Die Eismonde der Gasriesen Jupiter und Saturn sind zurzeit die aussichtsreichsten Kandidaten für außerirdisches Leben in unserem Sonnensystem. Europa mit einem möglichen salzigen Ozean unter seiner Oberfläche und Enceladus mit seinen heißen Geysire und auch einen möglichen Ozean, könnten Mikrobielles Leben (Mikroorganismen) unterstützen. Ähnlich wie das Mikrobielle Leben unter extremen Bedingungen hier auf der Erde.

Jetzt wurde das JWST Beobachtungs-Pogramm: The sub-surface oceans of Europa and Enceladus abgeschlossen. Man darf auf die Ergebnisse gespannt sein und welche Schlussfolgerungen die Wissenschaftler aus den Daten ableiten – Immer noch Top Kandidaten für Mikrobielles Leben oder Flop? Bleibt es beim Staus Quo oder sorgt das JWST für eine Überraschung?

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GTO 1250

Wed Jan 4 14:16:59 GMT 2023

Principal Investigator: Geronimo Villanueva
PI Institution: NASA Goddard Space Flight Center
Investigators (xml)

Title: Probing the sub-surface oceans of Europa and Enceladus with JWST
Cycle: 1
Allocation: 10.4 hours allocation change history
Exclusive Access Period: 0 months

Program Status: Program has been Completed

Program Coordinator: Weston Eck

MIRI Reviewer: Misty Cracraft

NIRCAM Reviewer: Bryan Hilbert

NIRSPEC Reviewer: Tracy Beck

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OBSERVATIONS
Folder Observation Label Observing Template Science Target
Observation Folder

1 NIRCam Europa NIRCam Imaging (1) EUROPA
2 NIRSpec Europa NIRSpec IFU Spectroscopy (1) EUROPA
3 MIRI Europa MIRI Medium Resolution Spectroscopy (1) EUROPA
9 MIRI Europa-BKG MIRI Medium Resolution Spectroscopy (3) EUROPA-BKG
4 MIRI/Img Europa MIRI Imaging (1) EUROPA

Observation Folder
5 NIRCam Enceladus NIRCam Imaging (2) ENCELADUS
6 NIRSpec Enceladus NIRSpec IFU Spectroscopy (2) ENCELADUS
7 MIRI Enceladus MIRI Medium Resolution Spectroscopy (2) ENCELADUS
8 MIRI/Img Enceladus MIRI Imaging (2) ENCELADUS

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ABSTRACT
Do the icy moons, Europa and Enceladus, host habitable conditions at submerged hydrothermal vents? We propose to perform high spatial and spectral resolution observations of the jets emanating from these moons, measuring volatile abundances and isotopic ratios. Such measurements will reveal unprecedented information regarding the processes acting beneath the moons’ thick ice crusts, and the potential for habitability of the subsurface oceans.

OBSERVING DESCRIPTION
Introduction and Background: Do the icy moons, Europa and Enceladus, host habitable conditions at submerged hydrothermal vents? The right balance of energy sources, temperature, pressure and chemical diversity leads to prosperous environments for life on Earth. Thanks to the plentitude of recent discoveries of extremophile organisms, the limits for such conditions have greatly expanded, and the hypothesized sub-surface oceans on these moons represent one of the most habitable niches in our Solar System. Observations with JWST will permit to probe these habitats with
unprecedented sensitivity and spatial resolution, revealing unique information regarding the processes acting beneath the moons’ thick ice crusts, and the potential for habitability of the sub-surface oceans.

Europa: The surface of this moon of Jupiter is surprisingly young, as revealed by a crater retention age of only 10-100 Myr (1), suggestive of ongoing resurfacing. Furthermore, ice fractures and moving lineae are indicative of underlying tectonic activity and/or volcanic eruptions. By integrating this morphological information with that obtained by radio-tracking from the Galileo spacecraft, a possible ocean (or a low-density convective ice layer) of 80-170 km thickness is inferred to be present below Europa’s icy crust (2, 3). More recently, water vapor plumes were observed above the frigid
south polar regions (4), and linked to the previously identified fractures or lineae. Particularly interesting was the fact that the intensity of the plumes varied according to its distance from Jupiter, a strong indicator of tidal heating and flexing in Europa. Such tidal energy could provide enough heat to
generate a liquid ocean underneath the ice, further establishing the sub-surface of Europa as an astrobiologically relevant site, with a potential for habitability. The presence of liquid water and of possible volcanic/hydrothermal sub-surface activity would resemble ecosystems on Earth, but no markers suggesting these processes are active in Europa have been detected.
Enceladus: As with Europa, Saturn’s moon Enceladus shows a relatively young surface, linear fractures with enhanced temperatures – termed “tiger stripes” (5), and collimated plumes of water (6, 7). However, unlike Europa, the presence of a global sub-surface ocean is not suggested for Enceladus. Instead, smaller non-continguous reservoirs containing pressurized liquid water beneath its southern pole have been suggested.

Using ravitational studies, Iess et al. (8) established the depth of this reservoir to be 30-40 kilometers, and to extend to south latitudes of ~50 degrees. The presence of natural radioactivity, together with an active surface could suggest a long-term water cycle. This would move material (as well as any organic compounds deposited on the surface) deep into these liquid-water reservoirs, thus providing a potential for habitability. Little is known about.

Quelle: https://www.stsci.edu/jwst/science-execution/program-information.html?id=1250