A novel strategy to seek bio-signatures at Enceladus and Europa

TL;DR

This paper proposes a laboratory and observational strategy using infrared spectroscopy and polarimetry to detect bio-signatures in water plumes from Enceladus and Europa, combining experimental and telescope-based approaches.

Contribution

It introduces a novel combined laboratory and astronomical method to identify bio-markers in icy moon plumes, utilizing advanced differential measurement techniques.

Findings

Laboratory experiment setup for detecting bio-markers in water samples.

Assessment of ground-based and space telescopes for observing icy moon plumes.

Analysis of technical challenges and potential success rates of the proposed observations.

Abstract

A laboratory experiment is suggested in which conditions similar to those in the plume ejecta from Enceladus and, perhaps, Europa are established. Using infrared spectroscopy and polarimetry, the experiment might identify possible bio-markers in differential measurements of water from the open-ocean, from hydrothermal vents, and abiotic water samples. Should the experiment succeed, large telescopes could be used to acquire sensitive infrared spectra of the plumes of Enceladus and Europa, as the satellites transit the bright planetary disks. The extreme technical challenges encountered in so doing are similar to those of solar imaging spectropolarimetry. The desired signals are buried in noisy data in the presence of seeing-induced image motion and a changing natural source. Some differential measurements used for solar spectropolarimetry can achieve S/N ratios of $10^5$ even in the presence of systematic errors two orders of magnitude larger. We review the techniques and likelihood of success of such an observing campaign with some of the world's largest ground-based telescopes, as well as the long anticipated James Webb Space Telescope. We discuss the relative merits of the new 4m Daniel K. Inouye Solar Telescope, as well as the James Webb Space Telescope and larger ground-based observatories, for observing the satellites of giant planets. As seen from near Earth, transits of Europa occur regularly, but transits of Enceladus will begin again only in 2022.