Uranium and thorium play a vital role in the plate tectonics and volcanism of planets. Consequently, the amount of these two metallic elements influences the ability of any planet to support advanced life. Recently, a research team from the University of Washington, including FACTS for FAITH contributing author and astronomer Guillermo Gonzalez, determined that the abundance of uranium and thorium relative to iron in the interstellar medium has been declining for the past 4.5 billion years.1 This suggests that only a planet formed 4.5 billion years ago could possibly possess enough uranium and thorium to sustain plate tectonics and volcanism long enough for advanced life to be possible. 2
The star of such a planet would need to have been formed more recently than five billion years ago (see “Search for Planets Draws a Blank,” page 8). Therefore, the number of stars that might be candidates to possess a planet with the capacity to support advanced life is just a tiny percentage of the total stars in existence. Stars that formed significantly earlier than about five billion years ago or later than about 4.5 billion years ago would not be candidates.
- Guillermo Gonzalez, Donald Brownlee, and Peter Ward, “The Galactic Habitable Zone: I. Galactic Chemical Evolution,” Icarus (2001), pre-press.
- Hugh Ross, The Genesis Question (Colorado Springs: NavPress, 1998), 42-44.