Finding Life Beyond Earth and Solar System – Space and Science Documentary

Finding Life Beyond Earth and Solar System  - Space and Science Documentary Listen

A livestream from The Universe published in Space

Life as we know it is a planetary phenomenon: its origin appears to have required interactions among liquid water, a gaseous atmosphere, and minerals provided by a solid planetary surface. The energy required to produce the appropriate chemical reactions was available from solar ultraviolet light, bombardment by charged particles, meteoritic impacts, local volcanism, hydrothermal vents, lightning discharges, coronal discharge, and even acoustic shocks.

A nearly circular orbit about a stable star promotes fairly uniform conditions for the billions of years required (at least on Earth) for life to evolve from single cells with no nuclei to multicelled intelligent organisms. The evolution and dispersion of life on Earth have radically altered the surface, oceans, and atmosphere of this planet in ways that are discernible from a remote observational vantage point. During the past 1.5 to 2 billion years, a distant observer would have found presumptive evidence for life on Earth in the oxygen-rich nonequilibrium chemistry of the Earth's atmosphere. More recently, the microwave signals generated by human technology could provide that same remote observer with circumstantial evidence for the existence of some form of intelligence on the planet Earth.

These two examples of life detection should apply to other planets as well. Isolating the light or thermal radiation of a distant planet from the brilliance of its star would enable us to examine the spectrum of the planet and search for chemical evidence of the existence of life. This evidence would take the form of some massive departure from chemical equilibrium, a large amount of free oxygen being the most obvious example and probably the most observationally traceable. However, the detection of trace gases such as CH4, NH3 N2O (nitrous oxide), and CS2 (carbon disulfide) in excess of the amounts predicted by chemical equilibrium and plausible nonequilibrium sources might also provide presumptive evidence for life if the 4-to 11-µm region of the spectrum could be accessed. Detection of signals generated by an extraterrestrial technology would be even more compelling evidence that life is not uniquely confined to Earth. (Although searches for such signals have become known as SETI [the search for extraterrestrial intelligence], in reality such searches could detect only those intelligent forms that utilize an electromagnetic technology.) In this chapter, both of these approaches to the detection of life outside the solar system are discussed