Miniature gravity detector to peer inside planets

by prashanth on August 31, 2009 · 0 comments

in Tips & Tricks,social networking

miniatorThanks to a nifty new silicon gadget, namely a miniature gravity detector, peering beneath the surface of Mars and other planets to reveal buried geological features could get easier.

According to a report in New Scientist, the device, called a gravity gradiometer, has been designed to measure how much the force of gravity changes from place to place, enabling it to map a planet’s gravitational field.

The idea is to take two masses, each hanging from a spring. If one mass is slightly closer to a planet’s surface, it will feel stronger gravity and pull more on its spring than the other mass.

Compare the pulls on the two springs, and the gravity gradient over that part of the planet can be worked out.

A gravity gradiometer aboard the European Space Agency’s GOCE satellite is currently probing earth’s gravity field, but it has a mass of hundreds of kilograms.

Being so heavy, it would be prohibitively expensive to send such a device on a deep-space mission.

So, Jaap Flokstra and his colleagues at the University of Twente in Enschede, the Netherlands, designed a device weighing just 1 kilogram.

It uses a single wafer of silicon, which can be chiselled using methods developed for microchip fabrication.

In the design, the two test-masses are only a few centimetres apart – compared with half-a-metre in GOCE – so any difference in the gravitational force felt by the masses would be minute.

To detect such small differences, the masses would be held on ultra-delicate springs and the position of each mass measured to within about 1 picometre by a comb-like device whose capacitance varies as the mass moves up or down.

The team calculates that such a device, placed in a spacecraft in orbit around a planet, could sense changes in the gravity field due to geological features of about 200 kilometres across or bigger.

It could detect how deep mountains plunge into the mantle below, say, or look for subterranean oceans such as the sea suspected to lie beneath the south pole of Saturn’s moon Enceladus.

It could pick up changes in gravity due to geological features of 200 km across or bigger.

“We are aiming at building a demo set-up to use on earth in a few months,” said team member Reinder Cuperus.

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