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Five months ago this month, ESA's GOCE gravimetric mapping satellite has finally given way to gravity, but its results still provide buried treasures, offering a new insight into the remains of hidden lost continents. at the bottom of the Antarctic ice floe.
A team of researchers from the German University of Kiel and the British Antarctic Survey published this week its latest results based on GOCE in the journal Scientific Reports.
Nicknamed "Formula 1 Space", the GOCE (Exploration of Circulation and Circulation) mission has been circling the Earth for more than four years, from March 2009 to November 2013. This sleek and smooth satellite, without moving parts, was designed around a single goal: to measure the gravitational attraction of Earth more precisely than any previous mission.
GOCE flew at an altitude of just 255 km, more than 500 km closer than a typical Earth observation satellite, to maximize its sensitivity to gravity.
During its last year in orbit, with a well-maintained xenon propellant reserve, GOCE was maneuvered further down, just 225 km above sea level, for even more accurate gravity measurements. The propellant that keeps him resistant to atmospheric drag was finally used in October 2013 and he returned to the atmosphere three weeks later.
GOCE's main product was a high-fidelity or "geoid" global gravity map, but the mission also mapped localized gravitational gradients – measures of how quickly the acceleration of gravity changes – in all directions of movement, up to a resolution of 80 km.
The team from Kiel University and BAS converted this patchwork of 3D gravimetric measurements into curvature-based 'shape indices' in the different regions of our planet, similar to the contours of a map.
Professor Jorg Ebbing of Kiel University, lead author of the study, comments: "Satellite gravimetric data can be combined with seismological data to produce more consistent 3D images of crust is crucial to understanding the interactions between plate tectonics and deep mantle dynamics. "
In combination with the existing seismological data, these gravity gradients show great sensitivity to the known characteristics of the terrestrial "lithosphere", the solid crust and the part of the molten mantle below.
These features include dense rocky areas called cratons – remnants of ancient continents discovered at the heart of modern continental plates – highly folded 'orogenic' regions associated with mountain ranges and finer crust of ocean bottoms.
The new window on the deep basement offered by these data offers new information on the structure of all the continents of the Earth, but especially of Antarctica. With more than 98% of its surface covered by ice with an average thickness of 2 km, the southern continent remains largely a white spot on current geological maps.
"These gravimetric images are revolutionizing our ability to study the least understood continent of the planet, Antarctica," said co-author Fausto Ferraccioli, scientific head of geology and geophysics at BAS.
"In East Antarctica, we see an exciting mosaic of geological features that reveal fundamental similarities and differences between the crust found under Antarctica and the other continents to which it has been attached until there are 160 millions of years. "
The results of the gravity gradient show that West Antarctica has a finer crust and lithosphere compared to those of East Antarctica, which consists of a mosaic of old cratons separated by younger orogens, thus revealing a family with Australia and India.
These discoveries have more than a purely historical geological interest. They give clues to the influence of the continental structure of Antarctica on the behavior of the ice sheets and on the speed with which the Antarctic regions will recover in response to the melting ice.
Roger Haagmans, scientist of ESCE's GOCE mission, added: "It is interesting to note that the direct use of gravity gradients, measured for the first time with GOCE, leads to an independent new look on the Earth, even under a thick layer of ice.
"It also provides context for how the continents may have been connected in the past before they split due to the movement of the plates."
Related Links
GOCE at ESA
Beyond the ice age
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