Earth’s ice ages shaped by tiny tugs from Mars

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Earth’s ice ages shaped by tiny tugs from Mars

You wouldn’t think that Mars could have an influence on Earth’s ice ages. Mars is only half the size of Earth. It has just 1/10 of Earth’s mass. Plus, depending on where they are in orbit around the sun, the two worlds can be separated by tens to hundreds of millions of miles. Still, scientists at the University of California Riverside said on January 12, 2026, that small gravitational tugs from Mars help shape the cycles that drive long-term climate patterns on Earth.

Scientists had long thought Mars’ gravitational pull was too weak to impact Earth’s climate. But some recent studies have suggested otherwise. So Stephen Kane, a professor of planetary astrophysics at UC Riverside, decided to run some computer models to see for himself. Kane said:

I knew Mars had some effect on Earth, but I assumed it was tiny. I’d thought its gravitational influence would be too small to easily observe within Earth’s geologic history. I kind of set out to check my own assumptions.

Kane and colleagues published their study in the peer-reviewed journal Publications of the Astronomical Society of the Pacific on December 18, 2025.

The cycles that shape our climate

How much solar energy Earth receives is what determines our climate. And there are three cycles, called Milankovitch cycles, that affect how much radiation Earth receives from the sun. These cycles are based on orbital mechanics. NASA describes the three Milankovitch cycles as:

eccentricity, or the shape of Earth’s orbit
obliquity, or the angle Earth’s axis is tilted with respect to Earth’s orbital plane
precession, or the direction Earth’s axis of rotation is pointed

Kane created computer simulations of how these cycles change over tens of thousands to millions of years. He ran the simulations showing the whole solar system, and then played with the size of Mars, increasing it and decreasing it, including removing it altogether. And for two of the cycles, the team found that removing Mars made the two cycles vanish.

Mars’ impact on our climate

The two cycles that Mars’ presence impacts are Earth’s eccentricity and obliquity. These two characteristics influence how much sunlight different areas of Earth get.

Let’s take a closer look at how Mars influences the tilt (obliquity) of Earth. Currently, Earth has a tilt from straight up and down of about 23.5 degrees. Kane said:

As the mass of Mars was increased in our simulations, the rate of change in Earth’s tilt goes down. So increasing the mass of Mars has a kind of stabilizing effect on our tilt.

In other words, if Mars were larger, it would dramatically change the pattern of ice sheet growth and retreat on Earth.

Mars’ pull on Earth’s eccentricity – or how circular or stretched out our orbit is around the sun – has an impact, too. In a grand cycle that lasts 2.4 million years, Mars’ gravitational pull slightly shifts Earth’s path around the sun.

Earth’s ice ages

Earth has survived at least five major ice ages. In fact, we’re in one now. An ice age is when there are permanent ice sheets at the poles. And sometimes during the ice ages, glaciers can advance and cover much of the globe. It was only about 11,000 years ago that the last major ice sheet – the Wisconsin glaciation – retreated after covering much of North America.

The Milankovitch cycles have helped to bring about and also end these different ice ages. And now we know that Mars plays a role in these cycles as well. Kane mused:

Without Mars, Earth’s orbit would be missing major climate cycles. What would humans and other animals even look like if Mars weren’t there?

Impacts on other solar systems

The computer simulations suggest that life on distant worlds could even be influenced by small, outer, lifeless planets. Kane said:

When I look at other planetary systems and find an Earth-sized planet in the habitable zone, the planets further out in the system could have an effect on that Earth-like planet’s climate.

Our solar system and neighboring planets have even more of an impact on our lives than we might have first thought.

Bottom line: Computer simulations show the presence of Mars affects the cycles that cause Earth’s ice ages and climate changes.

Source: The Dependence of Earth Milankovitch Cycles on Martian Mass

Via UC Riverside

Read more: Gravity between Mars and Earth drives climate and currents

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