Gravity Explorer mission still unearths secrets hidden on our planet

The new model produced in ESA’s 3D Earth study shows for the first time how different the sub-lithospheric mantle is under different oceans, and provides insight into how the morphology and rates of ridge propagation Mid-ocean can be related to the deep chemical and thermal structure. Credit: ESA / Planetary Visions

Despite the end of ESA’s GOCE mission more than seven years ago, scientists continue to use gravity data from this remarkable satellite to dig deeper and uncover secrets about our planet. Recent research shows how scientists combined GOCE data with measurements taken at the surface to generate a new model of the Earth’s crust and upper mantle. This is the first time that such a model has been created in this way – and it sheds new light on the processes of plate tectonics, which, in turn, are linked to phenomena such as earthquakes and volcanic eruptions.

The lithosphere, which includes the hard crust of the planet and the partially melted upper part of the upper mantle, is fundamental to plate tectonics.

Plate tectonics describes how the crust is divided into a mosaic of plates that slide laterally over the malleable top of the upper mantle and in doing so give rise to new seabeds along mid-ocean ridges, mountains, volcanoes. and earthquakes. A better understanding of these processes depends on knowledge of the differences in temperature and chemical composition of the lithosphere.

Geophysicists traditionally measure the speed at which seismic waves travel when an earthquake occurs to determine the distribution of underground physical properties. The speed of seismic waves is governed mainly by the temperature of the subterranean rocks and to a lesser extent by the density.

Here, the gravity data from space can be added to the image because the strength of the gravity signal is related to the density. In addition, satellite data is uniform in coverage and precisionand satellites cover areas where ground measurements are scarce.

For more than four years, GOCE has mapped Earth’s gravity with extreme detail and precision. This has led to remarkable discoveries, from the depths below the surface of our planet to the heights of the atmosphere and beyond.

New research published in International Geophysical Journal describes how scientists generated a new model of the lithosphere using the combined power of GOCE gravity data and seismological observations combined with petrological data, which come from studying rocks brought to the surface and from laboratories where pressures and Extreme temperatures of the Earth’s interior are replicated.

Javier Fullea, of the Complutense University of Madrid and the Dublin Institute for Advanced Studies, and also co-author of the article, said: “Earlier global models of the crust or lithosphere suffered from limited resolution or were based on a single method or data set.

“Only recently available models were able to combine multiple geophysical data, but they were often only at regional scales or were limited by how the different data are integrated.

“For the first time, we were able to create a new model that combines multiple global-scale terrestrial and GOCE satellite data sets in a joint inversion that describes the actual temperature and rock composition of the mantle.”

Jesse Reusen, Delft University of Technology, added: “This new model provides a picture of the current composition and thermal structure of the upper mantle which can be used to estimate viscosity. In fact, it has already been used to estimate the remaining postglacial uplift – or land elevation after the weight of the ice has withdrawn – following the melting of the Laurentide ice sheet in Canada, thus improving our understanding of the interactions. between the cryosphere and the solid Earth. This research was published last year in the Geophysical Research Journal. “

The new model produced in ESA’s 3D Earth study shows for the first time how different the sub-lithospheric mantle is under different oceans, and provides insight into how the morphology and rates of ridge propagation Mid-ocean can be related to the deep chemical and thermal structure.

Steady State Gravitational Field and Ocean Circulation Explorer (GOCE)

Launched on March 17, 2009, the ESA Steady State Gravity Field and Ocean Circulation Explorer (GOCE) mission was the first Earth Explorer mission in orbit. This new mission has provided a wealth of data to bring a whole new level of understanding of one of Earth’s most fundamental natural forces – the gravity field. This sleek, high-tech gravity satellite has embodied many firsts in its design and the use of new technologies in space to map the Earth’s gravity field in unprecedented detail. Credit: ESA – AOES-Medialab

Roger Haagmans, ESA, said: “Our GOCE mission never ceases to impress. The data he provided over his four years of life in orbit continues to be used to understand the complexities of our planet. Here we see it shining with a new light on the structure of the Earth deep beneath our feet. Even though the processes occur at depth, they have an effect on the Earth’s surface – from the generation of new seabed to earthquakes, so in turn, affect us all.

“In addition, this is a remarkable result of the 3D Earth project and another important step towards achieving one of the main objectives of our Science for Society program: to develop the most advanced reconstruction of our solid Earth from heart to heart. surface, and its dynamic processes. “

The algorithms and results of these studies will be the subject of the 3D Earth Spring School: a virtual event taking place from March 29 to April 1.

Reference: “WINTERC-G: mapping of the thermochemical heterogeneity of the upper mantle from the coupled geophysical-petrological inversion of seismic waveforms, heat fluxes, surface elevation and satellite data from gravity ”by J Fullea, S Lebedev, Z Martinec and NL Celli, March 10, 2021, International Geophysical Journal.
DOI: 10.1093 / gji / ggab094

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