Quakes aren鈥檛 unique to Earth 鈥� a lander has detected more than 700 of them on Mars. And new research shows that some of them may occur seasonally.
The NASA InSight lander, which touched down on the Red Planet in November 2018, brought seismometers and placed them on the surface using a robotic arm. These instruments have been gathering information since shortly after the landing.
鈥淚t鈥檚 really cool that we鈥檙e finding so many marsquakes, and there鈥檚 so much about this planet that we鈥檙e still finding out,鈥� says at Brown University in Rhode Island.
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Daubar and her colleagues studied the data on Martian quakes and found that there are different categories. Some are deeper and larger, perhaps comparable with a magnitude 3 or 4 earthquake, and don鈥檛 appear to be seasonal.
But smaller, shallower marsquakes detected by the lander peak in frequency during the northern hemisphere鈥檚 summer.
The team modelled probable causes for these shallower quakes and found they aren鈥檛 likely to be caused by the orbit of Mars鈥檚 moon Phobos and they don鈥檛 seem to be due to asteroid impacts. They correspond more to the distance of the sun from Mars.
Intense summer sunlight could be causing the ground to crack, producing these tremors. Or it could be that it causes melting of carbon dioxide ice hidden in some deep, but narrow, valleys where the sun can only reach the bottom during the northern summer.
鈥淚t鈥檚 intriguing. We wouldn鈥檛 have expected it. These quakes are relatively small, but still with a fault plane [the surface involved in the seismic movement that causes a quake] the size of a large building front,鈥� says at the Swiss Federal Institute of Technology in Z眉rich, who was also on the team.
It is also possible that changes in carbon dioxide ice loads could be causing these quakes. But Daubar says most CO2 ice on Mars is concentrated towards the poles, and quakes there wouldn鈥檛 necessarily be picked up by the InSight sensors from so far away.
Journal reference: Earth and Planetary Science Letters.
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