Evrim Yazgin
Cosmos science journalist
New analysis of marsquakes could explain the evolution of Mars and why it is so lop-sided.
Mars’s southern hemisphere has a thicker crust and an elevation 5 to 6km higher than the northern hemisphere of the planet. This unexplained phenomenon is called the “Mars dichotomy”.
The southern hemisphere actually makes up close to two-thirds of the planet’s total surface area. Because Earth is also not a perfect sphere, the southern hemisphere on our planet is also a bit larger than the north, but this is much more pronounced on Mars.
The new study, published in the journal Geophysical Research Letters, might help solve dichotomy which co-author Hrvoje Tkalčić calls “one of the biggest mysteries in the solar system”.
There are 2 theories to explain the Mars dichotomy.
One, called the “endogenic hypothesis,” suggests convection in the Red Planet’s mantle might be behind the difference between the 2 regions.
The mantle sits between the planet’s core and the crust. Convection of the liquified rock in this region transfers heat from one part of the planet to another.
The other, “exogenic hypothesis,” puts forward that astronomical events such as collisions with other planetary bodies or asteroids caused Mars’s lopsidedness.
To study this, the team looked at marsquakes – the equivalent of earthquakes on our planet.
“We analysed waveform data from so-called low frequency marsquakes captured by NASA’s InSight seismograph on Mars,” says Tkalčić, a geophysicist at the Australian National University.
“In doing this, we located a cluster of 6 previously detected, but unlocated marsquakes in the planet’s southern highlands”.
The southern hemisphere is far less studied than the north.
“The data, when compared with the well-documented northern hemisphere marsquakes, reveal how the planet’s southern hemisphere is significantly hotter,” Tkalčić explains. “Understanding whether convection is taking place offers clues into how Mars has evolved into its current state over billions of years.”
The new evidence supports the endogenic hypothesis for the Mars dichotomy.
“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,” Tkalčić says.
The researchers say that InSight could lead the way for future planetary missions on Mars to study seismic activity.
Such research could also help explain the ancient climate on Mars – something which is key to answering the question of whether the planet was ever home to life.
