Overview

Space is not empty. Between the stars, there are giant clouds of gas and dust. In these freezing, irradiated clouds, chemistry is happening. Atoms are hooking up to form water, alcohol, and even the building blocks of life. Astrochemistry is the study of the molecular universe.

Core Idea

The core idea is Chemistry in Extreme Conditions. On Earth, chemistry happens in warm beakers. In space, it happens at -260°C, in a vacuum, blasted by UV radiation. Reactions happen on the surface of tiny dust grains.

Formal Definition

The study of the formation, destruction, and excitation of molecules in astronomical environments.

Intuition

We used to think space was too hostile for complex molecules. We were wrong. Space is a factory.

  • Stars: The ovens that forge the elements (Fusion).
  • Interstellar Clouds: The freezers where the elements stick together to form molecules.

Examples

  • Sagittarius B2: A giant gas cloud near the center of the galaxy. It contains billions of liters of alcohol (ethanol and methanol) and smells like raspberries (ethyl formate).
  • Buckminsterfullerene (C60): “Buckyballs.” Soccer-ball shaped carbon molecules found in space. They are incredibly stable.
  • Glycine: The simplest amino acid. We found it on a comet (Rosetta mission). This suggests the ingredients for life might have been delivered to Earth from space.

Common Misconceptions

  • Space is just Hydrogen: It’s mostly Hydrogen (90%) and Helium (9%), but that remaining 1% (“Metals”) is where all the interesting chemistry happens.
  • We go there to sample it: Mostly we do it from Earth using Radio Telescopes (Spectroscopy). Each molecule broadcasts a specific radio frequency.
  • Cosmic Dust: Tiny grains of soot and sand. They act as “meeting places” for atoms to find each other and react. Without dust, the universe would be boring.
  • Prebiotic Chemistry: The chemistry that leads to life.

Applications

  • Origins of Life: Understanding how organic molecules form in space helps us understand how we got here.

Criticism / Limitations

  • Distance: We can’t bring a sample of a nebula back to the lab. We have to rely on remote sensing, which can be ambiguous.

Further Reading

  • Tielens, A.G.G.M. The Physics and Chemistry of the Interstellar Medium.
  • Shaw, Andrew. Astrochemistry: From Astronomy to Astrobiology.