NASA Team – NASA aims to expand science across every world we visit, and human exploration of Mars in particular offers an enormous opportunity in the near future. Accordingly, our framework for avoiding harmful contamination must reflect our current scientific knowledge and be informed by the pragmatic implementation plans of robotic and crewed missions we will seek to undertake.
In the 1960s, the Committee on Space Research (COSPAR) was asked to establish international guidance to help nations “avoid harmful contamination” of other worlds. COSPAR set the threshold that a mission was required to have less than a 1 in 10,000 chance (≤1×10⁻⁴) of exposing a celestial body of interest to terrestrial life that could survive and proliferate. The chosen threshold was simply based on the limits of dry-heat sterilization technology available at the time. To frame how long such strict controls should apply, COSPAR subsequently introduced the Period of Biological Exploration (PBE), based on the belief that robotic missions would soon be followed by human expeditions to Mars to investigate the question of life on Mars. Human exploration did not progress as quickly as all believed. During this period more conservative measures for “avoiding harmful contamination” were progressively adopted, including extending the PBE to 50 years from launch, and the introduction of “Special Region” parameters. We are now operating at the close of the original 50-year PBE, with potential implications for future NASA robotic and crewed missions, as well as international, commercial, or private missions. Our long-standing policies were designed in a different era.
The purpose of this directive is to modernize NASA’s planetary protection framework, to move from procedure-heavy, prescriptive bioburden rules towards quantitative, analysis-driven contamination modeling that incorporates the best available data including but not limited to microbial release mechanisms, transport pathways, survivability limits, and spacecraft reliability. Updating our framework to reflect decades of scientific progress will enable NASA to explore faster, increase science output, and prepare for human missions while appropriately avoiding harmful contamination.
Directive: Planetary Protection Framework Modernization
NASA will immediately initiate a return to the original performance‑based probabilistic limit of ≤1×10⁻⁴ per mission as a baseline while a modernization assessment proceeds. Our objective is to further reduce this threshold, based on what current science, reliability data, and NASA’s goals support. Astrobiology missions that are actively searching for evidence of life in target regions will continue to carry existing requirements commensurate with the need of their specific scientific investigations.
Direct the NASA Planetary Protection Officer, under OSMA and in consultation with SMD, to:
Lead a modernization assessment of NASA’s planetary protection requirements across all solar system bodies that NASA explores, and deliver recommendations for implementation by December 2026.
In this effort, with support from OIIR, engage with international partners, such as COSPAR as appropriate, without presuming commitments or timelines, to maintain constructive alignment while preserving NASA’s aims.
Jared Isaacman
NASA Administrator
Astrobiology,
