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. Xe/ 129 Xe 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 H 2 O and NH 3 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.

Scientific rationale for Saturn׳s in situ exploration

“…We described the concept of a Saturn probe as the next natural step beyond Galileo's in situ exploration of Jupiter, and the Cassini spacecraft's orbital reconnaissance of Saturn. Several missions designs have been discussed, all including a spacecraft carrier/orbiter and a probe that would derive from the KRONOS concept previously proposed to ESA (Marty et al, 2009). International collaborations, in particular between NASA/USA and ESA/Europe may be envisaged in the future to enable the success of a mission devoted to the in situ exploration of Saturn.…”

“…An atmospheric entry probe at Saturn would in many respects resemble the Jupiter Galileo probe. The concept was put forward for Saturn in the KRONOS mission proposal (Marty et al 2009). Giant Planet probe concept studies have been studied by ESA in 2010 3 .…”

Saturn's Exploration Beyond Cassini-Huygens

“…Theses two questions are deeply linked, but a long-standing paradox arises when one try to answer them jointly: numerous arguments suggest that the rings are young (<10 Direct imaging of particle size distribution 8 years) because of fast evolutionary processes (erosion due to meteoroid bombardment, surface darkening, viscous spreading, see the chapter by Charnoz et al). However, in the current state of our knowledge, it seems very improbable that they originated less than 1Ga ago, mainly because of the too low cometary flux (Harris, 1984, Charnoz et al, 2008, and chapter by Charnoz et al). To solve this paradox, it is proposed that the ring material is constantly reprocessed due to self-gravity and collisions, and thus, may appear much younger.…”

Exploration of Planetary Hyperspectral Images with Unsupervised Spectral Unmixing: A Case Study of Planet Mars

“…Since its first appearance aboard a spacecraft in 1989, this remote sensing technique has been used to study the surface and the atmosphere of Mars, Venus, Jupiter, Saturn, the Moon, etc. [1][2][3][4][5][6][7][8]. The main advantage of imaging spectroscopy is its ability to map the chemical composition and the physical state of planetary materials, thus providing clues about the geological and environmental evolution.…”