Though we still won’t be able to refill our oxygen tanks in outer space at this moment, the discovery of molecular oxygen gas is still momentous. Scientists have discovered molecular oxygen gas in the famous Orion Nebula (not constellation), which is about 1500 light years away from us.
The excitement surrounding this discovery stems from the fact that even though atomic oxygen (i.e. individual oxygen atoms) are found, molecular oxygen (i.e. molecules of oxygen) has never been found till now. The history of this search is long and stretches back 230 years.
What’s the difference?
Molecular oxygen is made up of two atoms of oxygen, which are bound together. On Earth, atomic oxygen is hardly found in the atmosphere and most of it lies in the ozone layer. This is because, in absence of energetic ionising radiation like UV rays, one atom of oxygen always tends to bond with another atom of oxygen and attain a state of lower energy, giving rise to the oxygen molecule, which is more stable than the oxygen in the atomic form. But conditions in space are different. Ionising radiations flood the inter-stellar medium.
Oxygen, being the third most abundant element in the Universe, after Hydrogen and Helium, occurs, surprisingly, in predominantly atomic form. Hydrogen fills up 98% of the total elemental mass of the Universe, followed by Helium at roughly 1.9%. The rest 0.1% is contributed by all other elements in the cosmos.
Discovery and the principle behind it
This discovery is credited to the European Space Agency’s Hershel Space Observatory. Actually, the Swedish telescope, Odin, has spotted signatures of molecular oxygen (by looking at the colour/frequency of the radiated light) in 2007. Hershel has confirmed that discovery using its infrared detectors.
All elements leave radiate light of some specific frequency when excited. The radiation frequency is the signature of an element, much like fingerprint is an identity of a person. Even molecules have radiation spectrum, which distinguishes it uniquely. Atomic and molecular oxygen has different patterns of radiation and, by studying the peaks (highs) and troughs (lows or valleys) in the spectrum, scientists can confirm the presence of the element with absolute certainty. This has been the greatest achievement of spectroscopy.
As is usual in science, any discovery opens up new questions and this is no different. Scientists can now look into the question of why molecular oxygen occurs in certain cosmic pockets, while atomic oxygen is so widespread. Also note that the presence of molecular oxygen doesn’t say anything about the existence of life.
The charm of Orion never seems to fade.