SEIS instrument can both locate meteorite impacts and scan the interior of Mars

Launched by NASA in May 2018, the InSight mission aims to study the internal structure of the planet Mars. Its SEIS seismometer, for which ISAE-SUPAERO produced, under the supervision of CNES and IPGP, the noise model and the specification of the scientific software to operate it, continues to reveal the secrets of the red planet. An international research team involving scientists from ISAE-SUPAERO, CNRS, Nantes University, Université Claude Bernard Lyon and Université Paris Cité-Institut de physique du globe de Paris, published on September 19 in the journals Nature Geoscience and Journal of Geophysical Research – Planets important scientific results for the understanding of the formation and thermal evolution of Mars.

SEIS seismometer delivers first seismic and acoustic waves from a meteorite impact on Mars

Prior to NASA’s InSight mission, details of the internal structure of Mars, and the depth of the boundaries between crust, mantle, and core, were relatively imprecise. Furthermore, impact cratering is a fundamental process that shapes planetary surfaces and atmospheres. Recent impactors form new craters and excite acoustic and seismic waves during their entry into the atmosphere and impact on the ground. They can therefore be detected by both the SEIS seismometer and the imagers orbiting Mars.

To date, the seismometer onboard InSight has identified and located four impacts that occurred on the surface of Mars. To do this, the sound waves emitted by the impacts have been detected by the tiny deformations of the ground they produce as they pass over the seismometer. Then, the arrival times and the polarization of the seismic and acoustic waves were used to estimate the locations of the impacts.

These craters were formed by a Sept. 5, 2021, meteoroid impact on Mars, the first to be detected by NASA’s InSight. Taken by NASA’s Mars Reconnaissance Orbiter, this enhanced-color image highlights the dust and soil disturbed by the impact in blue in order to make details more visible to the human eye. Credits: NASA/JPL-Caltech/University of Arizona

These observations, which are the first known on a planet other than Earth, were confirmed by orbital imagery of the associated craters. The dimensions of the craters and the estimates of the meteorite trajectories allow to understand and model the recorded seismograms. By knowing the location of these sources, the detected impacts allow to image the Martian interior. The first arrivals of seismic waves confirm the previously determined models of the crust.

“Knowing the structure of the Mars crust and its level of heterogeneity allows us to learn more about its evolution over time. It is important to understand that it is in the core of this crust that the radioactive elements that make the planet’s temperature fluctuate are concentrated. Its level of fracturing also tells us about the Red Planet’s capacity to renew its surface,” explains Raphaël F. Garcia, a professor of planetary geophysics at ISAE- SUPAERO who coordinated this study.

The sound of a meteoroid striking Mars – created from data recorded by NASA’s InSight lander – is like a “bloop” due to a peculiar atmospheric effect. In this audio clip, the sound can be heard three times: when the meteoroid enters the Martian atmosphere, explodes into pieces, and impacts the surface. Credit: NASA/JPL-Caltech/CNES/IPGP

The sound of a meteor hitting Mars – created from data recorded by NASA’s InSight lander – sounds like a “bloop” due to a particular atmospheric effect. In this audio clip, the sound can be heard three times: when the meteoroid enters the Martian atmosphere, explodes into pieces, and impacts the surface. Credit: NASA/JPL-Caltech/CNES/IPGP

These observations provide the first ground-based evidence of the distance-amplitude scaling relationships of seismic waves generated by impacts on Mars. They confirm the link between the seismic moment of impacts and the vertical moment of the impactor. This development demonstrates the ability of planetary seismology to estimate impact rates and to image the internal structure of planetary objects in the solar system.

These scientific analyses, the result of an international collaboration between researchers from different laboratories, are published in the journal Nature Geoscience.

“As part of the InSight mission, obtaining impact records was the last scientific goal we had not yet met. These results prove that with a single seismometer, we are able to feel Mars “vibrate” but also to hear the sound of explosions and thus locate impacts. This instrument could be deployed on other planets to study their internal structure. As such, one of the sensors of the SEIS spare model will fly to the far side of the Moon in the Farside Seismic Suite (FSS) instrument in 2025,” concludes Raphaël F. Garcia.

Learn more about the first meteoroid impact NASA’s InSight lander detected on Mars in this video.
Credits: NASA/JPL-Caltech

The SEIS seismometer records more than 20 earthquakes and allows an echography of the interior of Mars

Based on about 20 earthquakes detected on Mars by the French seismometer, the work carried out by seismologist Mélanie Drilleau and many scientific experts allows to refine the knowledge of the interior of the red planet. Thanks to the recordings of the SEIS seismometer, scientists have been able to set up the most complete Martian seismic database published to date.

Thus, the majority of the recorded earthquakes come from an area called Cerberus Fossae, where many seismic faults are located, which are most likely the source of these earthquakes. The analysis of the seismic waves that propagate inside the planet, in a way similar to an ultrasound, has allowed to establish a more accurate model of the structure of the interior of Mars.

“In particular, we estimated that the Martian crust is compatible with a gabbro-type rock, a magmatic rock that is the main component of the oceanic crust on Earth,” explains Mélanie Drilleau, a CNRS research engineer at ISAE-SUPAERO. “This new work also confirms the discoveries made last year and published in the journal Science, notably that the interior of Mars is warmer now than in the past.

This study, the result of a strong international collaboration involving five French laboratories (ISAE-SUPAERO, Institut de Physique du Globe (CNRS/IPGP/Université Paris Cité), Laboratoire de Planétologie et Géosciences (CNRS/Nantes University/Université d’Angers), Laboratoire de Géologie de Lyon: Terre, planètes, environnement (CNRS/ENS de Lyon/Université Claude Bernard Lyon 1), Laboratoire J-L Lagrange (CNRS/Observatoire de la Côte d’Azur), as well as the Royal Observatory of Belgium, ETH Zurich and the Jet Propulsion Laboratory, has just been published in the American scientific journal Journal of Geophysical Research – Planets. It is a further step towards understanding the formation and thermal evolution of Mars.

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