Oxygen, a fundamental component of our world and universe, is represented by the chemical symbol O and holds the atomic number 8. It belongs to the chalcogen group within the periodic table, characterized as a highly reactive nonmetal and a potent oxidizing agent. This means it readily forms compounds called oxides with most other elements and various other compounds, a process critical to many natural phenomena.

Remarkably, oxygen is Earth's most abundant element, and when considering the vastness of the universe, it ranks as the third-most abundant, trailing only hydrogen and helium. Under typical atmospheric conditions (standard temperature and pressure), two oxygen atoms come together to form dioxygen (O2), a gas that is both colorless and odorless. This diatomic oxygen gas currently accounts for approximately 20.95% of Earth's atmosphere, a percentage that has fluctuated significantly over geological timescales. Beyond the atmosphere, oxygen forms nearly half of the Earth's crust, predominantly in the form of various oxides, showcasing its pervasive presence.

Its significance extends deeply into the realm of biology and energy. Dioxygen is indispensable for the energy release processes central to life, powering both combustion and aerobic cellular respiration. Furthermore, oxygen atoms are integral to many major classes of organic molecules found in living organisms, including proteins, nucleic acids (the building blocks of genetic material), carbohydrates (sugars and starches), and fats. It is also a key constituent in the inorganic compounds that form the shells of marine animals, the enamel of teeth, and the structure of bones. Indeed, a substantial portion of the mass of living organisms is attributed to oxygen, primarily as a component of water, the essential solvent and medium for life.

The continuous replenishment of oxygen in Earth's atmosphere is a testament to the power of photosynthesis, a process carried out by plants, algae, and some bacteria. Using the energy from sunlight, these organisms convert water and carbon dioxide into oxygen and glucose. Due to its extreme chemical reactivity, free oxygen cannot persist in the atmosphere without this constant biological regeneration. Another fascinating form, or allotrope, of oxygen is ozone (O3). High in the atmosphere, the ozone layer plays a crucial protective role by strongly absorbing harmful ultraviolet UVB radiation, shielding the biosphere from its damaging effects. However, ozone found closer to the Earth's surface is often a byproduct of smog and is considered a significant air pollutant, illustrating its dual nature depending on its location.

The Unraveling of Oxygen's Identity

The journey to understanding oxygen as an element is a compelling tale of independent discovery and scientific insight. While Michael Sendivogius is credited with isolating it before 1604, the element's discovery is most commonly attributed independently to two prominent scientists: Carl Wilhelm Scheele, who achieved this in Uppsala in 1773 or earlier, and Joseph Priestley in Wiltshire, in 1774. Priestley often receives priority because his findings were published first. However, Priestley initially referred to oxygen as "dephlogisticated air," failing to recognize its fundamental nature as a distinct chemical element.

The true breakthrough in understanding came in 1777 when Antoine Lavoisier, a French chemist, coined the name "oxygen" (from Greek roots meaning "acid-former," as he mistakenly believed it was essential for all acids). Lavoisier was the first to correctly identify oxygen as a chemical element and, crucially, to accurately characterize the pivotal role it plays in combustion, thereby revolutionizing chemistry.

Oxygen's Widespread Applications

Oxygen's unique properties make it invaluable across a vast array of industrial, medical, and technological applications. In heavy industry, it is critical for the efficient production of steel, enhancing the combustion process. It's also utilized in the manufacturing of plastics and textiles. Its high reactivity makes it essential for various metalworking techniques, including brazing, welding, and cutting of steels and other metals. In aerospace, liquid oxygen serves as a powerful rocket propellant, enabling space exploration. Medically, oxygen therapy provides vital support for patients with respiratory conditions, while in environments where air is limited or absent, such as aircraft, submarines, spacecraft, and underwater diving equipment, oxygen forms the backbone of life support systems, ensuring human survival.

Apollo 13: A Striking Testament to Oxygen's Indispensability

The harrowing journey of Apollo 13 stands as a poignant historical example of oxygen's absolute necessity, not just for life itself, but for the intricate systems supporting human endeavors in extreme environments. Launched on April 11, 1970, Apollo 13 was the seventh crewed mission in the ambitious Apollo space program and the third intended to land astronauts on the Moon. However, this lunar landing was tragically aborted just two days into the mission when an oxygen tank within the service module (SM) suffered a catastrophic failure.

The incident began innocently enough: a routine stir of an oxygen tank ignited damaged wire insulation inside it. This led to a powerful explosion that vented the entire contents of both of the SM's oxygen tanks into the vacuum of space. The loss of oxygen was immediately critical, as it was essential not only for the crew's breathing but also for generating the electrical power that ran the Service Module's propulsion and life support systems. With these vital systems compromised, the Command Module's (CM) own systems had to be completely shut down to conserve its limited resources for the perilous journey back to Earth and the final reentry. This drastic measure forced the crew — Commander Jim Lovell, Command Module Pilot Jack Swigert (a late replacement for Ken Mattingly, who was grounded due to rubella exposure), and Lunar Module Pilot Fred Haise — to take refuge in the Lunar Module (LM), transforming it into an emergency lifeboat.

With the Moon landing canceled and the lives of the three astronauts hanging by a thread, mission controllers in Houston faced an unprecedented challenge: bringing the crew home alive. The LM, originally designed to support two men on the lunar surface for just two days, now had to sustain three men for four days during their improvised slingshot around the Moon. The crew endured immense hardship, grappling with severely limited power, a chillingly cold and damp cabin, and a severe shortage of potable water. A particularly critical problem arose from the need to adapt the Command Module's square carbon dioxide scrubber cartridges to fit the Lunar Module's round system, a vital task to prevent the astronauts from suffocating. Through remarkable ingenuity and collaboration between the crew and Mission Control, a successful, improvised solution was devised, utilizing materials readily available on board.

The perilous situation of the astronauts temporarily reignited widespread public interest in the Apollo program; tens of millions of people around the world watched anxiously as the capsule successfully splashed down in the South Pacific Ocean on April 17. A subsequent investigative review board attributed the incident to faults in the preflight testing of the oxygen tank and the use of Teflon inside it, which contributed to the ignition. The board recommended crucial changes, including minimizing the use of potentially combustible materials inside such tanks, improvements that were implemented for future missions like Apollo 14. The extraordinary story of courage, ingenuity, and survival aboard Apollo 13 has since been dramatized multiple times, most famously in the critically acclaimed 1995 film Apollo 13, based on Jim Lovell's 1994 memoir Lost Moon, and an episode of the 1998 miniseries From the Earth to the Moon.

Frequently Asked Questions About Oxygen and Apollo 13

What is oxygen and where is it found?

Oxygen is a chemical element with the symbol O and atomic number 8. It's a highly reactive nonmetal, abundantly found as the most prevalent element in Earth's crust and, in its diatomic gas form (O2), making up about 20.95% of the Earth's atmosphere. It's also the third-most abundant element in the universe.

Why is oxygen so crucial for life on Earth?

Oxygen is essential for life because it is used in aerobic cellular respiration, the primary process by which living organisms generate energy. It's a key component of water (H2O), the major constituent of lifeforms, and is found in fundamental organic molecules like proteins, nucleic acids, carbohydrates, and fats. It's continuously replenished in the atmosphere by photosynthesis.

Who is credited with discovering and naming oxygen?

Oxygen was independently discovered by Carl Wilhelm Scheele (1773 or earlier) and Joseph Priestley (1774), though Sendivogius had isolated it earlier. Priestley published his findings first but didn't recognize it as an element, calling it "dephlogisticated air." Antoine Lavoisier coined the name "oxygen" in 1777 and correctly identified its nature as a chemical element and its role in combustion.

What happened to the oxygen tanks on Apollo 13?

During the Apollo 13 mission, a routine stirring of an oxygen tank ignited damaged wire insulation inside it, causing an explosion. This explosion ruptured the tank and vented the contents of both of the Service Module's oxygen tanks into space, depriving the spacecraft of its primary oxygen supply for breathing and electrical power generation.

How did the Apollo 13 crew survive without their main oxygen supply?

The crew survived by using the Lunar Module (LM) as a "lifeboat." Although designed for two men for two days on the Moon, Mission Control and the crew ingeniously improvised procedures to extend its life support capabilities to sustain three men for four days. This involved conserving power, managing water, and finding a critical solution to adapt carbon dioxide scrubbers to prevent suffocation.