Mars' gravity alters Earth's orbit, warming the climate and stirring the deep ocean over eons

Earth and Mars don’t just circle the Sun. They also tug on each other. Because the planets sit tens of millions of miles apart, that pull is comparatively weak.

Still, gravity’s impact is ever present, and over eons, the effects build up until they become measurable in surprising ways.

Scientists call the tiny tugs between Earth and Mars gravitational perturbations. About every 26 months, the planets reach an opposition, when they move closest to each other. During those moments, Mars gives Earth’s orbit a slight nudge.

That nudge doesn’t “steer” Earth in any dramatic way. Over millions of years, though, it can slightly change the shape of Earth’s orbit and the way Earth tilts.

Those slow changes can alter how much sunlight reaches Earth over long stretches of time, and that can affect climate patterns.

Deep ocean currents and eddies

The deep ocean moves constantly. It carries heat, salt, and dissolved gases around the planet. It also shapes the ocean floor. When deep currents run stronger, they can disturb sediment and leave uneven records behind.

Geological evidence spanning over 65 million years suggests that deep-sea currents on Earth undergo recurring cycles of strength every 2.4 million years.

Scientists call these cycles “astronomical grand cycles.” During stronger phases, the deep ocean can develop powerful eddies that reach the abyssal depths and erode sediment that had quietly piled up.

What the team noticed

Researchers at the University of Sydney used satellite data to map sediment accumulation on the ocean floor across millions of years.

They found gaps in the seafloor record. Those gaps can appear when stronger deep currents disrupt normal sediment deposition.

“The gravity fields of the planets in the solar system interfere with each other, and this interaction, called a resonance, changes planetary eccentricity, a measure of how close to circular their orbits are,” explained study co-author Dietmar Müller, a geophysics professor at the University of Sydney.

A long climate pulse

In this study’s idea, resonance between Earth and Mars changes Earth’s orbital eccentricity in a repeating way. At certain points in that cycle, Mars’ gravitational pull draws Earth slightly closer to the Sun.

That position increases solar radiation and warms the climate. Earth then drifts back again. The full pattern repeats about every 2.4 million years.

“Our deep-sea data spanning 65 million years suggests that warmer oceans have more vigorous deep circulation,” explained Adriana Dutkiewicz, the study’s lead author and a sedimentologist at the University of Sydney.

The researchers also emphasized one point that matters right now. This slow, million-year cycle does not explain today’s rapid climate warming.

Human greenhouse gas emissions heat the planet on a much shorter timeline and through a different physical cause.

AMOC and ocean eddies

Ocean scientists watch the Atlantic Meridional Overturning Circulation (AMOC) closely. Many people call it an ocean “conveyor belt.”

It transports warm water from the tropics toward the Northern Hemisphere and helps move heat into the deep ocean. Some scientists warn that it could weaken sharply in the coming decades.

“We know there are at least two separate mechanisms that contribute to the vigor of deep-water mixing in the oceans,” Müller noted.

Even if a big circulation pattern slows, smaller-scale mixing can still keep deep water from going stale. Eddies can move water around, help distribute oxygen, and keep heat from getting locked into one layer for too long.

“This will potentially keep the ocean from becoming stagnant even if Atlantic meridional overturning circulation slows or stops altogether,” Adriana Dutkiewicz concluded.

Mars’ link to Earth’s climate

We tend to think of the deep ocean as something passive. A cold, slow place where stuff settles and sits. This study flips that.

The deep ocean has a pulse, and that pulse runs to a beat set tens of millions of miles away. Mars and Earth, locked in their slow gravitational back-and-forth, leave fingerprints on the seafloor every 2.4 million years.

When the cycle peaks, the abyss gets restless. Currents pick up. Eddies churn. Sediment that had been quietly stacking up for ages gets swept aside.

It’s a strange thing to picture – a planet you can barely see in the night sky helping stir the bottom of our ocean.

None of this rewrites what’s happening to Earth’s climate now, and the researchers are clear about that. Mars isn’t behind the heat we’re feeling. That’s on us, and on a timeline measured in decades, not millions of years.

The study is published in the journal Nature Communications.

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