Life on Earth was “born” when meteorites splashed into thousands of “warm ponds”
The environment needed for life to be kickstarted on Earth may have been created by meteorites splashing into ponds of water.
Seemingly confirming a concept that has been around since Darwin, these meteorites are believed to have splashed into “little warm ponds” somewhere between 3.7 and 4.5 billion years ago and “leached” essential elements needed for life to begin.
Calculations made by researchers at McMaster University and the Max Planck Institute in Germany suggest that these ponds were full of “nutrient-rich broth”. The wet and dry cycle of early Earth’s weather caused the basic molecular building blocks found in the ponds to bond and become self-replicating RNA molecules. These RNA molecules became the first genetic code for life on the planet.
“No one’s actually run the calculation before,” said lead author Ben K.D. Pearce. “This is a pretty big beginning. It’s pretty exciting.”
“Because there are so many inputs from so many different fields, it’s kind of amazing that it all hangs together,” co-author Ralph Pudritz added. “Each step led very naturally to the next. To have them all lead to a clear picture in the end is saying there’s something right about this.”
The researchers claim that this evidence suggests life began when the Earth was still forming, with continents emerging from the oceans, meteorites hitting the planet – including those carrying the building blocks of life – and no protective ozone to filter the sun’s rays.
The spark of life, the authors continued, happened when RNA polymers were created. These are essential components of nucleotides, brought to Earth by meteorites, reaching sufficient levels in pond water and bonding together as water levels fell and rose through cycles of precipitation, evaporation and drainage. This combination of wet and dry conditions was “necessary for bonding”, the paper published in the Proceedings of the National Academy of Science, explained.
This rudimentary form of life is said to have eventually developed into DNA. “DNA is too complex to have been the first aspect of life to emerge,” Pudritz said. “It had to start with something else, and that is RNA.”
According to the calculations, the “necessary” conditions would have been seen in thousands of ponds across Earth. In the early days of the solar system, meteorites were far more common, and could have landed in thousands of these ponds, widely distributing the building blocks of life. As a result, it was more likely that the bonding would have occurred in these ponds than in hydrothermal vents – a leading, rival theory about how life on Earth began.
The calculations also appear to rule out space dust being the source of the so-called life-generating nucleotides. In particular, they show that while such dust would have carried the necessary building blocks, it didn’t deposit them in sufficient concentrations to give life the boost it needed.
Pearce and Pudritz now plan to test their theory next year when the McMaster Origins of Life lab opens, set up to recreate pre-life conditions in a sealed, controlled environment.