Quite a few books on astrobiology have come out in recent years. Perhaps many readers would find this shortish one's reportorial style to their liking. I personally prefer the depth and insights found in professional astronomer Chris Impey's (_Talking About Life_) interviews of numerous experts.

Author Mark Kaufman believes that before the end of the century, maybe well before, scientists will have determined that life exists elsewhere in the universe, and his book makes a fascinating and compelling case for it. Before they can do that however, scientists will have to determine exactly what life is, a question that is surprisingly hard to answer because it is not always clear what is alive and what is not. One example is the case of desert varnish, an extremely slow growing patina found on desert rocks that may be showing properties of life. Or maybe not, that’s still being researched.

The more scientists learn about life on Earth, the stranger it seems. It used to be taken as scientific gospel that all forms of life reproduce regularly, need an energy source, and depend on having an environment that isn’t exceedingly hot, cold, acidic, alkaline, or salty, and isn’t under crushingly high pressure or full of radiation, but living things have been found in all of these circumstances. Extremophile life forms manage just fine in scalding hot hydrothermal ocean vents, highly acidic rivers, arsenic filled lakes, glacial ice, clouds high in the sky, and rocks that are miles underground. Finding life in these almost other worldly places may mean life can exist in other harsh seeming environments, like under the Martian surface or in the icy oceans of Jupiter’s moon Europa.

It turns out that Mars was much more habitable than Earth in the long ago days when the Earth was recovering from a collision with another planet that broke off what is now our moon. Mars became the barren landscape it is now after it somehow lost its magnetic field and atmosphere, but if some form of life was already established it may still survive deep underground, since scientists have found that life exists in similar conditions on Earth.

The elements that are needed for life on Earth, which include carbon, oxygen, nitrogen and hydrogen, are found all over the universe, so scientists are aiming strong telescopes at distant stars looking for planets that might be able to support life as we know it, or maybe life as we’ve never conceived of it. The nebulas that form stars produce complex carbon molecules and these may be seeding any nearby planets with the building blocks of carbon based life.

Kaufman is confident that there is life elsewhere in the universe, but he does a thorough job presenting the conflicting opinions and many unsolved issues of the extraterrestrial life question, including the controversies surrounding the 1976 Viking mission to Mars and whether the Muchison meteorite from Austraila shows evidence of otherworldly organic carbon. The last chapter covers the moral, religious and ethical implications of discovering that we may be sharing the universe with other, possibly intelligent, living beings. What obligations would we have to such creatures? What would they mean for the world’s religious beliefs? These issues are part of an ongoing discussion by ethicists, philosophers, and religious leaders, including the Vatican.

If you follow news reportage about extremophiles, exoplanets and the search for life, this book will connect the dots and provide context to stories as recent as the “Goldilocks” planet, the new revelations about the famous “primordial soup” experiments, and the microbes found with high levels of arsenic in Mono Lake, California. First Contact is so irresistibly interesting I found myself reading the best parts aloud to whoever happened to be around me at the time. ( )

Imagine the proverbial search for the needle in the haystack. Fortunately, anyone searching knows what a needle is. Multiply the strands of hay billions of times and you're approaching one of the haystacks in which those in search of extraterrestrial life are working. Yet their effort struggles with a fundamental question: How do you define "life"? As science journalist Marc Kaufman points out in a new book, the answer is not as easy as it might seem. More important, the definition ultimately arrived at could mean we already have proof that life exists beyond Earth.

To say that Kaufman's book, First Contact: Scientific Breakthroughs in the Hunt for Life Beyond Earth, surveys a huge range of possible haystacks is an understatement. He takes us from beneath the surface of our planet, where scientists hunt for and study "extremophile" microbes that alter our views of what is necessary for life to exist, to observatories and labs searching deep space for extraterrestrial signals or exoplanets, planets outside the solar system. Not only does the book suggest the breadth of the effort, it reveals how each aspect reveals ideas and science never before suspected.

For example, there is the question of what Kaufman calls "a possible shadow biosphere." Is there life on Earth that was not previously considered life? First Contact takes us to research at an alkaline lake in California that led NASA to announce in December 2010 the discovery of an organism that uses arsenic in its cellular structure, an element that is not one of the six essential elements necessary for life on Earth. If terrestrial "life" can be arsenic-based and extremophiles can exist in circumstances previously thought incapable of supporting life, it becomes that much more likely that life exists off the planet,

In exploring these investigations and their ramifications, Kaufman does what excellent science reporters do -- he translates at times difficult concepts into language those of us who barely passed "Bonehead Chemistry" can understand. This is no small feat, given that Kaufman himself was new to the field of astrobiology and, as he puts it, some of those involved in the effort use "a language that can often seem mysterious and impregnable." Perhaps due to the need to keep the information as accessible as possible, Kaufman tends to a bit of repetition. That is a relatively minor flaw in light of his approach. Whether descending into the South African mines, visiting observatories in Australia or going to California's Mono Lake, First Contact also introduces the reader to the scientists. Readers aren't left with the science and what the scientists are studying. Kaufman, science writer and national editor at The Washington Post, also personalizes the researchers and their work.

This also enables readers to better grasp some of the ongoing debates about whether we have already discovered extraterrestrial life. First Contact reviews the questions surrounding whether Mars landers found evidence of life on that planet. Kaufman updates the ongoing debate that began some 15 years ago when scientists suggested their study of a meteorite from Mars contained microfossils of primitive bacteria. He also explores the scientific studies going on beyond Earth, Mars and the solar system. He explains how scientists search for exoplanets and how older instruments utilize new technology and computing power to crunch massive amounts of data to plot one or two points. Even long-recognized efforts introduce debates. Thus, when SETI, the Search for Extraterrestrial Intelligence using radio telescopes, makes an appearance, Kaufman introduces readers to the question of whether it is wise for us to broadcast or announce our presence to possible extraterrestrial intelligence.

Even if we don't reach a universal definition of life first, Kaufman suggests we may be on the cusp of one of the greatest "Eureka!" moments in human history. Given how how broad-based the search for extraterrestrial life has become, the fundamental question may become what its discovery means for human society.

(Originally posted at A Progressive on the Prairie.)