The origins of my new book - "First Contact: Scientific Breakthroughs in the Hunt for Life Beyond Earth" - lie more in journalism than in science. As a relatively recent convert to space and science writing at the Washington Post, I took the opportunity some years ago to attend a journalism "boot camp" at MIT titled rather grandly, "The Universe."

Almost all the presentations were interesting - explaining supermassive black holes, galaxy formation, the multiverse - but the talk that changed my personal path was delivered by Sara Seager, the Ellen Swallow Richards Professor of Planetary Science at MIT.

A young woman bursting with enthusiasm and knowledge (she was appointed to her position at the tender age of 34), she talked to us about exoplanets and their atmospheres - her specialty. Then she spoke words that I wasn't expecting to hear at MIT: "Sometime in the next generation, we will find signs of life beyond Earth."

Those signs could be on Mars, on one of the moons of Jupiter or Saturn, or in the atmospheres of distant exoplanets heavy with elements and compounds (oxygen, ozone) that generally can't exist in large concentrations without biology. Seager said she intends to be part of that effort and hopefully that discovery. As a longtime journalist but much shorter time science writer, my primary reaction was that of a reporter: My goodness, what a story!

What followed was three years of traveling the world to meet and learn from dozens of researchers involved in a myriad of other aspects of what I came to understand to be the booming discipline of astrobiology.

My journeys took me deep into the gold mines of South Africa to learn about extremophiles; to the mouth of an Alaskan volcano to understand better the chemistry and geology that could form the building blocks of life; to Chile's Atacama Desert with NASA scientists trying to understand methane releases on Mars at the European Southern Observatory; to Australia to watch planet-hunting at work, and to Japan to observe an unprecedented 23-facility SETI observation set in a different culture than ours.

Along the way, I had the pleasure of getting to know some of the best and brightest scientists in the far-flung field - from Princeton's extremophile expert Tullis Onstott and NASA Goddard's meteorite analyst Danny Glavin, to astrochemist Pascale Ehrenfreund and theoretical physicists and cosmologists Lee Smolin and Lord Martin Rees. To my delight and great benefit, I found all to be willing - eager, even - to spend their time to explain what they were doing and why.

What I learned was exciting and surprising to me, in both the details and the larger import. Because what the scientists told (and showed) me was that the search for life beyond Earth is further progressed than generally understood, and that the future for learning much more is bright indeed. Perhaps most important, what I came to understand is that the scientific logic for the existence of extraterrestrial life is very strong.

I liken it to the long-held hypothesis in astronomy that the cosmos is filled with exoplanets; a theoretical conclusion that had to wait for confirmation until the technology and knowledge needed to find them came along. With that confirmation - and the understanding that exoplanets are common around the 10,000,000,000,000,000,000,000 stars of the known universe - one essential prerequisite for extraterrestrial life was definitively met.

The other prerequisites, as I came to understand them, are: The lesson from extremophile studies that life is both extraordinarily tenacious and able to survive in conditions considered impossible not long ago; the understanding that the chemical building blocks for life (including complex carbon compounds) are ubiquitous in the universe; and the growing evidence that Mars was once wet and warm, and that it regularly belches out methane that just might be created from biological sources.

Put all these understandings (and more) together and you have a template for life beyond Earth. The increasingly credible hypothesis that the massively large number of stars in the known universe are home to billions of planets in potentially habitable zones just adds to the logic of life.

Because astrobiology takes in so many fields and approaches, it's impossible to predict what will happen in the years ahead - completely off-the-radar yet highly significant discoveries may be just around the corner. NASA's Mars Science Lab is sure to substantially increase our sense of the habitability of the planet, just as Kepler will be telling us far more about the census of exoplanets and to some extent their nature.

The history of astrobiology is undeniably filled with controversy - today's big discovery can be tomorrow's afterthought. But the field is also undeniably moving forward in hundreds of ways. That dynamism is part of what makes it so compelling - that, and the real possibility astrobiology will deliver significant discoveries in the years and decades ahead.

As "First Contact" describes, humans have imagined and longed for the existence of life in the skies and space beyond Earth for untold centuries. Some of the best scientific minds in the world, using some of the most advanced technology around, are now engaged in an unprecedented effort to find signs of that extraterrestrial biology. If they succeed (or is it when?), our own world will change forever.

Excerpt from "First Contact", used with permission
Science moves ahead on hunches. Tullis Onstott, a Princeton University geobiologist, first descended into a South African gold mine on a hunch in 1996, using $6,000 of his own money and carrying, instead of the usual pickaxes and dynamite, a small hammer, a chisel, some vials for collecting water, and some sterilized bags for collecting rocks.

Over the next decade, he and his fellow mine divers found microbes that broke nearly every rule of life. Until then, it was taken as scientific fact that to survive, a creature needs an energy source and an environment that isn't extremely hot or cold; isn't overly acidic, alkaline or salty; isn't suffused with radiation; or isn't under great pressure. Creatures also need to reproduce or split with some regularity. On his first trip into the mines, Onstott found microbes living as far down as two miles that struck out on virtually all of these counts.

His prized discovery, made a few years later and confirmed in 2006, was of a bacterium nourished by food - molecules, actually - split apart by energy released by the radioactive decay of surrounding rocks. The microbe also needs some minerals to survive and some water, which is hidden from human view until miners open up tunnels and bore holes, tapping into underground lakes, streams and even tiny fissures within the rocks. Not only do these microbes live and move around miles below the surface, but also they seem to split - that is, reproduce - as seldom as once a century.

A reading of the genome of Onstott's astounding bacterium, as well as analysis of the "age" of the water that is often its home, says that the microbe has not seen the light of day, or interacted with anything produced from sunlight, for perhaps up to 40 million years. But it has DNA, reproduces and is clearly alive.

The researchers who sequenced its genome found that the microbe has highly unusual abilities to take in needed carbon and nitrogen from nonliving sources - very useful abilities, given the absence of carbon-based life in its isolated and unrelentingly harsh environment.It even had genes for a tail of sorts, a whiplike growth that would allow it to swim to hidden sources of nourishment.

The bug, Onstott concluded, is widespread in a 130-mile-long subterranean region of the gold belt of South Africa. To honor the creature and the world to which it long ago traveled and made its home, the team (co-directed by geologist Lisa Pratt of Indiana University) sought a name in line with the achievement - first of the bug's existence, and then their discovery of it.

They found it in the secret Latin inscription on a scrap of parchment that Professor von Hardwigg, hero of the Jules Verne classic "A Journey to the Center of the Earth," comes across at the beginning of the book. The parchment directs him to a volcano in Iceland and tells him: Descende, audax viator, et terrestre centrum attinges (Descend, bold traveler, and you will attain the center of the Earth). And so the world was introduced to Desulforudis audaxviator, extremophile par excellence.

South Africa is today the center of Onstott's research not because similar microbial life doesn't exist far below New York or London or Tokyo, but simply because it is where the deepest mines have been dug. Onstott had first explored the deep underground for microbes as part of a Department of Energy drilling program in Savannah, Ga., and later at a Texaco well site in western Virginia.

Frustrated by his limited results and fearing contamination in his samples, he cast around for alternatives and landed on South Africa's gold, platinum and diamond mines - with shafts descending two miles and more. But mine owners were reluctant to let strangers into their domains. It took Onstott and others two years of negotiating to get into the mines to later achieve their breakthroughs.

Today, he and Esta van Heerden, the head of the Extreme Biochemistry research group at the University of the Free State in Bloemfontein, have won the confidence of the people who run many of the mines of the Witwatersrand Basin, the most productive in the world. When a potentially interesting section of mine is opened, or is going to be shut in forever, the mine operators now call van Heerden to give a heads-up.

Their cooperation has been a godsend to astrobiology and has led Onstott and others to conclude that D. audaxviator and untold trillions of other underground microbes also live miles below your shopping center, your bedroom, your favorite national park. Or miles below the surface of Mars, for that matter. Eons ago, our most similar planetary neighbor was far more hospitable to life than was Earth, which had endured the collision with a smaller planet that produced the moon.

But Mars somehow lost its magnetic field, its atmosphere and, thus, its ability to hold liquid water on its surface or to protect against solar radiation and deadly ultraviolet light. Mars scientists have long speculated that primitive organisms met the new challenges by descending below the surface and adapting through a desperate evolution. Now, living proof exists of a potentially parallel scenario on Earth.