Unlocking Secrets: How Marsquakes Could Solve One of the Solar System’s Greatest Mysteries

A recent study has sparked interest in Mars’ internal structure. Scientists have noticed differences in marsquakes between the northern and southern hemispheres. This observation hints that the Red Planet may be built quite differently in these two regions. Understanding this could finally explain why Mars’ southern hemisphere stands higher than the north by 5-6 kilometers (3-4 miles), a mystery that has puzzled researchers for years.

Mars features two distinct hemispheres. The southern half is primarily highlands, while the northern half contains vast plains. According to Professor Hrvoje Tkalčić from the Australian National University, about two-thirds of Mars is made up of highlands, predominantly in the south. The unique contrast between these two hemispheres is unlike anything else seen in our Solar System.

For a long time, scientists have debated what caused these differences. One theory suggests the northern hemisphere may be the result of large asteroid impacts, while another points to internal processes on Mars. Tkalčić believes that studying marsquakes could provide valuable insights into this debate.

NASA’s InSight mission has been instrumental in this research. It has recorded numerous marsquakes, revealing that Mars remains geologically active. Some quakes originate from meteorite impacts, while others indicate ongoing internal activity. Recent analyses suggest Mars has a solid core, adding another layer to our understanding.

On Earth, seismologists find quake origins by analyzing seismic waves at multiple stations. However, with only one seismometer on Mars, this becomes challenging. Despite this limitation, researchers identified one quake cluster from the Cerberus Fossae area in the northern plains and another from Terra Cimmeria in the southern highlands. While the data from Terra Cimmeria was less reliable, it provided enough information for researchers to compare the two regions.

The study measured the attenuation quality factor (Q) of the seismic waves from both regions. The southern cluster had a Q value of 481-543, while the northern cluster showed values of 800-2,000. These figures suggest that seismic waves travel differently through the two hemispheres, which could be due to varying internal conditions.

The likely driver behind this difference is temperature. Tkalčić and his colleague Professor Weijia Sun propose that the mantle under the southern highlands is hotter, affecting how seismic waves propagate.

They argue that the differences we see on the surface reflect deeper geological processes. It’s unlikely that a single ancient asteroid impact caused such a divide. Instead, they believe that convection flows within Mars are responsible for transferring heat and creating these hemispheric variations.

Tkalčić, as a seismologist, admits he doesn’t fully understand the exact reasons for these convection processes. However, past modeling suggests that hotter mantle material can maintain such differences over time. The uniqueness of Mars’ hemispheres is one of the many mysteries that continues to intrigue scientists.

To further investigate these findings, more seismic detectors will be needed. Unlike Earth, which has thousands of seismic stations, Mars currently only has one. This limitation makes it tough to pinpoint the origins of marsquakes accurately.

InSight, which landed near Mars’ equator in the Northern Lowlands, was strategically chosen for optimal solar power and landing ease. The location turned out to be beneficial for comparing the two quake clusters since they are roughly equidistant from the lander.

The causes of many marsquakes remain a puzzle. While impacts are understood, researchers are still unsure if some quakes might be volcanic in origin. More exploration, particularly in the highlands, may shed light on these questions.

This fascinating research is detailed in an open-access paper published in Geophysical Research Letters.

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