How Mars Quietly Shapes Earth’s Climate Cycles Over Millions of Years
Earth’s climate history is full of dramatic swings. Over millions of years, the planet has shifted repeatedly between ice ages and warmer interglacial periods. Scientists have long understood that these changes are driven by slow variations in Earth’s orbit and axial tilt, known as Milankovitch cycles. What’s becoming clearer now is that Earth’s climate story is not written by the Sun and Earth alone. A growing body of research shows that Mars, despite being relatively small, plays a surprisingly important role in shaping these long-term climate rhythms.
Earth’s Climate Is Influenced by Its Planetary Neighbors
Milankovitch cycles arise because Earth does not move through space in isolation. The gravitational pull of other planets continuously tugs on Earth’s orbit, subtly altering three key parameters over long timescales: orbital eccentricity (how stretched Earth’s orbit is), axial tilt or obliquity (the angle of Earth’s spin axis), and precession (the slow wobble of that axis). Together, these changes affect how sunlight is distributed across the planet, especially at high latitudes, influencing ice sheet growth, sea levels, and global temperatures.
For decades, scientists have focused primarily on the influence of Jupiter and Venus, whose large masses make them obvious gravitational players. However, a new detailed analysis reveals that Mars exerts a much stronger influence on Earth’s climate cycles than previously appreciated, particularly when it comes to shorter and longer periodic variations seen in geological records.
Simulating a Solar System With Different Versions of Mars
The new findings come from a computational study led by astronomer Stephen R. Kane, in which researchers ran long-term simulations of the inner solar system. In these simulations, Mars’s mass was systematically altered, ranging from zero mass (effectively removing Mars from the system) up to ten times its current mass. The goal was to see how Earth’s orbital parameters responded over millions of years under different gravitational conditions.
By tracking changes in Earth’s eccentricity, axial tilt, and precession, the researchers could identify which climate cycles remained stable and which depended strongly on Mars’s presence. The results clearly showed that Mars is not a minor background player. Instead, it acts as a crucial component in shaping Earth’s orbital behavior.
The Reliable 405,000-Year Climate Metronome
One of the most stable features across all simulations was the 405,000-year eccentricity cycle. This long-period cycle is driven primarily by gravitational interactions between Venus and Jupiter, and it remained present regardless of how Mars’s mass was changed. Scientists often refer to this cycle as a kind of climate metronome because it provides a steady, predictable rhythm underlying Earth’s long-term climate variations.
Geological records from ocean sediments and ice cores show clear evidence of this 405,000-year cycle stretching back hundreds of millions of years. Its stability makes it especially useful for dating ancient climate records and understanding Earth’s deep-time climate history.
Why the 100,000-Year Ice Age Cycle Depends on Mars
In contrast, the more familiar ~100,000-year eccentricity cycles, which are closely associated with the pacing of ice ages, turned out to be highly sensitive to Mars’s mass. In the simulations, increasing Mars’s mass caused these cycles to lengthen and gain strength, indicating stronger gravitational coupling among the inner planets.
When Mars’s mass was reduced, these shorter cycles weakened or changed character. This finding is important because the ~100,000-year cycle dominates Earth’s climate record over the past several million years, particularly during the sequence of ice ages that shaped much of modern Earth’s surface.
The Disappearance of the 2.4-Million-Year Grand Cycle
Perhaps the most striking result of the study involved a much longer climate rhythm known as the 2.4-million-year grand cycle. This cycle, which contributes to long-term climate variability, arises from slow resonances between the orbital motions of Earth and Mars.
In the simulations where Mars’s mass approached zero, this grand cycle vanished entirely. Its disappearance showed that Mars’s gravitational influence is essential for creating the specific orbital resonance responsible for this long-period variation. Over millions of years, this cycle affects how much solar energy Earth receives and helps shape long-term trends in climate stability.
Mars and Earth’s Axial Tilt
Mars also influences Earth’s axial tilt, a key factor in determining the strength of seasons. Earth’s obliquity currently varies on a cycle of about 41,000 years, a pattern clearly recorded in geological data. The new simulations revealed that this obliquity cycle becomes longer as Mars’s mass increases.
In an extreme scenario where Mars is ten times heavier than it is today, Earth’s dominant tilt cycle shifts into a 45,000 to 55,000-year range. Such a change would significantly alter the timing and intensity of ice sheet growth and retreat, potentially leading to a very different long-term climate regime.
Reading Climate History in Rocks and Ice
Evidence of these orbital cycles is preserved in ocean sediment layers and Antarctic ice cores, which record changes in sea level, temperature, and ice volume over millions of years. Variations in Earth’s precession index and obliquity control how much sunlight reaches critical latitudes, such as 65° North, a region especially sensitive to ice sheet formation.
The fact that Mars helps shape these cycles means that Earth’s climate archive is, in a sense, also a record of planetary interactions within the solar system.
What This Means for Exoplanets and Habitability
Beyond Earth, these findings have important implications for the study of exoplanets. When scientists evaluate whether an Earth-like planet might be habitable, they often focus on its distance from its star. This research highlights that neighboring planets matter too.
A terrestrial planet with a nearby companion of the right mass and orbital configuration could experience climate variations that prevent extreme freezing or overheating. In some cases, these interactions might help stabilize climates over long periods, potentially making planets more favorable for life.
A Broader View of Earth’s Climate System
The study underscores a growing realization in planetary science: Earth’s climate is the product of a complex gravitational ecosystem, not just internal processes or solar influence. Mars, often thought of as a minor player compared to Jupiter, turns out to be a crucial supporting force in shaping Earth’s long-term climate behavior.
Understanding these subtle interactions deepens our appreciation of how finely balanced our planetary system is—and how even small changes could have reshaped Earth’s climate history in profound ways.
Research paper:
Stephen R. Kane et al., The Dependence of Earth Milankovitch Cycles on Martian Mass (2025), arXiv
https://arxiv.org/abs/2512.02108
