"I don't know," said Jonner. "Those are our orders. Now, we leave the groundcars here and go on foot to Marsport. Check equipment, everyone." "Say," commented Farlan after a moment, "I don't seem to have any sunburn lotion." "You can have mine," said Aron, laughing. "This far from the sun, I haven't been sunburned yet, and don't expect to be." "Haven't been on Mars a year yet, have you?" suggested Tyruss. "No," admitted Aron. "I came from Earth with the last space fleet and escaped in a lifeboat. Why?" "There's an Earth-sun conjunction coming up. Every time the Earth swings between Mars and the sun, everybody on Mars gets a bad sunburn. When it comes, you better cover yourself with lotion, because clothes don't protect you and even if you're in a city, the domes and house roofs are transparent to pick up the sun's heat." "We have enough among us," said Jonner. "Besides, if our mission goes off on schedule, we'll be back at base by the time the Earth-sun conjunction starts. Let's head for Marsport." * * * * * The six men crouched in the concealing canal sage near the edge of Marsport, the spaceport outside Mars City. The blue mist was a heavy fog that swirled around them. In the lighted circle of the spaceport area three stubby, two-stage gravity-boats sat upright, about a hundred yards apart. These were the heavy duty rockets that plied back and forth to Phobos, Mars' inner moon and Marscorp's natural space station, entering the planetary atmosphere of Mars where spaceships could not go. Workmen stirred busily around one of the G-boats; a guard stood at the entrance port of each of the other two. Jonner tried to assess the evidence, to decide which of his five companions was the Marscorp spy. How Marscorp had found out about the expedition, how the credentials had been forged, how the rendezvous had been learned, did not matter now. Marscorp could not know their plans beyond the rendezvous in the desert, because only he and Sir Stanrich had known the orders Sir Stanrich had given him for this mission. The fact that Stein and Wessfeld had arrived together from Charax eliminated them as suspects, for the Charax command would have known whether one or two men were to be sent from there. Jonner did not believe Tyruss was the spy. Jonner had won his space papers just before the Rebellion began, but it was logical that Sir Stanrich would send a more experienced space captain to handle their ship. That left Farlan and Aron, from different sections of the Hadriacum front. Which one? In their specialties, Farlan was an alternate to Stein as an astrogator, Aron an alternate to Wessfeld as an engineer. But every spaceman could handle every other spaceman's duties in an emergency, and it was hard to say which task they had decided to double up on.