Image Credit: ESA, Comet 67P/Churyumov-Gerasimenko
To exclude any false-positive data of the new discovery due to imaginable instrumental defect, the researchers checked oxygen levels at various different distances from the comet.
More oxygen was spotted closer to the comet, and as the spacecraft soared further away, it discovered less oxygen. Moreover, the ratio of water to oxygen in the 67P atmosphere stayed constant over months that ROSINA was gathering measurements.
Oxygen is currently the fourth compound spotted by ROSINA while examining 67P. Earlier the researchers announced the detection of water, carbon monoxide and carbon dioxide.
More to add here, this is the third time that oxygen molecules have been discovered in the Solar System outside the Earth's atmosphere. The other findings of oxygen were made on the icy moons of Jupiter and Saturn.