Any way to dump unwanted cargo?

Many times while exploring I find myself inconveniently distant from a place to sell all my cargo, and in some of these times I find a treasure trove of a planet just begging me to take all its high-valued wealth.  However, my cargo hold may be clogged up with a bunch of very low value resources.  In SC2, it was a simple task to dump unwanted cargo, but I can't seem to figure it out here.  Is it possible?  If so, how?  So many planets and moons are just taunting me while I feel powerless to exert my dominance.