When 252P/LINEAR passed just 14 lunar distances from Earth on 21 March, the comet was galloping across the far southern sky at a rate of almost ten degrees per day. Now rapidly heading north, 252P finally appears in the predawn UK sky. While moonlight will interfere with current observations, the comet is much brighter than predicted.
New research suggests that some of Saturn’s icy moons, as well as its famous rings, might be modern adornments. Their dramatic birth may have taken place a mere 100 million years ago. This would date the formation of the major moons of Saturn, with the exception of more distant Titan and Iapetus, to the relatively recent Cretaceous Period — the era of the dinosaurs.
By convention, mountains on Saturn’s largest moon, Titan, are named for mountains from Middle-earth, the fictional setting in fantasy novels by J.R.R. Tolkien. Unfortunately for “Lord of the Rings” fans, Titan’s highest peak is not Doom Mons, but a trio of ridges known as Mithrim Montes, where the tallest peak is 10,948 feet (3,337 metres) high.
In this image from NASA’s Cassini spacecraft we see a crater duo on Saturn’s 698-mile-wide moon Dione. The upper of the pair, named Italus, is overprinted on a grouping of ancient troughs called Petelia Fossae. The lower crater, Caieta, sits atop a feature named Helorus Fossa. Fossae on Dione are believed to be tectonic features.
Now just ten weeks from opposition, Mars is growing in both apparent size and brightness in the pre-dawn sky as the distance between our two worlds decreases. On the morning of Wednesday, 16 March, around the onset of UK nautical twilight, the Red Planet passes just 0.15 degrees from double star Graffias in the constellation Scorpius.
Similar in many ways, Saturn’s moons Tethys and Rhea (left and right, respectively) even share a discoverer: Giovanni Cassini, namesake of the NASA spacecraft that captured this view. Although somewhat different in size, Rhea (949 miles across) and Tethys (660 miles) are both composed largely of ices and are generally thought to be geologically inactive today.
In the pre-dawn twilight of Tuesday, 1 March, the 21-day-old waning gibbous Moon acts as a convenient celestial guide to planets Saturn and Mars. For observers in the centre of the British Isles, the best time to see this triple conjunction is shortly before 6am GMT, when the trio are highest in the sky to the south.
Three of Saturn’s moons — Tethys, Enceladus and Mimas — are captured in this group photo from NASA’s Cassini spacecraft. Tethys appears above the rings, while Enceladus sits just below centre and Mimas hangs below and to the left of Enceladus. This view looks toward the sunlit side of the rings from narrowly above the ring plane.
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