The brilliant colors of Grand Prismatic Spring in Yellowstone National Park are due, in part, to extremophilic bacteria [Image is in the Public Domain]
The life forms are odd in a number of respects. The first is that they're anaerobic -- they don't need oxygen to survive. The second is that they metabolize sulfur, primarily in the form of iron sulfate, better known as pyrite or fool's gold. It's a food chain completely unhooked from light -- for nearly every other organism on Earth, the energy they contain and utilize can ultimately be traced back to sunlight. Here, if you follow the energy backwards, you arrive at the geothermal heat from the mantle of the Earth producing reduced (high energy) compounds that can support a food web, similar to what you see in deep-sea hydrothermal vents.
"It's a fascinating system where the organisms are literally eating fool's gold to survive," team member Barbara Sherwood Lollar said in an interview with NBC News. "What we are finding is so exciting — like ‘being a kid again’ level exciting." The ecosystem is in the Laurentian Shield, one of the oldest and most geologically-stable places on Earth, so it's likely that this thriving community deep underground has been there for a billion years or more. "The number of systems we've looked at so far really is limited, but they probably had a single origin at some point in life’s four-billion-year history." As far as their discovery, she added, "We see only what we look for. If we don't look for something, we miss it."
And it's a lot to miss. The current research springboards off a 2018 report sponsored by the Deep Carbon Observatory conducted by a team led by Cara Magnabosco, a geobiologist at the Swiss technical university ETH Zurich, which estimated that some 5 x 10^29 cells live in the deep Earth.
For those you who don't like scientific notation, that's five hundred thousand trillion trillion organisms. Put succinctly, it's a really freakin' huge number.
Considering the (to us) inhospitable conditions a lot of these organisms live under, it raises hopes of finding life in other, perhaps unexpected, places in the universe. Astronomers talk about the "Goldilocks zone," the region around a star that has temperatures where water is a liquid, and that to host life a planet would have to have a similar mass to Earth and be orbiting a star relatively similar to the Sun. The University of Toronto research suggests that may be placing unnecessary and inaccurate strictures on where life can exist, and that we may have to rethink our definition of what we mean by "hospitable conditions."
"We're finding we really don't understand the limits to life," Sherwood Lollar said.
Which also raises the question of whether we'd recognize alien life if we saw it. Star Trek may have been prescient; they expanded the boundaries of what we think of as life by featuring aliens that were gaseous, crystalline, thrived at searing temperatures, could tolerate the chill dark vacuum of space, or were composed of pure energy. While some of these -- at least at first glance -- seem pretty far-fetched, what the current research suggests is that we shouldn't be too hasty to say, "Okay, that's out of the question."
"We've literally only scratched the surface of the deep biosphere," said Robert Hazen, mineralogist at the Carnegie Institution’s Geophysical Laboratory in Washington, and co-founder of Deep Carbon Observatory. "Might there be entire domains that are not dependent on the DNA, RNA and protein basis of life as we know it? Perhaps we just haven’t found them yet."
This week's Skeptophilia book recommendation is pure fun: science historian James Burke's Circles: Fifty Round Trips Through History, Technology, Science, and Culture. Burke made a name for himself with his brilliant show Connections, where he showed how one thing leads to another in discoveries, and sometimes two seemingly unconnected events can have a causal link (my favorite one is his episode about how the invention of the loom led to the invention of the computer).
In Circles, he takes us through fifty examples of connections that run in a loop -- jumping from one person or event to the next in his signature whimsical fashion, and somehow ending up in the end right back where he started. His writing (and his films) always have an air of magic to me. They're like watching a master conjuror create an illusion, and seeing what he's done with only the vaguest sense of how he pulled it off.
So if you're an aficionado of curiosities of the history of science, get Circles. You won't be disappointed.
[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]