When we’re told about newly released satellite images of our Earth, we imagine beautiful swathes of green and blue with the occasional white of swirling storm clouds or snow-topped mountain ranges. But rarely do we picture a multi-colored root vegetable. ‘Potato Earth’ is the name being given to the new images of the globe as created by the European Space Agency’s (ESA) incredibly sleek GOCE satellite. The new map, known as a ‘geoid,’ traces the varying degrees of influence that the pull of gravity from the mass of rock under our feet has on the earth’s surface with unrivaled precision.
After two years of low-flying orbit the GOCE satellite has returned images that give scientists access to the most accurate model of the geoid ever produced. Gravity is strongest in yellow areas and is weakest in blue areas.
According to the ESA the geoid represents the surface of “an ideal global ocean in the absence of tides and currents, shaped only by gravity.” It is a crucial reference for measuring ocean circulation, sea-level change and ice dynamics – all affected by climate change.
Gravity does so much more than simply keep our feet on the ground. It is fundamental to how the oceans distribute the heat from the sun around the globe and it plays an important role in the tectonic movements of the Earth’s crust. The GOCE images can help us better understand what’s going on deep within the Earth when huge earthquakes – like the one that hit Japan last month – strike by giving us a 3D view of the forces at work beneath our feet.
The differences in the Earth’s gravitational signals are incredibly weak so in the GOCE geoid they have been magnified 10,000 times. But this does nothing to lessen the scale of the impact this can have on us in day-to-day life. For example, a boat off the coast of Europe (shown in bright yellow) can sit 180m “higher” than a boat in the middle of the Indian Ocean (show in deep blue) and still be on the same level plane.
The GOCE project has funding until 2012, but it was feared the satellite’s mission may not even last until then. Because of its very low altitude of approximately 255km, lower than any other satellite in orbit, GOCE is propelled forward by an engine so it can move through the remnants of atmosphere still present at this altitude. However the ESA now believe the satellite has enough propellant to keep it in orbit until 2014.
The images provide groundbreaking insight into the processes at work above and below the surface of the Earth thanks to its own gravitational pull. The GOCE is already proving its worth and Rune Floberghagen, ESA’s GOCE Mission Manager, was happy to announce that additional data is expected over the next few months that can add to the accuracy of the geoid. It could turn out to be the most useful potato the world has ever known.