Illustration of a water-covered planet viewed from its surface: In the foreground is rippling water reflecting pink, yellow, and white light from a glowing phenomenon in the distance, in the middle of the illustration. Surrounding the bright phenomenon are bright stars and translucent clouds visible in front of a dark background.
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Otherworldly Oceans

Cover of the October 2023 issue of Eos

This month, we’re diving deep into outer space.

Our solar system’s ocean worlds—planets and moons covered in ice-crusted oceans—are weird, wonderful, and ripe for exploration. And that’s exactly what scientists are encouraging space agencies to do, says Kimberly Cartier in “Uranus: A Time to Boldly Go.” The ice-blue ice giant tilts more than 90°, is enormous itself but ringed by micrometer-sized particles, has many moons that remain largely invisible…and don’t get us started on the planet’s magnetosphere. “Every aspect of the Uranian system challenges our most basic understanding of how planets work,” says planetary scientist Mark Hofstadter.

Planetary scientists interested in ocean worlds like Enceladus and Europa are first getting their feet wet on terra firma. In “Marine Science Goes to Space,” Damond Benningfield provides a sea-sized view of how ocean worlds are redefining what constitutes a habitable zone and how missions in development, like JUICE and Europa Clipper, are relying on terrestrial deep-sea scientific advances to look for oceanic activity that’s out of this world. Meanwhile, older missions are still contributing to the discourse, as archival Cassini data helped scientists identify phosphorus—the rarest element necessary for life as we know it—on Enceladus.

In addition to the ocean, planetary scientists are keeping an eye on Earth’s volcanoes to help them understand dazzling extraterrestrial eruptions. Some of these eruptions, however, don’t really have an earthly analogue. The ice volcanoes of the outer solar system likely erupt in volatiles such as ammonia (as opposed to silicates such as feldspar), offering hints about habitability on their host world. Topographic evidence of these icy eruptions is as ephemeral as the eruptions themselves, as “you can’t make relief with water,” says volcanologist Sarah Fagents. Fellow volcanologist Erik Klemetti explores “Cryovolcanism’s Song of Ice and Fire.”

Back on Earth, researchers have meticulously recorded changes in the environment in what some scientists argue should be internationally recognized World Heritage Data Sets. Emma J. Rosi, Emily S. Bernhardt, Irena Creed, Gene E. Likens, and William H. McDowell make the case for protecting data sets as varied as the Keeling curve and the flowering dates of Kyoto’s cherry trees. Read “Taking the Pulse of Global Change with World Heritage Data Sets” to learn more.

—Caryl-Sue Micalizio, Editor in Chief

Citation: Micalizio, C.-S. (2023), Oceans of opportunity, Eos, 104, Published on September 25 2023.
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