Solar system simulations starting from varied initial conditions suggest that Earth-like planets can emerge naturally from planet formation.
Computer simulations of planetary systems can now begin from thousands of different starting conditions, allowing researchers to explore how worlds might emerge without assuming the final outcome. Over the past three decades, these models have advanced from relatively simple approximations to far more sophisticated simulations.
At the recent Origins 2026 conference in Paris, Nader Haghighipour presented simulations designed to reconstruct how our solar system may have formed without building its familiar planetary arrangement into the model from the outset.
Haghighipour, a planetary scientist at the University of Hawaii in Manoa, said the models differ from earlier approaches because they begin with many randomized starting conditions and allow the laws of physics to determine how each system develops. This approach produces a broader range of possible outcomes rather than steering the simulations toward the solar system scientists already know.
“After about thirty years of doing terrestrial planet formation in one specific way, we have reached a point where we realized that the modeling done we have done in the past has many limitations and can’t be pushed any further,” Haghighipour told me in Paris.
Simulations started without a preset solar system
The most viable environment for the formation of habitable planets, one that emerges organically from the evolution of a stellar nebula and is free from any specific assumption, is a protoplanetary disk with a non-uniform distribution of solid material, Haghighipour writes in his Origins conference paper. We have carried out more than 1000 simulations of the late stage of terrestrial planet formation for a variety of distributions of planetesimals and planetary embryos, Haghighipour writes.
As Haghighipour points out, no one knows our solar system’s precise starting point, or how random objects of different sizes were distributed in the initial protoplanetary disk.
So, we had to go back to the beginning and start from scratch, letting the physics of planet formation take over and take us forward, says Haghighipour. That is, without accommodating what we already know about our solar system, he says.
Earth emerged naturally from the simulations
Haghighipour and colleagues found that formation of Earth at one Earth-Sun distance (or an astronomical unit) is a natural outcome of the evolution of our solar system.
We find that Venus appears about 28 percent of the time and maintains its orbit, sometimes in the habitable zone of the stars, sometimes slightly outside, says Haghighipour. Mars appears a number of times as a small object in the vicinity of the current orbit of Mars, he says.
Haghighipour talks new models of our solar system. Credit: Bruce Dorminey
Haghighipour and colleagues’ models then simulated these hypothetical planetary bodies’ interactions with one another. Previously, such simulations would sometimes take six to eight months to run; now they can be done within six to eight weeks on current laptop computers.
Even a small variation in initial conditions can have a great impact on the final product of a given solar system, says Haghighipour.
Planet formation could guide life searches
After life originated (we don’t know how and will never know), life developed branches and bifurcated so that it could find a way to stay in sync with Earth’s evolution, says Haghighipour.
Given the commonality of Earth-sized planets (including small super-earths) in the habitable zones of solar-type stars, it would be completely logical to consider that Earthly life is common, says Haghighipour.
But can we detect life around other solar systems?
Finding life on other planets is a very complicated thing; our technology is not at that level, says Haghighipour. But this type of study will enable us to understand the characteristics of a planet like Earth and the physical processes that went into its formation and how it became habitable, he says.
There is no reason to believe that our Earth is a fluke, says Haghighipour.
Adapted from an article originally published in UniverseToday.
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