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InSight

Taking Mars' pulse at ETH Zurich?

NASA's unmanned InSight mission will make this possible by landing geophysical instruments on the surface of the Red Planet, allowing us to explore its interior. The instruments on board will include a seismometer to record marsquakes and meteorite impacts. Several groups at ETH Zurich are responsible for the sensor's data acquisition and control electronics and will evaluate and interpret the acquired data.

News

2021-11-23

Using ambient noise to uncover three billion years of Mars's past

Using ambient noise to uncover three billion years of Mars's past

There are two ways to find out what lies deep beneath our feet: you can either drill a hole, or you can use seismic waves to create an image of the subsurface. In recent decades, seismologists have developed and improved techniques that use ambient noise to map structures in the near-surface layers down to a depth of several hundred metres. Using technologies tested on Earth, seismologists have now mapped structures on another planet for the very first time. These analyses provided a glimpse into three billion years of Mars's past, as detailed in a study recently published in Nature Communications.

Since NASA's InSight mission landed on Mars in November 2018 and installed a seismometer, the Marsquake Service, led by ETH Zurich and involving the Swiss Seismological Service (SED), has been regularly analysing the recorded seismic data. In addition to identifying numerous marsquakes, researchers used these data to make statements about the structure of the planet's interior. They built a profile of the planet's crust, mantle and core but could not yet reveal much about the near-surface structures. However, shallow subsurface is vital to understanding Mars's geological history.

Rather than using marsquake signals to look into the subsurface, the new study utilises the ambient noise recorded at times without marsquakes. On Earth, such noise is generated by ocean waves, wind and human activity. Over the past few decades, the SED has developed methods to analyse ambient noise. These methods are used to define the structure of the local geology and to determine whether the local subsurface tends to attenuate or amplify seismic waves. This information is crucial for determining a site's earthquake hazard and analysing unstable landslide zones on mountains or in lakes.

On Mars, ambient noise is triggered by the wind, which generates seismic waves when interacting with the planet's surface. Based on analyses of this ambient noise, researchers can now image for the first time the shallow subsurface of Mars and study its geological history at depths ranging from a few dozens to two hundred metres. In contrast to Earth, Mars has never been home to any active plate tectonics. The planet has been shaped by phases of active volcanism that covered large areas with basaltic lava plateaus. The new analyses provide now a detailed image of the subsurface at the InSight landing site and show a top layer of three meters sand (regolith) and loose rock about 20 metres thick that has been fissured by thousands of meteorite impacts. Below are layers of lava flows that covered the planet between 1.7 and 3.6 billion years ago. These lava layers are divided by sediments lying at around 30 to 75 metres deep. The seismic image of the layer-cake geological stratification allows researchers to trace, for the very first time, the most important geological events that have occurred at the InSight landing site on Mars over the last three billion years.

When humans land on Mars one day, they need to know what lies under their feet. The question of whether these near-surface layers contain water is, for example, particularly interesting. The results of this latest study demonstrate that established techniques to investigate Earth are helping to answer such questions on Mars.

Hobiger, M., Hallo, M., Schmelzbach, C. et al. The shallow structure of Mars at the InSight landing site from inversion of ambient vibrations. Nat Commun 12, 6756 (2021).
https://doi.org/10.1038/s41467-021-26957-7

2021-07-23

The anatomy of a planet

The anatomy of a planet

Researchers at ETH Zurich working together with an international team have been able to use seismic data to look inside Mars for the first time. They measured the crust, mantle and core and narrowed down their composition. The three resulting articles are being published together as a cover story in the journal Science.

Since early 2019, researchers have been recording and analysing marsquakes as part of the InSight mission. This relies on a seismometer whose data acquisition and control electronics were developed at ETH Zurich. Using this data, the researchers have now measured the red planet’s crust, mantle and core – data that will help determine the formation and evolution of Mars and, by extension, the entire solar system.

Mars once completely molten

We know that Earth is made up of shells: a thin crust of light, solid rock surrounds a thick mantle of heavy, viscous rock, which in turn envelopes a core consisting mainly of iron and nickel. Terrestrial planets, including Mars, have been assumed to have a similar structure. “Now seismic data has confirmed that Mars presumably was once completely molten before dividing into the crust, mantle and core we see today, but that these are different from Earth’s,” says Amir Khan, a scientist at the Institute of Geophysics at ETH Zurich and at the Physics Institute at the University of Zurich. Together with his ETH colleague Simon Stähler, he analysed data from NASA’s InSight mission, in which ETH Zurich is participating under the leadership of Professor Domenico Giardini.

No plate tectonics on Mars

The researchers have discovered that the Martian crust under the probe’s landing site near the Martian equator is between 15 and 47 kilometres thick. Such a thin crust must contain a relatively high proportion of radioactive elements, which calls into question previous models of the chemical composition of the entire crust.

Beneath the crust comes the mantle with the lithosphere of more solid rock reaching 400–600 kilometres down – twice as deep as on Earth. This could be because there is now only one continental plate on Mars, in contrast to Earth with its seven large mobile plates. “The thick lithosphere fits well with the model of Mars as a ‘one-plate planet’,” Khan concludes.

The measurements also show that the Martian mantle is mineralogically similar to Earth’s upper mantle. “In that sense, the Martian mantle is a simpler version of Earth’s mantle.” But the seismology also reveals differences in chemical composition. The Martian mantle, for example, contains more iron than Earth’s. However, theories as to the complexity of the layering of the Martian mantle also depend on the size of the underlying core – and here, too, the researchers have come to new conclusions. 

The core is liquid and larger than expected

The Martian core has a radius of about 1,840 kilometres, making it a good 200 kilometres larger than had been assumed 15 years ago, when the InSight mission was planned. The researchers were now able to recalculate the size of the core using seismic waves. “Having determined the radius of the core, we can now calculate its density,” Stähler says.

“If the core radius is large, the density of the core must be relatively low,” he explains: “That means the core must contain a large proportion of lighter elements in addition to iron and nickel.” These include sulphur, oxygen, carbon and hydrogen, and make up an unexpectedly large proportion. The researchers conclude that the composition of the entire planet is not yet fully understood. Nonetheless, the current investigations confirm that the core is liquid – as suspected – even if Mars no longer has a magnetic field.

Reaching the goal with different waveforms

The researchers obtained the new results by analysing various seismic waves generated by marsquakes. “We could already see different waves in the InSight data, so we knew how far away from the lander these quake epicentres were on Mars,” Giardini says. To be able to say something about a planet’s inner structure calls for quake waves that are reflected at or below the surface or at the core. Now, for the first time, researchers have succeeded in observing and analysing such waves on Mars.

“The InSight mission was a unique opportunity to capture this data,” Giardini says. The data stream will end in a year when the lander’s solar cells are no longer able to produce enough power. “But we’re far from finished analysing all the data – Mars still presents us with many mysteries, most notably whether it formed at the same time and from the same material as our Earth.” It is especially important to understand how the internal dynamics of Mars led it to lose its active magnetic field and all surface water. “This will give us an idea of whether and how these processes might be occurring on our planet,” Giardini explains. “That’s our reason why we are on Mars, to study its anatomy.”

Reference

Khan A et al.: Upper mantle structure of Mars from InSight seismic data. Science, 373, (6553) p. 434-438.

Stähler S et al.: Seismic detection of the Martian core. Science, 373, (6553) p. 443-448. doi:10.1126/science.abi7730

Knapmeyer-Endrun B et al.: Thickness and structure of the Martian crust from InSight seismic data. Science, 373, (6553) p. 438-443. doi:10.1126/science.abf8966

Further information

InSight mission information

Detailed ETH News article: Advancing to the core thanks to marsquakes

2021-06-22

New ETH podcast episode: One universe - two perspectives

New ETH podcast episode: One universe - two perspectives

While Domenico Giardini, Professor of Seismology and Geodynamics, already has his hands on Mars, Adrian Glauser, Senior Researcher at the Institute for Astronomy, has to be patient. Among many others, Adrian worked on the James-Webb-Telescope that shall finally launch this fall, with a delay of many years. Both researchers talk about their work in the ETH Podcast and contemplate the universe's dimension to time on planet earth.

You can learn more about the podcast here and listen to the episode on Spotify, Apple Podcasts, Stitcher and Google Podcasts.

2021-04-06

After the storms: InSight detects large marsquakes

After the storms: InSight detects large marsquakes

NASA’s InSight mission detected two large marsquakes as summer emerges, the winds calm, and the dust settles. Now, after one Martian year (687 Earth days) the Marsquake Service led by ETH Zurich and operated by the Seismology and Geodynamics group and the Swiss Seismological Service is faster than ever at characterizing seismic activity on the red planet.

After several months of windy weather and dust storms, the atmosphere of Mars is becoming quiet again and the seismometer on the InSight lander started recording significant marsquakes. In early March, two new marsquakes with magnitudes of 3.3 and 3.1 were observed. Within 12 hours of the data arriving on Earth, researchers at the Marsquake Service at ETH Zurich determined the location, magnitude and, in one case, even the focal mechanism. This rapid result demonstrates that the whole chain of data recording, transmission, and analysis set-up by the InSight mission is functioning efficiently and rapidly. These moderately sized events recorded at over 1,200 km distance and by a single station (that would not even be observed by a similar station on Earth), are sufficient to confirm the emerging geological interpretation of the internal structure and surface tectonics of the red planet acquired over the past year on Mars.

Since the beginning of the Mars InSight mission on 26 November 2018, over 500 marsquakes have been recorded. With magnitudes between 1 and 4, these are small events compared to terrestrial earthquakes. Only a few of these marsquakes could be reliably located, determining both the direction and distance from the seismometer. The recently detected, larger marsquakes are located in Cerberus Fossae, a long graben system about 1,200 km from Elysium Planitia, where InSight landed. They have an extensional mechanism consistent with the regional tectonic setting showing that the Martian crust is still undergoing active deformation.

In the InSight mission, data recorded on Mars are relayed back to Earth in regular transmissions, often multiple times a day, via the NASA Deep Space Network. They are promptly compiled and controlled for quality by the Jet-Propulsion Laboratory (JPL) in the U.S. and the National Centre for Space Studies (CNES) in France, and delivered to the Marsquake Service located at ETH Zurich in Switzerland. The Marsquake Service is responsible for the first analysis of the Mars data, with the goal of identifying marsquakes and releasing periodic marsquake catalogues – the starting point for further scientific investigations. This is a collaborative ground service operation that includes on-duty seismologists from ETH Zurich, Institut de physique du globe de Paris (IPGP), University of Bristol, and Imperial College London. At the start of the mission, the data recorded on Mars was full of surprises and difficult to decipher. After a full year of processing seismic data from Mars, the Marsquake Service is now able to fully characterise the signals within just a few hours after having been recorded on Mars. This performance is comparable to that achieved by modern seismic networks on the Earth.

Recognizing the successful performance of InSight, NASA has approved the extension of the mission for a second Martian year. Unfortunately, the red dust which characterises all the pictures of Mars is also accumulating on InSight’s solar panels, reducing the panel’s power production and raising concerns about the long-term operation of the mission.

To learn more about the NASA InSight mission visit www.insight.ethz.ch or www.mars.nasa.gov/insight/

Access the joint press release about the recent Marsquake.

InSight lander

Explore the interactive graphic and learn more about the InSight lander and its instruments.

Twitter

Follow the NASA InSight mission on Twitter! @NASAInSight