A Meteorite Splashing Into Might Have Been The H-Hour Of Life On Earth
Darwin might have guessed it right.
Life on earth began more than 3 million years ago, evolving from the most basic of microbes into a dazzling array of complexity over time, but how did the first organisms on the only known home to life in the universe develop from the primordial soup?
The question of where humans came from and our origins has been a nagging question. In an attempt to try and answer this universal question, humanity has created gods, pseudo scientific hypothesis and also thrown into the mix are some plain old guess work. While many of these theories have since been debunked, they still serve a purpose when it comes to sparking imagination and thinking out of the box.
One of the many theories out there and possibly the most popular one yet, is of the bearded Victorian sage, Charles Darwin suggesting life began in ‘some warm little pond with all sorts of ammonia and phosphoric salts, light, heat, electricity etcetera present’.
Surprisingly though, this theory might be the most accurate according to evidence-based calculations carried out by scientists at McMaster University in Canada
and the Max Planck Institute in Germany.Charles Darwin first singled out volcanic pools, or ‘warm little ponds’, as the breeding ground for the first life forms in the 19th century. Darwin once wrote in a correspondence that the chemicals found such ponds closely resemble the cell’s composition of its cytoplasm.
“Because there are so many inputs from so many different fields, it’s kind of amazing that it all hangs together,” said co-author Ralph Pudritz of the McMaster’s Origins Institute and its Department of Physics and Astronomy.
“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.”
Scientists at McMaster University and the Max Planck Institute in Germany claim life originated sometime between 3.7 and 4.5 billion years ago with the help of meteorites.
In their new study, the team found that what sparked life were essential components of nucleotides which were delivered by cosmic objects. Their simulations suggest that if these building blocks reached a high enough concentration in pond water, these could bond together as the water level rose and fell through frequent cycles of precipitation, evaporation, and drainage. Early Earth was constantly battered by meteors, so those were certainly not in low supply.
Eventually, these favorable conditions led to the creation of RNA polymers, which are similar to DNA in the sense that both carry genetic information. The researchers’ calculations suggest that in time some of these chains folded over and spontaneously replicate themselves by drawing other nucleotides from their environment. Replication is an essential prerequisite for the definition of life.
There’s a growing body of evidence showing that meteorites can indeed carry the essential components of nucleotides, the building blocks that make up RNA and DNA. Scientists first realized that there were components of DNA in meteorites in the 1960s, but it wasn’t until 2011 that researchers proved that they were actually created in space and didn’t just represent contamination from terrestrial life. That year, NASA-funded researchers at the Goddard Astrobiology Analytical Laboratory found the nucleobases adenine and guanine, as well as hypoxanthine and xanthine, in samples of comet Wild 2 from NASA’s Stardust mission.
The chemical building blocks of RNA molecules, called nucleobases, have been found in carbon-rich meteorites. Those were raining down on the early Earth at a much higher rate than they are now, suggests evidence based on the age of craters on the moon.
Using published data, Pearce and his colleagues estimated the number of ponds at the surface of the early Earth and the concentration of nucleobases in those ponds delivered by the meteorites splashing into them.
They propose that those ponds may have dried up at some times of the year, concentrating the building blocks of RNA and allowing them to link together — something that’s been shown to happen in the lab. Rain would re-form the pond and mix up the building blocks, allowing them to link into longer chains the next time the pond dried up.
The team says this is the first time anyone has assembled together information about the conditions on the early Earth and experiments on chemically building RNA, filled the gaps by calculating the physics that they would have undergone through the process, and put all the puzzle pieces together to see whether it was feasible for life to get its start this way.
The results have been published in the journal Proceedings of the National Academy of Sciences.
The results shouldn’t be considered foolproof just yet. This study is based on mathematical models, which aren’t quite enough to prove the hypothesis.
Dmitry Semenov, co-author of the paper and a researcher at the Max Planck Institute for Astronomy said: “Based on what we know about planet formation and the chemistry of the solar system, we have proposed a consistent scenario for the emergence of life on Earth. We have provided plausible physical and chemical information about the conditions under which life could have originated. Now it’s the experimentalists turn to find out how life could indeed have emerged under these very specific early conditions.”
