A new study reveals that Mars, despite its small size, significantly influences Earth's orbital patterns that drive ice ages. Researchers simulated varying Mars's mass and found it affects key climate cycles. This discovery highlights the role of smaller planets in planetary climates.
Astronomers have uncovered an unexpected influence of Mars on Earth's climate, particularly the cycles that trigger ice ages. Stephen Kane at the University of California, Riverside, led a team that modeled Earth's orbit under different scenarios for Mars's mass, ranging from 100 times its current size to its complete absence. Kane approached the research skeptically, noting Mars is only a tenth the mass of Earth, yet the simulations showed profound effects.
Earth's climate is shaped by orbital variations, including the eccentricity of its path around the sun and the tilt of its axis. These are influenced by the sun and other planets. A key feature is the 'grand cycle,' spanning 2.4 million years, during which Earth's elliptical orbit stretches and contracts, altering sunlight distribution and long-term climate shifts.
Without Mars, this grand cycle and a 100,000-year eccentricity cycle vanish, altering the rhythm of ice ages, though not eliminating them entirely. Kane explained, “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.” Boosting Mars's mass shortens and intensifies these cycles, while a 405,000-year cycle, driven by Venus and Jupiter, persists unchanged.
Mars also stabilizes Earth's axial tilt, which wobbles every 41,000 years. Greater Mars mass reduces this wobble's frequency; a smaller Mars increases it. The findings, published in Publications of the Astronomical Society of the Pacific (DOI: 10.1088/1538-3873/ae2800), urge caution in assessing exoplanet habitability. Sean Raymond at the University of Bordeaux emphasized, “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.” Kane added a warning: “We can’t ignore the smaller objects... because those smaller planets like Mars are really having a bigger impact than we thought.”
This work underscores that even minor planets can sway climates, complicating evaluations of distant worlds.