Experiments measure freezing point of alien oceans to help search for life
Search | Science | UW News Blog
May 3, 2022
Researchers from the University of Washington and the University of California at Berkeley conducted experiments that measured the physical limits to the existence of liquid water in icy alien worlds. This blend of geoscience and engineering was made to facilitate the search for extraterrestrial life and the upcoming robotic exploration of the oceans on the moons of other planets.
The results were recently published in Cell Reports Physical Sciences.
“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.
The icy moons of Jupiter and Saturn – 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 likely below zero degrees Celsius and at higher pressures than anything on Earth,” the Journals said. “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. NASA is also leading 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.
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.
Tag(s): Baptiste Journals • Faculty of Environment • Department of Earth and Space Sciences • space sciences