News Release 

'Mars quakes': First seismological data help understand the Red Planet's composition

University of Cologne

The SEIS seismometer from NASA's InSight mission measured a total of 174 probable 'Mars quakes' in the first months since its launch at the end of February 2019. That is slightly more than one quake every two days. These data provide the first comprehensive proof that - besides the Earth and the Moon - Mars is also seismically active. The data, which were generated with the participation of Cologne-based researcher Dr Brigitte Knapmeyer-Endrun from the University of Cologne's Institute of Geology and Mineralogy, have been published in Nature Geoscience and Nature Communications.

Martian quakes are not as frequent and not as strong as earthquakes. None of the quakes reached a magnitude of 4. On Earth, such quakes would be perceptible for measuring instruments or even people in the immediate vicinity, but they would not cause any damage. However, even the weak Mars quakes provide valuable data on the planet's composition. 'This is the first time seismology was conducted on Mars. The new data therefore give us completely new insights into the structure of the planet', says Knapmeyer-Endrun, who contributed to developing the Mars seismometer. She is now researching the structure of the Red Planet's crust.

Scientists assume that Mars - similar to Earth - has an onion-like structure. The core is enveloped in a rock mantle and a crust on the very outside. Seismological measurements can provide important information about the composition and thickness of the various layers. An earthquake creates waves that run along the surface and waves that go through the interior of the planet. They pass through the layers at different speeds and are refracted and reflected at the boundaries. When and where the waves reach the surface therefore allows for inferences about the inner structure of the planet.

The scientists are optimistic that an analysis of the Mars quakes will provide such information. 'A first result indicates a layer of rock 10 kilometres thick, in which the waves spread at relatively slow speeds. We therefore assume that this layer is not composed of intact basalt, but fissured or chemically altered rock', says Knapmeyer-Endrun.

Quakes similar to those on Mars occur on Earth more than a thousand times a year. One explanation for the relative weakness of these quakes could be that Mars, unlike Earth, probably consists of only one continuous tectonic plate. On Earth, on the other hand, tensions that build up and then erupt between adjacent plates generate most of the strong quakes.

To find out more about the deeper interior of Mars, the InSight mission's researchers hope for a stronger quake in the coming months. On Earth, violent tremors occasionally occur even within a tectonic plate. The waves they trigger penetrate deeper into the planet - with a little luck even to the core.

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