"You are right, Spacer Lynn," she acknowledged. "For a moment I forgot I was a Psychologist--it's a quality about you that for an instant made me feel less a scientist and more a ... but never mind. We'll be together for the Deity knows how long, and it's futile to begin by quarrelling. Lean forward so you can see this chart, I'll explain." "We'll be together, did you say?" Mark was delighted. "Then give me a dozen problems!" "Yes," she replied dubiously. "As a Psychologist I'll be part of the expedition. You'll find that this one problem will be more than enough." The girl pressed a button on her desk and one of the undamaged walls began to glow until it became an astro-map, a reproduction of charted space. Each planet was indicated in relative size, and in the lower center, pulsing angrily a thin red line marked "Comet" seemed to be approaching inferior conjunction with Terra. "Is that the problem?" Mark asked. "Simple! When it enters Terra's orbit, life on Terra ceases. Evacuation's the only possible solution. I knew that comet was approaching, but not being an Astronomer I didn't compute its trajectory. Besides, being on Io is like being in exile--news hardly ever reaches us there. Will it destroy Terra completely?" "No, not entirely. At first, indications were that it would enter the orbit of our system at such an angle that Terra would be destroyed. However, we've checked with the observatories on Pluto since then, and it has been determined that it will merely enter the field of attraction sufficiently to shift the axis to opposition. Of course, this will render Terra unfit for habitation ... perhaps for a century or two ... therefore, as you realized, evacuation's the answer." "I'm listening," Mark said earnestly, as the magnitude of the problem before them struck him. "However, you're aware I'm not an astronomer, and the technique of evacuation could best be handled by the Council itself. I'm afraid I still don't quite see what my role's to be.... But whatever it is, I'm ready." "Turn your attention to this plotting chart," Doctor Fortun indicated the map on her desk. "These areas marked in red have already been affected. Tremors have increased and volcanic openings are occurring in these and these areas, never dangerous before. While you were on Io awaiting orders for another exploratory journey, we began to attempt resettlement of our _Civicans_ and _Ruralians_ on other Planets--even giving them their choice of occupations and of planets ... quite a concession you must agree." "Quite!" The irony in his voice seemed to escape her. * * * * *