The origin of life on Earth is a profound mystery — including when it started and how the ingredients for it were assembled. And a new study aimed at answering the latter question finds that some building blocks didn’t need to have formed on Earth, but could have arrived from space.
The study, published April 17 in Science, recreated the conditions of interstellar space to determine whether an important set of ingredients — carbon, carbon monoxide, and ammonia — could combine there to create peptides, or small chains of amino acids, essential to life on Earth. If so, these peptides could have been delivered to Earth after its formation to aid in the development of early life.
Initial conditions
The interstellar medium is the material that exists between stars. It includes the massive molecular clouds from which stars and their planets are born.
“Peptides are forming in molecular clouds under natural conditions. As these clouds evolve, they eventually condense and form new stars and planetary systems,” study lead author Serge Krasnokutskiy, a postdoctoral researcher in astrophysics at the Max Planck Institute in Germany, says.
This means that peptides likely existed in the solar system at its outset, rather than forming uniquely on the early Earth out of the chemical soup on its surface. And those peptides “can continue forming even after the protoplanetary disk and the Sun have been formed Krasnokutskiy adds.
The team also found that most organic matter that went into Earth was likely destroyed during the planet’s formation. Instead, new organics were transported by meteors and comets back to Earth’s surface later on, Krasnokutskiy says.
The process of ingredients for life arriving via extraterrestrial material is known as panspermia.
Bringing space down to Earth
The results all draw from a lab experiment simulating the conditions of space instead of direct measurements, though Krasnokutskiy says a tentative detection of peptides in a meteorite was published in October 2020 in the Journal of Proteome Research. Additionally, “the detection of peptides directly in space is more challenging but could be possible during a space mission to a comet,” he says.
The exact role of peptides in the formation of life isn’t well known. Scientists still aren’t sure how ro when the soup or organic materials available here began to self-reproduce and kick off life, despite attempts to recreate these conditions in the lab. But by answering where and how peptides formed in the material that later became comets and asteroids, we can gain key insight into where the chemicals in the prebiotic soup came from in the first place.
“Peptides have proven to be effective catalysts and if delivered to young planets, they could help in the generation of diverse organic and biomolecules,” Krasnokutskiy says. “This could be a promising area for future exploration,” he says, when it comes to learning how life here — and elsewhere in the universe — might have begun.
