Could there be more life on Earth’s surface? Jupiter’s orbit shape plays an important, overlooked role on Earth

Visual examples of orbital eccentricity. Credit: Phoenix7777/Public Domain

Of all known planets, Earth is as friendly to life as any planet could possibly be – isn’t it? If Jupiter’s orbit changes, a new study shows Earth could be more hospitable than it is now.

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

Using detailed models based on data from the solar system as it is now known, UC Riverside researchers created an alternative solar system. In this theoretical system, they found that if Jupiter’s orbit became more eccentric, this in turn would cause major changes in the shape of Earth’s orbit.

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

Between zero and 100 degrees Celsius, the Earth’s surface is habitable for several known life forms. If Jupiter pushed Earth’s orbit to become more eccentric, parts of Earth would sometimes move closer to the sun. Parts of the Earth’s surface now below freezing would become warmer, raising temperatures in the habitable range.

This result, now published in the Astronomical magazineturns two long-held scientific assumptions about our solar system on its head.

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

The researchers are interested in applying this finding to the search for habitable planets around other stars called exoplanets.

Could there be more life on Earth's surface?

A habitable zone, shown here in green, is defined as the area around a star where liquid water, an essential ingredient for life as we know it, could be present. Credit: NASA/JPL-Caltech

“The first thing people look for when searching for exoplanets is the habitable zone, the distance between a star and a planet to see if there is enough energy for liquid water on the planet’s surface,” said Stephen Kane, UCR- astrophysicist and co-author of the study.

During its orbit, different parts of a planet receive more or less direct rays, giving the planet seasons. Parts of the planet can be pleasant in one season and extremely hot or cold in another.

“Having water on the surface is a very simple first metric, and it doesn’t take into account the shape of a planet’s orbit, or seasonal variations that a planet may experience,” Kane said.

Existing telescopes can measure the orbit of a planet. However, there are other factors that can affect habitability, such as how much a planet is tilted toward or away from a star. The part of the planet that tilts away from the star gets less energy, making it colder.

The same study found that moving Jupiter much closer to the sun would cause an extreme tilt of the Earth, bringing large areas of Earth’s surface below freezing.

It’s more difficult to measure a planet’s tilt or mass, so the researchers would like to work on methods that help them estimate those factors as well.

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

“It’s important to understand the impact Jupiter has had on Earth’s climate over time, how its effect on our orbit has changed us in the past, and how it could change us again in the future,” said Kane.

Venus could be habitable today, if not for Jupiter

More information:
Pam Vervoort et al, System architecture and planetary obliquity: implications for long-term habitability, The Astronomical Magazine (2022). DOI: 10.3847/1538-3881/ac87fd

Provided by University of California – Riverside

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