universe are very interesting and deserve serious consideration. These questions offer many philosophical and theological implications." Surveys of beliefs on the issue, especially the "religious crisis" survey of theologian Ted Peters, have shown that almost no one, regardless of faith tradition, feels that the detection of life beyond earth would be a devastating blow to their own religious beliefs. Most Christians seem to feel that finding simple life elsewhere could be seen as a natural extension of the gracious life-giving power of God, and would be compatible with a biblical worldview. Indeed, Dominican Father Augustine Di Noia affirms, following Funes, that "Christians have always understood that the entire cosmos is a creation of God, that any life anywhere is a divine creation. There would be absolutely no motive for scandal if scientists were to establish the existence of life elsewhere."

And yet when it comes to the possibility of intelligent life and civilizations beyond Earth, Christians face a tough consideration of how seemingly Earth-bound works of God could extend beyond. How would original sin, the atonement of Christ Jesus, and the Incarnation (that is, God in human form) transfer to intelligent non-humans elsewhere? Physicist and author Paul Davies muses, also in the Post, that "The real threat [to Christianity] would come from the discovery of extraterrestrial intelligence, because if there are beings elsewhere in the universe, then Christians, they're in this horrible bind. They believe that God became incarnate in the form of Jesus Christ in order to save humankind, not dolphins or chimpanzees or little green men on other planets." Well, maybe not actually a horrible bind at all, if we give God some credit for being able to redeem Creation beyond Earth in ways that may not have been fully revealed to Earthlings. Billy Graham says, "I firmly believe there are intelligent beings like us far away in space who worship God. But we have nothing to fear from these people. Like us, they are God's creation." [1]

Beyond UFOs is a rich, slow, and rewarding read. Rich because it is full of some of the most interesting current interdisciplinary science regarding planets and life that you can find, blending astronomy, geology, history, and astrobiology in a single narrative. Slow because each page is so full of interesting content that you don't want to skim. Rewarding because Bennett is simply a fantastic writer and presenter, making the read thoroughly enjoyable. No science expertise required.

Bennett bookends Beyond UFOs with a fundamental question known as Fermi's paradox: If life is indeed prevalent in the universe, and if even some of these inhabited worlds harbor intelligent civilizations, then why haven't we encountered them? Where is everybody? Having explained why reports of alien sightings and abductions are not credible, Bennett speculates on three possible answers to the paradox: we are truly alone in the universe; there have been many civilizations scattered throughout the galaxies, but—ominously—all of them "have destroyed themselves before reaching the point at which their technology could take them to the stars"; or, finally, Bennett's preferred solution: advanced life is everywhere, but we are not yet ready and able to detect it. If astrobiology continues to develop at its present pace, perhaps that will change.

Jennifer Wiseman is an astronomer, speaker, and author. After heading the Laboratory for Exoplanets and Stellar Astrophysics at NASA's Goddard Space Flight Center for several years, she recently assumed the role of Senior Project Scientist for the Hubble Space Telescope. She also directs the Dialogue on Science, Ethics, and Religion for the American Association for the Advancement of Science. The opinions expressed in this review are her personal views.

1. As quoted by Ted Peters in Science, Theology, and Ethics (Ashgate, 2003), p. 126.

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