Original reports, explanations and news from their publishers.
When New Horizons flew past Pluto in July 2015, the former ninth planet became a world of mountains and glaciers. Its new classification had changed its place in a list, but the flyby showed how much remained to explain about the place itself.
4 min read
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Cassini discovered that Enceladus sends water vapour and icy grains into space. Flying through that material gave scientists access to a buried ocean without landing on the moon or drilling through its frozen shell.
4 min read
NASA/JPL/Space Science Institute
Voyager 1 revealed an erupting plume on Io in 1979. Juno later returned close enough to measure how this small rocky moon deforms and loses heat. The energy driving its volcanoes comes from an orbit continually disturbed by Jupiter and neighbouring moons.
4 min read
NASA/JPL/University of Arizona
When Galileo flew past Ganymede in 1996, its instruments found something no spacecraft had measured at another moon: an internally generated magnetic field. That discovery made the largest moon of Jupiter a place to investigate both a metallic core and a buried ocean.
3 min read
NASA/JPL-Caltech/SwRI
Galileo’s images of Callisto show bright impact scars scattered across dark, ancient ground. Its magnetic measurements raised a separate question: could a moon that preserves so much old terrain still contain a salty ocean?
4 min read
NASA/JPL
New Horizons photographed Pluto’s large moon Charon on 14 July 2015. A belt of enormous fractures cut across the encounter hemisphere, suggesting that the icy crust had stretched. One explanation begins with water freezing deep below the surface.
3 min read
NASA/Johns Hopkins APL/SwRI
Images from Mars Reconnaissance Orbiter show Phobos as a battered, irregular moon dominated by Stickney crater. Its less visible change is orbital: Phobos is gradually moving closer to Mars because it travels around the planet faster than the planet turns.
3 min read
NASA/JPL-Caltech/University of Arizona
Mars Reconnaissance Orbiter photographed a dusty, cratered Deimos in February 2009. Its small, irregular shape resembles an asteroid. Explaining how that object ended up on a nearly circular orbit around Mars is harder than identifying the resemblance.
3 min read
NASA/JPL-Caltech/University of Arizona
Mimas looks like a frozen, heavily battered moon in Cassini’s photographs. Yet an analysis published in 2024 found that subtle details of its motion were best explained by a global ocean. The apparent contradiction is a question of timing.
3 min read
NASA/JPL/Space Science Institute
Voyager 2’s January 1986 flyby revealed sharp boundaries between Miranda’s cratered ground, ridged regions and enormous scarps. A small moon had somehow undergone major deformation. Researchers are still using those few close images to test what could have supplied the heat.
3 min read
NASA/JPL
Cassini’s September 2007 flyby showed an abrupt contrast on Iapetus: dark terrain beside bright ice, with surprisingly little middle ground. Dust can start the difference, but sunlight and the movement of water molecules help explain why it becomes so strong.
4 min read
NASA/JPL-Caltech/Space Science Institute
Cassini’s September 2005 encounter revealed deep, closely packed cavities across Hyperion. The moon was unusual in another way: it did not keep one orderly face towards Saturn. Its uneven shape and changing gravitational torques produce chaotic rotation.
3 min read
NASA/JPL-Caltech/Space Science Institute
