Guest Editorial

Although nature refuses to respect national boundaries, that’s what the American media Chauvanistically chose to label last month’s spectacular celestial event. On 21 August 2017, a partial solar eclipse was visible across practically the entire North American continent, laying a narrow swath of totality all the way from the Pacific to the Atlantic. Muriel and I traveled to an area of maximum totality, to observe the event with thirty friends gathered on a small private airport in central Tennessee (see this photo). The view of the corona was awesome – but that’s not what this column is about.

It is an interesting cosmic coincidence that, as viewed from Earth, both the Sun and the Moon subtend exactly one-half a degree in the sky, allowing each to totally eclipse the other when their alignments coincide properly. More significant to astrobiologists is that the mass of the Moon is sufficient to raise tides in the waters that cover two thirds of our home world. It is widely believed that these tides were at least partially responsible for creating conditions suitable for the genesis of life.

Perhaps the existence of life on other worlds will similarly depend upon the presence of a large moon, orbiting at the right distance to raise tides in the cosmic soup. But, our technology is presently unable to detect such satellites of the satellites of distant suns. All that is about to change.

To date, our most powerful tool for detecting exoplanets has been the Kepler space telescope. Since its launch in 2009, the Kepler mission has been responsible for the detection of over three thousand planets orbiting neighboring stars – all in the single, tiny speck of the sky that the spacecraft has been able to monitor. A good percentage of these other worlds appear to be orbiting in the habitable zones of their stars – the region where temperatures are right for water to exist in liquid state. How many more potential life sites might exist in the rest of space? Most estimates are in the millions; some optimists say billions. But, on which (of any) of these many worlds will life actually have swum in the oceans and crawled out onto shore? That could well depend upon the presence of moons.

The technological successor to the Kepler spacecraft will be the James Webb Space Telescope (JWST), scheduled for launch roughly a year from now. This $10 Billion US investment is poised to return scientific dividends of inestimable value. We in the SETI community are hoping it will be capable of detecting not just an abundance of other worlds in the habitable zones of their stars, but perhaps the very moons orbiting those exoplanets. After all, most of our own sun’s retinue of planets are orbited by a variety of natural satellites – the Assumption of Mediocrity suggests that other planetary systems should be no different If water worlds are orbited by massive moons, might the tides raised by those moons be sufficient to stir the pot of life? Stay tuned for future discoveries sufficient to boggle the imagination!

Disclaimer: The opinions expressed in editorials are those of the individual authors, and do not necessarily reflect the position of The SETI League, Inc., its Trustees, officers, Advisory Board, members, donors, or commercial sponsors.