During a conversation with Werner von Kerman, he said to me that once you are in orbit, the TWR is not important, and can be as low as necessary. I replied him that many celestial bodies need trust to land on them, but said that "anyway, on most airless worlds, kerbals weight like an ant".
It happens that threre exists an engine specifically made for ants, the Ant engine. The challenge is to test how much the assertion is true. The conditions are
-A kerbal needs minimal confort, so will not tolarate anything less than mk1 lander can.
-The only propulsion allowed is a single Ant engine (and no rcs, no eva pushing).
-A single ship begins from LKO, with periapsis/apoapsis between 70km and 80 km. It can be hyperedited there. The ship can split, but then only one part will have the Ant engine.
-The mission ends when the ship (which should consist at least of the command module containing the kerbal) lands safely on Kerbin.
Tylo is impossible as the Ant engine is not even capable of lifting the mk1 lander can. Making history is allowed as it does not seem to allow anything useful here. For the others worlds, here are the levels of glory
-Easy: Minmus
-Medium: Gilly, Bop, Pol, Ike, Mun, and Minmus with Mk1-3 command pod
-Hard: Eeloo, and Gilly, Bop, Pol with Mk1-3 command pod
-Ant-man: Vall, Moho
Remarks: Its not clear if Vall/Moho are possible, but I cannot prove it isn't... Heavy ships are essentially useless, as their terribly low TWR make orbital maneuver difficult. For Jool/Eeloo, using eve assists is very useful as it decreases necessary V infinity at Kerbin, and long trusts lowers Oberth effect. On high gravity worlds like Mun/Eeloo, an orbital rendez-vous seems necessary. I have personnaly managed to land on Minmus, Gilly, Bop, Pol with mk1 lander can, let's see your creativity!