II · THE DISCOVERY · HISTORY OF SCIENCE
Methane
The simplest alkane — one carbon, four hydrogens — turned out to be both an economically attractive fuel and a transparent trap for infrared radiation in the atmosphere.
At a glance
- Discovered
- 1777
- Discoverer
- Alessandro Volta
- Chemical formula
- CH₄ (one carbon, four hydrogens)
- State
- Gas at standard temperature and pressure
- Classification
- Group-14 hydride, simplest alkane
Look closer
One carbon, four hydrogens
The chemical formula CH₄ describes the structure: a single carbon atom bonded to four hydrogen atoms. This makes methane the simplest of the alkanes — a family of hydrocarbons where carbon atoms are linked by single bonds. That simplicity is structural, not trivial: the compound behaves in specific ways because of how those five atoms are arranged.
Transparent to visible light, not to infrared
Methane in the Earth's atmosphere is transparent to visible light but absorbs infrared radiation. That means sunlight passes through it, but the heat radiating back from the Earth's surface does not. This is the mechanism that makes methane a greenhouse gas: it lets energy in and traps some of it on the way out, warming the atmosphere in the process.
A gas at standard conditions
Methane is a gas at standard temperature and pressure, which makes it economically attractive as a fuel — it is abundant — but also difficult to capture and store, since containing a gas requires more infrastructure than handling a liquid or solid. That tension between availability and practicality shapes how methane is used.
The story
Alessandro Volta identified methane in 1777. The compound he found is a hydrocarbon — an organic molecule made of hydrogen and carbon — and among the simplest of them. Its chemical formula, CH₄, describes one carbon atom bonded to four hydrogen atoms. That structure places it in a family called the alkanes, where carbon atoms are linked by single bonds, and makes it the simplest member of that family.
Methane is a gas at standard temperature and pressure, which is to say at the conditions a person experiences standing on the Earth's surface on an ordinary day. That matters because it determines how the substance behaves and how it can be used. A gas is harder to capture and store than a liquid or solid, requiring tanks or pipelines rather than barrels or sacks. But methane is abundant on Earth, found both below ground and under the seafloor, formed by geological processes and by biological ones. The largest reservoir of methane is under the seafloor in the form of methane clathrates — a structure where methane molecules are trapped inside a lattice of water ice.
When methane reaches the surface and enters the atmosphere, it is known as atmospheric methane. In the atmosphere, methane is transparent to visible light but absorbs infrared radiation. Sunlight passes through it, but the heat radiating back from the Earth's surface does not pass through as easily. This behaviour makes methane a greenhouse gas: it allows energy to enter the atmosphere and traps some of it on the way out, warming the air in the process.
Methane is the main constituent of natural gas, the mixture of gases extracted from underground deposits and burned for heat and power. Its abundance and energy content make it economically attractive as a fuel, but its behaviour as a greenhouse gas means its release into the atmosphere has consequences for climate.
Methane has also been detected on other planets, including Mars, which has implications for astrobiology research — the study of life beyond Earth.
Why it mattered then
Before Volta identified methane in 1777, the gas existed in marshes and coal mines, sometimes igniting without explanation. Naming the compound and distinguishing it from other gases gave natural philosophers a substance they could study: its composition, its sources, its behaviour when burned. That clarity mattered for understanding what was happening underground and in the air, and for making sense of the flammable gases that miners encountered. The identification did not immediately lead to large-scale use — capturing and storing a gas required infrastructure that took time to develop — but it established methane as a distinct chemical entity rather than an unexplained phenomenon.
Why it matters now
Methane is now the main constituent of natural gas, extracted from underground deposits and burned for heat and power in homes, factories and power stations. Its abundance on Earth makes it an economically attractive fuel, though capturing and storing it remains difficult because it is a gas at standard temperature and pressure. At the same time, methane in the atmosphere acts as a greenhouse gas, transparent to visible light but absorbing infrared radiation, which means it traps heat and contributes to warming. That dual role — as a fuel and as a climate-active gas — shapes how methane is managed today. Methane has also been detected on other planets, including Mars, which has implications for astrobiology research, the study of life beyond Earth.
The surprising detail
The largest reservoir of methane on Earth is under the seafloor, in the form of methane clathrates. A clathrate is a structure where methane molecules are trapped inside a lattice of water ice, stable under the cold and pressure of the deep ocean. The reference material describes this as the largest reservoir, without giving quantities or comparing it to land deposits. Whether that methane can be extracted, or whether warming oceans might release it, are questions that remain open.
What is disputed
The reference material states that methane has been detected on Mars, with implications for astrobiology research, but does not describe what those implications are, what the detection consists of, or whether the methane is of geological or biological origin. The lesson reports the detection but makes no claim about what it means beyond the general field it touches.
Remember this
Methane is the simplest alkane and the main constituent of natural gas, identified by Volta in 1777 and now both a fuel and a greenhouse gas.
Test yourself
Methane is transparent to visible light but absorbs infrared radiation. What does that difference in behaviour mean for the atmosphere?
It means methane acts as a greenhouse gas. Sunlight, which is mostly visible light, passes through methane in the atmosphere and reaches the Earth's surface. The Earth then radiates heat back as infrared radiation, and methane absorbs some of that infrared rather than letting it pass through. The result is that energy enters the atmosphere more easily than it leaves, warming the air. This is the mechanism behind methane's role in climate: not that it blocks sunlight, but that it traps heat on the way out.
Go deeper
Image: Goldoro99, CC BY-SA 4.0. Licence: CC BY-SA 4.0. Source.