Gravity field

GRACE and GOCE are two gravity missions giving us the possibility to get a deeper look into the gravity field of our planet. I have been involved in two main directions to exploit these satellite data.

With my co-authors, I have demonstrated, for the first time, that flows in the Earth’s core can have a gravity signature in satellite data. For decades, man has dreamt of exploring the deep Earth and particularly its core, but to go there following Jules Verne’s “Journey to the centre of the Earth” is just fantasy. The techniques of surface geophysics have allowed us to investigate the Earth’s core indirectly. In recent years a wealth of information has been gained about core dynamics thanks to the interpretation of magnetic field variations recorded by ground observatories and satellites; large scale material flows have thus been inferred. This result opens up the possibility of studying core dynamics with additional geophysical data sets besides those of magnetism, geodesy and seismology. Much should be gained in the future from joint analyses of these independent sources of information.

GOCE mission gibes an unprecedented three-dimensional view on Earth's gravity. This new image of our planet's gravity is made possible by gradiometry, a measurement concept onboard a satellite for the first time: the GOCE set of accelerometers are indeed able to sense the variations of Earth's gravitational attraction inside the satellite in 3D, which requires a high precision and makes it a unique mission. I have been involved in studies illustrating that in the three-dimensional way allowed by GOCE, the force that pulls us downwards varies from one place to another due to the dynamic processes and uneven distribution of mass inside the planet. Much should be gained in the future from joint analyses of these maps, together with other geophysical datasets, to image the Earth’s interior. The knowledge of the gravitational shape of the Earth as derived from GOCE is crucial for many fields of application – indicating how striking is the idea that the global horizontal, a gravity level surface, has bumps and lumps.