A heat flow and physical properties package for the surface of Mercury

European Space Agencies fifth cornerstone mission BepiColombo includes a 'S urface Element' to land a scientific payload on the surface of Mercury. The current strawman payload includes a heat flow and physical properties pack age (HP3), focussing on key thermal and mechanical properties of the near-s urface material (down to a depth of 2-5 m) and the measurement of heat flow from Mercury's interior, an important constraining parameter for models of the planet's interior and evolution. We present here an overview of the HP 3 experiment package and its possible accommodation in a self-inserting 'mo le' device. A mole is considered to be the most appropriate deployment meth od for HP3, at least in the currently-assumed case of an airbag-assisted so ft landing architecture for the Mercury Surface Element. (C) 2001 Elsevier Science Ltd. All rights reserved.