But the ultimate fate of the methane is even more interesting. As it is destroyed by ultraviolet light, it should form reactive organic species that recombine into more complex hydrocarbons like ethane and propane. These would fall with the methane rains, but unlike methane, they wouldn't re-evaporate. Rather, they should collect in lakes or seas, at a rate of about four inches every million years. Over the life of the Solar System, enough ethane and propane should have rained out of Titan's atmosphere to create at least one large ocean.
Looking at Titan in cloud-penetrating infrared, we see light areas and dark areas. For some time, the leading theory (and everyone's hope) was that the dark areas were hydrocarbon seas, while the bright ones were continents made of water ice or something similar.[12]
[FOOTNOTE 12: 1/29/07]
Unfortunately, it's not that simple.
Part of the Cassini mission is to map as much of Titan as possible from space, with a total of 45 flybys scheduled by mid-2008. These mapping missions use two basic instruments: radar, and infrared cameras that use wavelengths that provide at least semi-transparent “windows” through Titan's haze.
One of the mappers’ goals is to look for impact craters. But by October 2005, they had found only two, says Elizabeth Turtle, a planetary scientist at the University of Arizona.
"We expected many more,” adds Rosaly Lopes, a volcanologist with NASA's Jet Propulsion Laboratory in Pasadena, “especially compared to the other satellites of Saturn, where craters are plentiful."
The paucity of craters means that Titan's surface (or at least the portion surveyed so far) is geologically young—constantly being weathered away by wind and rain. The emerging picture, Lopes says, is of a surprisingly young, “incredibly dynamic” landscape, constantly being altered by wind, rain, and volcanic activity. There may also be earthquakes. The imaging team has found long lines that look like scarps or rift valleys, presumably created by motions in the planet's crust similar to those that occur along California's San Andreas Fault.
One of the most exciting early discoveries was a suspiciously lake-shaped feature near the South Pole, about the size of Lake Ontario. “Its perimeter is intriguingly reminiscent of the shorelines on Earth,” says Turtle, “smoothed by erosion and deposition."
More evidence that it might be a lake comes from the fact that it lies in Titan's cloudiest region, where methane rainstorms might be particularly common. But it could also be a dry lakebed, where liquid once stood but is now long gone. The acid test would be to catch the glint of reflected light from its surface, but so far that's not been seen.
Infrared observations can only determine the shapes of features. It's hard to determine their topography because even in the infrared “windows,” looking at Titan is like looking at an earthly landscape under the flat light of a very hazy day, with no shadows to define the local relief.
Radar mapping does better. It confirms much of what the infrared images appear to show: that the dark areas are smooth lowlands, while the bright ones are uplands. One particularly interesting find is something that looks a lot like a coastline, with a bay surrounded by uplands. Other features include river channels that appear to spill outwash onto the plains, much like earthly river deltas.
Then on late July radar-mapping flyby, the Cassini team struck gold, finding a region with dozens of large, dark patches that looked like lakes. Lots and lots of lakes, up to 70 kilometers in diameter. The discovery made Titan the only body in the Solar System other than Earth appearing to have bodies of liquid at its surface.
Some were fed by river-like channels from the surrounding highlands. But others showed had no such inlets. This probably means that they're fed by methane aquifers—"methanofers” is the term used by Ellen Stofan, lead author of a study announcing the find in the January 4, 2007 issue of Nature—not far below the surface.
"Just like on Earth, if you dig deep enough, the depression fills up,” says Stofan, who shares her time between Proxemy Research, in Virginia, and University College of London, England. “There's a subsurface methane table."
Other researchers have generated weather models showing how methane “moisture” could evaporate from the lakes to fuel rainstorms, ranging from gentle drizzles to mammoth, gully-washing thunderstorms.
* * * *
Cat Scratches
The radar images also revealed vast expanses of thin, parallel striations, up to 100 miles long. “We called them cat scratches because they look like what cats do to furniture,” Lopes says.
Initially, the cat scratches puzzled the imaging team. Then someone realized that parts of Earth look very similar from space. There is still some debate, but the leading theory is that Titan has extensive dune fields like those in parts of the Arabian Peninsula. Though, of course, on Titan, the “sand” is probably comprised of ice crystals.
The imaging team has also found one large volcano and other possible lava flows. These are important because, if wind and rain are constantly eroding the highlands, something must be creating new material to be eroded. Otherwise, the entire planet would be flat.
The volcano, named Ganesa Macula for the Hindu god of good fortune, takes a shape called a “pancake dome.” That makes it similar to features on Venus, produced by the oozing of high-viscosity lava with low gas content. But unlike earthly or Venusian volcanoes, Ganesa Macula would erupt “cryolava,” comprised of a gelatinous ammonia-water mix which, at 175 degrees K (—140 degrees F), is “hot” only by Titan's frigid norms. Despite the low gas content, these lavas could release enough methane to the atmosphere to replenish that which is destroyed by sunlight.
But we didn't merely study Titan from space. We also landed on it.
The Cassini mission carried a second probe, called Huygens, which detached from the main one on Christmas Day, 2004, and parachuted to the surface on January 14, 2005.
The landing didn't get as much news coverage as it deserved, because the day after the two probes separated, Indonesia was hit by the largest earthquake the world had seen in four decades, and most people's attention was directed toward the ensuing tragedy. But Huygens quietly did its job, and the results are now trickling into the scientific journals.
With an atmosphere four times as thick as the Earth's, Titan is a dream-world for exploring by parachute—especially because, unlike the Solar System's other hard-surfaced, dense-air planet (Venus), its atmosphere is cool, free of corrosive chemicals, and basically friendly to electronics. “The atmosphere that makes it so hard to see makes it one of the easiest planets to land on by parachute,” says Laurence Soderblom, an astrogeologist with the U.S. Geological Survey in Flagstaff, Arizona.
It took the probe two-and-a-half hours to descend, after which it survived on the surface for at least an hour. It may have survived longer, but at that point, Cassini passed below the horizon and telemetry was cut off.
The probe had a battery of cameras that rotated as it fell, permitting them to scan in all directions. As the probe drifted on the wind, the cameras could look at the same terrain from different angles, allowing the pictures to be built into three-dimensional images via a technique similar to that used for converting aerial photos of the Earth into contour maps.
As of late 2005, only two sets of these images had been produced, each covering upland areas of about 1 kilometer by 3 kilometers. One reveals a region of multiply-branched drainages, like the headwaters of earthly creeks in well-watered regions. The other shows a region where the drainages are stubbier and less intricately branched, as is common in spring-fed canyonlands. In both cases, the surrounding land is steep, rugged, and complex, with slopes of up to 30 degrees—the type of thing future astronauts would find difficult to walk across, and another great setting for a science-fictional story of high-stakes hide-and-seek. The steep terrain also means that when the methane rains fall, they create flash floods with enough power to carve deep valleys, despite a surface gravity that is only 13.9 percent of Earth's.
"Even though the bedrock i
s water ice and the rain is methane,” Turtle says, “it could be a very earthlike place."
To the joy of the research team, the probe came down in one of the dark plains, not far from a major “shoreline” boundary with the adjacent highland.
The goal had been to hit one of the dark areas, in the hope it might be a lake or ocean, but it was pure luck to come down so close to a boundary.
When the probe touched down, Soderblom says, “We didn't know whether it would go sploosh, splat, or tinkle. Instead, it went thud, hitting moist sand, somewhat like crème brûlée.” High levels of methane in the atmosphere indicated that liquid methane was nearby, but apparently it was underground, not in a pool on the surface. Perhaps some of the hoped-for ethane is in the same place.
The landing site was close enough to one of the river deltas that it's covered in rounded “rocks” of ice, carried by floods running out of the nearby highlands. These rocks range from about one to six inches in diameter. This means that by the time they reached the landing site, the floods had slowed enough to leave bigger rocks behind, but were moving fast enough to scour smaller ones away: exactly what geologists see with earthly flash floods.
"The most striking finding,” says Soderblom, “is that a place I expected to be alien and un-earthlike turned out to resemble a modern textbook in geomorphology."
From a science-fictional perspective the Cassini/Huygens mission also teaches a broader lesson.
For years, science fiction writers have viewed gas giants as uninteresting places. Perhaps they are. But their moons: that's a different story. Gas giants, it would seem, have collected some of the most interesting real estate in our own solar system, and there's no reason to believe they wouldn't do so elsewhere, as well.
Based on the Cassini mission, if I were an interstellar explorer looking to find strange new worlds, I wouldn't waste time with the scattered rocks of the inner system: I'd head straight for the nearest gas giant and start exploring its satellites.
Copyright ©2007 Richard A. Lovett
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FATHER HAGERMAN'S DOG by SCOTT WILLIAM CARTER
People adopt new technologies at their own rates and in their own ways....
Rounding a bend on the gravel road, the low sun momentarily blinding him, Marty finally came to the white picket fence that was the edge of Father Hagerman's farm. Everybody called it a farm even though it was only a few acres, because that's what Father Hagerman wanted it called, and nobody in their right mind contradicted Father Hagerman.
Marty's collar was damp with perspiration. The dashboard fan blasted a steady stream of warm air. Turning onto the dirt drive, he saw a white cottage nestled among a grove of birch trees. A dozen chickens pecked at the ground next to a large, fenced-in garden full of corn, cabbage, and other vegetables. He remembered picking pumpkins there every October with his mother, back when they lived down the road.
He killed the engine. The Gonzo curled in the passenger seat—nobody would be able to tell it apart from a golden retriever at a glance—opened its eyes and perked up its ears. Marty checked his appearance in the mirror, straightening his tie and brushing his unruly black hair out of his eyes. He frowned, thinking about the con artist who got him into this mess. The Gonzos sell themselves! You'll not only make enough money for college, you'll be able to buy a house! What a bunch of garbage. After a month of trying, he was just hoping to break even on his investment.
He got out of the van, smiling his salesman's smile, and looked up as the screen door banged open.
His smile faded when he saw that Father Hagerman was dressed in nothing but white jockey undershorts.
The old man, over six feet tall and as thin and tan as a copper wire, held his hand over his eyes to block the sun. Then he threw his arms wide.
"Marty!"
He bounded down the wooden steps. Mortified, Marty used the van door as a shield, thrusting out his hand in the hopes that no other physical contact would be required.
Hagerman pumped Marty's hand furiously, his thick glasses glinting in the sunlight. “Marty, my boy,” he said.
"Hello, Father,” Marty said.
Even though Hagerman had been kicked out of the seminary for seducing nuns some fifty years back, he still insisted on being called Father. He was bald on top, but the hair on his chest was thick and white. When Hagerman opened his mouth, Marty saw that most of his teeth had been capped with gold. The last Marty had heard, Father Hagerman was worth over ten million dollars, all of it inherited from his parents’ oil drilling days. His chief occupation the last fifty years, other than playing at being a farmer, had been writing angry letters to the local Two Spoons Gazette.
Hagerman finally stopped shaking Marty's hand, stepping back and appraising Marty as if he were livestock up for auction. Marty did his best to keep his gaze at eye level.
"I remember you when you was just a pup,” Hagerman said, and put his hand out, waist-high. “Got kids yet?"
Marty laughed. “No, sir. I'm only twenty-one. Still in college."
"Well, sheeoot,” Hagerman said, which was something Marty remembering him saying often. “That don't stop most kids these days. How about this weather? Too damn hot for clothes, I'll tell you that. What brings you here?"
Marty was trying to decide the best way to answer that question when a mangy gray mutt, as fat as Hagerman was thin, pushed open the screen door and slumped onto the porch. The animal's mixture was impossible to guess. It looked out at Marty with glassy eyes, a line of slobber dribbling from its mouth. The mutt's fur was patchy and thin, and one ear was missing.
Marty smiled. If this was his competition, then selling the Gonzo was going to be easy.
"Well, sir,” he said, “I've got a little something I'd like to show you."
Hagerman's thin white eyebrows arched. Marty wasn't sure how the old man was going to react when he found out why Marty was there. He remembered the time Hagerman chased off a pair of Mormon missionaries with a shotgun.
"Well, I see you have yourself a dog,” Marty said, warming into his sales persona. “Now what I've brought with me—"
"That there is Chib,” Hagerman chirped.
"That's an interesting name. What I also think you'll find interesting—"
"Stands for Cold-Hearted Insane Bitch. If you spend five minutes with her, I think you'll agree it's fitting."
Marty lost his train of thought. “Er..."
"Hell, you look positively piqued, boy,” Hagerman said. “Why don't you come in and have some lemonade? I'll read you some scripture. I'm doing Matthew."
He turned to the house. His bony back was even more tan than the rest of him.
"Sir,” Marty said, realizing he was going to have to be more direct, “I've come to see if you might like to buy a Gonzo 450."
The old man had put one foot on the creaking porch. He turned, confusion registering on his face.
Marty cleared his throat. “A Gonzo..."
"I heard you. What is it?"
Hagerman's lips were pressed into a thin line. Marty wondered if he was making a mistake. This was, after all, the man who had challenged the local postman to a duel after the postman informed him the price of stamps had gone up three cents.
"Well, sir, it's a dog,” Marty said. “Not just any dog, mind you. A special kind of—"
"I got a dog,” Hagerman snapped.
"Yes, sir. I see that, sir. But this—"
"So you came all the way here to sell me a dog?"
"No, no. I came to see you. But this isn't an ordinary—"
"How long has it been since you've been here? Four, five years? And you come trying to sell me a dog. I've always had one dog. I'm always going to have one dog. No need for more."
Frustrated, Marty turned to the still-open van. “Gonzo, come!” he shouted.
The robot leapt out of the car, landing gracefully next to Marty. It wagged its tail but otherwise stood motionless. Chib raised her head for a moment, then slumped ba
ck onto the porch.
"Nice retriever,” Hagerman said. He squatted next to the robot, scratching it behind the ears. “Obeys well. But I'm still not buying it."
"It does more than obey well,” Marty said. “It obeys perfectly."
Hagerman stood. “All dogs crap on the carpet once in a while."
"As I was trying to say, sir, the Gonzo 450 isn't an ordinary dog. It's a robot."
Hagerman laughed. “A robot dog?"
"That's right."
"Kind of like them metallic-looking bag boys at the grocery store?"
"You got it. Only these robots are made to look and act like the real thing, only better."
"Hell, I wouldn't have known unless you said so. I read about these in the paper. How do I know you ain't joshing me?"
Marty looked back at the Gonzo 450. “Roll onto your back, Gonzo,” he said. The dog complied, putting all four feet in the air. Marty got down on his knees and popped open the chest compartment, revealing the battery. He pulled out the plug, holding it up so Hagerman could see it.
"You recharge him every night,” Marty said. “It's the only way to know he isn't real."
"Looks like a her."
"Oh, well, yeah. They come standard as females, but you can get males, too."
"With little peckers and everything?"
"Um ... yes, sir. That's right."
Hagerman slapped his knee. “Well, sheeoot. What will they think of next? A robot dog with a pecker. I thought I had seen it all. They don't hump other dogs, do they?"
Marty felt a flush spread across his face. “No, sir. No, they don't need to do that."
"Could you program them to do it?"
"Ah..."
"Just kidding,” Hagerman said, punching Marty so hard in the arm that Marty stumbled back against the van. “So you drove all the way up here to sell me a robot dog? They out of robot vacuum cleaners or something? Look, son, you know I'm not going to buy one, so I'm sorry to waste your time. You say hello to your mom and dad for me."
Analog SFF, June 2007 Page 9