When a Comet Met Ganymede

Captured by NASA’s Galileo spacecraft on April 5, 1997, this image shows Enki Catena, a 161.3-km (100-mile) long crater chain on the surface of Jupiter’s moon Ganymede. Named after the Sumerian god of fresh water, Enki Catena is thought to have been formed when a comet approached too close to Jupiter and was torn into 13 pieces, each impacting Ganymede in…

Ganymede Gets a Little Geologic Love

We don’t get to hear a lot about Ganymede these days, what with everyone paying so much attention to Titan and Enceladus and Europa and several other moons out there. Which is too bad because 1. Ganymede is plenty fascinating in its own right; and 2. it’s the LARGEST MOON IN THE SOLAR SYSTEM (and…

Meet Metis – Jupiter’s Closest, Quickest Moon

Everyone’s heard of Jupiter’s four most famous moons Europa, Io, Callisto, and Ganymede—we’ve known about them for over 400 years, thanks to Galileo—but giant Jupiter has many more moons than that. To date there are thought to be 69 natural satellites orbiting Jupiter. 53 are officially named, while 16 are awaiting further confirmation. So you’d…

OSIRIS-REx Captures a Picture of Jupiter from L4

NASA’s OSIRIS-REx may be designed to study asteroids close up but recently it’s captured a view of something farther away and much, much larger: the giant planet Jupiter and three of its largest moons at a distance of over 400 million miles! The image was taken on Feb. 12, 2017, when the spacecraft was 76 million…

Eppur Si Muove: Galileo’s Big Night, 407 Years Ago Today

407 years ago tonight, on January 7, 1610, the Pisan astronomer Galileo Galilei looked up at a brilliantly-shining Jupiter through his own handmade telescope and saw three bright little “stars” next to it, stirring his natural scientific curiosity. Further observations over the next several nights showed that the planet wasn’t moving relative to the little “stars” as it…

Juno Just Hours from Jupiter Arrival

After nearly 5 years of traveling through space NASA’s Juno spacecraft is just a few dozen hours away from entering orbit around Jupiter, the Solar System’s largest, most massive, and most extreme planet. “We are ready,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute (SwRI). “The science team is incredibly excited…

Icy Enceladus Shines in the Latest Images from Cassini

On Wednesday, Oct. 14 2015, Cassini performed its scheduled “E-20” close pass of Enceladus, a 320-mile-wide moon of Saturn that is now famous for the organics-laden ice geysers that fire from cracks in its southern crust. E-20 is the first of a series of three flybys to be performed before the end of 2015, specifically timed to…

Eppur Si Muove: Galileo’s Big Night

Note: This is an edited repost of an article from 2014. 405 years ago tonight, January 7, 1610, the Pisan astronomer Galileo Galilei looked up at a bright Jupiter at opposition through his handmade telescope and saw three little “stars” next to it, which piqued his natural scientific curiosity. He soon realized that these little…

Jupiter’s Moons Make Ghostly Auroral “Footprints”

We have all marveled at incredible photos and time-lapse videos of Earth’s auroral displays, captured by talented photographers that have braved the frigid nighttime temperatures of remote high-latitude locations as well as by those privileged few living in orbit aboard the International Space Station. But our planet isn’t the only one with curtains of light crowning its…

Saturn and Titan Show Off Their Crescents

It may not be in color but that doesn’t make it any less beautiful: this stunning image from Cassini shows Saturn and its largest moon Titan – the second-largest moon in our solar system, after Jupiter’s Ganymede – from their night sides, both showing their crescents against the blackness of space. Titan’s crescent nearly wraps all…