Cassini continues to make discoveries at Saturn

Unanswered questions remain about magnetic field, ring composition, and atmosphere.
By Laurel Kornfeld | Jul 26, 2017
NASA's Cassini Saturn orbiter is pleasantly surprising scientists by continuing to make discoveries about the planet and its rings even as it proceeds through its Grand Finale, which will end with a September 15 plunge into Saturn's atmosphere.

Currently, in its 15th of 22 dives between the innermost rings and the giant planet, the orbiter has made several significant discoveries as well as captured the highest resolution images taken since its arrival at the Saturn system in 2004.

Significantly, the spacecraft has found Saturn's magnetic field to have no tilt and be closely aligned with the planet's rotational axis. This is puzzling to scientists because current theories state planets' magnetic fields must be tilted to keep currents flowing through their metal cores.

Lack of a tilt should cause the currents to stop, resulting in the magnetic field's complete disappearance.

A tilted magnetic field would also allow scientists to measure the daily wobble of the planet's interior, from which they could determine the length of its day. Without this, that length remains unknown.

Cassini magnetometer investigation leads Michele Dougherty of Imperial College in London believes something deep within Saturn's atmosphere could be hiding the nature of the magnetic field and hopes data collected by the orbiter, even during its final plunge into the planet, could provide answers to the mystery.

During the first dives the spacecraft made between the innermost rings and the planet, scientists used its antenna to shield it from potentially hazardous particles. When no such particles were detected during passage through the D ring, they chose to allow Cassini's Cosmic Dust Analyzer (CDA) instrument to observe from behind the antenna.

CDA captured very tiny particles, which mission scientists hope will provide insight into the D ring's composition.

High-resolution images taken of the C ring shows it to contain strange bands dubbed plateaus, which have different textures than other parts of the ring.

Closeup images of the cloudscape taken on April 26 and June 29 were combined into mosaics and a new movie.

Cassini's Ion and Neutral Mass Spectrometer (INMS) will study deeper into Saturn's atmosphere when the orbiter makes its final five flights into the outer atmosphere. Data collected then is expected to shed light on atmospheric composition.

"Cassini is performing beautifully in the final leg of its long journey," said project manager Earl Maize of NASA's Jet Propulsion Laboratory in California.

"Its observations continue to surprise and delight as we squeeze out every last bit of science that we can get."


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