The Murchison meteorite, which fell in Australia in 1969, holds dust grains older than the Solar System. Among them are tiny graphite grains smaller than a thousandth of a millimeter. In five such grains, researchers found the isotope strontium-84: its atoms are slightly lighter than ordinary strontium.
Such strontium could not have formed in a quiet star like a red giant. It is produced only by very massive stars: those that end their lives in supernova explosions. In the oxygen-rich interior of such a star, light strontium isotopes are created by a special process: proton capture. The explosion then flings them into space along with carbon dust.
The graphite grains bearing this strontium are like tiny time capsules. They condensed in the outer layers of the exploded star, mixing with material from its scorching depths. Now, billions of years later, these dust grains have ended up in a meteorite and told us about a cataclysm that occurred before the Sun was born.
The Murchison meteorite contains more than 70 different amino acids, the building blocks of life, many of which are not found on Earth.
In Stanislaw Lem's novel "Solaris," the planet's ocean recreates structures from people's memories, just as presolar grains preserve the memory of stellar explosions.