The Internet has been abuzz lately with several articles and posts claiming that "at least a trillion alien civilizations have almost certainly existed in the universe."1 These claims are founded on the following four presuppositions:
- The density and kinds of planets throughout our galaxy and all other galaxies in the universe are roughly the same as what we observe in the vicinity of our solar system.
- About 20 percent of all planets are habitable.
- Life inevitably will arise on all habitable planets.
- The probability of a technologically advanced civilization arising from simple life is better than one chance in 10 billion.
Origins of Life (my book coauthored with Fazale Rana) demonstrates that from a naturalistic perspective assumption #3 is certainly incorrect. The probability of a naturalistic origin of life happening on a habitable planet is mathematically indistinguishable from zero.2 Since zero times any other factor or set of factors equals zero, then from a naturalistic perspective the number of alien civilizations besides our own in the universe is zero.
There is also much I could say about why assumptions #1 and #4 are deeply flawed, but I will focus on a new discovery that establishes that far, far less than 20 percent of all planets are habitable.
Assumption #2 only takes into account the water habitable zone, which is the range of distances from a planet's host star that could conceivably permit liquid water to exist on the planet's surface at some time during the planet's history and at some place on the planet's surface. Indeed, about 20 percent of the more than 3,000 planets discovered so far fall within this water habitable zone. The percentage drops precipitously, however, if one does not allow the greenhouse effect of the planet's atmosphere to take on a value that perfectly compensates for the host star's brightness. It takes another precipitous drop if one desires the planet to retain liquid water on more than 10 percent of its surface for more than a billion years. (Liquid water must be present on a planet's surface for at least 3.5 billion years for there to be even the remotest possibility of the planet sustaining advanced life.)
In addition to the water habitable zone, there are seven additional known habitable zones. I listed and briefly described these habitable zones in a previous article.3 In chapter 7 of my forthcoming book, Improbable Planet (release date September 6, 2016), I provide a detailed explanation of all eight of these habitable zones.4 I make the point that a planet is only a truly habitable candidate if it resides in all eight habitable zones. So far, the only known planet that resides in all eight of these habitable zones is Earth.
Figure 1: Venus Express Spacecraft
Image credit: Wikimedia Commons /Andrzej Mirecki
Now, a ninth habitable zone has been discovered—the electric wind habitable zone.5 This discovery is thanks to an electron spectrometer on board the European Space Agency's spacecraft Venus Express (see figure 1). This instrument measured the electric potential in Venus's atmosphere (see figure 2). Venus's atmospheric electric field at 10 volts proved to be far stronger than what any astronomer had expected. The high voltage drives an electric wind in Venus's atmosphere that is powerful enough to drive all heavy ions in Venus's ionosphere into interplanetary space. These heavy ions include oxygen ions that once belonged to water molecules.
Figure 2: Venus’s Cloud Structure as Seen in Ultraviolet Light by the Pioneer Venus Orbiter
Image credit: NASA
Previously, astronomers presumed that the solar wind was responsible for drying out Venus. This new discovery shows that Venus's electric field is the dominant desiccating factor.
The Venus Express research team determined that Venus's proximity to the sun explains its strong atmospheric electric field. Venus receives twice as much ultraviolet radiation as does Earth. All this ultraviolet radiation results in a high density of free electrons and ions in Venus's atmosphere, which generates a strong electric field above Venus's surface.
Confirmation that Venus's proximity to the sun explains its strong atmospheric electric field comes from failed attempts to detect atmospheric electric fields on Earth and Mars. In both cases, instruments establish that Earth and Mars possess atmospheric electric fields weaker than 2 volts.6
The discovery of a strong atmospheric electric field on Venus has serious implications for the possible habitability of exoplanets (planets beyond our solar system). The discovery implies that any planet with an atmosphere thicker than 1 percent of Earth's and any planet that is closer to its star than about 90 percent of Earth's distance from the sun will very likely possess an atmospheric electric field strong enough to completely dry out the planet.
The vast majority of exoplanets currently classified as habitable are closer to their stars than 90 percent of Earth's distance from the sun. Thus, they no longer can be classified as habitable. To put it another way, for the vast majority of stars, the water habitable zone does not overlap the electric wind habitable zone.
The discovery of the electric wind habitable zone means that for a planet to be a viable candidate for possibly sustaining life, it must simultaneously reside in nine different habitable zones. It seems that nothing less than the supernatural handiwork of God will suffice to explain how a planet could meet all these known conditions for habitability.