Particle physics experiments

Experiments measure freezing point of alien oceans to aid search for extraterrestrial life

The gray and blue layers in the left panel show the deep, ice-covered ocean on Europa, a moon of Jupiter that may harbor extraterrestrial life. This ocean is believed to be much deeper than the oceans on Earth. New research suggests where to find liquid water in these environments. Credit: Image by NASA/JPL-Caltech, with edits by Baptiste Journaux

University of Washington (UW) and University of California, Berkeley (UC Berkeley) conducted experiments that measured the physical limits of the existence of liquid water in icy extraterrestrial worlds. This combination of geology and engineering was made to aid in the hunt for extraterrestrial life and the upcoming robotic exploration of the oceans on the moons of other planets.

The results were recently published in the journal Physical Sciences Cell Reports.

“The more stable a liquid, the more promising it is for habitability,” said co-corresponding author Baptiste Journaux, acting assistant professor of Earth and space sciences at UW. “Our results show that cold, salty, high-pressure liquids found in the deep ocean of other planets’ moons can remain liquid at a much colder temperature than they would at lower pressures. This extends the range of possible habitats on icy moons and will allow us to determine where we should look for biosignatures or signs of life.

Natural and false color views of Europe

This image, taken by the Galileo spacecraft in 1996, shows two views of Jupiter’s ice-covered satellite Europa. The image on the left shows the approximate natural color while the right is colored to accentuate the features. Europa is about 3,160 kilometers (1,950 miles) in diameter, about the size of Earth’s moon. Credit: NASA Jet Propulsion Laboratory

Jupiter and SaturnThe icy moons of , including Europa, Ganymede, and Titan, are our solar system’s top candidates for hosting extraterrestrial life. These ice-encrusted moons are thought to harbor huge liquid oceans, up to several dozen times the volume of oceans on Earth.

“Despite its designation of ‘blue marble,’ Earth is remarkably dry compared to these worlds,” said Journals.

The oceans on these moons can contain various types of salts and are expected to range from about 100 miles deep on Europa to over 400 miles deep on Titan.

“We know water supports life, but most of the oceans on these moons are probably below freezing. Celsius and at pressures higher than anything known on Earth,” said Journals. “We needed to know how cold an ocean can get before it freezes over, including in its deepest abyss.”

The study focused on the eutectic, or the lowest temperature at which a salt solution can remain liquid before freezing entirely. An example is salt and water – salt water stays liquid below the freezing temperature of pure water, one of the reasons people sprinkle salt on the roads in winter to prevent ice formation.

The experiments used UC Berkeley equipment originally designed for the future cryopreservation of organs for medical purposes and for food storage. For this research, however, the authors used it to simulate the conditions thought to exist on the moons of other planets.

Journals, a planetary scientist and expert in water and mineral physics, worked with engineers at UC Berkeley to test solutions of five different salts at pressures up to 3,000 times atmospheric pressure, or 300 megapascals, or about three times the pressure in Earth’s deepest ocean trench. .

“Knowing the lowest possible temperature for salt water to remain liquid at high pressure is key to understanding how extraterrestrial life could exist and thrive in the deep oceans of these icy ocean worlds,” said the co-corresponding author. Matthew Powell-Palm, who did the work as a postdoctoral researcher at UC Berkeley, also co-founder and CEO of cryopreservation company BioChoric, Inc.

Journals recently began working with NASA’s Dragonfly mission team, which will send a rotorcraft in 2027 to Saturn’s largest moon, Titan. " data-gt-translate-attributes="[{" attribute="">Nasa also leads the Europa Clipper mission in 2024 to explore Europa, one of many moons orbiting Jupiter. Meanwhile, the European Space Agency will send its spacecraft JUICE, or Jupiter Icy Moons Explorer, in 2023 to explore three of Jupiter’s largest moons: Ganymede, Callisto and Europa.

“The new data obtained from this study may help researchers better understand the complex geological processes observed in these icy ocean worlds,” Journals said.

Reference: “On the pressure dependence of aqueous salt eutectics” by Brooke Chang, Anthony N. Consiglio, Drew Lilley, Ravi Prasher, Boris Rubinsky, Baptiste Journaux and Matthew J. Powell-Palm, Physical Sciences Cell Reports.
DOI: 10.1016/j.xcrp.2022.100856

The other authors are Boris Rubinsky, Brooke Chang, Anthony Consiglio, Drew Lilley and Ravi Prasher, all at UC Berkeley. The study was funded by the National Science Foundation and NASA.