Sometime around 2021 a small metal cylinder will burn its way through the icy surface of Europa, one of the many moons of Jupiter. It will have left our planet at obscene speeds (anywhere up to 55,000 km/h) as part of a small family of drones sent to explore the Jovian system. The travel time could be less than 12 months. If Cryobot manages to tunnel through the 10-30km of ice we expect, we hope to find life waiting below. Simple bacteria are the most likely suspects, followed by much larger, geothermally-powered colonies of organisms, similar to those found in Earth’s deep oceans. Most excitingly, a recent study has suggested that the hidden ocean of Europa may hold enough oxygen to support up to 300 million tonnes of, well… fish. Or their equivalent.
The very idea of fish existing on Europa is mind bending, but not implausible. Light is not the challenge, the challenge for any prospective Europan creature is navigation. Mexican tetra seek out food without any form of sight due to a keen sense for ripples in their surroundings. This ability is provided by a “lateral line” of pores that form a sense organ common to many species of fish. But Mexican tetra are cave dwellers; their ecosystems are small. Europa is expected to possess an ocean 100km deep, holding twice the volume of Earth’s waters, and taking up all of the space between its icy shell and the rock beneath. Sharks, who possess a much wider range than Mexican tetra, also possess an advanced form of the lateral line. In order to hunt more efficiently they have a facility for detecting changes in the local electrical impulses that accompany all life, and possibly magnetic fields into the bargain.
To have reached Europa safely Cryobot will require a hefty amount of electromagnetic shielding and careful planning. Jupiter’s magnetic field is immense. A ring of plasma surrounds it as rock does Saturn, and a column of electromagnetic radiation arcs between the gas giant and one of its many moons. A previous mission into Jovian space (Voyager 2) has lost data due to interference, and anything flying in the wrong place, at the wrong time, risks being fried. Against the turmoil of Jupiter’s influence, prey objects on Europa may be invisible to magnetic detection, but there are other uses for such a talent. Magnetoreception (although poorly understood) has been observed in birds, bees, lobsters and turtles and in each case plays an important role in navigation. Aside from a dependence on the underwater equivalent of a strong sense of ’smell’ (as seen in salmon, catfish and sharks), Europan fish, if they exist, may very well interact with their environment entirely through pressure change and magnetism.
The question then becomes, how do we interact with them? Galileo, our most successful Jovian mission to date, was deliberately incinerated in Jupiter’s atmosphere in order to prevent contamination of its moons with Earth bacteria, lest we inadvertently mimic The War of The Worlds. The 2020 mission development team are already looking into extreme forms of sterilization for both Cryobot and Hydrobot, the rover that will be released once its parent punches through the ice. Cryobot is even being deliberately designed such that the channel it melts can refreeze in its wake, keeping Europa’s isolated waters cut off from the air.
With significant lag time in communication between different parts of our solar system, interference from Jupiter, and no small amount of ice in the way, communication links between Hydrobot, Cryobot, and the other orbiters in system will be strained. Any autonomy we can develop will be a huge boon. Fortunately, 2009 has been a good year for autonomy. Autonomous aquatic explorers are soon to be released off the shore of California to find and manage larval fish reserves, and robotics in Washington have started to take care of relatively simple tasks (like navigation) independent of human control, leaving only the big decisions to their human handlers. Terrestrial trials such as these are likely to be invaluable: By 2020 we will have enough robotic expertise to make a hunt for extraterrestrial life, regardless of form, truly feasible. Because everything we need, we already have.
All that remains is to propel what we have several hundred million miles, and hope that it doesn’t get eaten by eyeless electromagnetic sharks.
