In 2010, NASA launched a 12-pound, loaf-of-bread-sized satellite with two Bacillus populations; radiation exposure reached about 15 times that of the ISS orbit

Space exploration and spaceflight research often evoke images of astronauts and large spacecraft, but some of the most revealing experiments have flown on satellites no bigger than a loaf of bread. However, O/OREOS, a spaceflight mission conducted by NASA, worked in quite a different way. In terms of size and weight, the entire spacecraft did not exceed about 12 pounds and was roughly the size of a loaf of bread. Even so, it addressed a key question: how can living organisms survive in a radiation environment far harsher than the one experienced by astronauts.

O/OREOS, short for Organism/Organic Exposure to Orbital Stresses, launched on 19 November 2010 aboard a U.S. Air Force Minotaur IV rocket from Kodiak, Alaska, according to NASA Ames Research Center's mission overview on eoPortal. Two separate cultures of Bacillus subtilis bacteria were located on the spacecraft in their dried state and designed for automatic activation during various periods of the mission.

The orbit that made this mission unusual


Most biological experiments conducted in low Earth orbit ride on or near the International Space Station, which operates at a 51.6-degree inclination. O/OREOS, however, was launched into an orbit with a very different inclination, a 72-degree, 650-kilometer orbit that passed it near the north and south magnetic poles on each orbit. This orbit exposed the satellite to relatively less protection from the planet's magnetosphere, as well as to higher levels of radiation in the inner Van Allen Belt, along with 30% of its orbits passing through the South Atlantic Anomaly, an area where the planet's magnetosphere is weaker and charged particles accumulate, as Nicholson and colleagues describe in their overview of the O/OREOS mission published in Advances in Space Research.

The paper presenting the mission’s first results, ‘The O/OREOS Mission: First Science Data from the Space Environment Survivability of Living Organisms (SESLO) Payload’, published in the journal Astrobiology, quantified the radiation environment inside the satellite as having a total dose rate about 15 times that in the orbit of the International Space Station.

Two strains of the same bacterium, sent up side by side

The biology experiment aboard this spacecraft, known as SESLO (Space Environment Survivability of Living Organisms), loaded dried spores of Bacillus subtilis 168, a wild-type strain and Bacillus subtilis WN1087, a radiation-sensitive mutant that lacks the non-homologous end joining DNA repair system, into separate microwells. Pairing the two strains let scientists isolate radiation's specific role: because WN1087 lacks the DNA-repair machinery to fix radiation damage, it should show more pronounced harm than the wild-type strain if radiation, rather than microgravity or another factor, was driving the observed effects.

Each population remained dry and inactive until particular moments of the mission when the onboard systems rehydrated new wells using a nutrient medium and a color indicator that changed its color as spores germinated. The readings of the color indicator were then sent to Earth via telemetry. This procedure was performed three times throughout the entire mission: two weeks, three months and six months after the spacecraft was launched.

How six months in orbit affected the bacterial spores

The more comprehensive results of this mission can be found in another paper, 'Nanosatellites for Biology in Space: In Situ Measurement of Bacillus subtilis Spore Germination and Growth after 6 Months in Low Earth Orbit on the O/OREOS Mission', published in the journal Life on the MDPI publishing platform. After two weeks and three months of spaceflight, the space sample grew and germinated more slowly than the ground control kept under Earth conditions, but still ended up reaching the same level of growth in the end. After 181 days in orbit, however, researchers reported that spore germination and growth appeared hindered and abnormal in the spaceflight samples.

The researchers noted, however, that they were cautious in explaining the cause of this effect. Namely, the slower initial germination was not unique for the flight samples, as it could also be observed for some of the ground controls; thus, making it rather difficult to attribute this effect only to the presence of cosmic rays in space. The abnormally growing spores after six months of the experiment are the effect that is the most consistent with the effects of radiation, though.

Why NASA built the mission this way

The narrative of the O/OREOS project presented by NASA itself portrays it as both a proof-of-concept and a scientific experiment simultaneously. NASA's overview of the project presents O/OREOS as a demonstration that even a shoebox‑sized nanosatellite can carry two independent science experiments and operate them autonomously for months at a time without a human crew having to intervene. It was significant because it allowed any future biological experiments on nanosatellites such as O/OREOS to not have to rely on getting slots in the International Space Station or even Shuttle flights to study life in space.

What this mission is left unresolved

O/OREOS was not built to find out for sure how life reacts to heavy doses of radiation. O/OREOS carried two strains of one bacterial species for one trip on one orbit with high radiation. How to distinguish the effect of being in space, including weightlessness, from the effects of radiation dosage is not clear in this type of experiment using dried spores because both factors were present during the whole time and could not be studied separately.

O/OREOS demonstrated that it was possible to fit an automatic biology lab into the body of a bread‑loaf‑sized nanosatellite. This technology — building on groundwork already laid by the earlier PharmaSat mission (2009), became the basis for subsequent missions like SporeSat and EcAMSat.