News – Advances in astronomical observation have led to the discovery of an astonishing number of extrasolar planets, some of which are believed to have an Earth-like rocky shape. Learning more about their internal structure could provide important clues about their residential capacity.
Led by Lawrence Livermore National Laboratory (LLNL), a team of researchers aims to solve some of these mysteries by understanding the properties of iron oxide – one of the most healthy members of the Earth – at the real pressures and temperatures likely to occur on the interior of these large rocky planets. The results of their tests were announced today in Geology of nature.
“Due to the small amount of data available, most interior structure models for rocky exoplanets adopt a larger version of the Earth, made up of an iron core, surrounded by with a coating with silicates and heavily oxygenated. However, this approach largely ignores the different potential properties of proportional materials at higher pressures than those contained within the Earth, ”he said. Federica Coppari, LLNL physicist and lead author on the study. “With the growing number of confirmed exoplanets, including those believed to be rocky in nature, it is vital to better understand how their building blocks will be conduct themselves deep within these groups. “
Using large lasers at the University of Rochester’s Omega Laser Facility, the researchers extracted a sample of iron oxide to nearly 7 megabars (or Mbar – 7 million times the Earth’s atmospheric pressure), conditions that are expected to inland rocky exoplanets about five times larger than Earth. They flashed extra lasers at a small metal foil to create a short burst of X-rays, clear enough to capture a small X-ray image of the tight sample.
“Accurate timing is crucial because the state of maximum pressure is maintained at no more than 1 billion seconds,” Coppari said. Since X-ray contrast is ideal for measuring the distance between atoms and how they are arranged in a crystalline surface, the team found that when iron oxide is compressed to higher pressures the 3 Mbar – the inner heart pressure of the Earth – it transforms to a different degree, where the atoms are more packed.
“It is very interesting to find the high pressure iron oxide structure at higher temperatures than those inside the Earth as this form is expected to have a much lower viscosity than the earth. a crystal structure found at environmental conditions and in the Earth’s crust, ”Coppari said.
Combining the new data with previous measurements of magnesium oxide, another key component of rocky planets, the team built a model to understand how the phase shift in iron oxide could affect their mixing ability. They found that the mantle of terrestrial exoplanets could be quite different than is usually expected, with the appearance of very different viscosity, electrical conductivity and astronomical properties.
“The most remote conditions expected within large rocky Super-Earths favor the emergence of new and complex mineralogy where the composite materials mix (or unmix), flowing and deforming in a completely different way than in the guise of the Earth, ”Coppari said. “Not only does mixing play a part in the formation and evolution of the planet, but it also has a profound effect on astronomy and conductivity, which at the end over in relation to residency capacity. ”
Looking ahead, this research is expected to stimulate further experimental and theoretical studies aimed at understanding the mixing properties of the composite materials at unprecedented pressures and temperature conditions.
“There is still so much to learn about materials in extreme conditions and even more about the creation and evolution of planets,” she said. “It is fascinating to think that our laboratory experiments can look into the inner structure of distant planets with unprecedented intent and contribute to a greater understanding. depth of the universe. ”
The work was supported by the Department of Energy’s Office of Science. Co-authors include Raymond Smith, Marius Millot, Sebastien Hamel and Jon Eggert from LLNL; Jue Wang, Donghoon Kim and Thomas Duffy of Princeton University; and Ryan Rygg from the University of Rochester.