The search for alien life has ramped up to a fever pitch lately. METI (Messaging Extraterrestrial Intelligence) International is ramping up plans to send purposeful, information-rich signals into space in 2018. Astronomers gathered a few weeks ago to discuss the neutron star that is the source of mysterious fast radio bursts first detected in 2001 and posited to be evidence of an advanced alien civilization. The news is rife with reports of possible alien life.
With that in mind, we spoke to Daniel Apai, Assistant Professor of Astronomy and Planetary Sciences at the University of Arizona. Apai is the Principal Investigator of the Earths in Other Solar Systems (EOS) Team, a NASA-funded astrobiology research program that seeks to learn how and where habitable, earth-like planets form. Here is part 1 of our interview.
RECURSOR: If it is possible for life to evolve elsewhere, where would you expect it to evolve?
APAI: As of now, the only place we know that hosts life is Earth; based on that, we expect that life can evolve on similar planets. We have several other reasons to believe that planets are the best environment for life to evolve: They can provide relatively stable physical and chemical conditions. They may often have all the ingredients complex life needs. And — at least on habitable planets — the temperatures are warm enough but not too high to allow liquid water to exist. Liquid water is an essential component for terrestrial life for multiple reasons, and we expect it to be also a requirement for extra-terrestrial life forms.
Nevertheless, if the conditions are right — the ingredients for life are available, energy is available, and temperatures are suitable — environments other than planets can potentially allow life to emerge. The key questions are how stable are the conditions, and how long does it take for life to emerge.
What would life be like if it evolves in places like stars and space, rather than planets?
To be clear, we do not think that stars can provide the right environment for life to exist inside them; temperatures are just too high to allow the existence of complex molecules. Similarly, in space where temperatures are mostly extremely cold, we do not expect unprotected life to survive. Rather, we expect that life will need some intermediate temperatures: warm enough to allow active chemistry to occur (that is, not fully frozen) but cold enough that complex molecules can exist.
The idea that life could exist in room-temperature layers of atmospheres of otherwise uninhabitable planets (like Venus) or low-mass brown dwarfs (Jupiter-like but unbound objects) is very interesting and has been around for a long time. Among others, Carl Sagan has explored it. This idea is inspired by the fact that in Earth’s atmosphere, including in water vapor droplets in clouds, we can frequently find organisms in active or dormant states. Few, if any, of those organisms, however, live permanently in the atmosphere. Probably they are most likely traveling through, transported by winds and dust particles.
Daniel Apai is an astrophysicist specializing in studies of the formation and atmospheres of extrasolar planets with the long-term goal of identifying planetary systems capable of supporting life. The author of over ninety refereed research papers, he has also edited and consulted on multiple books. Apai is principle investigator of major programs on the Hubble and Spitzer Space Telescopes, and is currently serving as Assistant Professor in the Department of Astronomy and Department of Planetary Sciences at the University of Arizona. He can be reached through his blog, distantearths.com.