“The main objectives of the mission have been achieved“, congratulated Philippe Lognonné, geophysicist at the Institut de physique du globe de Paris (IPGP) and scientific manager of the Martian seismometer SEIS (Seismic Experiment for Interior Structures), during a press conference organized on July 21, 2021 at the IPGP. Embarked and deposited on the surface of Mars in December 2018 by the Nasa InSight lander (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport), the seismometer whose production Philippe Lognonné directed reveals, for the first time, the internal structure of the Red planet. The thickness and subdivisions of the crust in particular, but also the structure of the mantle, the heat flow that escapes from the heart of the planet as well as the size of the core, results from two years of measurements and analyzes detailed in several publications of the journal Science dated July 23, 2021. Now among this harvest of results, “this is the size of the Martian core – much bigger than expected! – which is the biggest surprise“, points out Philippe Lognonné.
An ultrasound of the bowels of Mars
Very little was known, so far, about the bowels of Mars. The estimates concerning the radius of the core were between 1,600 and 1,900 kilometers, which is a particularly wide range. Planetologists speculated on its composition and wondered if it was still liquid and if it was made, like the Earth, of a solid seed surrounded by a liquid envelope. The analysis of the seismic waves recorded during a Martian year (that is to say about two Earth years) made it possible to answer most of these questions.