Martian Catastrophe

Sargent Zales was awakened in the small hours of the morning by an obnoxiously loud communications device. Maris was on the talker when he answered. “Zales here, What's up, sir?”
“Get down to the base ASAP, Sargent. Mars is under attack! Call your men.”
“Under attack? Holy shit, Lieutenant! I mean, uh, yes sir. I'll be right there, sir.” Zales disconnected and called his men before waking his wife.
“Honey? Wake up! I have to go to the base, we're on alert. Lieutenant Maris just called and said Mars is under attack!”
“Hmmmphft... whah... WHAT? Mars is under attack? Who's attacking us, Venusians?”
“I guess, I don't know any more than you, all he said was that we're under attack and I have to get there ASAP. Holy shit! Mars hasn't been at war for a hundred years! Where's my pants, honey? Holy shit!”
Back on the base, Lieutenant Maris was debriefing Private O'Brien.
“No sir,” O'Brien said, “none of the Venusian rockets went south. They were slightly north of the planetary plane, less than a percent, and they looked like they were going towards Saturn. If I may ask, sir, what's going on?”
Maris was grave. “Brace yourself, Private. Everybody in the southern hemisphere of Mars appears to be dead. We've found no survivors. There was massive ionizing radiation, we don't know the cause.”
O'Brien went pale, even paler than was usual with the pasty-skinned Martians – most of his family lived in the southern hemisphere. And a lot of his friends lived there, too. Military command was in the southern hemisphere as well, and Colonel Gorn was probably now in charge of Mars' remaining military. Thank Deimos the civilian government was in the north!
“Blimey,” O'Brien thought, even though there hadn't been anything resembling an Englishman or an Irishman for millions of years and they speak a completely different language ten million years in our future.
“Sir? ...everybody?” A tear left O'Brien's eye, and he blushed, trembling.
“Private, you can mourn later. Right now we need you, and badly. Those screens could mean Mars' survival. The entire south was flooded with gamma rays and we need to make sure the north doesn't get hit too.”
“Y-yes sir,” he stammered. “Galaxy!” he said. Everybody dead? It was beyond his comprehension. He put his focus on the screens.
“And Private,” Maris continued, “it may have been a natural phenomenon. We don't know the cause yet.”
 
A while later, Zales showed up. “O'Brien!” he said, “Did the lieutenant tell you...”
“Yeah, Sarge, he was here a little while ago.”
“Have you called Dennis?”
“No, I've been too busy manning these screens.”
“Call her, I'll take over. Fucking shit, I can't believe this is happening!”
O'Brien's wife was watching a newscast and went paler than normal for a Martian when the talker signaled. A commercial message was playing on the screen as the device signaled. “Pist,” the screen said. “An affordable levitator that will work in any floater! Remember, Pist means quality! Get the original! Get Pist!”
The Pist jingle followed.
“Larry?” she said as the commercial played its Pist jingle. “What's wrong? What's happened?”
“Oh honey,” he sobbed. “They're all dead!”
“Who's dead? Larry...”
“Oh, Galaxy, Dennis, everybody! The Venusians came up with some sort of gamma ray weapon that murdered everyone on the south side of the planet. They're all dead! Everyone! My family...”
“We interrupt this newscast for some breaking news,” the newscast interrupted after the commercial break was over, of course not interrupting the commercial.
“Everybody? Larry...”
O'Brien sobbed. “As far as we can tell. Look, honey, I wish I could come home but we need to make sure they can't hit this hemisphere too,” he said, tears streaming down his face. “Damn those murderous ghouls! Galaxy, but I hope Hoo decides to nuke 'em once and for all.”
“Oh dear, oh dear, oh dear,” Dennis said. “Look, Larry, I'll make lunch for you guys and bring it there. Oh, my...”
O'Brien went back to his screens, wiping tears from his face. It was too horrible to contemplate. If they hit the north, too...