Artists view of the internal structure of Mars showing the propagation of diffracted waves from the September 2021 meteorite impact to the SEIS seismometer of the InSight mission. The presence of this basal layer assists discuss the observed trajectory of Phobos, Marss closest moon. In contrast, the solid mantle above this layer is more rigid and seismically improperly attenuating, as suggested by the detection at the surface area of Mars of waves associated with seismic events of fairly low magnitude.
“The thermal blanketing of Marss metallic core by the liquid layer at the base of the mantle indicates that external sources are needed to generate the magnetic field tape-recorded in the Martian crust throughout the very first 500-800 million years of its development. SEIS data are formatted and distributed by the Mars SEIS Data Service of IPG Paris, as part of the National Observation Service InSight to which LPG also contributes and, for Seismo activities at the School, GéoAzur.
Mars Evolution
This new structure design, released today, October 25, 2023, in the journal Nature, is not only more consistently reasonable with all available geophysical data, but also describes better the development of Mars since its formation.
In specific, the evidence of this stratification of the Martian mantle clarifies the unusually sluggish propagation, hitherto inexplicable, of diffracted waves from the September 2021 meteorite effect by their trajectory in the lower and fully molten part of the basal layer, where seismic velocities are low.
For several older seismic events, the arrival times of waves measured at the surface area of Mars are suitable with reflections of shear waves at the top of the molten layer (located several 10s of kilometers above the metallic core) and not at the core-mantle interface, as formerly assumed.
Lastly, the existence of this basal layer assists explain the observed trajectory of Phobos, Marss closest moon. Undoubtedly, the partly molten and upper part of the basal layer effectively dissipates the deformations generated by Phoboss gravitational attraction. In contrast, the strong mantle above this layer is more rigid and seismically improperly attenuating, as suggested by the detection at the surface of Mars of waves associated with seismic occasions of reasonably low magnitude.
Henri Samuel, CNRS researcher and geodynamicist at the IPGP, discusses the brand-new model for the internal structure of Mars, proposed in a post published in the journal Nature. This model, built utilizing seismic data recorded on Mars following a meteorite impact, and which discusses all the geophysical observations, revolutionizes our vision of the internal structure of the Red Planet and its development.
Redefining Mars Core
The presence of this molten layer at the base of the mantle suggests a metal core 150 to 170 km smaller (i.e., a radius of 1650 ± 20 km) and 5 to 8% denser (i.e., 6.5 g/cm3) than previous seismic estimates. This denser core would therefore be made up of an alloy with less light elements than previously needed, and more suitable with cosmochemical information from the analysis of Martian meteorites and high-pressure experiments.
The research group therefore proposes that Mars most likely experienced an early lava ocean phase whose condensation produced a steady layer at the base of the mantle, highly enhanced in iron and radioactive components. The heat launched by the latter created a basal layer of molten silicates situated above the core, overlain by a thinner partially molten layer.
Implications for Mars Thermal and Magnetic Properties
The research study more states that such stratification of the mantle insulates the metal core, thereby preventing it from cooling and generating a thermal eager beaver. “The thermal blanketing of Marss metal core by the liquid layer at the base of the mantle implies that external sources are required to create the magnetic field tape-recorded in the Martian crust throughout the very first 500-800 million years of its advancement. These sources might be energetic impacts, or core motion produced by gravitational interactions with ancient satellites which have ever since disappeared,” explains Henri Samuel.
Contrasting Earth and Mars
This stratified structure of the interior of the mantle of Mars, which contrasts with that of the Earth, shows a various internal advancement of these two planets. Mélanie Drilleau, research engineer at ISAE-SUPAERO and co-author of the research study, explains that “the discovery of this stratification in the Martian mantle opens new research horizons, considering that the seismic information taped by the SEIS instrument of the InSight mission will now be reassessed in the light of this brand-new paradigm.”
Reference: “Geophysical evidence for an enriched molten silicate layer above Mars core” 25 October 2023, Nature.DOI: 10.1038/ s41586-023-06601-8.
About InSight and SEIS.
NASAs InSight mission formally ended in December 2022 after more than four years of collecting special science data on Mars.
JPL handled the InSight objective on behalf of NASAs Science Mission Directorate. InSight is part of NASAs Discovery program, handled by the Marshall Space Flight Center (MSFC), NASAs Huntsville, Alabama facility. Lockheed Martin Space in Denver developed the InSight probe, including its cruise phase and lander, and supported operation of the spacecraft for the objective. CNES was the prime specialist for SEIS and the Paris Institute of Globe Physics (Université Paris Cité/ IPGP/CNRS) assumed scientific obligation. CNES finances the French contributions, coordinates the global consortium (*) and was accountable for the integration, testing and supply of the complete instrument to NASA. IPGP designed the VBB (Very Broad Band) sensors, tested them before their delivery to CNES and contributes to the operation of VBBs on Mars.
The SEIS and APSS operations were performed by CNES within FOCSE-SISMOC, with the support of the Centro de Astrobiologia (Spain). SEIS data are formatted and dispersed by the Mars SEIS Data Service of IPG Paris, as part of the National Observation Service InSight to which LPG also contributes and, for Seismo activities at the School, GéoAzur. Daily recognition of earthquakes was performed by InSights Mars Quake Service, a collective functional service led by ETH Zurich to which seismologists from IPG Paris, the University of Bristol (UK), and Imperial College London (UK).
A number of other CNRS laboratories consisting of LMD (CNRS/ENS Paris/Ecole polytechnique/Sorbonne University), LPG (CNRS/Nantes University/Le Mans University/University of Angers), IRAP (CNRS/University of Toulouse/CNES ), the LGL-TPE (CNRS/Ecole Normale Supérieure de Lyon/Claude Bernard University Lyon 1), the IMPMC (Sorbonne University/National Museum of Natural History/CNRS) and LAGRANGE (CNRS/Universit é Côte dAzur/ Observatoire of the Côte dAzur) are participating with the IPGP and ISAE-SUPAERO in the analysis of information from the InSight objective. These analyses are supported by CNES and the National Research Agency as part of the ANR MArs Geophysical InSight (MAGIS) project.
( *) in cooperation with SODERN for the production of the VBB, the JPL, the Swiss Federal Institute of Technology in Zurich (ETH, Zurich Switzerland), limit Planck Institute for Solar System Research (MPS, Göttingen, Germany), the Imperial College London and the University of Oxford offered the SEIS subsystems and are involved in the clinical exploitation of SEIS.
Artists view of the internal structure of Mars showing the proliferation of diffracted waves from the September 2021 meteorite impact to the SEIS seismometer of the InSight mission. Their trajectory goes through the lower, completely molten part of the silicate layer at the base of the mantle, where seismic velocities are low. Credit: IPGP/ CNES/ N. Starter
Current information obstacles preliminary NASA InSight Mars Lander objective findings about Mars internal structure. Scientists have actually found a molten silicate layer at the Martian mantles base, recommending a smaller and denser core than previously approximated.
The very first information from NASAs InSight objective made it possible to identify the internal structure of Mars in a series of papers from the scientific team published in the summer season of 2021. Given that then, the analysis of brand-new data created by a powerful meteorite impact that took place on September 18, 2021, questioned the very first price quotes of the internal structure of the Red Planet.
By studying the proliferation times of waves created by this impact, an international team led by Henri Samuel, CNRS researcher at the Paris Institute of Globe Physics, and involving researchers from CNRS, ISAE-SUPAERO, and Université Paris Cité supported by CNES and ANR, as well as co-authors from the Royal Observatory of Belgium, the Universities of Maryland and Bristol, the Zürich Polytechnic School, the Russian Academy of Sciences, and NASAs Jet Propulsion Laboratory, demonstrated the existence of a molten silicate layer at the base of the Martian mantle overlying the metallic core.
