Life On Earth Is Good, But It Can Be Better

Of all known planets, Earth is as friendly to life as any planet could possibly be—or is it? If Jupiter’s orbit changes, a new study shows Earth could be more hospitable than it is today.

When a planet has a perfectly circular orbit around its star, the distance between the star and the planet never changes. Most planets, however, have “eccentric” orbits around their stars, meaning the orbit is oval-shaped. When the planet gets closer to its star, it receives more heat, affecting the climate.

Using detailed models based on data from the solar system as it is known today, University of California researchers created an alternative solar system. In this theoretical system, they found that if gigantic Jupiter’s orbit were to become more eccentric, it would in turn induce big changes in the shape of Earth’s orbit.

“If Jupiter’s position remained the same, but the shape of its orbit changed, it could actually increase this planet’s habitability,” said Pam Vervoort, UCR Earth and planetary scientist and lead study author.

Jupiter’s massive size and gravitational pull deflects most large asteroids hurling towards the habitable zone in our solar system, where Earth orbits the sun. The habitable zone is the range of orbits around a star within which a planetary surface can support liquid water, and surface temperatures remain between zero and 100 degrees Celsius. This temperature range makes Earth’s surface also habitable for multiple known life-forms, even if very cold or hot areas are less favorable for life.

“Many are convinced that Earth is the epitome of a habitable planet and that any change in Jupiter’s orbit, being the massive planet it is, could only be bad for Earth,” Vervoort said. “We show that both assumptions are wrong.”

In the model, the researchers changed the eccentricity of Jupiter’s orbital path, eventually crossing Earth’s orbit. Gravitational disturbances generated by the massive gas giant then pushed Earth’s orbit to become more eccentric. As a direct result, Earth would get closer to the Sun and the degree to which Earth is tilted toward or away from the Sun would decrease. Parts of the Earth’s surface that are now sub-freezing would get warmer, increasing temperatures in the habitable range.

This same model found that if Jupiter were positioned much closer to the Sun, it would induce extreme tilting on Earth, which would make large sections of the Earth’s surface sub-freezing.

“It’s important to understand the impact that Jupiter has had on Earth’s climate through time, how its effect on our orbit has changed us in the past, and how it might change us once again in the future,” explains Stephen Kane, UCR astrophysicist and study co-author.

Ultimately, the movement of a giant planet is important in the quest to make predictions about the habitability of planets in other systems as well as the quest to understand its influence in this solar system.

The paper “System Architecture and Planetary Obliquity: Implications for Long-term Habitability” is published in The Astronomical Journal (2022). Materials provided by Jules Bernstein, University of California, Riverside.

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