Threshold: Chapter Nineteen

    "Enceladus." The general pronounced the little moon’s name carefully.

    "Yes, General," Anthony said. "After I reported the initial find, I did continue my research. Since I knew of the connections I was able to determine a few more facts to confirm the labeling."

    Hohenheim nodded. "Very good. I had hoped for something in the Jupiter system, but we are provisioned for Saturn as a possibility. Tell me what makes Enceladus a good possibility, aside from simply finding markings on one of the diagrams?"

    Currently, only Hohenheim and LaPointe were present, as the general wanted to evaluate the situation himself privately. Anthony activated the meeting room display. A rotating image appeared of a mostly-white sphere, covered with noticeably varying terrain ranging from small craters to faintly-blue striped cracks.

    "Enceladus has been sort of an enfant terrible for us astronomical types in the past few decades," Anthony said. "It’s much smaller than many of the really large moons like Ganymede, Europa, or our own Luna. In fact, at about five hundred kilometers across, it is quite a bit smaller than our Ceres here. According to many theories of celestial body formation, it should therefore be a relatively static body, a dead rock or iceball floating in space.

    "Instead, it is one of only a very few bodies in the solar system with known volcanic activity. It has a surface indicating recent resurfacing—in some areas it may have the most recent surfaces in the solar system." He gestured at the faintly-striped areas. "The false-color images overlaid here show what are sometimes whimsically called ‘tiger-striping’, but what is significant about them is that they include crystalline water ice—possibly less than a thousand years old, or even newer, given our detection of cryovolcanism—and some organic compounds. There are however other areas of Enceladus which are much, much older on the surface."

    A cutaway view of the miniature world appeared. Hohenheim frowned. He was of course familiar with cutaway views of Earth and other worlds, but this one was… odd. It appeared that the majority of the little moon was cold, but that at one point, near the south pole, it was significantly heated. Totally asymmetric and not at all consistent with anything he had ever seen before.

    "I see your expression, General, and you’re correct. That’s called a diapir. The conventional description is that it is lower-density heated material rising to the surface near the south pole. Models of Enceladus have tended to converge on this structure, but what has caused the structure you see has been a matter of furious debate." Anthony paused. "Until now."

    Hohenheim slowly turned to stare at the grinning scientist. "Are you saying…?"

    "Where is the energy coming from, General? That’s been the constant debate. Actually, it’s been two debates. First, where the energy comes from, because not all models of the tidal forces active on Enceladus appear capable of supplying all of the energy needed. Second, why it’s only apparently active in this one location. One can of course come up with all sorts of theories, and I assure you many have. Enceladus is very small, so perhaps it is not as differentiated as a larger body would be. But other evidence argues against this, such as the geological and chemical makeup. Tidal heating of differentiated magmatic chambers—which being liquid would flex more than the solid material around them—could explain the existence of isolated hot spots… if the tidal heating were sufficient. But many models don’t show the tides as being quite sufficient.

    "Yet there is clearly liquid water present in large quantities on Enceladus. Nearly pure water, in fact, as no ammonia or other materials were detected in many of the plumes. This is itself quite notable, as this means the liquid is at a temperature in the Earthly range—at least freezing point of zero Celsius or two hundred seventy-three Kelvin. That is a quite drastic departure in both expected temperature and expected chemistry for that part of the Solar System. Much larger bodies, such as Jupiter’s Europa, are known to have liquid water beneath the surface, but it was really quite unexpected to find evidence of it on Enceladus."

    Anthony pointed again to the off-center southern heated area, the diapir. "The best models we’ve been able to make, however, have given us this considerable problem: the tidal forces just aren’t quite enough. They’re fairly close on a cosmic scale, but we’re missing a terawatt or so."

    "After all this time?" the general said finally. "That is not possible."

    "With all due respect, General, it may be possible. The aliens used self-repairing redundant technology in a number of ways. If the device or devices in question were intended to operate for some unbounded amount of time, they may have simply continued to do so. Or, as I think more likely, they may have operated for long enough to create the current situation. On an astronomical scale, remember, even sixty-five million years is relatively short. If they had succeeded in creating a diapir or something similar, there is sufficient tidal heating to make it likely that it would still be slowly cooling to this day. We would not notice the change on our timescale. But if they did such a thing, somewhere on Enceladus would be a truly massive installation."

    Hohenheim stared at the image, trying to envision it. The distant moon was indeed tiny compared to Earth, but he had spent more than enough time in space to recognize how vast even Enceladus was. Enough power to slowly reshape an entire small world…

    He nodded sharply. "Very good. We must begin preparations. Subtly, of course. We must not alert the Ares people on Ceres to our new intentions. I believe I will arrange an apparent recall of Odin to Earth. Obviously we will not go there, but preparations for departure will be similar. Very well done, Doctor LaPointe. I am sorry you have been forced into duplicity with your colleagues, but in the long run I hope you will find it was worthwhile. At the least you shall be the first on the site."

    LaPointe managed a smile. "Thank you, General. I appreciate your sympathy. I’d better get back to work, though."

    "Indeed. No point in failing to gather any additional data."

    As the astronomer left, Hohenheim shook his head. Objectively, he was taking quite a risk. The symbols were undoubtedly those of one of the alien bases, and similar to those for Ceres—that is, the markings of the group of aliens who had lost their battle and apparently been evicted from the system. However, if some device capable of producing such power had been left running, it seemed to Hohenheim fairly likely that it could have destroyed the base when it finally broke down—as any device must have broken down after millions of years.

    But he was also paid for his intuition, and his intuition said that this was it. And, he admitted, there was also the voyage itself. The course would take them through the Jupiter system, the massive planet’s gravity well providing them with additional velocity. Hohenheim also knew that in the many months they had been on station, the mass-beam had not been idle. There were more surprises and demonstrations in store for those watching Odin, and he was looking forward to a bit of showing off. At the very least, the crew of Odin would be famous as the first human beings to ever visit the Outer System.

    Now, however, he had to have a long talk with Mr. Fitzgerald. There might very well be complications when the time came to leave, and he had to be ready to deal with them all.