Implementing Planetary Protection Measures on the Mars Science Laboratory

Abstract

The Mars Science Laboratory (MSL), comprising a cruise stage; an aeroshell; an entry, descent, and landing system; and the radioisotope thermoelectric generator-powered Curiosity rover, made history with its unprecedented sky crane landing on Mars on August 6, 2012. The mission's primary science objective has been to explore the area surrounding Gale Crater and assess its habitability for past life. Because microbial contamination could profoundly impact the integrity of the mission and compliance with international treaty was required, planetary protection measures were implemented on MSL hardware to verify that bioburden levels complied with NASA regulations. By applying the proper antimicrobial countermeasures throughout all phases of assembly, the total bacterial endospore burden of MSL at the time of launch was kept to 2.78×10⁵ spores, well within the required specification of less than 5.0×10⁵ spores. The total spore burden of the exposed surfaces of the landed MSL hardware was 5.64×10⁴, well below the allowed limit of 3.0×10⁵ spores. At the time of launch, the MSL spacecraft was burdened with an average of 22 spores/m², which included both planned landed and planned impacted hardware. Here, we report the results of a campaign to implement and verify planetary protection measures on the MSL flight system.

Implementing Planetary Protection on the Atlas V Fairing and Ground Systems Used to Launch the Mars Science Laboratory

“…Hence, these systems were operating at cleanliness levels that far exceeded the requirements. Furthermore, the surfaces of the PLF were even cleaner and were shown to harbor a mere 4.65 spores/m 2 , which was even cleaner than the average 22 spores/m 2 reported on the MSL flight system hardware (Benardini et al, 2014). Sample blanks exhibited no colony counts.…”

Application of the ATP assay to rapidly assess cleanliness of spacecraft surfaces: a path to set a standard for future missions

“…The amount of ATP in units of mmole/sample was then established by multiplying the calculated ATP concentration by the total sample volume. Individual ATP samples were then grouped into broad spacecraft “zones.” Zones were based on the broader spacecraft subsystems representing several larger flight system and launch vehicle components, such as the backshell, descent stage, heatshield, and rover (Benardini et al 2014). Finally, averages for bioburden densities and ATP mmole/zones were calculated for the specified spacecraft zones.…”

Identification and Characterization of Early Mission Phase Microorganisms Residing on the Mars Science Laboratory and Assessment of Their Potential to Survive Mars-like Conditions

“…Samples were collected and processed by the Jet Propulsion Laboratory ( JPL) MSL Planetary Protection Implementation Team (Benardini et al, 2014). Cotton swabs and polyester wipes were used to collect samples (*25 cm 2 and 1 m 2 , respectively) from exterior surfaces of MSL.…”

“…Over the last decade, a number of studies have reported on the microorganisms that are detectable in spacecraft assembly facilities during prelaunch preparations despite the precautions that were taken to reduce the microbial load (La Duc et al, 2004, 2007bKempf et al, 2005;Benardini et al, 2014). Previous studies testing survival of Earth microorganisms in simulated martian conditions have focused on spore-forming microorganisms, particularly bacteria of the Bacillus genus, since spores are hardy forms of terrestrial life that can survive Mars-like conditions (Horneck, 1993;Nicholson et al, 2000;Riesenman and Nicholson, 2000;Schuerger et al, 2003;Link et al, 2004;Newcombe et al, 2005;Tauscher et al, 2006;Zenoff et al, 2006;Fajardo-Cavazos et al, 2010).…”

“…During the preparation stages of a spacecraft such as the Mars Science Laboratory (MSL), a microbial sampling campaign is undertaken to verify the microbial bioburden requirement throughout the mission buildup and testing phases. The microorganisms are collected during the campaign using the NASA Standard Assay (Benardini et al, 2014). Isolates are heat shocked, plated on tryptic soy agar (TSA) at 32°C, enumerated, isolated, and preserved for future study.…”