DEE WILSON CONSULTING
Book Review:
A 'mind-boggling' search for new planetary life
The Secret Life of The Universe: An Astrobiologist's Search for the Origins and Frontiers of Life
Nathalie Cabrol, 2023
Cabrol's book contains fascinating, mind-boggling information regarding the search for life in our solar system, the Milky Way galaxy and in other galaxies (125 billion galaxies is the current estimate of total galaxies). Much of the information in this book was news to me as the pace of discovery in astronomy and astrobiology has expanded so rapidly in recent decades with the deployment of powerful new telescopes on Earth and outside Earth's atmosphere.
Cabrol explains that that the concept of "habitability for life" has changed markedly with the discovery of possible underground oceans, past or present, on Mars and several moons of Jupiter and Saturn, as well as on Pluto. Space missions that have landed on Mars and flown close to the outer planets in our solar system and Pluto have hit the jackpot in scientific discovery, and changed scientific views on where life in our solar system might be found: Europa ( a moon of Jupiter), Enceladus ( a moon of Saturn), Titan ( a moon of Titan, the largest moon in the solar system), Pluto, as well as rogue planets not bound by gravity to a sun. In addition, more than 5500 exoplanets, i.e., planets outside our solar system, have already been found and 10,000 additional possible exoplanets have been discovered in just a small part of the Milky Way galaxy since 1992.
It appears that organic molecules, the building blocks of life, are widespread in our solar system and the larger cosmos. Cabrol states:
" ... the elementary compounds that make the life we know, carbon, hydrogen, nitrogen, oxygen, phosphorous and sulfur ... are common in the universe ... Organic molecules and volatiles are found at the surface of Mars, in the geysers of Saturn's tiny moon Enceladus, in the atmosphere of Titan, in Triton's stratosphere, and on comets. We also discovered them on asteroids, not to mention dwarf planets Ceres and Pluto, and these are only a few examples. Much farther way still, nearly two hundred types of prebiotic complex organic molecules were detected in interstellar clouds near the center of our galaxy. They included the kinds that could play a role in in forming amino acids - the building blocks of the life we know. Granted that organic molecules are not life, but they are the elemental building blocks life uses for its carbon and hydrogen backbone, and they are everywhere."
Cabrol comments on what has already been discovered regarding exoplanets:
"Environmental extremes come aplenty with exoplanets. There are so many of them we can probably find anything our imagination can conceive. ... So far, we have discovered planets that reflect less light than coal. On others, it rains molten iron, molten glass or diamonds. Some planets have clouds of metal vapor or rainfall of liquid rubies and sapphires like on Wasp 421 b.
"Planets such as Gliese 1132 b , like a lizard losing its tail, regrew a second atmosphere after losing its first. ... There is a "hot Jupiter tidally locked to its parent star (which) found a way to equalize these temperature differences between day and night sides. It regulates them with insanely fast winds reaching nearly six times the speed of sound, possibly even topping out at 22,000 miles per hour." The oldest planet discovered to date is 12.7 billion years old, "formed barely a billion years after the Big Bang."
"This diversity of worlds reflect a dynamic and wild universe where every possible scenario and stages of planetary evolution seem to play out in front of our eyes all at once."
Cabrol sums up current scientific thinking regarding habitable worlds in the Milky Way galaxy : "Before Kepler (space telescope launched in 2009) we knew of about a dozen exoplanets, most of them extreme worlds by any stretch of the imagination. Since then, Kepler showed there could be 300 million potentially habitable planets in out galaxy alone in the most conservative estimate ..."
A new evaluation that used both Kepler data and ESA's Gaia mission data estimates that 50--75 percent of sun- like stars have rocky planets capable of sustaining liquid water on the surface, "representing 2 to 3 billion planets", along with billions (or trillions) of moons and rogue planets in the Milky Way galaxy alone. As fantastic as these estimates of habitable worlds in sun like solar systems seem, they are likely an large underestimate of habitable worlds, Cabrol asserts, because it is possible that life may have developed in other types of star systems, e.g., M dwarfs and K type (orange dwarfs) stars, the latter of which have lifetimes between 15 and 45 billion years vs. our solar system's 10 billion year life span. K type stars make up 13% of the Milky Way's star population, according to Cabrol.
Cabrol asserts, "The possibilities (for discovering life in the universe outside Earth) are endless," but therein lies the problem for deciding where to look. She speculates that AI systems will be used to examine huge amounts of data generated by new powerful telescopes, and guide the search for extraterrestrial life.
Cabrol discusses the Rare Earth hypothesis at length, i.e., the idea that the events that led to life on Earth are exceedingly unlikely and that life as we know it may be a one- off. She asserts, "... the Rare Earth hypothesis does not leave any room to consider alternative paths toward life and complexity. ... It does not consider the possibility of alternative biochemistries or similar biochemistries with distinct characteristics, and it is much too early to refute these notions. In this phase of our journey, we have to remain humble and remember that we are barely getting started on our quest for life beyond Earth."
-- Dee Wilson