Jupiter’s icy moon Europa is a potential hotspot for life, with a liquid ocean possibly hiding under a thick ice crust. Studying this ocean could change the way we think of icy worlds, so researchers from Arizona State University are working on a way to study it without drilling.
The team is developing a compact seismometer that can “take the pulse” of the moon. By measuring the tides and underground movements, the device will be able to establish how thick the ice crust is, whether it holds pockets of water, and how often and easily the ocean comes to the crack seen on its surface.
“We want to hear what Europa has to tell us,” said team leader Hongyu Yu, of ASU’s School of Earth and Space Exploration, in a statement. "And that means putting a sensitive ‘ear’ on Europa’s surface."
NASA is planning a mission to Europa, but there are no confirmed plans to send a lander there. Nevertheless, they are investigating the potential suite of instruments that such a probe would need, as a standard seismographer wouldn’t cut it.
The seismographer we use on Earth to measure earthquakes functions with a spring-and-mass mechanism. It has to stay vertical and needs to be put in place without jolts or too many shakes – not the ideal combination to send on a space mission 588 million kilometers (365 million miles) away.
“Our design avoids all these problems," Yu explained. "This design has a high sensitivity to a wide range of vibrations, and it can operate at any angle to the surface."
"And if necessary," he added, "they can hit the ground hard on landing.”
The team tested their SESE (Seismometers for Exploring the Subsurface of Europa) by hitting it with a sledgehammer – and it survived.
SESE are sensitive enough to measure how the ice of Europa changes and to learn about the activity of the surface. Based on observations from orbit, the surface is estimated to be 15 to 25 kilometers (10 to 15 miles) thick and no older than 100 million years (as it has very few craters).
However, being relatively young doesn’t tell us about its activity, as it might have been active then and not now or it continues to change today. Based on recent Hubble observations of plumes, Europa’s surface might be experiencing fractures and changes even today.
While the seismographers were developed with Europa in mind, they are definitely versatile. The team thinks that with just minor adjustment, it could be deployed on Mars, Venus, and other planets and moons.