Table 1 Overview of surface bioburden requirements for category IV missions (applicable to robotic missions with landing on Mars), as given by the 2021 COSPAR Policy on Planetary Protection1.

From: An airlock concept to reduce contamination risks during the human exploration of Mars

Category

Description

System level

Maximum bioburden (spores)

Maximum bioburden density (spores m−2)

IVa

No search for extant Martian life

Full system

3 × 105

300

IVb

Search for extant Martian life

Full system, or subsystems involved in life detection

30, or as required by the nature and sensitivity of the life-detection experiments

3 × 10−2

IVc (1)

Investigations in Special Region, with landing site in Special Region

Full system

30

3 × 10−2

IVc (2)

Investigations in Special Region, with landing site outside Special Region

Full system, or subsystems in direct contact with the Special Region

30

3 × 10−2

  1. The requirements apply to exposed or accessible spacecraft surfaces. “Spores” refer to aerobic microorganisms which survive a heat shock of 80 °C for 15 min and are cultured on TSA at 32 °C for 72 h. Special regions are areas within which terrestrial organisms are likely to replicate, or which have a high potential for hosting extant Martian life.