Titan

Titan Alpha

The ethane rainstorm slowly moved across the land, raining fat drops of liquid that spattered onto the slushy ground and drummed against the armored hull of Titan Alpha. The sensors showed that despite the frigid temperature of the ground, the falling rain did not freeze but flowed across the ice, even eroding it slightly as it ran downslope along gullies and rills.

Alpha’s master program decided to follow the slightly sloping ground, gathering data as it moved slowly onward. Collectors in the roof took in samples of the drumming rain for analysis. The liquid was largely ethane, although a complex mix of other hydrocarbons were present, as well as 14 percent liquid water.

Liquid water was an important biomarker; the biology program was immediately activated to participate in the analysis. The master program, meanwhile, pondered a conundrum: How can water remain liquid at temperatures of nearly two hundred degrees below zero? It took all of fifty-three billion nanoseconds before the master program arrived at a tentative conclusion. The water can remain liquid because it is mixed with the ethane and other hydrocarbons, which, together with the high atmospheric pressure, raises the freezing point of the fluid far enough to allow the mixture to remain liquid.

The biology program was instructed to search for organic molecules and/or viable organisms in the water-laced ethane samples. Organics were there in plentiful, easily identifiable amounts. Actual organisms, unicellular or even protocellular molecular organisms, were not found.

While this sampling and analysis was being performed, Alpha continued heading down the slight slope of the ground, following the rivulets of the ethane-water mixture across the muddy landscape. The rain was actually clearing much of the methane slush from the underlying ice, sluicing it downhill in gurgling streams. At last the rainstorm passed, and Alpha’s infrared sensors scanned the higher clouds that perpetually covered the sky. A faint glow low on the horizon showed where the Sun was. There was an even fainter patch of light higher above, several degrees wider. The navigation program concluded that it was the planet Saturn, Titan’s primary, the planet around which it revolved. Even under the best magnification, though, nothing of the planet’s main body or its rings could be resolved through the murky clouds.

The forward sensors reported a sizable stream ahead, a meandering brook of ethane-laced water flowing across the vehicle’s projected path. Width eleven meters. Depth unknown.

After four billion nanoseconds, the master program decided to follow this stream to see where it led. Consulting both the geology and biology programs, the master program concluded that the stream most likely fed into one of the seas. It found an imperative in the geology program: If there are ethane streams, determine how they mix with the known seas. A similar requirement existed in the biology program: If organic molecules are located on the surface, determine if they have developed into viable organisms.

Titan Alpha followed the flowing stream toward one of the ice-encrusted seas that dotted the moon’s frozen ground.