Icy Worlds

Astrobiology Recon Missions: Using Ice-penetrating Radar To Find Liquid Water On Other Worlds

By Keith Cowing
Press Release
European Geosciences Union
April 19, 2024
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Astrobiology Recon Missions: Using Ice-penetrating Radar To Find Liquid Water On Other Worlds
Europa Clipper — NASA

The first clue for finding life on other planets is finding liquid water. The moons of Saturn and Jupiter like Enceladus, Ganymede, Europa, and Callisto are suspected of holding oceans of liquid water beneath icy crusts. Similarly, some exoplanets beyond our solar system likely host liquid water, crucial for habitability.

But detecting water, when we can’t physically access these celestial bodies, poses challenges. Ice-penetrating radar, a geophysical tool, has proven capable of detecting liquid water on Earth and beneath Mars’ South polar cap.

Now, this instrument is aboard the JUICE spacecraft and it is on its way to Jupiter’s icy moon Ganymede and will also be aboard the Europa Clipper spacecraft, which will be launched to Europa later this year. What can we expect to learn from these missions and how can we use ice-penetrating radar for future planetary exploration? Dr Elena Pettinelli of Roma Tre University, with extensive experience in planetary exploration using ice-penetrating radar, will delve into the utility of this technology in her presentation next week at the European Geosciences Union General Assembly EGU24.

ESA JUICE mission — ESA

Dr. Pettinelli, who was part of the team that discovered a subglacial stable body of liquid water on Mars, will trace the historical applications of ice-penetrating radar in planetary exploration before she dives into prospective uses of ice-penetrating radar in locating and characterizing liquid water.

Scientists hope to use ice-penetrating radar to determine the depth and chemistry of water beneath the icy surface of Jovian moons. Dr. Pettinelli explains that the radar’s penetration depth correlates with ice salinity; saltier ice impedes radar transmission to a greater extent. “Depending on the behavior of the radio waves, we might be able to better tell the distribution of salt,” she says, which her team then ground-truths through laboratory experiments.

“We can use all this information to improve our understanding of the distribution of liquid water in the solar system,” Dr. Pettinelli says. “There’s much more water than we thought 20 or 30 years ago, and it’s really interesting to use this technique to try to understand where the water could be.”

NASA’s Jet Propulsion Laboratory built and shipped the receiver, transmitter, and electronics necessary to complete the radar instrument for JUICE, the ESA (European Space Agency) mission to explore Jupiter and its three large icy moons. Here the transmitter undergoes vibration testing at JPL. Credits: NASA/JPL-Caltech

In search for liquid water using radio waves: from Earth to the icy moons of Jupiter, EGU General Assembly 2024

Elena Pettinelli Roma Tre University, Mathematics and Physics, Italy ([email protected])

Radar sounder (or Ice-penetrating radar) is one of the most suitable geophysical instruments to explore planets and moons given the very dry and/or cold conditions of their crusts, which favor the penetration of the radio waves at great depth. The first ever planetary subsurface radar was tested on the Moon, during the Apollo 17 mission: the ALSE (Apollo Lunar Sounder Experiment) multifrequency radar sounder operating onboard the Apollo Service Module (ASM) (Porcello et al., 1974).

After this successful experiment more than twenty years passed before another radar sounder was included in the payload of a planetary mission. MARSIS was launched in 2003, on board Mars Express, and SHARAD in 2007 onboard Mars Reconnaissance Orbiter. Since the successful deployed on Mars, such radars collected data for more than 15 years, mapping the structures of the Martian poles and discovering the first extraterrestrial stable body of subglacial liquid water below the South pole cap. Six orbiting radar sounders have been employed so far to explore the Moon, Mars and the 67P/GC comet, and some of them are still in full operation today.

The Jupiter icy moons will be the next destination of a new generations of radars: RIME, already on his way to Ganymede onboard JUICE and REASON that will be launch this year onboard Europa Clipper. These radars will explore the icy shells of Europa, Ganymede and Callisto to establish their habitability conditions and in search for evidence of liquid water. Finally, also Venus will be investigated in the next decade by a similar radar to help understand the geological and climatic evolution of the Earth twin.

In this talk I will discuss the new opportunities and challenges for the radar sounder community in the years to come.


Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻