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In the wake of the discovery of so many supposedly "habitable" planets, I have been bombarded with questions about how the discovery of extraterrestrial life would impact my biblical creation model. A lot has happened in the eighteen years since I first teamed up with other Christian astronomers to answer that question.1
Article originally appeared in
Article originally appeared in
Life's Remains on Other Solar System Bodies
I've been on record since the 1980s predicting that the remains of living things will be found on the Moon, Mars, and some other solar system bodies. What makes this discovery inevitable is that millions of tons of Earth's soil have been exported throughout the solar system due to large meteorites striking Earth. A large meteorite impacting Earth generates enough energy to cause rocks, soil, dust, and water on Earth to be ejected into interplanetary space. Much of that material eventually lands on the Moon, Mars, Venus, and Jupiter's and Saturn's moons.
The quantity of exported Earth life is far from trivial. On average, one ton (about 1,000 kilograms) of Earth's soil contains 100 quadrillion microbes. When rocks, soil, dust, and water are ejected from Earth after a meteorite hits, embedded microbes and small multicellular life-forms are ejected along with them. On average, about 200 kilograms of material from Earth have been deposited on every square kilometer of the Moon.2 For Mars, the figure is about two kilograms per square kilometer.
Is there a chance that viable Earth life resides on some other solar system body? The probability is remote, but not zero. Some microbes on Earth can withstand intense radiation, long desiccation periods, and highly saline solutions. If, by some incredibly lucky chance, some of these microbes should traverse the distance from Earth to Mars in hundreds of years rather than the typical millions of years, they might survive the journey, and if, by a further incredibly lucky chance, they should land in a briny Martian pond near Mars's equator on an exceptionally warm day, they might live briefly on that planet.
Is it possible that remains of Earth life have been transported to some other planetary system? The answer is yes. However, by the time such remains would reach an exoplanetary system, they would be so degraded as to be unrecognizable as originating from a living organism.
Biblical Constraints & Options on Extraterrestrial Life
The Bible teaches that God created "extraterrestrial" life—the angels. Unlike humans, angels are purely spiritual creatures; they lack physicality and so are not confined in their existence or movement to the universe, nor are they constrained by the physical laws governing it.
But as to whether God created physical extraterrestrial life subject to the laws of physics, Scripture is silent. Christians, therefore (unlike nontheists), are free to believe whatever they like about extraterrestrial physical life—with one caveat: Hebrews 9:26 and 28 says of Jesus Christ that "he has appeared once for all at the culmination of the ages to do away with sin by the sacrifice of himself. . . . So Christ was sacrificed once to take away the sins of many."
This passage asserts that there is just one sacrifice for the sins of all and that this one sacrifice took away the sins of many people. Thus, it strongly implies that there is only one physical, rational, and spiritual species in the universe that is in need of redemption from sin. To argue otherwise would require expanding the definition of people to include non-human physical-rational-spiritual creatures on other planets, combined with the doctrinally aberrant notion that no incarnation (Christ assuming an appropriate form) was necessary on those planets to save its intelligent inhabitants from their sins.
There is no passage of Scripture, however, that explicitly excludes the possibility of God's having created physical living creatures on other planets that are not in need of spiritual redemption. For example, God could have designed a planet far, far away on which he created bacteria, or a planet on which he also created mosses, ferns, and trees, or even a planet on which he went so far as to create animals as active and intelligent as dolphins and crows. The Bible could even countenance the existence of creatures on another planet that are as intelligent and spiritual as we humans are, provided they never sinned and, thus, had no need of redemption.
An Interesting Question
The contemplation of extraterrestrial life does raise an interesting theological question: Would it be more in keeping with God's revealed character for him to have created life on many other planets, or for him to have limited his creation of physical life to only our planet?
It doesn't take much exploration of Earth to recognize that God has packed our planet with as much life as possible, in forms as diverse, beautiful, and elegant as possible. As the psalmist declares, "How many are your works, Lord! In wisdom you made them all; the earth is full of your creatures" (Psalm 104:24).
It seems that God really enjoys creating. Given how much he relishes it, we might ask, why would he limit his creation of life to just one planet? Thus, one might deduce from this aspect of God's character that extraterrestrial life should be abundant and widespread throughout the universe.
On the other hand, one can marshal biblical support for the notion that God is conservative in performing miracles. That is, he limits his miracles to those necessary to achieve his purposes. God's primary purpose in creating humans, I contend, is to create physical-spiritual beings with the capacity to freely love and enjoy him forever, and, even after they have fallen away from him, to still have the free-will capability to choose to be redeemed by him from their evil and ultimately from suffering and death as well.
This purpose raises a question: On how many planets would God need to create physical-spiritual beings like us in order to fulfill this purpose? The most likely answer, theologically, seems to be one. Thus, based on God's not performing gratuitous miracles, we would expect exoplanetary systems not to contain life.
Astrophysical Constraints on Extraterrestrial Life
Skeptics cite a common rebuttal to the view that God has limited his creation of life to just our planet. They point to the vast size of the universe and the enormous number of planets existing in it, and contend that it is wasteful not to have living creatures on more of those planets. There are at least two responses to this argument.
First, there could be no Earth—that is to say, no planet capable of sustaining life—unless the universe were precisely the mass and size that it is. A universe even a tiny bit less massive than ours would never possess elements heavier than helium. A universe a tiny bit more massive wouldn't possess elements lighter than iron. Likewise, unless the mass, expansion rate, and size of the universe were as exquisitely fine-tuned as they are, the universe would never have produced galaxies, stars, and planets. In other words, given the physical laws God chose to govern the universe, there is no chance of a single planet like Earth existing, on which physical intelligent life is possible, without the universe being exactly the mass, size, and age that it is.3
Second, everywhere beyond our planet that astronomers look, they see conditions hostile to advanced physical life. Out of all the galaxies we have observed, ours is the only one that possesses all the characteristics needed for advanced physical life to be possible within it.4 Out of all the thousands of planetary systems we've observed, our solar system is the only one possessing the planets, asteroids, and comets advanced physical life needs to have in place.5 In fact, each planet in our solar system must be exactly as it is—in terms of size, mass, composition, orbital pattern, and so on—for advanced life to be possible on Earth.
Astronomers (and readers of Salvo 39) also know that Earth is the only planet out of the more than 3,500 that have been discovered that resides in all nine known habitable zones.6 Furthermore, out of the millions of known stars that have been measured in sufficient detail, the Sun is the only one possessing the characteristics required for advanced physical life to be sustainable on one of its planets—Earth.
Astrophysical evidence, therefore, leans strongly towards the position that God has limited his creation of physical life to our planet.
Does this mean we humans are alone then? No. When a person receives God's offer of redemption from sin, the Holy Spirit at that moment takes up permanent residence within that person. Thus, anyone who is a new creature in Christ is not alone, not now and not for all eternity. Also, Hebrews 13:2 says many of us have entertained angels without knowing it. Even if we have not had "physical" contact with angels, the Bible says they are intently observing us to learn about God's grace.
More Evidence of the Supernatural
But what if extraterrestrial life does exist? Well, it is already well established that life on Earth could not have begun through any conceivable naturalistic pathway,7 but rather must have been initiated through a divine miraculous intervention. Therefore, the discovery of life in another planetary system would indicate another instance of such divine intervention, meaning our universe would contain not just one origin-of-life miracle, but two. The more exoplanetary systems on which life was discovered to exist, the more origin-of-life miracles would be established. Thus, the possible discovery of extraterrestrial life would yield even more evidence for the supernatural handiwork of God.
It is debatable, however, whether the discovery of extraterrestrial life would cause a large number of nontheists to disavow their atheism and become Christians. If nontheists refuse to recognize life's origin on Earth as a supernatural event, they are unlikely to perceive the divine origin of life on another planet.8 Nevertheless, I remain hopeful that some open-minded people will be persuaded by the evidence and the demeanor of Christians. •
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