New research based on huge simulations involving hundreds of processors on the Australian National Computing Infrastructure using parameters run through a unique geodynamics code simulating the development of the interior of planets, showed that many early planets would have tended to develop a magnetic field and plate tectonics than planets formed later in the Milky Way, which is favorable to the development of life.
“These conditions are becoming increasingly rarer in our galaxy,” said Craig O’Neill, world expert in simulating planetary interiors and evolution and director of Australia’s Macquarie Planetary Research Center, due to change in the overall chemical balance over time for diverse reasons, such as material coalescing into stars and planetary bodies, or being expelled through supernova. This means that the interstellar material available to form planets is significantly different to that available in the early galaxy.
Optimum Conditions for Plate Tectonics
“Plate tectonics is important for habitability, and it looks like the optimum conditions plate tectonics existed for planets forming early in the galaxy’s lifespan, and may be unlikely to easily recur. For life, maybe that was as good as it gets,” added lead scientist O’Neill.
“Because of the great distances involved, we have a limited amount of information on these exoplanets, but we can understand some factors, such as position, temperature, and some idea of the geochemistry of the exoplanets. This allows us to model how they develop,” added O’Neill at the recent Goldschmidt geochemistry conference about the 4158 exoplanets discovered to date by missions such as NASA’s Kepler spacecraft, with the closest yet found orbiting the star Proxima Centuri, which is about 4 light years from Earth.
Act as a Thermostat
“Plate tectonics act as a kind of thermostat for the Earth creating the conditions which allow life to evolve,” observed O’Neill. “The Earth has a lot of iron in its core, and we had assumed that this would be necessary for tectonic development. However we found that even planets with little iron may develop plate tectonics if the timing is right. This was completely unexpected”.
The Right Geochemistry
“Planets which formed later may not have developed plate tectonics, which means that they don’t have this built in thermostat. This doesn’t just affect the surface temperature, this means that the core stays hot, which inhibits the development of a magnetic field. If there’s no magnetic field, the planet is not shielded from solar radiation, and will tend to lose its atmosphere. So life becomes difficult to sustain. A planet needs to be lucky to have the right position and the right geochemistry at the right time if it’s going to sustain life”, said Professor O’Neill.
Importance of Large Simulations
“Over the last few years, amazing projects such as the NASA Kepler mission have located thousands of planets orbiting around other stars,” said Sara Russell, Professor of Planetary Sciences and leader of the Planetary Materials Group at the Natural History Museum, London who was not involved in the study. “However, these exoplanet observations alone provide very basic information. It is so important to combine observing campaigns with large simulation projects like this, that really tell us something about the geological evolution of planets formed at different stages of galactic evolution. This enables us to build a picture of what these strange worlds might look like, and how habitable they may be.”
The image at the top of the page was created by an international team of astronomers who discovered that the Milky Way’s disc of stars becomes increasingly ‘warped’ and twisted the further away the stars are from the galaxy’s center. “We usually think of spiral galaxies as being quite flat, like Andromeda which you can easily see through a telescope,” says Richard de Grijs, a co-author and astronomer from Australia’s Macquarie University. This first accurate 3D map of our galaxy revealing its true shape as warped and twisted, used 1339 ‘standard’ stars . The artist’s impression of the warped and twisted Milky Way disk was created by Chen Xiaodian.
The Daily Galaxy, Max Goldberg, via The Goldschmidt Conference