The crater under Lake Malaren is about 10km from three heating plants that supply Stockholm with warmth.

ECONOMIST: Geothermal energy

By 2003, it should be clear whether the Malaren crater can yield a reliable, and commercially viable, supply.

ECONOMIST: Geothermal energy

The impact that created the Malaren crater (which happened about a billion years ago) fragmented 250 cubic kilometres of rock.

ECONOMIST: Geothermal energy

To test the idea, Dr Henkel and his team have begun boring into the Malaren crater in order to map its cracks.

ECONOMIST: Geothermal energy