. Author manuscript; available in PMC: 2019 Feb 1.

Published in final edited form as: Space Sci Rev. 2017 Dec 13;214(1):19. doi: 10.1007/s11214-017-0439-4

Table 4.

Indicator elements and their control limits. Individual elements serving as representatives or indicators of suites of elements important for various scientific investigations. Each element has a carbonaceous chondrite derived contamination limit in the sample, which is then converted into a surface requirement for the sampling system in the third column. The fourth column shows the abundance of each element if it were to contaminate a surface at 100 A/2 (assuming pure spherical particles). Thus, meeting the 100 A/2 requirement meets the C and Ni limits, but contamination knowledge is needed to ensure that unexpectedly high levels of K, Sn, Nd, and Pb are not major contributors to the contamination

Element	Indicator	Contamination limit (ng/cm²)	Level 100 (particles) + A/2 (NVR) (ng/cm²)
C	Organics	1000	34 + 500
K	Terrestrially abundant lithophile	170	14 + 500
Ni	Extraterrestrially abundant siderophile	34,000	143 + 500
Sn	Industrial contaminant	0.53	117 + 500
Nd	Lanthanide, lithophile	1.5	113 + 500
Pb	Chalcophile, geochronology, industrial contaminant	180	182+500