This book examines current scientific knowledge regarding the potential existence of extraterrestrial life through the multidisciplinary framework of astrobiology.

Based on more than four decades of the author's experience, including university courses, public lectures, and extensive engagement with scientific literature across multiple fields, this volume offers readers a structured and accessible pathway into one of today’s most dynamic areas of research.

Beginning with ancient philosophical perspectives, the book traces a coherent trajectory through biology, the evolution of stars, the formation of the Solar System, and scientific considerations concerning the possible presence of other intelligent beings in the Galaxy. It presents a wide-ranging scientific reflection on humanity’s place in the Universe, integrating insights from numerous disciplines and spanning centuries of intellectual inquiry.

In the coming years, new space missions throughout the Solar System and increasingly sophisticated analyses of exoplanetary atmospheres will open an unprecedented frontier in our understanding, one that is likely to lead to transformative discoveries.

Today, long-standing questions assume renewed significance: How did Earth and its atmosphere form and evolve, and when did life first emerge on our planet? Decades of research by geologists and biologists have produced possible answers, yet the discovery of more than 6,000 planets orbiting other stars, many broadly comparable to Earth, renders these questions even more compelling.

Biological insights further indicate that life on such extrasolar worlds could differ profoundly from terrestrial life, shaped by environments as distinctive as the isolated ecosystems found on remote islands on Earth.

Addressed to students and educated general readers, this book provides a rigorous and engaging introduction to the scientific foundations, open questions, and prospects of the search for life beyond our planet.

Giuseppe Galletta (born 1954) graduated in Astronomy from the University of Padua in 1975. After early teaching and a CNR fellowship, he worked as an astronomer at the Padua Observatory until 1986, when he joined the University of Padua as a professor, a role he held until retiring in 2020. He is affiliated with SIF, IAU, and ISSOL. He has taught extensively in Padua and Milan Bicocca and supervised numerous undergraduate and doctoral theses in Italy and France.

Since 1978, he has collaborated with Italian and international scientists. He discovered a category of galaxies with elongated structures revealing triaxial stellar potentials; demonstrated the correlation between isophote twisting and apparent ellipticity in elliptical galaxies and developed early models of their intrinsic shapes; and identified counter rotating gas in S0 and spiral galaxies, providing evidence for galaxy evolution through external matter accretion. From the mid 1990s, he also pursued astrobiology, teaching it since 2004 and co creating the LISA laboratory for Mars environment simulations. He continued research in galactic structure and astrobiology until retirement.

He has held numerous roles at the University of Padua and the CNR, participated in many international conferences, organized public astronomy outreach events, and contributed articles to scientific magazines. Details at https://www.galletta.it/gg.