Contamination Control for Ultra-Sensitive Life-Detection Missions

Jennifer L Eigenbrode,Christopher Mckay,Charles Lorentson,David Kusnierkiewicz,Antonios Seas,Erich Schulze,Faith Kujawa,Therese Errigo,Robert Gold,John S Canham,Alfonso F Davila

doi:10.3389/frspt.2021.734423

Abstract

A key science priority for planetary exploration is to search for signs of life in our Solar System. Life-detection mission concepts aim to assess whether or not biomolecular signatures of life are present, which requires highly sensitive instrumentation. This introduces greater risk of false positives, and perhaps false negatives. Stringent science-derived contamination requirements for achieving science measurements on life-detection missions necessitate mitigation approaches that minimize, protect from, and prevent science-relevant contamination of critical surfaces of the science payload and provide high confidence to life-detection determinations. To this end, we report on technology advances that focus on understanding contamination transfer from pre-launch processing to end of mission using high-fidelity physics in the form of computational fluid dynamics and sorption physics for monolayer adsorption/desorption, and on developing a new full-spacecraft bio-molecular barrier design that restricts contamination of the spacecraft and instruments by the launch vehicle hardware. The bio-molecular barrier isolates the spacecraft from biological, molecular, and particulate contamination from the external environment. Models were used to evaluate contamination transport for a designs reference mission that utilizes the barrier. Results of the modeling verify the efficacy of the barrier and an in-cruise decontamination activity. Overall mission contamination tracking from launch to science operations demonstrated exceptionally low probability on contamination impacting science measurements, meeting the stringent contamination requirements of femtomolar levels of compounds. These advances will enable planetary missions that aim to detect and identify signatures of life in our Solar System.

Highlights

IntroductionRobotic missions that aim to detect, identify, and measure possible biomolecules, determine signatures-of-life parameters, and determine whether life exists or has existed in an extraterrestrial planetary environment (McKay et al, 2013; Reh et al, 2016; Hand et al, 2017; Eigenbrode et al, 2018; Turtle et al, 2018; Williford et al, 2018; MacKenzie et al, 2021) must implement steps that mitigate the risks of false positive detections
Launch Vehicle Environment This paper addresses the particular concern of a possible transfer of particles and organic compounds from the rocket fairing to a clean spacecraft, especially to critical surfaces along the sample path within the instrument systems
Results show that the seal provides a high level of isolation of molecular contaminant diffusion, even when an extremely high external molecular contamination fraction was applied in the model

Summary

Introduction

Robotic missions that aim to detect, identify, and measure possible biomolecules, determine signatures-of-life parameters, and determine whether life exists or has existed in an extraterrestrial planetary environment (McKay et al, 2013; Reh et al, 2016; Hand et al, 2017; Eigenbrode et al, 2018; Turtle et al, 2018; Williford et al, 2018; MacKenzie et al, 2021) must implement steps that mitigate the risks of false positive detections. Possible sources of false positives in missions evaluating signatures of life ( referred to as “lifedetection missions”) include contaminants such as terrestrial cells, cellular parts, biomolecules, and anthropogenic interferences. Contamination control in planetary missions has largely focused on meeting Planetary Protection bioburden requirements, i.e., the abundance of viable cells or spores on spacecraft surfaces (National Academies of Sciences, Engineering, and Medicine, 2018; 2020). Other potential sources of contaminants include inadvertent human manipulation or exposure of the spacecraft to a contaminating environment, such as the interior of a rocket (LV) fairing Such contamination can potentially interfere with science measurements if present along the sample path (COSPAR Policy on Planetary Protection, 2020; for category IVB and V missions to targets of interest in “understanding the process of chemical evolution or the origin of life”)

Methods

Results

Discussion

Conclusion