NASA’s Cassini spacecraft has begun returning its best-ever views of the northern extremes of Saturn’s icy, ocean-bearing moon Enceladus. The spacecraft obtained the images during its 14 October flyby, passing 1,142 miles (1,839 kilometres) above the moon’s surface. Mission controllers say the spacecraft will continue transmitting images and other data from the encounter for the next several days.
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. “The northern regions are crisscrossed by a spidery network of gossamer-thin cracks that slice through the craters,” said Paul Helfenstein, a member of the Cassini imaging team at Cornell University, Ithaca, New York. “These thin cracks are ubiquitous on Enceladus, and now we see that they extend across the northern terrains as well.”In addition to the processed images, unprocessed, or “raw,” images are posted on the Cassini mission website.
Cassini’s next encounter with Enceladus is planned for 28 October, when the spacecraft will come within 30 miles (49 kilometres) of the moon’s south polar region. During the encounter, Cassini will make its deepest-ever dive through the moon’s plume of icy spray, sampling the chemistry of the extraterrestrial ocean beneath the ice. Mission scientists are hopeful data from that flyby will provide evidence of how much hydrothermal activity is occurring in the moon’s ocean, along with more detailed insights about the ocean’s chemistry — both of which relate to the potential habitability of Enceladus.Cassini’s final close Enceladus flyby will take place on 19 December, when the spacecraft will measure the amount of heat coming from the moon’s interior. The flyby will be at an altitude of 3,106 miles (4,999 kilometres).
In the bright evening twilight of 14, 15 and 16 July, observers in the British Isles and Western Europe can see the waxing gibbous Moon pass by Mars, first-magnitude star Antares in Scorpius, then Saturn. This series of conjunctions occurs very low in the southern sky for UK-based astronomers, while Australasian observers are ideally placed to view the spectacle almost overhead.
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.
A hundred days have passed since Mars was closest to Earth this year, but the Red Planet can still be seen in the early evening sky close to the jewel of the solar system, Saturn. If you wish to identify this pair of planets, then a convenient celestial marker in the form of the waxing crescent Moon passes by on the evenings of 8—9 September in the UK and Western Europe.