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New analysis of marsquakes, which are similar to earthquakes, could offer clues into how Mars has evolved over billions of years, according to from The Australian ������ýapp University (ANU) and the Chinese Academy of Sciences. 

The findings could help explain why the Red Planet’s southern hemisphere, which covers about two-thirds of the planet’s surface, has a thicker crust and is between five to six kilometres higher in elevation compared to its northern hemisphere – a phenomenon known as the Martian dichotomy. 

The researchers say differences between the two regions of Mars were likely shaped by convection – the transfer of heat from one place to another – in the Martian mantle over hundreds of millions to billions of years ago. The mantle is the inner layer of Mars sandwiched between the crust and the core. 

According to geophysicist and study co-author, ANU Professor Hrvoje Tkalčić, the difference in the Red Planet’s hemispheres is “one of the biggest mysteries in the solar system”. 

“We analysed waveform data from so-called low frequency marsquakes captured by NASA’s InSight seismograph on Mars,” Professor Tkalčić said. 

“In doing this, we located a cluster of six previously detected, but unlocated marsquakes in the planet’s southern highlands, in the Terra Cimmeria region.” 

Study co-author Professor Weijia Sun from the Chinese Academy of Sciences put the dichotomy in perspective. He said the difference in elevation is “pretty much the height of the highest ranges on Earth”. 

According to the researchers, the southern hemisphere is a less studied area of Mars. 

“The data from these marsquakes, when compared with the well-documented northern hemisphere marsquakes, reveal how the planet’s southern hemisphere is significantly hotter compared to its northern hemisphere,” Professor Tkalčić said. 

“Understanding whether convection is taking place offers clues into how Mars has evolved into its current state over billions of years.” 

Professor Tkalčić said there are two competing hypotheses to explain the origin of the Martian dichotomy: the first, referred to as the endogenic hypothesis, states convection in the Red Planet’s interior formed the dichotomy.  

The second school of thought, known as the exogenic hypothesis, believes astronomical events in space shaped the hemispherical differences. 

The new findings are a breakthrough for the endogenic hypothesis. They provide the first observational evidence supporting it. 

“On Earth, we have thousands of seismic stations scattered around the planet. But on Mars, we have a single station, so the challenge is determining the location of these marsquakes when you have only a single instrument,” Professor Tkalčić said. 

According to the researchers, the InSight lander could become a prototype for future planetary missions. The InSight lander collected data about marsquakes, Martian weather and the planet’s interior from 2018 to 2022. 

“Deciphering the formation of this dichotomy could also have some implications for the paleoclimate changes on Mars,” Professor Sun said. 

The study is published in .