Reasons to Believe

Sulfur-Poor Earth Conducive to Life

Earth's assortment of elements and compounds distinguishes it from other more "ordinary" planets. As examples, given its size and distance from its star, Earth is extremely water-poor, very carbon-poor, and extraordinarily rich in uranium, thorium, and gold. Each of these anomalies proves to be a vital requirement for advanced life. Two planetary scientists recently discovered yet another life-essential incongruity to the abundance of elements and compounds on this planet. Earth is sulfur-poor and especially poor in the sulfur compounds most hazardous to life.

This discovery arose out of measurements collected from Mars. The researchers determined that the Martian mantle contains at least three to four times as much sulfur as does Earth's mantle and that during the later stages of Mars' history its volcanic gas emissions are ten to a hundred times richer in sulfur and sulfur compounds than similar emissions on Earth.1 At the same time in the Red Planet's history its atmosphere was tenuous, just one bar or less. Such a thin atmosphere implies that the sulfuric volcanic gases that Mars retained were dominated by the heavier sulfur dioxide (SO2) rather than hydrogen sulfide (H2S). This sulfur dioxide would have penetrated any possibly existing persistent water layer on Mars, making the water layer much too acidic for the origin of life or for the maintenance of anything other than the most extreme acidophilic bacterial species.

Too much sulfur on a planet is deadly to life, but the planetary scientists' paper does not indicate whether Earth or Mars is an exception among planets. Sulfur ranks as the tenth most abundant element in the universe. Its abundance by weight is 500 parts per million. Compare this with 1,100 parts per million for iron, 700 for silicon, and 600 for magnesium, which rank seventh, eighth, and ninth, respectively. The relative weights are close when considering their abundance in the universe. In Earth's crust, on the other hand, sulfur ranks only as the seventeenth most abundant element and its abundance by weight is 0.04 percent. The abundance levels for iron, silicon, and magnesium are 4.10, 27.71, and 2.30 percent respectively. Thus, relative to iron and magnesium, sulfur in Earth's crust is fifty times less abundant than it is in the universe.

In this case, Earth, not Mars, is the exception. The anomalously low sulfur abundance in our planet's crust raises the question of how this came about.

Two extraordinary events in Earth's history reshaped both its crust and its interior.2 The first was a low-velocity collision with a planet the size of Mars when Earth was just 30-50 million years old. Because of the depth of Earth's ocean at the time (much deeper than today's), the angle at which the Mars-sized planet struck Earth, and the low velocity of the collision (less than 4 kilometers/second), our planet was not destroyed but transformed. Its core became bigger and denser and much of Earth's lighter weight material was dispersed into the interplanetary medium, some of which coalesced to become the Moon. Much of the sulfur in Earth's crust and mantle either sank into Earth's core or was ejected from the planet altogether.

The second extraordinary event was the late heavy bombardment. This event occurred 3.9 billion years ago (peaking at about 3.85 billion years ago) when the outward movement of Jupiter and Saturn from the Sun resulted in a mean motion resonance that destabilized the Kuiper Belt of asteroids and comets. This destabilization sent hundreds of thousands of asteroids and comets crashing into the inner solar system. Earth—the largest inner solar system planet—took the most damage. Astronomers calculate that at least the upper 200 kilometers of Earth's volume was transformed into a 3,000° Centigrade (5,000° Fahrenheit) molten lava sea. The late heavy bombardment sent even more of Earth's crustal and mantle sulfur down into the core.

These Earth-reshaping events account for most of the extremely low abundance of sulfur in our planet's crust and add to the case for the rare Earth doctrine. Every one of Earth's exceptional characteristics discovered so far has proven to be essential for the support of life, and of advanced life in particular. These discoveries indicate that evidence for the supernatural, super-intelligent design of Earth is mounting.

  1. Fabrice Gailard and Bruno Scaillet, "The Sulfur Content of Volcanic Gases on Mars,"Earth and Planetary Science Letters 279 (March 15, 2009): 34-43.
  2. Hugh Ross, More Than a Theory (Grand Rapids: Baker, 2009), 135-40.

Subjects: Geophysical Design

Dr. Hugh Ross

Reasons to Believe emerged from my passion to research, develop, and proclaim the most powerful new reasons to believe in Christ as Creator, Lord, and Savior and to use those new reasons to reach people for Christ. Read more about Dr. Hugh Ross.