What’s the best way to explore Jupiter’s icy moon Europa? If tests by British scientists and engineers are anything to go by, bombing its icy crust with a heavy bullet-shaped penetrator should do the trick.
Europa holds significant promise as being a potential oasis for life in our solar system. Below its frozen, dirty surface, scientists know a liquid water ocean hides, protected from the ravages of space and heated by energy generated by gravitational interactions between the gas giant and moon. Forget the search for extinct microbes on Mars; some hypotheses hint at the potential for complex organisms evolving in Europa’s depths. And by “complex organisms,” we’re talking creatures potentially as complex as jellyfish.
The penetrator in flight during the ice impact test. Credit: QinetiQ
These ideas have recently been bolstered by some key discoveries that nutrients collecting on the icy surface are cycling into the ocean and oxygen levels in the Europan ocean could support a huge biomass. In short, the more we study Europa, the more it dares us to dive into its mysterious ocean, pushing us to seek out whatever lies beneath.
But there are huge challenges confronting any future manned or unmanned expedition to the Jovian moon. For one, the icy world has no atmosphere so mounting a surface mission would require a huge amount of energy to slow the lander safely; atmospheric breaking that slows Mars missions before landing simply does not exist on Europa. A Europa landing would have more in common with Apollo than Curiosity.
Also, to access the subsurface ocean, the mission would need some kind of novel drilling technique to drop a probe through the miles of icy crust. Either that, or we’d need to develop a strategy of landing a surface mission right next to a naturally-formed crevasse.
Now throw in the challenge of protecting your spacecraft from the ravages of Jupiter’s radiation belts and developing an energy source — likely nuclear — that will last for the duration of the mission and you have a beast of a proposition.
So, when a team of British engineers approached the idea of Europa exploration, they stripped the mission down to the basics. The Europa mission should consist, at least in part, of a high-velocity projectile that will use brute force to kick off exploration of this fascinating world.
Using a 10 ton block of ice and a 20 kilogram (44 lb) high-velocity penetrator, the team simulated impact velocities higher than what would occur if such a mission were chosen to explore Europa. At a rocket testing facility in Wales, they fired the bullet-shaped penetrator at 340 meters per second (760 miles per hour) — the speed of sound at sea level (on Earth) — into the ice block, decelerating at 24,000g. Sure, the penetrator turned the ice block into slush, but the key success was that the sensitive instrumentation inside the bullet survived intact. If this were a real “penetrator mission” to Europa, the bullet would have lodged itself deep inside the upper layers of the Europa ice, ready to do some science.
“It was really successful because the entry velocity was higher than expected and all the systems we’ve looked at so far have survived,” Marie-Claire Perkinson, the research program’s industrial leader from Astrium UK, told BBC News.
Now that tests are underway, the European Space Agency (ESA) is taking note.
“Penetrators offer a number of advantages over ‘soft landers’, which have to slow down to reach the surface safely,” explained ESA project manager Sanjay Vijendran. “They would enable you to get deep into the sub-surface essentially for free, up to three meters without having to drill. And being light means you can deploy a few at once from a single spacecraft orbiter.”
For all the details surrounding the technical challenges facing the penetrator, read the fascinating BBC News report by Jonathon Amos.
One can’t help but imagine that the first wave of Europa surface expeditions may consist of a flyby mission that would offload a fleet of ice penetrators that will guide their way, bunker buster-style, to their targets. By peppering the globe with these ‘smart bombs,’ we can begin what could be a new era of extraterrestrial life hunting, not on the dry surface of Mars, but in the depths of an extraterrestrial ocean.
Image credits: NASA, QinetiQ