Some of Uranus' moons likely have deep oceans lurking beneath their ice-capped surfaces, a new study by NASA shows.
Two of them, Titania and Oberon, may even have water warm enough to support life.
Scientists have recently pored through decades-old information collected by the veteran Voyager 2 spacecraft, which flew by Uranus in 1986 during its extended space mission. Armed with new computer modeling techniques, researchers reanalyzed the data and concluded four of the ice giant's 27 moons(opens in a new tab) probably have liquid water sandwiched between their cores and crusts.
The findings, published in the Journal of Geophysical Research, describe these Uranian water worlds(opens in a new tab) — Ariel, Umbriel, Titania, and Oberon — as probably holding briny oceans dozens of miles deep. They join a growing list of water worlds(opens in a new tab) being discovered throughout the solar system.
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The study challenges previous notions that moons of this size — between 700 and 1,000 miles wide — would be too small to retain the needed heat for an ocean layer, said Julie Castillo-Rogez, lead author from NASA’s Jet Propulsion Laboratory in Southern California.
The new computer models leveraged insights from previous missions that discovered ocean worlds in the solar system, including Saturn's moon Enceladus and the dwarf planet Ceres.
"When it comes to small bodies – dwarf planets and moons – planetary scientists previously have found evidence of oceans in several unlikely places, including the dwarf planets Ceres and Pluto, and Saturn’s moon Mimas," she said in a statement(opens in a new tab). "So there are mechanisms at play that we don’t fully understand."
This year the National Academies’ 2023 Planetary Science and Astrobiology Decadal Survey(opens in a new tab), which helps set the agenda for upcoming space missions, prioritized Uranus and its orbiting moons for exploration. The James Webb Space Telescope also recently turned its attention to the seventh planet from the sun, capturing an image of 11 rings around Uranus. To prepare for such a journey, NASA is trying to learn more about the tilted ice giant planet(opens in a new tab), roughly 2 billion miles from Earth.
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Uranus has captivated the scientific community because its size is the most common astronomers find among the cosmos, making it an ideal learning lab. Despite this, only one spacecraft has ever visited the area around the planet. Scientists have used ground-based telescopes to better understand its changing seasons and weather, but the dearth of information from a close encounter has left many questions unanswered: For starters, why is it the only planet whose equator is nearly at a right angle to its orbit, causing it to have such extreme seasons?
Advocates of probing Uranus(opens in a new tab) (Yes, I went there.) say the best case scenario for a mission is to launch around 2031 or 2032 to take advantage of Jupiter's gravity to get there faster.
Of the planet's five largest moons, only one of them, Miranda(opens in a new tab), was judged too small to retain enough heat for an ocean, according to the study. The researchers also found telescope evidence indicating material flowed onto the surface of Ariel relatively recently, perhaps surging from icy volcanoes.
But scientists have many more mysteries to solve, including where exactly the moons would get their heat to keep these waters from freezing. Uranus' gravitational pull is not enough, according to the study.
Experts have contemplated whether salts and ammonia(opens in a new tab), likely prevalent on the icy giant’s largest moons, could be acting as antifreeze. And they suggest a potential heat source: hot liquid rising up from the moons’ rocky mantles.
