Tiger: Concept Study for a New Frontiers Enceladus Habitability Mission

Abstract

Data returned from the Cassini–Huygens mission have strengthened Enceladus, a small icy moon of Saturn, as an important target in the search for life in our solar system. Information gathered from Cassini to support this includes the presence of a subsurface liquid water ocean, vapor plumes and ice grains emanating from its south polar region, and the detection of essential elements and organic material that could potentially support life. However, several outstanding questions remain regarding the connectivity of plume material to the ocean and the composition of the complex organic material. Herein we introduce Tiger, a mission concept developed during the 2020 Planetary Science Summer School at NASA’s Jet Propulsion Laboratory. Tiger is a flyby mission that would help further constrain the habitability of Enceladus through two science objectives: (1) determine whether Enceladus’s volatile inventory undergoes synthesis of complex organic species that are evidence for a habitable ocean, and (2) determine whether Enceladus’s plume material is supplied directly from the ocean or if it interfaces with other reservoirs within the ice shell. To address the science goals in a total of eight flybys, Tiger would carry a four-instrument payload, including a mass spectrometer, a single-band ice-penetrating radar, an ultraviolet imaging spectrograph, and an imaging camera. We discuss Tiger's instrument and mission architecture, as well as the trades and challenges associated with a habitability-focused New Frontiers–class flyby mission to Enceladus.

Domains of life sciences in spacefaring: what, where, and how to get involved

“…For example, recent evidence for liquid water on Mars 8 has sparked interest in the potential for microbial life to exist on the Red Planet or even to persist in the subsurface today. Similarly, studies of icy moons, such as those conducted to explore the Jovian moon Europa’s subsurface ocean 9 , 10 and the Saturnian moon Enceladus’ geysers of water vapor and ice, which are thought to be connected to a subsurface water body 11 , 12 have revealed possible habitats for life 13 . Astrobiologists also seek evidence of prebiotic chemistry and microbial life on other celestial bodies 14 , 15 .…”

Chirality in Organic and Mineral Systems: A Review of Reactivity and Alteration Processes Relevant to Prebiotic Chemistry and Life Detection Missions

“…Habitability and life detection missions commonly need to address issues related to contamination and outgassing in accordance with guidelines suggested by the International Committee on Space Research (COSPAR) for planetary protection (e.g., [48,511,512]). Missions and proposed mission concepts that address contamination control issues are typically or wholly concerned with adhering to the requirements set out by planetary protection (PP) guidelines, through verification and quantification of bioburden on instrument and spacecraft surfaces.…”

A multi-lander New Frontiers mission concept study for Enceladus: SILENUS

“…Many mission concepts have been developed to study Enceladus, e.g., ELF (Lunine et al, 2015;), Enceladus Orbilander (MacKenzie et al, 2021, EnEx (Konstantinidis et al, 2015), Etna (Deutsch et al, this issue), JET , THEO (MacKenzie et al, 2016), and TIGER (Spiers et al, 2021). Our mission concept is most similar to the Small Lander Large Orbiter explored as an alternative to the Flagship-class Enceladus Orbilander (MacKenzie et al, 2021).…”

“…Seismometers have been explored for landed components of other Enceladus mission concepts (Coustenis et al, 2009;Deutsch et al, this issue;MacKenzie et al, 2021;Vance et al, 2021), but our mission concept study is among the first to incorporate a seismic network. Additionally, though other mission concepts propose to operate on the edge of south polar darkness (e.g., Spiers et al, 2021), SILENUS presents a case for science operations that continue during a time period when the South Polar Terrain (SPT) is in complete darkness. More broadly, SILENUS is applicable to future mission concept studies not only in its science definition, exploration of trades, and orbit design, but also in its detailed characterization of landing sites based on scientific value, surface hazards, and previous characterization.…”

“…• Mission arrival between 2036 and 2042. The SPT region enters a period of ~10 years of darkness at latitudes ≥70 °during this time (e.g., Spiers et al, 2021). The majority of the potential launch windows considered will require landing in-situ instruments in darkness.…”