Scientists at Washington State University and the University of Chicago have uncovered conditions under which some carbon-rich planets can be composed of silica or diamonds. Planets of this type are not found in the solar system. The study, published in The Planetary Science Journal, is briefly reported in a press release on Phys.org.
Stars and planets form from the same cloud of gas and dust. Stars with a low carbon-to-oxygen ratio will have Earth-like planets composed of silicates with a small proportion of diamonds (0.001 percent). However, if stars have a higher carbon-to-oxygen ratio, then planets are more likely to be carbon-rich. In the presence of sufficient water, such rocks should be abundant in diamonds. At the same time, these planets are most likely always lifeless.
The researchers tested the hypothesis in a laboratory setting by simulating the high temperature and high pressure in the bowels of carbon planets using a diamond anvil cell. For this, a silicon carbide sample was placed in a cell, where the pressure reached 50 gigapascals, and it was heated to 2500 kelvin in the presence of water. The result was diamonds and silica.
Carbon-rich planets may not be geologically active due to their hardness, which in turn makes the composition of the atmosphere unsuitable for life.
