The central goal of Astrobiology is to understand the origins and evolution of life in the universe: how biogenic compounds combine to create life, how life affects - and is affected by - the environment from which it arose, and whether and how life might expand beyond its planet of origin. As practiced today, this emerging field is a very broad and intensely cross-disciplinary enterprise that includes a wide variety of work at the cutting edge of research in the life and physical sciences. The main disciplines relevant to astrobiology are astronomy and astrophysics (esp. planet formation and detection, planetary atmospheres, planetary systems dynamics, cosmochemistry), biochemistry (molecular chemistry, microbiology, genetics and information theory), biology (ecology, evolutionary and developmental biology), chemistry (organic and inorganic), geology (geochemistry and paleontology, oceanography, climatology), medicine (environmental health, epidemiology, neuroscience, ethics), anthropology (human origins), and philosophy.

Some of the specific questions and topics currently investigated by astrobiologists include:

• How do life and its host planet affect each other over time?
• How can we assess a planet's life history?
• How do you get from simple chemistry to self-replicating life forms?
• Life in extreme environments ('extremophiles'): is this how life started on Earth - and what we can expect to find on other planets?
• Large scale planetary impacts: ecosystem devastation and recovery.
• Planetary protection: preventing an undesirable interplanetary mix of life forms.
• Extrasolar planets: finding them and evaluating their biological potential ('habitability').
• Searching for - and communicating with - extraterrestrial intelligence.
• Nervous systems: how did Earth affect their development - and how will they respond to the space environment?
• Muscle and Bone: what happens when weight-bearing structures no longer have weight to bear?
• Is life a natural consequence of planetary formation?
• How are the raw ingredients of life formed, distributed, and recycled in the universe?
• What is the smallest, most fundamental level at which life perceives and responds to gravity?
• What will it take for terrestrial life to survive and adapt to environments in space and on other planets?
• How will human culture adapt and evolve in extraterrestrial environments?
• Why are we so interested in leaving Earth to explore the universe?
• Philosophical and ethical aspects of these questions.

Although seemingly disparate, these many questions and topics have recently been combined very effectively into large interdisciplinary projects, as scientists now realize that many of our oldest fundamental questions ('Where did we come from?') cannot be fully understood unless viewed from a larger perspective than just our own Earth.

This is perhaps best illustrated by the work of the new NASA Astrobiology Institute (NAI), founded in 1998. Now composed of 16 Lead Teams, which together represent over 700 investigators across the US and Europe, the NAI is devoted to the study of the origin and evolution of life in the universe. Through the NAI, biologists are now working with astronomers to describe the formation of life's chemical precursors, to discover new planets and determine their habitability; with chemists to understand the transition from molecular interaction to life itself; with geologists to search for evidence of water and key minerals on other planets; with paleontologists and evolutionary molecular biologists to look for and comprehend the earliest forms of life, as well as with climatologists, planetary scientists, etc. Also of great interest to NASA (particularly in the new context of President Bush's 'New Vision for Space Exploration' Program) and part of the NAI research is the study of the effects of outer space on living organisms from Earth, including the health effects of prolonged space travel on humans.