21 DEC 2018

The twelfth mission of NASA's Discovery program, InSight 1 has the goal of studying the interior of the red planet. Of the five French scientists selected to participate in the analysis of the mission data, there are two researchers from Sorbonne University laboratories: Daniele Antonangeli from IMPMC 2 and Aymeric Spiga at LMD 3. Spiga is in charge of verifying the objectives of the insight InSight project and the involvement of Sorbonne University.

Insight is the first Martian geophysical observatory © NASA / JPL-Caltech

The objectives of the INSIGHT mission

With the goal of studying the internal structure and thermal evolution of Mars, the InSight mission will identify the mechanisms that govern the formation of rocky planets in the solar system. As the first Martian geophysical observatory, InSight will measure the seismic activity of the red planet, its internal heat flux and rotational speed variations to better understand how the planet has evolved into a frozen desert.

"Today, we only know the surface of Mars and have access to its history only through this surface. What we imagine from the inside of the planet only comes from theoretical models made from what we know about the Earth, the evolution of Mars and how the inside of a planet evolves over time," says Aymeric Spiga.

What scientists hope to discover about the depths of Mars

"To reconstruct the history of the surface of Mars is also to reconstruct the history of its climate, which was a priori very different 4 billion years ago," says the researcher. Many scientists argue that a climate similar to that of the Earth existed on Mars early in its history.

"We know that in the past, there was a period of greater activity on Mars," says Spiga. “We would like to know why this activity stopped so quickly after the formation of the planet. Why did it lose its magnetic field about 4 billion years ago, and a little later the intensity of its volcanic activity?"

"One of the hypotheses," explains Aymeric Spiga, "is that because it is smaller than the Earth, Mars would have cooled faster. This would have helped to stop its volcanic activity and then remove its magnetic field.” One thing is certain: by losing its magnetic field, the planet was bombarded by the energy rays of the sun and lost part of its atmosphere. It would have gone from a habitable climate to a non-habitable climate.

In addition, "the presence of geological activity is a way of transferring molecules, such as water vapor, from the inside to the outside of the planet," adds Spiga. On Earth, for example, plate tectonics and volcanic activity have helped to determine its atmospheric composition and in particular its composition of greenhouse gases, which are essential to the development of life.

SEIS seismometer, a high precision instrument

The Seismic Experiment for Interior Structure (SEIS) is the main instrument of the mission. It will measure the waves from ground motion inside the planet, whether they are "Mars-quakes" or meteorite impacts. It will detect both small quakes due to low activity near the surface and large quakes with a magnitude greater than 4.5.

Because of its high precision, the design of this seismometer required the particular expertise of the French laboratories. The seismic data collected will benefit scientists around the world and Sorbonne University researchers will be directly involved in their analyses. They will enable scientists to deduce information about the surface, the structure (such as the size of the core or the thickness of the mantle), the plant’s composition and its internal activity.

Sorbonne University’s contribution

With the support of CNES 4, Sorbonne University is involved in the Insight mission through the contribution of its laboratories, notably the LMD and the IMPMC. The latter laboratory has worked on the construction of composition models of the interior of Mars from the data collected by the seismometer SEIS. These seismic data will be analyzed in light of the physical properties of the materials likely to compose the planet’s interior, properties measured in the laboratory at IMPMC. The LMD, meanwhile, participates in the analysis and modeling of  the meteorological and climatic data from Mars.

Assited by a small weather station placed on the surface, researchers will be able to measure the temperature and pressure continuously. This will enable them to better understand the composition of the atmosphere on Mars and to better identify the noise caused by winds that cause vibrations on the surface of the planet. Because it is essential to detect all seismic activity, even the smallest activity so that seismologists can remove the atmospheric noise that is masking the data.

Thanks to the two participating scientists from the Sorbonne University involved in the mission, Aymeric Spiga and Daniele Antonangeli at the LMD and the IMPMC respectively, will have access to a preview of all the measuring instruments used on Mars.

Watch the Insight probe's landing live on Monday, November 26, in the hall of the Cité des sciences et de l'industrie, in the presence of scientists and engineers, including the three researchers from Sorbonne University, Daniele Antonangeli, Violaine Sautter and Aymeric Spiga.

1. “InSight” stands for INdoor exploration using Seismic Investigations, Geodesy and Heat Transport 

2. Institute of Mineralogy, Materials Physics and Cosmochemistry (Sorbonne University/CNRS/Institute for Development Research/MNHN)

3.  Dynamic Meteorology Laboratory (Sorbonne University/CNRS/École Polytechnique/École Normale Supérieure) - Institut Pierre-Simon Laplace

4. National Center for Space Studies

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