Mars' metal core is insulated by a silicate layer that could be stopping its magnetic field

Embargoed until: Publicly released: 2023-10-26 02:00

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Mars' metallic core may be 150km smaller than previously thought, according to international researchers across two papers, who say they have found evidence for a fully molten silicate layer surrounding the metal core which could be preventing the Red Planet from producing a magnetic field. The team used data from NASA's Insight Lander, which was able to analyse the interior structure of Mars after a meteorite impact in 2021. They found that the metallic core is actually smaller and denser than previously thought, and is insulated by the silicate layer. According to the team, this insulating layer prevents it from cooling and generating a thermal dynamo, which is what traditionally produces a magnetic field around planets like Earth. External sources such as large meteorite impacts or gravitational interactions with ancient satellites (which have since then disappeared) may have generated the magnetic field recorded in the Martian crust during the first 500-800 million years of its evolution, they say.

Media release

From: Springer Nature

Planetary science: New insights into the internal structure of Mars (N&V)

Mars’s liquid iron core is likely to be surrounded by a fully molten silicate layer, according to a pair of studies published in Nature. These results offer a new interpretation of the interior of Mars, suggesting its core is smaller and denser than previously proposed.

The analysis of measurements from the NASA InSight lander’s Seismic Experiment for Interior Structure (SEIS) project in 2021 suggested the presence of a large but low-density core, composed of liquid iron and lighter elements such as sulfur, carbon, oxygen and hydrogen. However, these results suggest that the core has a higher proportion of lighter elements than is feasible according to estimates of the abundances of these elements early in Mars’s formation history.

Amir Khan and colleagues and Henri Samuel and colleagues examined the latest batch of seismic signals in combination with first principles simulations and geophysical models to produce their estimates for the size and composition of the Martian core. The two studies find that the liquid iron core of Mars is surrounded by an approximately 150 km-thick layer of near-molten silicate rock, the top of which was previously misinterpreted as the surface of the core. This decrease in core radius implies a higher density than estimated in the earlier InSight study. These estimates can more easily be reconciled with our existing knowledge of chemical abundance on Mars, as they require fewer alloying light elements to produce a stable liquid core.

In an accompanying News & Views, Van der Lee calls the results “the most accurate and precise estimates so far of Mars’ core and mantle structure”, and suggests that the findings further our understanding of terrestrial planet formation and composition.

Journal/
conference: Nature

Research:Paper

Organisation/s: ETH Zürich, Switzerland

Funder: Paper 1: Open access funding provided by Swiss Federal Institute of Technology Zurich. Paper 2: Co-authors affiliated to French laboratories thank the French Space Agency CNES and ANR fund (ANR-19-CE31-0008-08). J.B. acknowledges support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 101019965- ERC advanced grant SEPtiM). Additional support was obtained from IdEx Université Paris Cité ANR-18-IDEX-0001 for H.S., Z.X., P.H.L., J.B. and T.K. V.L. acknowledges support from NASA grant 80NSSC18K1628 and NASA SSERVI Cooperative Agreement 80NSSC19M0216. J.C.E.I. acknowledges UKSA grant ST/W002515/1. This is InSight Contribution Number 224.

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