This paper deals with a mobile array for mapping the electric properties of planetary surfaces, with a resolution of the order of a few meters in all dimensions. The principle of the measuring technique is first recapitulated; the prototype model of this novel instrument is then described. The array was operated at a frequency of 128 kHz over a site with apparent resistivities in the range 20--100 &OHgr; m and the experimental results are found to be in excellent agreement with those derived from another independent technique. It is demonstrated, from measurements collected on a second site with resistivities of the order of several kilo-ohm meters, that this new technique also yields information about the dielectric constant of the ground. This method is not only applicable to geological surveys on Earth but also appears particularly attractive for the exploration of the surface of other planets by means of landers, penetrators, or unmanned rovers. ¿1991 American Geophysical Union