Kronos: exploring the depths of Saturn with probes and remote sensing through an international mission

Abstract  
Kronos is a mission aimed to measure in situ the chemical and isotopic compositions of the Saturnian atmosphere with two probes
and also by remote sensing, in order to understand the origin, formation, and evolution of giant planets in general, including
extrasolar planets. The abundances of noble gases, hydrogen, carbon, nitrogen, oxygen, sulfur and their compounds, as well
as of the D/H, ⁴He/³He, ²²Ne/²¹Ne/²⁰Ne, ³⁶Ar/³⁸Ar, ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/(¹⁷O)/¹⁶O, ¹³⁶Xe/¹³⁴Xe/¹³²Xe/¹³⁰Xe/¹²⁹Xe isotopic ratios will be measured by mass spectrometry on two probes entering the atmosphere of Saturn at two different
locations near mid-latitudes, down to a pressure of 10 Bar. The global composition of Saturn will be investigated through
these measurements, together with microwave radiometry determination of H₂O and NH₃ and their 3D variations. The dynamics of Saturn’s atmosphere will be investigated from: (1) measurements of pressure, temperature,
vertical distribution of clouds and wind speed along the probes’ descent trajectories, and (2) determination of deep winds,
differential rotation and convection with combined probe, gravity and radiometric measurements. Besides these primary goals,
Kronos will also measure the intensities and characteristics of Saturn’s magnetic field inside the D ring as well as Saturn’s
gravitational field, in order to constrain the abundance of heavy elements in Saturn’s interior and in its central core. Depending
on the preferred architecture (flyby versus orbiter), Kronos will be in a position to measure the properties of Saturn’s innermost
magnetosphere and to investigate the ring structure in order to understand how these tiny structures could have formed and
survived up to the present times.