Cross section of the still image showing the impact (box) and consequences (main image) of a 3D simulation of a giant planetary impact using 100 million particles, colored by their internal energy, similar to their temperature. Credit: Dr. Jacob Kegerreis, University of Durham.
According to new research, the giant impacts that dominate the later stages of planet formation have a wide range of consequences for young planets and their atmospheres.
Research led by Durham University and involving Glasgow University, both from the UK, have developed a way to reveal the scale of atmospheric loss during planetary collisions based on 3D simulations of supercomputers.
Simulations show how Earth-like planets with thin atmospheres could have evolved in an early solar system, depending on how they are affected by other objects.
Using the COSMA supercomputer, part of the DiRAC high-performance computing facility in Durham, funded by the Council on Science and Technology Facilities (STFC), the researchers conducted more than 100 detailed simulations of different giant impacts on Earth-like planets , altering the speed and angle of impact each time.
Cross-section animation of the early stages of fast-forward / giant-impact 3D simulations using 100 million particles, colored by their material or internal energy, similar to their temperature. Credit: Dr. Jacob Kegerreis, University of Durham.
They found that the impacts of grazing, such as the one thought to form our Moon, led to much less atmospheric loss than a direct impact.
Head-on collisions and higher speeds led to much greater erosion, sometimes completely destroying the atmosphere along with some of the mantle, the layer beneath the crust of a planet.
The findings provide a greater understanding of what happens during these giant impacts, which scientists know are common and important events in the evolution of planets both in our solar system and beyond.
The findings are published in the Astrophysical magazine.
Our Moon is believed to have formed about 4.5 billion years ago after a collision between early Earth and a giant impactor, possibly the size of Mars.
It was unknown how much of Earth’s early atmosphere could have survived in this violent impact event, or how this would change for different collision scenarios.
Cross-sectional animations of the early stages of 3D simulations of a giant grazing / slow impact using 100 million particles, colored by their material or internal energy, similar to their temperature. Credit: Dr. Jacob Kegerreis, University of Durham.
In the case of Earth, the planet was relatively lucky with this collision, losing only between ten and 50 percent of its atmosphere depending on the precise scenario.
Lead author Dr. Jacob Kegerreis, whose research was funded in part by a STFC doctoral fellowship at Durham University’s Institute for Computational Cosmology, said: “We know that planetary collisions can have a dramatic effect on the atmosphere of a planet, but this is the first time that we have been able to study in detail the great variety of these violent events.
“Despite the remarkably diverse consequences that can come from different impact angles and speeds, we have found a simple way to predict how much atmosphere would be lost.
“This lays the groundwork for predicting atmospheric erosion from any giant impact, which would feed the planet-forming models as a whole. This in turn will help us understand both the history of Earth as a habitable planet and the evolution of exoplanets around other stars. “
The researchers are now running hundreds of other simulations to test the effects that different masses and compositions of colliding objects could have.
Co-author Dr. Vincent Eke of the Durham University Institute for Computational Cosmology said: “It now appears that the amount of atmosphere a planet loses due to these collisions depends on how lucky or unfortunate they are in terms of type of the impact they suffer. “
The other co-author, Dr. Luis Teodoro, from the University of Glasgow, said: “Our research shows how different impacts can eject anywhere from very little to an entire atmosphere through a variety of mechanisms.”
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Reference: “Atmospheric erosion by giant impacts on terrestrial planets” by JA Kegerreis, VR Eke, RJ Massey and LFA Teodoro, July 15, 2020, Astrophysical magazine.
DOI: 10.3847 / 1538-4357 / ab9810
The research was supported in part by the Durham University Institute of Computational Cosmology PhD Scholarship Fund.
