A liquid ocean in contact with a silicate interior makes Jupiter’s icy moon Europa a prime location for life. This possibility is compounded if geologic processes within its ice shell allow surface materials to mix with the ocean and recharge chemicals required for life. Unfortunately, this ice shell represents a barrier to direct exploration. Dr. Andrew Dombard from the University of Illinois at Chicago and co-authors have performed a concept study for a nuclear powered tunneling probe that can traverse through Europa’s ice shell and reach the ocean, carrying a payload that can search for evidence for extant/extinct microbial life.

An artist’s rendering of the Europa ‘tunnelbot.’ Image credit: Alexander Pawlusik, LERCIP Internship Program, NASA’s Glenn Research Center.

“Estimates of the thickness of the ice shell range between 1.2 and 18.6 miles (2 and 30 km), and is a major barrier any lander will have to overcome in order to access areas we think have a chance of holding biosignatures representative of life on Europa,” Dr. Dombard said.

Dr. Dombard and his colleagues presented a possible solution to this problem.

They performed a concept study for a nuclear-powered ‘tunnelbot’ that can penetrate the ice shell and reach the top of Europa’s ocean while carrying devices and instruments that can be used to search for signs of life or extinct life.

The bot would also evaluate the habitability of the ice shelf itself.

“We didn’t worry about how our tunnelbot would make it to Europa or get deployed into the ice,” Dr. Dombard said.

“We just assumed it could get there and we focused on how it would work during descent to the ocean.”

The tunnelbot would sample ice throughout the shell, as well as water at the ice-water interface, and would look at the underside of the ice to search for microbial biofilms.

The probe would also have the capability of searching liquid water ‘lakes’ within the ice shell.

Dr. Dombard’s team considered two designs for their bot: one powered by a small nuclear reactor, and the other powered by General Purpose Heat Source bricks — radioactive heat source modules designed for space missions.

Heat from both these sources could be used to melt the ice shell. Communications would be provided by a string of ‘repeaters’ connected to the bot by fiber optic cables.

The researchers presented their concept December 14 at the Annual Fall Meeting of the American Geophysical Union in Washington, D.C.

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Andrew J. Dombard et al. Gone Fishing: A Concept Study of a Tunneling Probe Mission to Europa. AGU 2018 Fall Meeting, abstract # P52C-05