IT IS the closest we have ever come to finding Earthâs primordial soup. Ancient rocks deep underground contain water that has been locked away for billions of years. It may never have been touched by life.
In 2007, geochemist at the University of Toronto in Canada and her team found treasure in a copper mine. Water gushing out of cracks in the rock, caused by mining, turned out to be over a billion years old. Now the group has made a similar find in a second mine, suggesting ancient rocks could be riddled with such time capsules, right back to the early days of life on Earth.
Sherwood Lollarâs team is now scouring the water for ancient forms of life, perhaps unknown to science. So far it seems it holds no life, but that is just as exciting because it means the water they found may be identical to that in which life began.
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If thatâs the case, it opens up an extraordinary opportunity to understand how life got started on Earth, and where (see âBeginnerâs guide to the origin of lifeâ). The find could also offer insights into how life may survive on other planets.
Sherwood Lollar first got a whiff of the hidden water over a decade ago, deep inside the in Timmins, Ontario, Canada. In a corridor more than 2 kilometres beneath the surface, she caught a whiff of gas from a fracture in the rock. Water dripped from the hole. Subsequent analyses revealed it to be between 1.1 and 2.7 billion years old (). The smell came from the sulphurous gases mixed in with the water, which also holds methane and hydrogen.
Crucially, as far as the team could tell, the water contained no trace of life. âIt speaks to this question of whether we can find an exotic small part of this planet that has not been touched by life,â says Sherwood Lollar. âThese fractures may have been isolated long enough that they retain chemistry that reflects the same kind of processes that were taking place before there was life on Earth. At that time, presumably the whole planet would have looked something like this.â
The discovery could have been a one-off, so the team has been looking for other places where ancient water exists in deep rocks. Last month at the in Sacramento, California, team member Chelsea Sutcliffe presented their results from two mines in the Sudbury basin, also in Ontario.
Like Timmins, the mines are dug into rock that is billions of years old. Sutcliffe collected water from 1.3 and 1.7 kilometres down, and so far it looks very similar to the Timmins water. The chemicals in the water are similar, and isotope ratios suggest it is similarly old. The team are now running further analyses: the noble gases in the water samples will provide a fairly precise age.
âIf they are seeing the same thing at Sudbury, thatâs pretty powerful,â says of Princeton University. This water is âan abiotic fringe zone â a place where life could exist but doesnât yetâ, he says. âThis is a zone thatâs been trapped for billions of years, providing a geological experiment on the genesis of life.â
âThe waterâs been trapped for billions of years, providing an experiment on the genesis of lifeâ
At most, the Timmins and Sudbury water is 2.7 billion years old â the age of the rock it is trapped inside. Thatâs about a billion years after life got started, so the researchers are not suggesting they have bottled the actual primordial soup in which life began. But the chemistry they are seeing corresponds to water that could have given rise to life.
âGeochemically, itâs the kind of site that has been invoked for the origins of life on our planet,â says Onstott. âYet here we see it isolated from the present-day DNA world.â
There are two leading theories for where life got started on Earth. Perhaps the most famous is Darwinâs ââ â a soup of organic chemicals bathed in sunlight. The other, which has gained popularity in recent years, is that deep-sea vents at the bottom of the ocean acted as a cradle for life, offering both heat and nutrition via fluids pumped up through Earthâs crust.
Thatâs where the ancient water from the Ontario mines comes in. The rocks they are held in were formed by hydrothermal vent systems at the bottom of the ocean, billions of years ago.
âI would say this is as close as we have come to bottling the warm little pond, in a warm little fracture,â says Sherwood Lollar. Onstott agrees: âThey are literally like Darwinâs warm little pond without the light.â
âI would say this is as close as we have come to bottling Darwinâs âwarm little pondââ
Having bottled Earthâs primordial soup, the researchers are now probing it to see what they can learn. It may be that chemical reactions deep underground have given rise to some of the very earliest stages in the formation of life, like the generation of amino acids, or the building blocks of DNA.
If they find anything like this, it would suggest that life can begin without light â good news for the quest for life on other planets. Many distant worlds have never received as much light as Earth, but it is suspected that some of them have hydrothermal systems similar to Earthâs deep-sea vents. Can such systems generate life in an otherwise dead world? We donât know for sure, but Sherwood Lollarâs water offers an unprecedented opportunity to find out.
âGiven the chemistry that we have all speculated might have led to life,â says Onstott, âgiven that itâs there and itâs been there for billions of years, should we not anticipate seeing some prebiotic reactions trapped in there? Once we can find these types of sites, we can turn all our instruments on them to see if we find things like a primitive RNA world.â
Regardless of whether we find such pre-life chemistry in the water, Sherwood Lollar says one thing is fairly certain: the fluids are still full of energy-rich chemicals, the same energy that may have helped to kick-start life.
Sutcliffeâs latest results from Timmins show that the ancient waters are now slowly being colonised. Something seems to be eating the chemicals that have been trapped there for billions of years. Itâs probably a modern organism that found its way into the ancient niche when it was cracked open by miners, and is now feasting. But the stuff it is eating has been around since lifeâs earliest days.
Beginnerâs guide to the origin of life
When did life begin?
We cannot say for sure but we can narrow it down. Assuming life didnât arrive on Earth via meteorites, it must have popped up in the last 4.5 billion years, after Earth formed. The young planet was blitzed by meteorites until 4 billion years ago, so it is unlikely life started before then. However, there are clear traces of single-celled life from 3.5 billion years ago, so it must have been before that. Our current best guess is 3.8 billion years ago.
Where did life begin?
We donât know, but there are lots of ideas. A popular one is that life appeared in the âprimordial soupâ, a mixture of simple chemicals that could react to form the building blocks of life. Darwin suggested this might have happened in ââ. Or life might have begun in the porous rocks of a hydrothermal vent on the seabed. Many other venues have also been put forward, including clay minerals and even ice.
What was the first life like?
We donât know that either. Many biologists think life began as RNA molecules, which can both carry genes and use chemical reactions to gain energy. But not everyone buys into this âRNA worldâ. It might be that the first life was a cycle of chemical reactions, with genes only appearing later. It could also be that life needed a container, such as a cell, before anything else. Michael Marshall
This article appeared in print under the headline âBottling the primordial soupâ
