page_title: Interplanetary contamination
section_title: Receiving facility
hierarchical_section_title: Interplanetary contamination / Back contamination issues / Suggested precautions for sample-returns / Receiving facility
caption_attribution_description: English: Scientists working inside positive pressure personnel suit at biosafety level 4 (BSL-4) laboratory of the NIAID Integrated Research Facility (IRF) in Frederick, Maryland. This image is part of "The NIAID Integrated Research Facility in Frederick, Maryland" video. Courtesy: National Institute of Allergy and Infectious Diseases.
context_page_description: Interplanetary contamination refers to biological contamination of a planetary body by a space probe or spacecraft, either deliberate or unintentional.
  There are two types of interplanetary contamination:
  Forward contamination is the transfer of life and other forms of contamination from Earth to another celestial body.
  Back contamination is the introduction of extraterrestrial organisms and other forms of contamination into Earth's biosphere. It also covers infection of humans and human habitats in space and on other celestial bodies by extraterrestrial organisms, if such habitats exist.
  The main focus is on microbial life and on potentially invasive species. Non-biological forms of contamination have also been considered, including contamination of sensitive deposits of scientific interest. In the case of back contamination, multicellular life is thought unlikely but has not been ruled out. In the case of forward contamination, contamination by multicellular life is unlikely to occur for robotic missions, but it becomes a consideration in crewed missions to Mars.
  Current space missions are governed by the Outer Space Treaty and the COSPAR guidelines for planetary protection.
context_section_description: To receive, analyze and curate extraterrestrial soil samples, NASA has proposed to build a biohazard containment facility, tentatively known as the Mars Sample Return Receiving Facility (MSRRF). This future facility must be rated biohazard level 4 (BSL-4). While existing BSL-4 facilities deal primarily with fairly well-known organisms, a BSL-4 facility focused on extraterrestrial samples must pre-plan the systems carefully while being mindful that there will be unforeseen issues during sample evaluation and curation that will require independent thinking and solutions.
  The facility's systems must be able to contain unknown biohazards, as the sizes of any putative Martian microorganisms are unknown. In consideration of this, additional requirements were proposed. Ideally it should filter particles of 0.01 µm or larger, and release of a particle 0.05 µm or larger is unacceptable under any circumstance.
  The reason for this extremely small size limit of 0.01 µm is for consideration of gene transfer agents (GTAs) which are virus-like particles that are produced by some microorganisms that package random segments of DNA capable of horizontal gene transfer. These randomly incorporate segments of the host genome and can transfer them to other evolutionarily distant hosts, and do that without killing the new host. In this way many archaea and bacteria can swap DNA with each other. This raises the possibility that Martian life, if it has a common origin with Earth life in the distant past, could swap DNA with Earth microorganisms in the same way. In one experiment reported in 2010, researchers left GTAs (DNA conferring antibiotic resistance) and marine bacteria overnight in natural conditions and found that by the next day up to 47% of the bacteria had incorporated the genetic material from the GTAs. Another reason for the 0.05 µm limit is because of the discovery of ultramicrobacteria as small as 0.2 µm across.
  The BSL-4 containment facility must also double as a cleanroom to preserve the science value of the samples. A challenge is that, while it is relatively easy to simply contain the samples once returned to Earth, researchers would also want to remove parts of the sample and perform analyses. During all these handling procedures, the samples would need to be protected from Earthly contamination. A cleanroom is normally kept at a higher pressure than the external environment to keep contaminants out, while a biohazard laboratory is kept at a lower pressure to keep the biohazards in. This would require to compartmentalize the specialized rooms in order to combine these in a single building. Solutions suggested include a triple walled containment facility, and one of the suggestions include extensive robotic handling of the samples.
  The facility would be expected to take 7 to 10 years from design to completion, and an additional two years is recommended for the staff to become accustomed to the facilities.
caption: Working inside a BSL-4 laboratory with air hoses providing positive air pressure to their suits
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