There are several problems with explosive excavation:<br /><br />1) Distruption of the surface<br /><br />2) Difficulty of access (sleep loose crater sides)<br /><br />3) Organic contamination at the ppm level (suprisingly but true, I had a student once studying organics in rocks from a mine and we found traces of all sorts of on organics that had been forced into the rock by the explosion. Some were traces of plastic bags, detonators, others were from diesel fuel combustion).<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em> Arthur Clarke</p> </div>