The Great Red Spot (GRS) is the solar system’s largest known storm, an Earth-sized anticyclone that has raged in the atmosphere of Jupiter for at least two centuries. But recent observations from Earth and space suggest that this iconic Jovian feature is undergoing huge changes that could herald its demise.
Jupiter, the solar system’s largest planet, is now visible low in the southeast three hours after darkness falls in the UK. Now’s the time to dust off your telescope, check its optical alignment and hone your Jovian observing skills – particularly since a series of double shadow transits of the planet’s large Galilean moons starts on 24 March 2018.
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.