Several recent news stories have reported that a mysterious anomaly in the orbit of NASA’s Cassini spacecraft around Saturn could potentially be explained by the gravitational tug of theorised Planet 9, existing far beyond the orbit of Neptune in our solar system. However, NASA cannot find any unexplained deviations in the spacecraft’s orbit.
NASA’s Cassini spacecraft has observed geysers erupting on Saturn’s icy moon Enceladus since 2005, but the process that drives and sustains these eruptions has remained a mystery. Now, scientists have pinpointed a mechanism by which cyclical tidal stresses exerted by Saturn can drive Enceladus’s long-lived eruptions.
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.
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.
NASA’s Cassini spacecraft spied details on the pockmarked surface of Saturn’s moon Prometheus (86 kilometres, or 53 miles across) during a moderately close flyby on 6 December 2015. This is one of Cassini’s highest resolution views of Prometheus, a moon which orbits Saturn just interior to the narrow F ring, which is seen here at top.
Although Saturn’s moons Dione (near) and Enceladus (far) are composed of nearly the same materials, Enceladus has a considerably higher reflectivity than Dione. As a result, it appears brighter against the dark night sky. This image was taken by NASA’s Cassini spacecraft in visible light with the narrow-angle camera on 8 September 2015.
NASA’s Cassini spacecraft has begun returning its best-ever views of the northern extremes of Saturn’s icy, ocean-bearing moon Enceladus. Scientists expected the north polar region of Enceladus to be heavily cratered, based on low-resolution images from the Voyager mission, but the new high-resolution Cassini images show a landscape of stark contrasts.
Water reserves found on the Moon are the result of asteroids acting as “delivery vehicles” and not of falling comets as was previously thought. Using computer simulation, scientists from the Moscow Institute of Physics and Technology and the RAS Geosphere Dynamics Institute have discovered that a large asteroid can deliver more water to the lunar surface than the cumulative fall of comets over a billion year period.
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