The complex molecules required for life on Earth might never have formed if it wasn’t for cosmic dust.
That’s the conclusion of a new study by researchers from Friedrich Schiller University, the University of Virginia, and Heriot-Watt University.
The earliest life on Earth began some 3.7 billion years ago. But its ingredients, the prebiotic organic compounds that make the complex chemistry of life possible, are even older.
Nearly a billion years further back, when Earth was only just forming, the planet was a swirling lump in the protoplanetary disk of gas and dust that surrounded our young star.
It is here, in the cold prehistory of the Solar System, that the story of complex chemistry – and therefore the road to life – began.
One of the leading acts of this period: the formation of ammonium carbamate out of carbon dioxide and ammonia reactions. Scientists know this to be the case because ammonium carbamate was recently detected in a protoplanetary disk for the first time by the James Webb Space Telescope.
What is it? A type of salt. It’s a component of urea, and a vital compound in Earthly forms of life.
To figure out how it got there, Dr Alexey Potapov recreated the conditions of the early Solar System in his lab in Jena. He supercooled samples of carbon dioxide and ammonia to the temperatures found in interstellar clouds, -260 degrees Celsius. The samples were then allowed to warm to a balmy -190 degrees, just like the conditions in the Sun’s protoplanetary disk.
But to really get the reaction going, a third ingredient was necessary: cosmic dust.
“Dust isn’t just a passive background ingredient in space. It provides surfaces where molecules can meet, react and form more complex species. In some regions of space, this dust chemistry is a prerequisite for making life’s molecular building blocks. We now know that surface reactions occur efficiently - more quickly - with the dust than without,” said Potapov’s colleague, Martin McCoustra of Heriot-Watt University in a press release.
This was the first time this sort of chemistry has been examined under these conditions, and it’s clear that without cosmic dust, the chemical reactions required for life would be too inefficient to form in great quantities.
“The findings suggest that dust grains play a far more active role in astrochemistry than previously thought. Floating through interstellar clouds and protoplanetary disks, these particles may provide the micro-environments where molecules meet and evolve into more complex forms,” Potapov said.
Now, scientists are one step closer to understanding the story of life before life.
“We’ve shown that dust can promote the chemistry needed to build more complex organics, even at extremely low temperatures. This could be how nature overcomes the harshness of space to kickstart chemistry that ultimately leads to life,” McCoustra said.