Titan Saturn System Mission (TSSM)
TSSM Science Goals & Objectives
Saturn’s largest moon Titan has been an enigma at every stage of its exploration. Discoveries by Voyager I in the 1980’s and Hubble Space Telescope observations in the 1990’s provided valuable insight into the secrets of this unique world from a distance but did not reveal the complexity of the surface that Cassini-Huygens would uncover beginning in 2004. These recent discoveries leave us with many questions that require a future mission to answer.
These include whether methane is out-gassing from the interior or ice crust today, whether the lakes are fed primarily by rain or underground methane-ethane aquifers (more properly, “alkanofers”), how often heavy methane rains come to the equatorial region, whether Titan’s surface supported vaster seas of methane in the past, and whether complex self-organizing chemical systems have come and gone in the water volcanism, or even exist in exotic form today in the high latitude lakes. The composition of the surface and the geographic distribution of various organic constituents remain poorly known. Key questions remain about the ages of surface features, specifically whether cryovolcanism and tectonism are actively ongoing or are relics of a more active past. Ammonia, circumstantially suggested to be present by a variety of different kinds of Cassini-Huygens data, has yet to be seen. The presence of a magnetic field has yet to be established. The chemistry that drives complex ion formation in the upper atmosphere was unforeseen and is poorly understood. A large altitude range in the atmosphere, from 400–900 km in altitude, will remain poorly explored after Cassini. Much remains to be understood about seasonal changes of the atmosphere at all levels, and the long-term escape of constituents to space.
No single target in the outer solar system encompasses such a breadth of disciplines within the planetary sciences as does Titan. It is a complete world in the sense that the Earth is, with the substitution of abiotic or prebiotic organic chemistry for life. Together Titan and Enceladus trump any other pairing beyond the asteroid belt for their promise of a wealth of new discoveries, and for their environments suitable for exploration in truly novel ways.
The key scientific questions for the Titan Saturn System Mission divide into three goals:
Goal A: Explore Titan, an Earth-like System
How does Titan function as a system? How are the similarities and differences with Earth, and other solar system bodies, a result of the interplay of the geology, hydrology, meteorology, and aeronomy present in the Titan system?
Goal B: Examine Titan’s Organic Inventory – A Path to Prebiological Molecules
What is the complexity of Titan’s organic chemistry in the atmosphere, within its lakes, on its surface, and in its putative subsurface water ocean? How does this inventory differ from known abiotic organic material in meteorites and contribute to our understanding of the origin of life in the Solar System?
Goal C: Explore Enceladus and Saturn’s Magnetosphere – Clues to Titan’s Origin and Evolution
What is the exchange of energy and material between the Saturn magnetosphere, solar wind and Titan? What is the source of geysers on Enceladus? Does complex chemistry occur in the geyser source?
Goal A: Explore Titan, an Earth-like System
Titan is a complex world more like the Earth than any other: it has a dense mostly nitrogen atmosphere, the only other place besides Earth to have one, it has an active climate and meteorological cycle where the working fluid—methane—behaves under Titan conditions the way that water does on Earth. And its geology—from lakes and seas to broad river valleys and mountains—while carved in ice is, in its balance of processes, again most like Earth. Beneath this panoply of Earth-like processes an ice crust floats atop what appears to be a liquid water ocean. Goal A seeks to understand Titan as a system, in the same way that one would ask this question about Venus, Mars, and the Earth.
Goal B: Examine Titan’s Organic Inventory – A Path to Prebiological Molecules
Titan is also rich in organic molecules—more so in its surface and atmosphere than any place in the solar system, including Earth (excluding our vast carbonate sediments). These molecules were formed in the atmosphere, deposited on the surface and, in coming into contact with liquid water may undergo an aqueous chemistry that could replicate aspects of life’s origins.
Goal B is to understand the chemical cycles that generate and destroy organics and assess the likelihood that they can tell us something of life’s origins.
Goal C: Explore Enceladus and Saturn’s Magnetosphere – Clues to Titan’s Origin and Evolution
For Goal C, two aspects of the Saturnian system must be studied. These are Enceladus, whose interior is exposed to analysis through an active plume-geyser system, and the Saturnian magnetosphere which is a medium of exchange of matter and energy with Titan. Here the objectives divide into exploring those aspects of the Saturnian magnetosphere directly related to Titan, and exploring the composition of the Enceladus plumes and whether the source region is liquid water (with implications for the sources of heating). Exploring Enceladus, if liquid water exists in its interior, adds a second target of astrobiological importance to the mission: a “two for one” in the search for life and its origins in the solar system. How Titan interacts with its Saturnian environment and what role Enceladus plays in both supplying material and being a separate source of information for the interior composition of Titan are the subjects of Goal C.
Learn more about the TSSM Flight System
