For a long time, we may have considered Mars as a spherical planet, just like Earth and other planets. However, recent discoveries reveal that Mars is actually not round. According to a study published in BBC Science Focus Magazine, this red planet is a triaxial ellipsoid – shaped like a rugby ball but with different sizes on its three axes. This irregularity is most noticeable in the high bulge in the Tharsis Rise area and the nearly opposite region called Syrtis Major.
Hypothesis of the Ancient Moon Nerio
Dr. Michael Efroimsky, an astronomer from the US Naval Observatory, recently proposed that the unusual shape of Mars may be caused by the existence of an ancient moon that is now lost. This moon was named Nerio, after the Roman goddess of war, who was the companion of Mars. According to this hypothesis, Nerio changed the shape of Mars through tidal forces, similar to how the Earth's moon affects our oceans. When Mars cooled, its distorted shape eventually became permanently frozen.
Effects of Tidal Forces
The tidal forces of Nerio also caused the elevated areas on Mars to become weaker and more susceptible to geological forces such as internal convection, tectonic shifts, and volcanic eruptions. All these factors contribute to the asymmetry of Mars. The study shows that a moon with less than one-third the mass of the Earth's moon, in a synchronous orbit around Mars, could create the initial triaxial shape of the planet. The equatorial bulge might have been larger if Nerio existed when Mars still had a magma ocean.
Loss of Nerio
Today, Mars has only two small moons: Deimos and Phobos. This suggests that at some point, Nerio either destroyed or was gravitationally ejected from the Martian system by another large body. Scientists are still unsure of the exact mechanism of Nerio's loss, but it may involve a collision or gravitational disturbance from another planet.
Implications of the Discovery
This discovery not only explains Mars' unique shape, but also provides new insights into the early history of the solar system. Mars, which is about half the size of Earth – diameter 6,790 km compared to Earth's 12,750 km – may have once been home to a moon that no longer exists. Further research is needed to confirm the Nerio hypothesis and understand how its loss affected Mars' evolution.
Reader Questions
This article answers a question from Otto Sykes, sent via email: "Why does Mars have such a strange shape?" To submit a question, please email us at questions@sciencefocus.com or leave a message on our Facebook, X, or Instagram (don't forget to include your name and location).
References
- BBC Science Focus Magazine: "Scientists have discovered Mars isn't round. And they're not sure why"
- Dr. Michael Efroimsky, US Naval Observatory
- Image credit: NASA/JPL
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*Original source: [sciencefocus.com](https://www.sciencefocus.com/space/scientists-discovered-mars-isnt-round-nerio-moon)*