Here’s a bit of wild speculation for the weekend:
Suppose there is intelligent life in the globe-spanning ocean on Europa. Given how small our space exploration budget is, and our generally declining investments in R&D, how likely is it that the Europan life would discover us before we discover it?
Any life or societies that evolve on Europa would do so underneath a shell of water ice. A human would no doubt find the environment claustrophobic, whether near the bottom of the ice shell or at extreme depths. Native Europans, though, would live comfortably with the perpetual presence of hydrostatic pressure. The creatures’ science would be familiar with the concepts of temperature and pressure. Some intrepid Europan theorists may even have extrapolated their equations to pressure = 0, but it’s likely that none of the creatures would have any firsthand experience with vacuum. The surface environment of the moon would therefore be totally alien and inhospitable; possibly, many of the creatures would have died in attempting to breach the ice before any succeed.
Would they even think to go up to the surface? I think so, as there is a strategic rationale. Without viscosity to slow them, and with about the same gravity as Earth’s moon pulling them down, a Europan army could move much more quickly over the surface of the moon than through the ocean. Europan kingdoms could launch surprise attacks if they were able to access the surface. Of course, the notion of doing this requires that the creatures realize that the ice over their heads has a surface. There may be ways to determine this from below, perhaps by watching for minute changes in lighting conditions, or even by direct observation of one of Europa’s surface cracks during its process of formation. Or maybe the Europans will just have to rely on explorers analogous to Earth’s Ferdinand Magellan.
Still, even with that strategic rationale, I think penetrating to the ice surface would be the Europan equivalent of the United States’ moon shot in the 1960s. That is, there would have to be a certain high level of technology, as well as a sufficiently well-organized political organization to support a successful attempt. The creatures of Europa would need to figure out how to support their high-pressure life requirements in the vacuum of space, not to mention figuring out how to tunnel or otherwise travel through anywhere from one to one hundred kilometers of ice. If the creatures aim for one of the cracks which may provide surface access from the ocean, then they would have only about a quarter of a Europan day (7/8 of an Earth day) to make the traversal before Jupiter’s tides close the crack again. Any way I look at it, I think that the creatures getting to the surface represents a tremendous achievement of technological prowess.
Once they get to the surface, the creatures would make a stunning array of discoveries. They may already know that their own world is spherical, but suddenly and immediately they would become aware – for the first time in their history – of Jupiter, the Sun, and the stars. In short order, they would discover the other large moons of Io, Ganymede, and Callisto. After spending some time making astronomical observations, they would see other Jovian moons, followed quickly by objects that orbit the Sun rather than Jupiter: Saturn, Mars, Earth, Venus, Uranus, comets. It would be an astonishing and groundbreaking time to be a Europan, as their worldview would experience revolution after revolution.
However, the downside of all this rapid discovery is that the Europan creatures’ science may lag behind the science of Earth. They would not have the long history of looking at the stars that we do. They might not have very good models for gravitational force. Until they get very good telescopes trained at the Sun, the very idea of fire or explosions might be foreign to them.
This is important for my main question, because without the concept of a gaseous explosion, the creatures would find it difficult to conceive and build rockets to begin a true space exploration program.
There is a way the creatures could start to explore their local system without developing rocket propulsion, though: it is conceivable to build large-scale catapults capable of accelerating objects to Europan escape velocity, which is only 2 km/s compared to the Earth’s 11 km/s. (“Only,” though that’s still very fast…Wolfram Alpha tells me that a reasonable comparison to the speed of 2 km/s is the X-15 rocket plane, though, which suggests to me that 1960s-equivalent Europans might have some hope to reach that speed technologically.) Surface-based accelerators would give the creatures the ability to explore the Jovian system.
Maybe a surface catapult plus a gravitational slingshot around Jupiter would allow the creatures to explore the wider Solar System. But I think that they need to develop some kind of rocket propulsion to have control over their efforts – or to return again. They also need to develop the sciences of orbital mechanics and Newtonian motion. These are disciplines that humans have been studying since the dawn of civilization. Our quantitative study of orbits and classical physics goes back to the 1500s.
I think the bottom line is this: if the Europan civilization has the same 7000 years of recorded history that human civilization does, and they reached the surface of their moon around the 1950s-1970s, even if they are more inherently curious and more willing to put forth exploration efforts than we are…they aren’t going to discover us first.
Unless we sit on our hands for a few hundred more years.