During control of cargo which should be lifted by Cygnus spacecraft to International Space Station, mold contamination was spotted. Mission is delayed, with NET status, for 20 March 2016.
Commercial supply missions for International Space Station could be considered as nothing unusual, they just became ordinary part of space launch schedule. Serious failures, like supply mission from 28 June 2015, when Dragon spacecraft burned on atop of exploding Falcon-9 rocket are, if we take under consideration frequency of commercial missions, unusual. Cooperation between NASA and Orbital ATK goes very well, which was confirmed by granting second Commercial Resupply Services for SpaceX, Orbital ATK with only one new contractor - Sierra Nevada Corporation. Generally, cooperation with commercial companies seems to be correct decision, even when some issues existing. Luckily issues, as described below, are usually spotted before any more serious problems could appear.
During control of cargo of Cygnus black mold contamination was discovered. It is not something unusual, if we consider that cargo was packed in foil cargo bags which are not breathable material. Little moisture could get into bag before closing and during further transport or storage; further contact of heat and some spores of Trichocomaceae could result with a problem. Of course problem was discovered thanks due the detailed control and security procedures; whole Cygnus and cargo are now planned to be disinfected what seriously effects on scheduled date for CRS mission. Now 22 March is considered as NET date, which could not be kept if disinfection would have to be repeated.
It is worth to explain why ordinary black mold which is possibly present in every house or car with air condition (not to mention warehouses or cellars) could be so dangerous for ISS. Generally black mold is not very harmful to people if its concentration is not high. It is able to produce some toxic substances, but in very small amount; one of such substances is aflatoxins which could cause the cancer. Of course to become serious threat to human health, molds should be kept in very specific conditions with humidity and specific temperature and multiply. Unfortunately on International Space Station with complicated air condition system, ventilation system between modules and Environmental Control and Life Support Systems (ECLSS) - Trichocomaceae could have very favorable conditions and could multiply and become serious threat. There is reason for fast multiplying of molds - it is atmosphere on ISS, very similar to conditions on Earth. Crew is not breathing with pure oxygen by with mixture of gases which is reached with oxygen produced in special system called Environmental Control and Life Support Systems (ECLSS). Combination of complicated ventilation system and earth-like atmosphere could result in extraordinary multiplying of black mold. Conditions of increased, comparing to normal, presence of mold, could effect on crew members, caused diseases or even forced crew to return to Earth in case of any serious health problems. It is worth to mention that ISS is close, hermetic environment where every additional microbiological activity could be a threat for crew members. In case of any presence of harmful mold, it could be necessary to abandon ISS by crew and perform disinfection of station, which could be very hard or even impossible. Another danger is fact that mold could multiply in carbon filters responsible for cleaning atmosphere of ISS form methane and ammonia. Any problems with methane level on ISS could cause multiple problems for crew remaining onboard. Next issue is not linked with crew members but with ISS itself. Chemical substances produced by molds and their corrosion effect on metal, rubber and plastic. If black mold would be taken from Earth to ISS, it could add some new corrosive substances to ISS atmosphere. It could result in faster degradation of crucial parts of such parts like for example seals in windows. Results of such corrosion are easy to predict and could be very dangerous like rapid leakage or decompression.
Problem of molds was spotted on Mir space station years ago, but even after years of development in chemistry there is no possibility of avoiding presence of molds in human environment.In spite of facts that every part of interior of ISS is painted with mold killing paint or is produced from mold resistant material, using mold killing chemicals, problem of presence of molds was not solved on ISS.