NASA Plans a Journey to the Ocean at the Center of an Icy Moon

Jules Verne enthralled generations of readers with the science fiction classic Journey to the Center of the Earth. In this epic tale, Professor Otto Lidenbrock and crew descend into an Icelandic volcano in the name of science. Now, a team of researchers from NASA's Jet Propulsion Laboratory propose that spelunking robots could similarly explore the subsurface oceans of icy moons.

Each year the NASA Innovative Advanced Concepts Program (NIAC) reviews visionary ideas that could change the future of space travel. NIAC revises what is possible by using technological developments to transform science fiction into science fact. Recently, NASA announced its 2016 Phase 1 mission concepts.

"The 2016 NIAC Phase I competition was fierce, as usual. All of the final candidates were outstanding, and limiting the choice to what fit in our budget was difficult," said Jason Derleth, NIAC program executive. "We hope each new study will push boundaries and explore new approaches—that's what makes NIAC unique."

Mars is traditionally pegged as the best place to look for life beyond Earth as the red planet was once Earth-like. However, there may be better options—such as Europa or Enceladus—further out into the Solar System. The two frosty moons (orbiting the gas giants Jupiter and Saturn respectively), both harbor subsurface oceans beneath a frozen exterior, which could be ideal for hosting life.

With a thick icy crust—as much as 62 miles (100 km) thick—Europa would present some issues for a drilling robot to reach the subsurface ocean. As such, researchers have turned their sights to Saturn's snowball moon, Enceladus. The tiny moon features a tantalizing terrain, with geyser-like plumes and surface scars (known as tiger stripes), which could provide the best point of access for a robotic probe.

Perhaps one of this year's most promising NIAC proposals was submitted by a team of researchers from JPL and proposes using robots to explore one of the icy moons, Jules Verne style. The Icy-Moon Cryovolcano Explorer (ICE, for short) aims to land on one of these moons and send a robotic explorer down the shaft of an ice volcano, where it will ultimately deploy a submersible to explore the ocean below.

Like the nesting dolls of science payloads, ICE would feature three modules, each needing to be deployed by the previous one. A surface module (SM) would land near the south pole of Enceladus and then deploy a descent module (DM) that would act much like a human alpinist. The team analyzed data from the plume and determined that the density of the material spewing out would not prohibit the DM from rappelling into the cavernous fissures. Once it reaches the subsurface ocean, the DM would release an autonomous underwater vehicle (AUV) to explore the salty depths of Enceladus' ocean.

ICE could be the future of exploring ocean worlds as it has unique advantages over drilling proposals. First, it allows for in-situ science within a cryovolcanic vent. NASA's Cassini spacecraft sampled the plumes of Enceladus, but larger material typically doesn't reach orbital height. Mineral grains larger than 1 micron are especially important as they can provide the biggest insight into habitability.

Second, descending into an already open fissure provides easier entry to the ocean below and allows for a higher chance of mission success than those that must drill or burrow through layers of thick ice.

Lastly, the ICE mission concept enables the submersible or AUV to explore the oceans of icy moons unhindered by facilitating communication and power to the AUV. Water interferes with communication and localization (how the submersible knows where it is), so ICE proposes the use of acoustic communication rather than radio waves. The DM will also act as a charging station for the AUV, thus eliminating the need for an RTG or other bulky power source.

This Phase 1 concept will explore the risks of such a mission, and allow researchers to further develop the science targets and power needs for such an undertaking. For this initial phase, JPL researchers will receive $100,000 to work on their project for nine months. If the ICE mission proves to be viable, it will receive a second round of funding in the amount of $500,000 for two more years of research and development.