This artist's conception shows a young, hypothetical planet around a cool
star. A soupy mix of potentially life-forming chemicals can be seen
pooling around the base of the jagged rocks. Observations from NASA's
Spitzer Space Telescope hint that planets around cool stars—the
so-called M-dwarfs and brown dwarfs that are widespread throughout our
galaxy—might possess a different mix of life-forming, or prebiotic,
chemicals than our young Earth.
Life on our planet is thought to have arisen out of a pond-scum-like mix
of chemicals. Some of these chemicals are thought to have come from a
planet-forming disk of gas and dust that swirled around our young sun.
Meteorites carrying the chemicals might have crash-landed on Earth.
Astronomers don't know if these same life-generating processes are taking
place around stars that are cooler than our sun, but the Spitzer
observations show their disk chemistry is different. Spitzer detected a
prebiotic molecule, called hydrogen cyanide, in the disks around yellow
stars like our sun, but found none around cooler, less massive, reddish
stars. Hydrogen cyanide is a carbon-containing, or organic compound. Five
hydrogen cyanide molecules can join up to make adenine—a chemical
element of the DNA molecule found in all living organisms on Earth.