Where Science and Faith Converge
TNRTB

Earth’s Unique Element Abundances

By - December 20, 2009
More

Earth is not at all ordinary in its assortment of elements and compounds.

For the planet’s size and distance from its star, it possesses an anomalous (abnormal) amount of every measurable element and compound. Today, the list of such uniquely abundant or scarce substances includes water, carbon, sulfur, phosphorus, uranium, and thorium. Each of these anomalous amounts proves to be a vital requirement for advanced life and a significant piece of evidence that Earth was supernaturally designed for humanity’s benefit.

A study performed by two MIT planetary scientists showed that Earth is actually lacking in both water and carbon. They produced the most detailed model to date of degassing during the accretion phase of planetary formation for planets ranging in mass from 1 to 30 times the mass of Earth.1 The team based their models on measurements of the bulk compositions in the most primitive meteorites found in the solar system. These ancient remnants of the solar system’s protoplanetary disk represent the material from which Earth formed. They contain up to 20 percent by mass of water.

Using the range of water and carbon found in such meteorites and modeling how much of that water and carbon would be retained in the formation process by Earths and super-Earths, the MIT scientists determined that degassing during the accretion process alone would result in water and carbon compounds making up to 20 percent and 5 percent of the mass of Earths and super-Earths, respectively. They found, too, that using even modest estimates of water and carbon in the meteorites resulted in Earths and super-Earths ending up with very deep oceans and very thick atmospheres.

The problem posed by deep oceans is that no conceivable amount of plate tectonic activity would ever produce continents. Without continents there would be no possibility for land life, and many important nutrient-recycling mechanisms would be absent. The problem posed by thick atmospheres loaded with carbon compounds is that such atmospheres would trap tremendous amounts of heat, would result in such high atmospheric pressures as to make lungs inoperable, and would block out so much stellar light as to impede photosynthesis.

While water and carbon are essential for life, too little or too much proves deadly, especially in the case of advanced life. Earth possesses the just-right amount of each. The MIT team’s study underscored Earth’s uniqueness. For a planet as large as it is and as far away as it is from its star, Earth is miraculously water- and carbon-poor. Water makes up just 0.02 percent of Earth’s mass; carbon just 0.003 percent.

Measurements on Mars reveal another way in which our life-friendly home is unusual among its planetary peers. Earth is sulfur poor, especially in the sulfur compounds most hazardous to life. Two planetary scientists, Fabrice Gaillard and Bruno Scaillet, determined that the Martian mantle contains at least three to four times as much sulfur as does Earth’s and that volcanic gas emissions during the late stages of Mars’ history are ten to a hundred times richer in sulfur and sulfur compounds than similar emissions on Earth.2

Mars’ atmosphere was tenuous (just one bar or less) during the late stages of its history. Such a thin atmosphere implies that the sulfuric volcanic gases Mars retains are dominated by heavier sulfur dioxide rather than by hydrogen sulfide. This sulfur dioxide can penetrate any existing persistent water layer on Mars, making such water 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 Gaillard and Scaillet do not address whether Earth or Mars is the exception among planets.

Sulfur ranks as the tenth most abundant element in the universe. Its abundance by weight is 500 parts per million. This compares with 1,100, 700, and 600 parts per million, respectively, for iron, silicon, and magnesium, which rank seventh, eighth, and ninth. Yet in Earth’s crust, sulfur ranks as only the seventeenth most abundant element. There, 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 is fifty times less abundant in Earth’s crust than it is in the universe.

Phosphorus, an element crucial for the assembly of DNA and RNA molecules, and likewise critical for metabolic reactions in all organisms, is super-abundant in Earth’s crust. Relative to magnesium and iron, phosphorus is four times more abundant in Earth’s crust than it is in the universe or the Sun.

Relative to magnesium and iron, uranium and thorium, which provide most of the energy driving plate tectonics, and thereby making continents possible, are about 10,000 and 1,000 times more abundant in Earth’s crust, respectively, than in the universe or the Sun. They are both much more abundant in the planet’s interior (the necessary location for the energy driving plate tectonics) than in the crust.

The table below summarizes Earth’s anomalous abundances of elements. Every one of our planet’s exceptional abundance characteristics discovered so far has proven to be essential for the support of life and of advanced life in particular. The evidence for the supernatural, super-intelligent design of Earth is mounting.

Earth’s Anomalous Abundances
carbon 500 times less
water 250 times less
sulfur 50 times less
phosphorus 4 times more
uranium 10,000 times more
thorium 1,000 times more

 


 

References:

 

  1. Linda T. Elkins-Tanton and Sara Seager, “Ranges of Atmospheric Mass and Composition of Super-Earth Exoplanets,” Astrophysical Journal 685 (October 1, 2008): 1237–46.
  2. Fabrice Gaillard and Bruno Scaillet, “The Sulfur Content of Volcanic Gases on Mars,” Earth and Planetary Science Letters 279 (March 15, 2009): 34–43.

Category
  • Extrasolar Planets
  • Extrasolar Planets
Tags
  • Earth/Moon Design
  • RTB 101 Article
  • Extrasolar Planets

About Reasons to Believe

RTB's mission is to spread the Christian Gospel by demonstrating that sound reason and scientific research—including the very latest discoveries—consistently support, rather than erode, confidence in the truth of the Bible and faith in the personal, transcendent God revealed in both Scripture and nature. Learn More »

Support Reasons to Believe

Your support helps more people find Christ through sharing how the latest scientific discoveries affirm our faith in the God of the Bible.

Donate Now

U.S. Mailing Address
818 S. Oak Park Rd.
Covina, CA 91724
  • P (855) 732-7667
  • P (626) 335-1480
  • Fax (626) 852-0178
Reasons to Believe logo