Iron Vapor Hints At Formation Of The Earth And Moon

According to Sarah Stewart, an Earth and Planetary Sciences Professor from UC Davis, understanding the process of  iron vaporization will shed light on how the core of the Earth grew. Now scientists from Sandia National Laboratory, UC Davis, Harvard University, and Lawrence Livermore National Laboratory, have conducted a study that involves simulating the violent condition of the Earth’s formation in order to obtain an in-depth understanding about this exact process and how the resulting iron rain may have affected the development of the Earth and Moon. This study, using a shock-and-release experimental technique, was conducted using the powerful radiation source, the Z-Machine of the Sandia National Laboratory.

The Z-Machine is the most powerful and efficient laboratory radiation source in the world, with the main purpose of understanding the behavior of matter under extreme conditions. Thus, the machine is also central in learning about nature, research involving fusion, and ensuring the reliability, security, and safety of nuclear weapons. The fact that Z-Machine provides the fastest, most precise and cost-efficient method in determining the behaviors of materials subject to high pressures and temperatures, makes it incomparable to other technology.

For this particular study, high shock pressures in the machine were used against iron samples by crashing aluminum plates into the iron. Thus, the scientists created a shock-wave procedure to find out what impact conditions were necessary to vaporize the iron.

They were able to determine that iron vaporizes at the shock pressure of 507 (+65, −85) GPa. This result is lower than the previous theoretical estimate of 887 GPa, and is readily achieved by the high velocity impacts at the latter stages of build-up. This implies that more vaporized iron was present during the Earth’s formation than was previously believed.
That being the case, the scientists propose that the impact vaporization of planetesimal cores disseminated iron over the surface of the developing Earth, which caused its chemical equilibration with the mantle to be heightened.

Lead author Richard Kraus explained that, rather than “iron in the colliding objects sinking down directly to the Earth’s growing core,” the iron became vaporized and was distributed on the surface through a plume of vapor. This essentially means that the iron mixes easier with the Earth’s mantle.

This study, which was published in Nature Geoscience on March 2, also provides information about the moon. According to scientists, though the Moon experienced similar conditions, the low abundance of elements that tend to bond to metallic iron present in the lunar mantle and crust can be due to the lower escape velocity of the Moon, which allowed the vaporized iron to escape its atmosphere.