Take the mass of curiosity, replace it with ISS-grade food, and it would be enough to sustain an astronaut on Mars for around a year and a half. I'm not saying it's easy, or cheap, or suitable for sustaining an actual colony, but it's doable. The most likely scenario for Mars for the foreseeable future is that we'll be sending Astronauts alongside everything they need, including shelter, food, water, etc.