Ocean Under the Ice

by Robert L. Forward

  “This is balloon explorer Tweedledum. It is obvious that Tweedledee has been exploring the wrong hemisphere to obtain the correct ice to snow ratio. The amount of ice cover I have surveyed is 46.3 percent compared to snow cover of 52.9 percent. Only 0.8 percent of the surface area is bare rock, most of it in the calderas of volcanoes just south of the equator. My sample return rocket will be full in 1.2 years.”

  “Doesn’t sound very promising, nothing but a frozen landscape,” said George.

  “Any signs of life?” asked Jinjur. There was a slight time lag before the reply.

  “None,” came the simultaneous joint answer from the two balloons on the opposite hemispheres of the planet.

  “Why are you echoing me?”

  “Echoing you? You were echoing me!”

  “I said ‘None’ first!”

  “No, I did!”

  “I did!”

  Jinjur made a motion near her imp like turning off a volume control knob and James stopped transmitting. “Tell them to keep up the good work and we’ll be back in a year or two to pick up their samples.”

  “Well,” said George. “As we expected, that leaves Zuni and Zulu. And they are both worth spending landers on, since they both have life-forms which we’ll want to examine firsthand. You can’t really learn much about a living organism by examining a few samples that were punched out of it by a robotic corer.”

  “Well,” mused Jinjur. “Since our exploration robots on Zulu have come across life-forms that use artifacts and seem to be intelligent, then it’s obvious that we should go there first.”

  A soft, but insistent voice spoke out from across the room. It was Reiki, who instead of using her imp to talk through James to Jinjur, was speaking directly at her. “If I may make a suggestion…”

  When Jinjur heard that phrase from Reiki, she knew that whatever Reiki had to say might be important and she should listen to it.

  “Certainly, Reiki,” said Jinjur. “Suggest on…”

  “Because of our involvement with the flouwen and the star-fish creatures on Rocheworld…” she started. (Reiki had always disliked the name ‘gummies’ and refused to use it.) “…and the minutes-long communications time delay between Rocheworld and Zulu, we have not had much opportunity to develop a working dialogue with the dominant life-forms on Zulu. Although it might seem obvious that we should go there first, it may be better to visit the other moon first. While the exploration crew on the ground are collecting samples of the vegetation and the animals on Zuni, the crew on Prometheus could be interacting with the Zulu aliens through the crawlers and improving James’s translation programs so that our ultimate visit there would be much more profitable.”

  “She has a point, there,” said George. “We’ll have to think carefully about which moon should be visited first.”

  “To really determine whether our translation programs are adequate for a visit, we ought to try them out in real time,” said Jinjur. “And that means getting close enough to Zulu that the communications time-lag is negligible. James? Get me Arielle…”

  “I listening,” replied Arielle.

  “What course did Tony leave us on?”

  “A trajectory inward to match up with Zouave.”

  “Change the target to Zulu.” She then looked across the deck to where Arielle was perched on her chair. Arielle now had one hand expertly flickering over the touch-screen, setting up the new trajectory for the lightsail, while the other held the remains of a sandwich of cucumbers and pickled ‘ponics-fish in soured pseudo-cream on pumpernickel bread. Jinjur then looked down at her console. James had automatically changed the display on Jinjur’s screen to the display on Arielle’s navigation console screen. The light-blue line that indicated their trajectory passed close to the surface of the giant planet Gargantua.

  “Zulu is closest in,” said Arielle through her imp. “If we to match orbits with it in minimum time, we must go inside Zulu orbit and catch it on other side. I can choose another approach, but that means slowing Prometheus down and it take eight days longer.”

  Jinjur turned to George, who had studied the atmosphere of Gargantua in some detail during their initial flyby of the gas giant. “Any problems with getting that close?”

  “I don’t think so,” said George. “James?”

  “We will be well above the atmosphere. Since we will be going in low near the equatorial plane there will be no radiation belts to worry about. I have calculated that the gravity gradients will not cause torques on the sail that the sail controller cannot cope with, but the strong magnetic field of Gargantua will cause some eddy current drag in the sail material. That is easily compensated by an adjustment in the incoming trajectory.”

  “Forgot about those little side effects,” said George, thankful that the nearly omniscient computer was always looking out for their welfare.

  “In a few days we be passing close to Zuni on way in,” added Arielle.

  “Good!” said Jinjur. “We’ll be able to check them both out at close range before we make a decision.”

  “In that case, I’m going to have an early dinner and hit the sack,” said George back through his imp as he swung himself off the control deck and up the central shaft to the living area deck above.

  * * *

  After a few days, their sunlight-powered infall toward Gargantua brought them close enough to Zuni that they could communicate with the robotic explorers they had left there without incurring a significant time delay. Jinjur and George were again together on the control deck, and Richard was at the planetary science console. Outside one of the portholes on the control deck, George could see the moon itself, a blue marble with a multitude of brownish-green dots overlaid with a swirling pattern of white clouds — looking like a miniature Earth, as seen from the island-dotted oceanic “hemisphere” between the Americas and Asia-Australia. Zuni was in three-quarter phase, with a sharp weather front that extended over the terminator onto the dark side, where its centerline could be traced by the multitude of lightning flashes lighting up the clouds.

  Richard started the report. “The exploration robots that were left at Zuni during our first flythrough of the Gargantuan moon system were the orbiter spacecraft, Bruce, to obtain synoptic imagery and global sensor data; a VTOL flyer, Orville, to provide high-resolution imagery from the air and to obtain samples from areas not easily accessible by the crawlers; and two amphibious crawlers, Bubble and Burble, to explore and obtain samples from the islands and the shallower waters. One of the crawlers, Burble, was lost during the first year.”

  George now remembered the laconic voice of the orbiter spacecraft Bruce as it reported the loss of one of the amphibious crawlers that had been exploring the oceans and islands of Zuni.

  “Burble is experiencing technical difficulties. Burble is submerging rapidly off the southern tip of island 105 east, 35 north. Burble has ceased communication.” There was a pause. “All indications are that Burble is no longer operational.”

  George recalled that he had been too busy coping with the activities on Rocheworld to respond with much feeling.

  “Right, Bruce, you, Orville, and Bubble carry on,” was about it, as he remembered.

  “For the global summary of Zuni, I’ll let Bruce give the report,” said Richard. On their screens was now a high-resolution computer-generated picture that had been built up from a combination of images taken by both Prometheus and Bruce.

  A calmly resonant computer voice spoke. “This is Bruce, I am presently in polar orbit about Zuni continuing my global survey of imagery, gravity, topography, and remote sensing. Zuni is a water-covered planetoid 3800 kilometers in diameter, a little larger than the Earth’s Moon. It has no large continents, but has a multitude of islands — ninety-five major ones. The atmospheric pressure is half an Earth atmosphere, and the surface gravity is 28% of Earth’s gravity. Zuni’s surface temperature is typically thirty to forty degrees centigrade, equivalent to the tropics on Earth. Since the orbit of the moon lies be
tween Zulu and Zouave, both of which are ice-covered, this temperature is anomalous. The full explanation awaits further analysis, but part of the reason is that Zuni is tidally locked to Gargantua, and when either Zulu or Zouave passes by, their gravity tides cause it to rock about its tidally locked position, creating heat by internal friction. Since it is rocked by two neighbors, it experiences twice as much heating. Another suspected cause is chemical. All three of the moons are too small to prevent their volatiles from escaping into space. Zulu loses water from its geysers, Zouave looses smog from its atmosphere, and Zuni looses air and water from its atmosphere. The escaped volatiles cannot escape from Gargantua’s gravity well and remain as gas toroids centered about the moon’s orbital track. Most of the gasses are eventually recaptured by the moons that had emitted them, but some of the smog from Zouave and some of the water from Zulu are collected by Zuni. The water and smog react chemically to give additional heating to Zuni. The reaction products obviously provide nourishment to the lifeforms on the surface. These definitely include plant-life, since my remote sensors detect the presence of complex organic compounds with absorption bands peaked at the Barnard spectrum, and free oxygen. This has been confirmed by the surface explorers, Orville and Bubble.”

  “Those ninety-five islands are all tops of volcanos,” added Richard. “Which really keeps the planet churned up. There isn’t going to be much “geo” down there to do geology on, but what there is, is going to be interesting.”

  “What did the surface exploration robots find?” asked Jinjur.

  “I could have Orville and Bubble make their own reports,” interjected James. “But there is so much detailed information to cover, that I shall condense their findings for you. In summary, the planet Zuni is full of life, both plant and animal, and, on land and in the water. Certainly, with only one flyer and one crawler working, not all of it has been found, much less examined and understood in detail. As expected, plant forms dominate, with some of them reaching very large sizes, some in height and some in breadth.” As James spoke, single shot pictures flashed up on the screen, most of them obviously taken by Burble in its traverses of the various islands it had briefly visited. There was a group of tall trees like coconut palms except that their canopies were quite large and overlapped. Around one of the smaller trees coiled a vine. There was a shot of a very dense thicket, behind which could be seen some stout trees about four meters tall, with some color in their foliage.

  “This thicket was so thick, that Bubble could not penetrate it to obtain images of the trees inside.”

  There was another tree, like a banyan tree with vertical supports growing down from the spreading horizontal branches.

  “There are also many plants in the water,” added James. “Some of them rooted in the shallows, usually near volcanic vent fields, and some of them floating like seaweed. In the plants live many kinds of small animals, that crawl, swim, and fly around. Many of them seem to have symbiotic relationships with the plants. None of the small creatures are large enough to have a significant brain.”

  There was a picture of a small six-legged green-furred animal peering out from the foliage, a blurred shot of a small owl-like bird with green feathers, and a picture of six fish with strainer-like mouths floating near a large underwater plant.

  When James had finished, Jinjur turned to George. “Well, there is definitely lots of animal life, but it seems very unintelligent,” she said. “The land creatures are extremely small and simple, and the ones in the ocean don’t look promising either.”

  “Yes,” said George. “It may not be intelligent life, but it is life, and definitely worth expending a lander on. For one thing, such a wide variety of living things would be interesting to study. And for another, the climate and terrain don’t seem to be as extreme as on the other moons. Let’s go take a look at Zulu, see if we have prepared ourselves enough to land there, and then reassess the situation.”

  “I agree,” said Jinjur. “James. Hook me up to Thomas.”

  At the navigation console, Captain Thomas St. Thomas tilted his head to listen to his imp.

  “Please set our course for Zulu, Thomas,” ordered Jinjur.

  “Aye! Aye! Ma’am,” replied Thomas in his best military manner, then his voice brightened up with anticipation. “We’re going to get a real close look at ‘Garg’ this time! I ought to get some swell pictures.” He took a look at the timing marks on the new trajectory for Prometheus that James had just calculated for him. “Shucks!” he muttered to himself. “I’ll be on navigation duty shift at the time of closest approach.”

  George immediately replied back through his imp. “I’ll be glad to take over your shift duty, since I was going to be here as a bystander anyway. That is, if Jinjur doesn’t need me for anything else?”

  “Aren’t you going to be doing some studies of the Gargantuan atmosphere along with Arielle?” reminded Jinjur.

  “Yes, but since navigation console duty at that time will involve nothing but watching James control the lightsail flutter, I could use the navigation console to do both at the same time.”

  “Sounds fine with me,” replied Jinjur.

  “Great!” replied Thomas. “I should be able to get some great pictures!” He crunched happily on one of his special crisps, enjoying the crunchy feel under his teeth as much as the super-hot Jamaican spice flavors on his tongue. With any luck, these photos might be sensational enough to transmit in his monthly electronic letter to the family on Earth. Although most of them barely remembered their most famous relative, since he had left Earth 45 years ago, they were still intensely proud of him, and the letters were read and discussed for weeks, while the reply, full of all the gossip from Kingston, was being composed — without regard to the fact that it would be six years before Thomas received it.

  “I’ll get my equipment laid out now, ready to go. Thanks a lot, George! I can hardly wait!”

  George couldn’t either. It was surprising how interstellar exploration was a lot like fighting a war. Months and years of doing nothing, then suddenly there was more to do than you could cope with. And, like a war, it occasionally got dangerous…. His mind went back to that still horrifying moment back on their first visit to Rocheworld, when he found himself ten kilometers up in the sky — falling headfirst toward the surface without a parachute. The only thing that had saved his life that time, was Thomas’s expert piloting of the Ascent Propulsion Stage. Thomas had swooped the rocket around and down, and scooped George right out of the sky, like George was the ball in the childhood cup-and-ball game. For that, George owed Thomas much more than a mere duty shift switch.

  * * *

  A few days later they started their flyby of the gas giant, Gargantua. Four times more massive than Jupiter, it emitted more thermal radiation generated by its internal gravitational contraction and chemical phase changes than it received in heat and light from its small primary, Barnard — which because of its greater density, was actually smaller in diameter than its major planet. If Gargantua had been slightly larger, it too would have been a star like Barnard — but even smaller and denser.

  The surface temperature of Gargantua was near the freezing point of water, which was much warmer than the three degree temperature of the empty sky, so the warmth from the large globe provided a major contribution to the heat input of the climatic cycles of its moons. Gargantua had a strong magnetic field, driven by the convection currents in its metallic hydrogen core, but its radiation belt was weaker than that of Jupiter because Barnard didn’t emit much solar wind.

  Gargantua rotated once every 162 hours, compared to the 10 hour rotation periods of Jupiter, Saturn, and Uranus. As a result, the weather patterns in its upper atmosphere were not the multitude of belts and zones found on the solar system gas giants, but instead consisted of a series of gigantic cyclones, spawned near the equator, and moving into the high latitudes, where they dissipated into storm fronts. Except for the scale, they looked similar to the weather patterns of Earth. Ga
rgantua had a larger rock core than Jupiter, and its liquid metallic hydrogen “ocean” and its gaseous atmosphere were proportionately thinner. As a result, the ocean and atmosphere were affected by the solid surface below. These showed up as permanent spots in the weather pattern. There were hot spots near the equator which were the seed spots for hurricanes, and colder areas which depleted the strength of any cyclone pattern that wandered near them. The larger hot spots were also identified with atmospheric “volcanoes”, gigantic upwellings of gaseous hydrogen driven by a hot spot under the metallic hydrogen ocean.

  In the lounge on the commons deck, David Greystoke and Deirdre gazed outward at the alien surface rolling, endlessly, before them. The massive planet filled the three-by-four meter viewport as the slow rotation of the sailcraft moved it ponderously by the window, its surface swirling with gigantic endless storms and pocked with violent atmospheric volcanoes.

  “Needs theme music,” said David, more loudly than he had meant. “Sorry,” he said more softly. “All that turbulence and activity, it seems impossible for it to be soundless. My mind keeps hearing chords, mostly loud and dissonant…” he broke off at Deirdre’s murmur of understanding.

  It was off-duty time for both of them. Deirdre slouched further into the sofa, her long legs stretched comfortably, while the wide shoulders relaxed. Her narrow, high-arched feet in the sleek boots were propped on the ledge in front of her. Foxx, awakened, also stretched, and yawned, and settled down again on the back of the woman’s neck. The imp holding Deirdre’s hair shifted slightly to avoid the animals furry tail, and one of its six “hands” settled down again on the side of Deirdre’s neck to continue its constant monitoring. David was sitting upright, intent and still. His slight frame was taut with creation. The music forming into patterns in his mind absorbed him utterly. The computers he tended with such skill and care would help him, later, to bring to all the crew a new vision of the gigantic storm he was watching, as he translated it into a sono-video concert.