On November 26, 2018, the NASA Mars Probe Insight landed on the Red Planet. The first scientific results of this mission are now available: Among other things, the data provide the first comprehensive evidence that Mars is seismically active – quakes occur regularly there. These shocks allow conclusions to be drawn about what the interior of the planet could look like. In addition, there is new knowledge about the magnetic fields and the weather on Mars, as the astronomers report.
Mars is our best-explored neighboring planet to date. It has been orbited for more than 15 years and rovers such as opportunity and curiosity are exploring its surface. How it looks inside the Red Planet, these technical Mars observers could not clarify. In order to uncover this secret, NASA sent the Landing Probe Insight to Mars. It landed in November 2018 and is said to provide valuable insights into the inner life of the planet – for this it is equipped with a variety of measuring instruments and even a drill. The first comprehensive findings are now available: Researchers present observations from the first ten months of the Insight probe on Mars in several specialist articles.
A quake every day
Among other things, the scientists provide the final proof that the red planet is trembling. The Mars probe’s seismometer had already recorded the signal of a weak vibration in April 2019 and was thus an indication of seismic activity. But only the evaluation of further data now clears up the last doubts: Mars is actually seismically active. As reported by Domenico Giardini from the Swiss Federal Institute of Technology (ETH) Zurich and his colleagues, Mars Insight registered 174 Marsquakes from February to September 2019 alone – on average a little more than one quake every two days. The measurements that have continued since then even point to an average of one seismic event per day. After the moon, Mars is only the second celestial body next to Earth on which natural quakes have been detected. The Red Planet appears to be significantly more active overall than the Earth’s moon. In contrast, its seismic activity cannot approach the dynamic earth.
According to the scientists, the Mars quakes that have been evaluated so far can be classified into two different categories: 150 of them are events of comparatively low magnitude, the waves of which spread within the crust of the Red Planet and are virtually trapped in it. The 24 other quakes, on the other hand, are stronger with magnitudes between three and four and extend to different depths of the planet’s mantle. These Martian earthquakes correspond to weak earthquakes that occur repeatedly on Earth in the midst of continental plates – in Germany, for example, on the southern edge of the Swabian Jura. Even tremors of this magnitude are at most easily noticeable without measuring instruments.
Notes on the internal structure
The quakes provide astronomers with information about the inner structure of Mars: “Based on the wave movements, we can draw conclusions about the geological layers within the planet,” explains co-author Vedran Lekic from the University of Maryland in College Park. Specifically, the data of the seismogram suggest: Similar to the moon, the crust of the red planet seems to be very jagged to a depth of a few kilometers. “Nevertheless, the seismic signals are more similar to those that we register on Earth than those that we know from the moon,” comments Martin Knapmeyer from the German Aerospace Center (DLR) in Berlin.
In addition, the results show that smaller amounts of fluids could be found in the Martian crust – possibly salty solutions. In addition, the propagation of the waves suggests that the upper cladding dampens them more than the lower cladding layers. So that statements about the deeper interior of the Red Planet are possible, the researchers hope for a stronger Mars quake. With a little luck, waves triggered by violent vibrations can even penetrate to the core of the planet and could then provide clues to its composition.
Where was the epicenter?
In the case of two evaluated earthquakes, the signals were so meaningful that the scientists were even able to identify their local origin. It was located close to the Cerberus Fossae region, around 1,600 kilometers from the Insight landing site – striking, almost parallel fractures in the surface of Mars, which have probably been caused by volcanic influence in the recent past. For this reason, astronomers assume that the seismic activity on Mars is at least partly caused by tectonic tensions. So far, cooling processes have been the main trigger: “On Mars, the cooling of the planet may be responsible for quakes,” explains Ulrich Christensen from the Max Planck Institute for Solar System Research. The formerly glowing hot stone ball is getting colder and smaller.
Other findings about the Red Planet are also surprising: for example, the observation that the local magnetic field at the landing site in the Elysium Planitia plane is ten times stronger than was predicted by observations from Mars orbit. According to the researchers, there must be magnetized rock deep within the planet’s crust within a radius of 150 kilometers. It was already known that Mars once had a global magnetic field like Earth and that weaker local magnetic fields still exist as relics of it. The Landesonde Insight has also closely monitored the atmosphere and the weather on the Rote Planten in recent months: among other things, it registered pressure and density fluctuations, infrasound waves and current eddies in the atmosphere – this is therefore more dynamic than expected.
Characteristic weather patterns
As the researchers found out, there are strong temperature fluctuations at the landing site during the day. “At lunchtime, the rising sun warms the fine sand on the surface to temperatures that are above freezing most days, while the thin air stays 10 to 20 degrees Celsius colder. At night, however, the temperatures then drop to minus 90 degrees Celsius and below, ”reports Nils Müller from the German Aerospace Center. During the day, as a result of the increase in temperature, a very characteristic weather pattern develops with refreshing winds and waning in the afternoon. The scientists even registered small wind pants – so-called dust devils – on the ground. “The fascinating thing about this data is that it gives us an idea of what a typical day looks like on another planet,” Lekic states.
In the future, more data from Mars Insight will help to better understand the Red Planet and its properties. “These observations will lead to new discoveries with regard to the interior of Mars and its geological history,” conclude researchers around Bruce Banerdt from the California Institute of Technology in Pasadena in an overview article in the journal “Nature Geoscience”. The spacecraft will continue to observe Mars for at least another year.
Source: Bruce Banerdt (California Institute of Technology, Pasadena) et al., Nature Geoscience, doi: 10.1038 / s41561-020-0544-y