Mars’s small size masks big influence on Earth’s climate, study finds

Despite being only about a tenth of Earth’s mass, Mars plays a surprisingly large role in shaping Earth’s long-term climate cycles, according to new simulations by Stephen Kane of the University of California, Riverside, and his colleagues.

By modelling scenarios in which Mars ranged from nonexistent to 100 times its current mass, the team found that the Red Planet strongly affects variations in Earth’s orbit and axial tilt—key drivers of ice ages and long-term climate change, NewScientist reveals.

“I came to this from a perspective of scepticism, actually, because I had trouble believing that Mars, which is only a tenth the mass of Earth, could have such a profound effect on Earth’s cycles, so that’s what motivated this study to turn that knob of Mars’s mass and see what happens,” says Kane.

When Mars was removed from the simulations, a major 2.4-million-year “grand cycle” in Earth’s orbital eccentricity disappeared, along with another 100,000-year cycle.

“It’s not to say that if we removed Mars then Earth wouldn’t have ice ages, but it would change that whole landscape of the frequency at which ice ages and related climate effects are occurring,” he adds.

Increasing Mars’s mass shortened and intensified some cycles, while a separate 405,000-year cycle—mainly controlled by Venus and Jupiter—remained unchanged. Mars also appeared to stabilise Earth’s axial tilt. The findings suggest that even small planets can significantly affect planetary climates, with implications beyond our solar system.

“We really need to know the orbital architectures of exoplanet systems really well to be able to reasonably have a grasp on the possible climate fluctuations on those planets,” says Sean Raymond at the University of Bordeaux.

Kane warns that the challenge is observational as well as theoretical:

“This is more of a warning than anything else: we can’t ignore the smaller objects, even though they are quite difficult to find, because those smaller planets like Mars are really having a bigger impact than we thought.”

By Sabina Mammadli