Can't be done in that space or that mass. The hard part isn't the 3D printing (and that isn't easy, as anyone can tell you 3D printing in a controlled temperatu

Can't be done in that space or that mass. The hard part isn't the 3D printing (and that isn't easy, as anyone can tell you 3D printing in a controlled temperature environment with precision manufactured feed stock is still a bit touchy, using on site crafted feed in an environment that shifts 100 degrees Celsius day to night is going to be very challenging) it is the materials extraction and processing. You basically have to mine, refine, and mold Martian soil into whatever end product you have, and you have no fossil fuels to get things up to temp. To do so at all would be a massive undertaking, to do so at any kind of scale in 300 kg (assuming that magically you ended up recalculating the trajectory or something to get all 300kg in one group on the surface) is, I'm pretty sure, beyond our technology at present.