According to the evolutionary theory of how the solar system came to be, Earth ought not to have water. The planets supposedly formed out of a disk of material left over from the sun’s formation 4.6 billion years ago. The planets would have formed gradually by amalgamation of tiny dust particles. The problem is, the early sun would have heated the inner solar system sufficiently to have evaporated and blown away any water present in the dust that eventually formed the Earth. Furthermore, as Earth formed through this hypothetical process, gravitational potential energy liberated would have heated the early Earth to a molten state, driving away any water that might have survived.
Given that water is abundant on Earth’s surface and probably in its upper mantle, where did all this water come from? According to the theory, objects that formed farther from the sun, say where Jupiter and the other three large planets are, ought to have contained much water. But how could that water have been transported to Earth? Comets are rich in water. They spend most of the time far from the sun where their water can remain frozen. However, once each orbit a comet passes close to the sun. We call this event perihelion. When near perihelion, the sun’s radiation sublimes some of a comet’s frozen water and other ices directly into gas. These gases are responsible for a comet brightening tremendously when near the sun. Since comets travel from distant regions of the solar system to close rendezvous with the sun, there is the possibility that comets can collide with Earth. In fact, many scientists think that a very small comet collided with Earth in 1908, in Tunguska, a region in Siberia. Decades ago scientists came to believe that all Earth’s water was delivered to Earth by such collisions.
However, this view has been challenged by recent studies of the type of water that comets contain. Nearly everyone knows that the chemical formula for water is H2O, meaning that water molecules consist of one atom of oxygen and two atoms of hydrogen. Less well known is that atoms of any element can come in different varieties that we call isotopes, depending upon how many particles are in their nuclei. Take hydrogen. Hydrogen can come in two naturally occurring isotopes. All hydrogen atoms have one proton in their nuclei, and for about 99.9% of hydrogen atoms on Earth, that is all that they have in their nuclei. But about one hydrogen atom out of a thousand on Earth also has a neutron in its nucleus. We call this rare isotope deuterium, for a word meaning two, because there are two particles rather than one in its nucleus. We call a water molecule that has an atom of deuterium heavy water, because it weighs about 5% more than normal water without any deuterium.
We learn about the chemical composition of astronomical bodies by studying their spectra. It is not easy, but it is possible to detect a subtle difference between the spectrum of heavy water and the spectrum of normal water. Astronomers now have measured the amount of deuterium in about 10 comets, and they show a range in deuterium levels, but all are higher than Earth’s amount. The first few comets measured were long-period comets, thought to come from the Oort cloud in the estimation of most evolutionary astronomers. Astronomers had held out hope that short-period comets, which supposedly come from the Kuiper belt, might have deuterium levels closer to those of Earth. This was supported by measurements of deuterium in a short-period comet, Comet Hartley 2 (103P/Hartley), less than four years ago that matched Earth’s deuterium content well. The orbit of Comet Hartley 2 suggests to most astronomers that it came from the supposed Kuiper belt, thus saving the day for the dominant theory of Earth’s water.
However, that optimism was short-lived, because in December the Rosetta spacecraft measured deuterium in another comet that supposedly came from the Kuiper belt, 67P/Churyumov-Gerasimenko (I discussed the Philae lander of this mission onto the surface of this comet in a recent blog). This comet has the highest yet measured deuterium abundance—three times higher than Earth’s. In response to this setback, the evolutionists now are turning to asteroids as the source of Earth’s water. In a recent Answers in Depth article, I discussed how astronomers now think that many asteroids are far wetter than they used to think. Deuterium measurements for the few asteroids so far measured are a better match for Earth’s deuterium ratio.
There is much left unasked in all of this. Why do comets that supposedly come from the Kuiper belt have such a range in deuterium? The pre-solar nebula, from which the solar system supposedly formed, was hypothesized to be thoroughly mixed, so there ought not to be such a range in deuterium abundance. The current thinking is that the Kuiper belt is the original source for all comets, and that the Oort cloud was populated from the Kuiper belt. Given that, why would there be a difference in deuterium abundance between the Oort cloud and the Kuiper belt in the first place? With the fixation on Earth’s deuterium, those sorts of questions were never asked in the first place.
What a different picture we get when we examine God’s Word. Water played a key role in the creation (2 Peter 3:5), with the first mention of water (“the deep”) on Earth at the very beginning in Genesis 1:2. God separated water above and below on Day Two, and finally caused the dry land to appear for the first time on Day Three. You see, God tells us that water was always present on Earth since its beginning, so there is no need to invoke comets or asteroids or some other source of water for the earth. Unfortunately, many Christians wish to merge evolutionary ideas with Genesis creation. Few of them seem to realize that accepting the latest evolutionary theories about the origin of Earth’s water directly contradicts what Scripture clearly teaches.