When we think of moons, our minds often drift to the one that orbits Earth. However, the solar system showcases a variety of moons, each with its own unique characteristics. For instance, Mercury lacks any moons, while Jupiter boasts a staggering 95. Mars, the red planet, currently has two small moons named Phobos and Deimos. Recent research suggests the intriguing possibility that Mars may have once possessed a third, larger moon. This theory revolves around Mars's triaxial shape, indicating it bulges similarly to Earth but along a different axis. A massive moon could have played a critical role in creating this distinctive shape.

Moons, which are celestial bodies orbiting planets or dwarf planets, come in various sizes, ranging from mere kilometers to several thousand. While Earth's Moon (capitalized for emphasis) is the most well-known, other fascinating moons abound in the outer solar system. From Ganymede, the largest moon, to Europa—a world covered in ice and believed to harbor an ocean beneath its surface—these celestial companions offer much to explore. Mars's moons, Phobos and Deimos, although smaller and irregularly shaped, provide insight into the planet's history as they are likely remnants from the asteroid belt.

Photographed by NASA's Mars Reconnaissance Orbiter, Phobos and Deimos are diminutive, irregularly shaped moons. Their origin story hints at a fascinating journey through the cosmos, likely having been captured from the main asteroid belt (NASA).

In a recent paper authored by Michael Efroimsky from the US Naval Observatory, the shape of Mars is examined to assess whether a third moon was ever present. The paper discusses how the triaxial nature of Mars manifests through its equatorial ellipticity, primarily influenced by the Tharsis Rise. A less pronounced bulge is also found near the Syrtis Major Planum region, situated directly opposite the Tharsis rise.

The image captured by ISRO's Mars Orbiter Mission reveals the stunning features of Olympus Mons, the Tharsis Bulge, and Valles Marineris, alongside visible clouds and the southern polar ice cap (ISRO).

Efroimsky's research proposes that the unusual bulge shape observed on Mars stems from two fundamental factors. Initially, the presence of a massive moon might have caused the planet's shape to morph due to its gravitational pull. This moon would have remained in a synchronous orbit, meaning that one side of Mars always faced it. Over time, this gravitational interaction would have led to the evolution of a triaxial ellipsoid shape, characterized by differing lengths across its three axes. The longest axis would align with the moon, while others would develop due to various tidal effects.

The second contributing element relates to the convection processes occurring beneath Mars's surface. Once the initial triaxial ellipsoid shape formed, the areas raised by tidal forces became increasingly susceptible to uplift influenced by volcanic, tectonic, and convection activities. This gradual enhancement contributed significantly to the triaxial ellipticity evident today.

Efroimsky's findings indicate that a moon with less than one-third the mass of Earth's Moon could create the initial triaxiality if it maintained a synchronous orbit around Mars. The research underscores the importance of the moon's existence during a time when Mars had magma oceans, as the asymmetry of its equator would be more pronounced. Conversely, this asymmetry would weaken if the moon appeared after Mars had solidified.

While further research is necessary to conclusively validate the second element, Efroimsky posits that tidal deformations could oscillate and generate heat. A moon in an elliptical yet synchronous orbit would appear to oscillate east and west around a fixed point in the sky. This behavior would enhance tidal deformation and internal heating within Mars, lending support to the idea that the red planet may indeed have housed a larger third moon in its formative years.

The exploration of Mars's potential third moon illuminates the dynamic history of this captivating planet and encourages deeper investigation into the forces that have shaped not only Mars but also other celestial bodies within our solar system.

FAQs

What are the names of Mars's current moons?Mars has two moons known as Phobos and Deimos.

How many moons does Jupiter have?Jupiter is home to 95 moons.

What is a triaxial shape?A triaxial shape is characterized by three axes of different lengths, resulting in a bulging appearance, which in Mars's case differs from its spherical shape.

Why is a third moon significant for Mars?The existence of a third moon could explain Mars's unique triaxial shape and provide insights into its geological history.

What are some notable moons beyond Earth?Some notable moons include Ganymede, Europa, and Titan, each exhibiting distinct features such as large sizes or subsurface oceans.

Final Thoughts

The intriguing possibility of a larger third moon orbiting Mars captures our imagination, hinting at a complex celestial dance that may have influenced the planet's development over billions of years. As we continue to investigate Mars and its moons, the mysteries of our solar system unravel, inviting us to ponder: Could there be more hidden secrets waiting to be discovered?