TCS Daily

Deep Space, Nein!?

By Kenneth Silber - November 30, 2004 12:00 AM

In the 1997 sci-fi movie Gattaca, Vincent Freeman (Ethan Hawke), would-be astronaut despite his lack of genetic engineering, describes the mystery of Saturn's moon Titan, his eventual mission objective. He blows cigarette smoke into a wine glass to illustrate Titan's thick, murky atmosphere. Nobody knows what's down there, he tells his girlfriend Irene Cassini (Uma Thurman).

In real life, though, a dramatic encounter may soon shed light on that very subject. The Cassini space probe (named after a 17th-century astronomer, not Uma's character) will make a close approach to Titan in mid-December. On Christmas Day, it will unleash a smaller probe, Huygens, that will plunge into Titan's atmosphere on January 14, 2005. Descending by parachute to the moon's surface, Huygens will capture an array of images, data, samples, and sounds. (Huygens will also broadcast some pop music to whoever might be listening.)

The technical complexities of exploring the outer solar system are formidable. So are the political complexities. The Cassini mission was targeted by antinuclear activists opposed to the spacecraft's use of plutonium-fueled electricity generators for its scientific instruments. The earlier Galileo mission to Jupiter generated similar opposition. Future controversies over nuclear energy in space can be anticipated. The Jupiter Icy Moons Orbiter, a mission proposed for launch around 2015, would use a fission reactor to fuel an electric ion engine far more powerful than conventional rockets.

Nor are the political tensions over deep-space exploration solely about nuclear energy. Budgetary pressures and conflicting program priorities have also erected hurdles to the outer solar system. Plans for a mission to Pluto, the solar system's only planet not yet visited by a probe, have had an on-again, off-again life, repeatedly disrupted by budget cuts. At present, NASA is planning on a launch of its New Horizons spacecraft in January 2006; this would swing by Jupiter for a gravity boost in 2007 and arrive at Pluto in 2015. Time is growing short, however. Pluto is moving further from the sun, such that after 2019 an expanding share of its surface will be in darkness and its atmosphere will likely freeze onto the planet, effects that will endure for well over a century.

Space missions always must scramble for public and political attention amid myriad other issues. Exploration of the outer solar system, moreover, is often overshadowed by space projects closer to home. Mars, the moon, and orbital space flight all have vocal constituencies prepared to devote political or economic capital to them. The scientific probes to the outer planets enjoy broad but relatively shallow support among space enthusiasts and the public overall. Yet the outer solar system holds vast scientific interest and technological possibility, including -- but by no means limited to -- the striking images that have been transmitted back by robotic probes over the past several decades.

In the long run, people might live out there. A future space-faring civilization might establish settlements on or near some of the dozens of moons of the giant gas planets, perhaps tapping the planets' vast stores of helium-3 as a nuclear-fusion fuel. Engineer and humans-to-Mars proponent Robert Zubrin, seeing outer colonization as a logical next step after the red planet, has argued that Saturn's moons are more hospitable for settlement than Jupiter's. Physicist Freeman Dyson, for his part, has written with enthusiasm about the habitation prospects of the Kuiper Belt, a vast swarm of small, icy bodies orbiting beyond Neptune and Pluto.

In the nearer term, the outer solar system presents a wealth of scientific questions and mysteries. The Galileo mission to Jupiter detected evidence of subsurface oceans on the moons Europa, Callisto and Ganymede, raising the possibility that life could exist on these bodies, perhaps in the vicinity of undersea volcanic vents. These three moons will be targeted by the Jupiter Icy Moons Orbiter. On Europa, the evidence suggests that liquid water may be near the surface, prompting scientific calls for the sending of an "icepick" probe.

Another enigma involves the Pioneer probes that conducted flybys of Jupiter and Saturn in the 1970s before heading toward the edge of the solar system. Unexpectedly, these two probes have been slowing down since they passed Uranus's orbit about a quarter century ago, as evidenced by the shorter wavelengths of their radio signals. It is unclear if the deceleration arose from a fuel leak or other tech problem, or if it points to some yet-unknown phenomenon in physics and astronomy.

Titan, soon to have its encounter with Huygens, is a particularly mysterious place. Saturn's largest moon may have substantial liquid on its surface, a distinction it would share only with Earth. Nobody knows whether the probe will hit rock, sink into mud, or splash down in an ocean of methane. Temperatures are extremely low, suggesting an environment unsuitable for life. But this smog-enshrouded moon may have been much warmer once, and its atmosphere contains organic molecules similar to the chemistry of the early Earth (and billions of years from now, Titan will become warm as the sun becomes a red giant). Titan may tell us something about life -- past, present or future.


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