During the Black Seed Scourge event (July 15,2015- July 19,2015) there is a highlighted capture mission on Jupiter called "Black Seed Scourge 2". You must capture both targets to complete the mission and you must complete the mission 3 times. Each time you complete it you will acquire one point (a maximum of three may be earned on Jupiter). Once you have a total of six points ( 3 earned on Venus and 3 earned on Jupiter) you will unlock the challenge. Finally, you must do this mission with only a melee weapon equipped.