Could more of the earth’s surface be home to life?

image: Visual examples of orbital eccentricity.
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Credit: Phoenix7777

Of all the known planets, Earth is as friendly to life as any planet could be – or not? If Jupiter’s orbit changes, a new study shows Earth may 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, which means that the orbit is oval in shape. As the planet approaches its star, it receives more heat, affecting the climate.

Using detailed data-based models of the solar system as it is known today, UC Riverside researchers have created an alternative solar system. In this theoretical system, they found that if Jupiter’s giant orbit became more eccentric, it would in turn induce major 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 the habitability of this planet,” said Pam Vervoort, UCR planetary scientist and lead author of the study.

Between zero and 100 degrees Celsius, the earth’s surface is habitable for multiple known life forms. If Jupiter pushed Earth’s orbit to become more eccentric, parts of the Earth would sometimes get closer to the sun. Parts of the Earth’s surface that are now below freezing would have warmed up, increasing temperatures in the habitable range.

This result, now published in Astronomical Journaloverturns two long-standing scientific hypotheses about our solar system.

“Many are convinced that Earth is the epitome of a habitable planet and that any change in Jupiter’s orbit, being the huge planet it is, could only be harmful to Earth,” Vervoort said. “We prove that both hypotheses are wrong.”

Researchers are interested in applying this discovery to the search for habitable planets around other stars, called exoplanets.

“The first thing people look for in an exoplanet search 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, with the result that the planet has seasons. Parts of the planet can be pleasant in one season and extremely hot or cold in another.

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

Existing telescopes are capable of measuring the orbit of a planet. However, there are additional factors that could affect habitability, such as the degree to which a planet is tilted towards or away from a star. The part of the planet tilted to the star would get less energy, causing it to become colder.

This same study found that if Jupiter were positioned much closer to the sun, it would induce an extreme tilt on Earth, which would cause large sections of the Earth’s surface to sub-freeze.

It is more difficult to measure the inclination, or mass of a planet, so the researchers would like to work on methods that help them estimate these factors as well.

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

“It is 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 may change us once again in the future,” Kane said.


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