An extraordinary measurement by a US lander and an international collaboration of all Mars satellites suggest that the neighboring planet is probably more geologically active than we thought.

All the continents and seas of the Earth are placed on thin slabs of stone relative to the size of our planet, which are in constant motion on top of a vast layer of bubbling magma. In the long term this tectonic movement is responsible for the breaking up and formation of continents, and in the short term we sometimes feel it when the edges of the plates rub and collide, which causes earthquakes.

Mars, on the other hand, is much smaller than Earth, and although both formed at roughly the same time, about 4.5 billion years ago, our neighbor cooled much faster, contracted, and the tectonic plates in its crust stuck together. Even if Mars is an unsympathetic place to live, for many other reasons, at least strong earthquakes – there is no place there. Or so we thought until now.

international collaboration

On May 4, 2022, the seismograph of the American InSight lander picked up an earthquake with a magnitude of 4.7 – the strongest that the lander’s instruments have picked up since it began its activity on the surface of Mars, 3.5 years earlier. The main cause of such loud noises on Mars are meteorites crashing into the face of the planet. Mars has a much thinner atmosphere than Earth, and does not have a large moon like ours, which protects against some of the damage. That is why the impact of large meteorites on its surface is a much more common event than here. The research team in charge of the lander’s seismograph, led by Benjamin Fernando (Fernando) from the University of Oxford in England, has over the years identified dozens of smaller tremors, and in many cases has been able to link them to signs of meteorite impacts.

The team was determined to confirm – or rule out – the possibility of such a collision this time as well. It is very difficult to detect a meteorite impact in real time if there is no camera in the area, but luckily it leaves signs. An impact that produces a relatively strong earthquake also naturally leaves a large crater. There are no less than seven active satellites orbiting Mars today, and Fernando and his colleagues managed to mobilize all the entities that operate them – the United States space agency NASA, the European Space Agency ESA, and also the space agencies of China, the United Arab Emirates, and India – whose satellite (Mangalyaan ) was still active, but ended his mission a few months later. The satellite operators scanned photographs of the surface and compared them to previous photographs in an attempt to locate a new crater or a cloud of dust that transforms following such an impact.

where humans can live safely on Mars, and which areas should be avoided!

The surface area of Mars is about 144 million square kilometers, similar in size to the land area on Earth. The scans of the vast area lasted several months, but no new crater was found in them, of the expected size – which, according to the strength of the earthquake, the researchers estimated to be about 300 meters in diameter. And in the end, the team concluded that the strong earthquake was caused by another source – internal – which suggests that the seismic activity in the Martian crust is much stronger than we thought until now.

“We still think that there is no tectonic plate activity on Mars today, so the cause of this event was probably mechanical stress that accumulated within the crust,” said Fernando. “Such stresses are the result of billions of years of evolution, including the cooling and contraction of different areas of the planet at an uneven rate. We still do not fully understand why there are stronger stresses in certain areas of the planet, and such results will help us investigate the matter more deeply. One day, they will help us understand where humans can live safely on Mars, and which areas should be avoided!”

The InSight lander, designed to study the interior of Mars, has been operating on its surface for more than four years. The contact with her was severed in December 2022, apparently after her solar panels were covered in sand, and lander was unable to generate the energy needed to continue her activities.

The many data the lander collected during her years of activity on Mars will keep researchers busy for many years to come, and has already shed quite a bit of new light on the geology of the neighboring planet. Among other things, she discovered that Mars has a thinner crust than Earth’s and a liquid core, and that although it has cooled much more than Earth, deep inside it may still be geologically active. The new findings will help us to better understand what is happening under the surface of our neighboring planet and what historical processes took place there, and may also expand our knowledge about the study of the formation and development of rocky planets, also in other solar systems.

And just as importantly, this research was the first time that all the satellites around Mars were mobilized for international and interplanetary cooperation, which made it possible to scan the entire surface of the planet. “This project represents a huge international effort to solve the mystery of the earthquake, and I am grateful to everyone who participated,” Fernando said. “I hope it will serve as a model for further international joint efforts in deep space.”