“I don’t think we were thrown out of the Garden of Eden. Just look around. We’re still in it, particularly when you compare the Earth with the Moon.”
It’s hard to disagree with the words of late Apollo moonwalker Alan Bean, but as astronomers search for Earth-like habitable worlds is our own planet as habitable as it could be?
No, say scientists, who suggest in a new paper published in the Astronomical Journal that changes in Jupiter’s orbit could make Earth more hospitable to life than it is today.
However, the giant planet’s future movements could also make Earth less habitable largely by affecting its tilt.
Our planet contains an estimated 8.7 million species, but vast swathes of its polar regions are lightly inhabited. “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 author of the study, which used computational simulations and modeling of the solar system.
This is how it could work. Earth orbits the Sun on a slightly (but only slightly) elliptical path. If Jupiter shifted in its own orbit then the gravitational effect could push Earth into a more elongated elliptical orbit. Earth would then sometimes get closer to the Sun that it ever does now, which could warm-up the polar regions—and make them more habitable.
“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,” said Vervoort. “We show that both assumptions are wrong.”
However, the same study found that if Jupiter moved closer to the Sun it would make Earth tilt more, which would have the effect of making large sections of the Earth’s surface dip below 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,” said Stephen Kane, UCR astrophysicist and study co-author.
The study was largely designed to inform exoplanet researchers currently looking for planets around other stars and judging their habitability. Whether exoplanets are tilted toward or away from a star isn’t something that scientists can tell with existing telescopes, but it’s important because the part of the planet tilted away from the star gets less energy, causing it to be colder.
“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’s enough energy for liquid water on the planet’s surface,” said Kane. “Having water on its surface is a very simple first metric and it doesn’t account for the shape of a planet’s orbit, or seasonal variations a planet might experience.”
Wishing you clear skies and wide eyes.