 Which planet was considered the new frontier?
But now, on Mercury, he was selling his guns into the weirdest of all his exploits—gambling his life against the soft touch of a woman's lips. On the hot, teeming planet of Mercury it was as refreshing as a cold plunge. He had fought in the deadly little wars of the Moons of Jupiter for years, then the Universal Debacle of 3368, after that the Martian Revolution as well as dozens of skirmishes between the Federated Venusian States. Why, at this time when the Earth Congress was about to grant them self-government, should they stage a revolution? Earth doesn't realize the seriousness of the situation." Other Earthmen are in control of the mines and the northern plantations.
 Mercury
 Mars  Earth  Mercury  Jupiter