[Editor’s note: this article has been updated to include the latest “superhabitable planet” data in the “Recent Developments” section at the end of the article.]
In a 2019 news article, researchers at the University of Puerto Rico at Arecibo took a look at the most recent number of extrasolar planets (around 4,000 [the number in 2022 is around 4,500]) in the habitable zone (also frequently called the Goldilocks zone) and applied an additional set of conditions needed for “life to form.” The loose definition of the habitable zone is that the planet must be just the right distance from its star so as to have liquid water—too close and the water would boil away, too far and the water would freeze. The new set of imposed conditions for life to form, based on a concept called the “abiogenesis zone,” is that the planet must also be in the area around a star where a planet could get enough UV (ultraviolet) light to start up prebiotic chemistry. If the planet receives too much UV light, then any organic molecules would be sterilized. According to the article, light is important in establishing the possibility of life, for
just being technically habitable does not mean that a world has the right conditions for life to arise. One leading explanation for life’s emergence on Earth is that ultraviolet light from the sun played a role. The idea is that UV light hitting simple molecules gave them enough energy to react with one another, forming the more complicated compounds required to make a living organism.1
However, after looking through a catalog of over 4,000 known exoplanets (only 49 of which were deemed in the habitable zone) and measuring them against the additional set of criteria, they concluded that only 8 of those 49 planets made the cut. Then after looking more closely at the remaining eight, they decided that most likely seven of those were gas giants and not an Earth-like rocky planet. Typically, planets larger than 1.7 times the size of the Earth are considered gassy planets. The one remaining planet just squeaks by the size requirements, being 1.63 times the size of Earth. The lone planet left on the list was Kepler-452b. Our astronomer, Dr. Danny Faulkner, wrote on this particular exoplanet shortly after its discovery in 2015 and listed several other potential problems with this planet: unknown composition and density, unknown atmosphere, and the possibility that its star’s luminosity could have caused the planet to suffer a runaway greenhouse effect.2
But even the New Scientist news article states they are not extraordinarily confident that Kepler 452-b might not be a gassy planet too.
This means that out of more than 4000 exoplanets, we may have only found one where life could evolve – or perhaps even none, if Kepler-452b turns out to be a gas planet. The only two planets we know for sure to be rocky and in both the habitable and abiogenesis zones are Earth and Mars. As far as we can tell, Mars doesn’t have any life.3
One of the astrobiologists associated with the research, Marcos Jusino-Maldonado, who presented his findings at the Lunar and Planetary Science Conference in Texas was quoted in the article saying, “It’s getting harder to find origins of life. It seems very unlikely.”4 Ramses Ramirez at the Tokyo Institute of Technology was also quoted in the article, bemoaning the status of the potential for life on these exoplanets: “If our goal is to find life, we need to be finding a lot more exoplanets than we can see with the technology we have now.”5
Dr. Faulkner has also pointed out that there are several other factors to consider to make a planet conducive to supporting life. The Earth is providentially placed in the habitable zone and is a rocky planet with a strong (but not too strong) atmosphere consisting of mostly nitrogen and oxygen, which is a life-conducive, non-volatile mix, whereas pure oxygen would be extremely volatile. Earth is also orbiting a stable rather than variable star. It also has a perfect distance from the sun and a significant mass that ensures it does not have synchronous rotation—which keeps it from having one side constantly facing away from the sun and be inhospitable to life.6 Additionally, Earth has a minor elliptical orbit; those with wildly elliptical orbits would go through deep freeze and boiling heat periods.7
The Bible clearly makes Earth the focal point of creation, not an insignificant planet in one of many solar systems—with man the center of his attention
From a biblical perspective, these findings are consistent with what Scripture says. We are told that God made the heavens and the stars (Genesis 1:1, 14–18) and formed the Earth to be inhabited (Isaiah 45:18), that all plant life was created by God (Genesis 1:11–12), that all living creatures were created by God (Genesis 1:20–25; Colossians 1:15–16), that mankind was directly created by God and is unique and made in the image of God (Genesis 1:26–27), and that since the fall of man the entire universe is under a curse (Romans 8:22). Furthermore, we are told that the heavens declare the glory of God (Psalm 19:1) and were created to give light (sun, moon, and stars), signs, seasons, and the ability to establish calendars for the inhabitants on Earth (Genesis 1:14–19).
The Bible clearly makes Earth the focal point of creation, not an insignificant planet in one of many solar systems—with man the center of his attention—and no other creatures on Earth are made in the image of God as we are. It is to Earth that God sent his Son to redeem man from sin, to restore fellowship with mankind, and (ultimately) to abolish the effects of the curse. If there were intelligent alien lifeforms in this present cursed cosmos, they could not be saved through the death of Jesus Christ, as they would not be the objects of Christ’s sacrificial death (Hebrews 2:14–17).
Apart from an evolutionary impetus to expect life to have formed via abiogenesis all over the universe, there is no reason to postulate that life could have formed elsewhere. However, the only other alternative would be to face the uneasy truth that Earth is a unique and privileged planet—something the evolutionary paradigm cannot admit. Even more ludicrous is to expect that life did form elsewhere, evolved to human-like or super-human intelligence, and then somehow seeded the Earth with life. But abiogenesis is an impossibility, both on Earth and on any other exoplanet—only life begets life. As this article points out, the search for planets capable of being amenable to life are nonexistent. But even if a planet where all of the factors being favorable for life to exist were found, there is no guarantee that it would actually have anything living on it. Unfortunately for evolutionary astrobiologists, the universal “planetary porridge” is too hot or too cold, and, apart from Earth, nothing is “just right.”
When the Kepler Space Telescope launched in 2009, its mission was to search for terrestrial planets (those near the size of the Earth), especially those in the habitable zone of their stars where liquid water might exist on the surface of the planet. Towards the end of its mission (2018) the focus was shifted to “superhabitable planets.” A superhabitable planet is described as one “in orbit around a K dwarf star, about 5–8 billion years old, up to 1.5 more massive than Earth and about 10% larger than Earth, mean surface temperature about 5°C higher than on Earth, moist atmosphere with 25–30% O2 levels, the rest mostly inert gases (e.g., N2), scattered land/water distributed with lots of shallow water areas and archipelagos, large moon (1–10% of the planetary mass) at moderate distance (10-100 planetary radii), and which has plate tectonics or similar geological/geochemical recycling mechanism as well as a strong protective geomagnetic field.”8
According to the authors of the study, “A closer look at the 24 candidates . . . reveals that 9 of them are orbiting around K stars, 16 of them are between about 5 and 8 billion years old and five of them are in the 10° range of the optimal temperature of a superhabitable planet as proposed by us (19°C; Table 3), with KOI-456.04 being the one with the most Earth-like temperature (Heller et al., 2020b). Only one of the candidates (KOI 5715.01) fits all three criteria, but it has a predicted lower global temperature than Earth when a gray atmosphere model is used that includes an approximation for a greenhouse effect [emphasis mine]. However, if the greenhouse effect is stronger than on Earth, KOI 5715.01 could conceivably be superhabitable.9
Other than the eyebrow-raising statement about superhabitable exoplanets needing to be about 5°C hotter than Earth’s current temperature (where’s the clamor from exoplanet climate alarmists?) this paper has nothing new to add, except to reinforce that Earth was uniquely created for life. Goldilocks is still dead!