Stone age

I've only got a few real obsessions.  My dogs.  Doctor Who.  Anything to do with astronomy.  Lost in Space.  The X Files.  Star Trek - The Next Generation.  The movie Contact.

I bet you're sensing a theme, here.  Other than my dogs, all of these have to do with the universe, space travel, and alien life.  And given how oddly my dogs act some days, I find myself wondering if they might not be alien spies as well.  Especially Rosie, who so often seems to be judging us.

"Unless I start getting steak for dinner, the report I'll be sending to the Mothership will be highly unflattering."

But even with that possible exception, it's evident that I have a bit of a fixation on the possibility of extraterrestrial life.  I'm well aware of the fact that with regards to life, we've still got a sample size of one; despite decades of looking, we have yet to find any unequivocal biosignatures, signs that life exists, anywhere else but here.  (Much less any signs of extraterrestrial intelligent life.  Much as I would love for some astronomer to become a real-life Ellie Arroway, no such luck... yet.)

In spite of all this, I still am very much of the opinion that life elsewhere in the universe is likely to be abundant.  I base this on the known facts that there are trillions of stars out there, in billions of galaxies, and that exoplanetary systems are common (i.e. the formation of the Solar System wasn't just a lucky fluke).  Optimistic estimates of some of the other variables in the Drake Equation are harder to defend, but I stand by my statement: a purely statistical argument suggests that many star systems have planets that support some kind of life.

One of the things that in my mind argues for life existing elsewhere in the universe -- even in environments that we might consider inhospitable -- is how many extreme habitats here on Earth turn out to host living things.  There's life in the desiccated, perpetual cold of the dry valleys of Antarctica, in highly alkaline (or highly acidic) hot springs, in boreholes miles deep, in hydrothermal vents in the oceanic abyss.  The odd little animals called tardigrades can survive extremes in temperature and pressure, radiation, and dehydration; they've even survived exposure to the vacuum of space.

And we're still finding new ones in unexpected places.  Take, for example, the microorganism -- or, rather, the traces of it -- that was the subject of a study this week in the journal Geomicrobiology.  A team out of Johannes Gutenberg Universität Mainz was studying samples of marble and limestone quarried in the parched deserts of Namibia, Oman, and Saudi Arabia, and found microscopic tunnels apparently excavated by some as-yet-unidentified microbe.

"We were surprised because these tubes are clearly not the result of a geological process," said Cees Passchier, who co-authored the paper.  "We were looking at the structure of the rocks to find out how continents came together to form the supercontinent Gondwana five hundred to six hundred million years ago.  At that time, carbonate deposits formed in the ancient oceans and turned into marble due to pressure and heat...  We noticed strange structures in this marble that were not the result of geological events.  These are old structures, perhaps one or two million years old...  What is so exciting about our discovery is that we do not know which endolithic microorganism this is.  Is it a known form of life or a completely unknown organism?  It must be an organism that can survive without light because the tubes have formed deep inside the rock.  We don't currently know whether this is a life form that has become extinct or is still alive somewhere."

Samples of marble with the "microburrows" [Image credit: C. Passchier et al.]

It seems like everywhere we look on Earth, we find life, which strengthens the hope of those of us who'd like to find life out there amongst the stars as well.  That microorganisms can live by tunneling their way through solid rock certainly suggests we should expand the parameters of the phrase "capable of supporting life."

Although most of it may not be at the point of sending out messages that could be picked up by our radio telescopes, my surmise is that most even remotely hospitable locales in the universe will turn out to be inhabited.  And just judging by the diversity of our terrestrial organisms, I also strongly suspect that what is out there will indeed turn out to be, in Darwin's immortal words, "endless forms most beautiful and most wonderful."

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Life in the shadows

In Michael Ray Taylor's brilliant1999 book Dark Life, the author looks at some of the strangest forms of life on Earth -- extremophiles, organisms (mainly bacteria) that thrive in places where nothing else does.  Surrounding hydrothermal vents under crushing pressures and temperatures over 100 C, buried underground below the deepest mines, frozen in Antarctic ice, floating in boiling, acidic hot springs.  Taylor himself is a veteran spelunker and got interested in the topic after running into the aptly-named snottites -- biofilms found in caves that hang downward from the ceiling and are the consistency of, well, snot.

The brilliant colors of Grand Prismatic Spring in Yellowstone National Park are due, in part, to extremophilic bacteria [Image is in the Public Domain]

Taylor's contention -- that such bizarre creatures are so numerous that they outnumber all other life forms on Earth put together -- got a boost from a piece of research published in the Journal of Geomicrobiology.  Written by a team from the University of Toronto -- Garnet S. Lollar, Oliver Warr, Jon Telling, Magdalena R. Osburn, and Barbara Sherwood Lollar -- it describes the discovery, 7,900 meters underground, of a thriving ecosystem of microbes in a mine 350 kilometers north of Toronto.

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."

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Life inside the snowball

Right now, here in the wilds of upstate New York, it's cold, gray, and snowy.  They say our area has a "four-season climate" -- but usually neglect to add that the four seasons are Almost Winter, Winter, Still Fucking Winter, and Road Construction.

On the other hand, if you know something about prehistory, it could be a whole lot worse, and in fact, has been more than once.  The last continental glaciation in this part of the world, the Laurentide, resulted in an ice sheet that buried the spot where I'm now sitting under three hundred meters of ice, and dug out not only the nearby Finger Lakes but the Great Lakes.  The southern edge of the ice sheet created the Elmira Moraine, only thirty miles south of me -- a moraine is basically the debris left behind when a glacier recedes -- and also Long Island, the sand and gravel soils of which were shoved forward as the ice sheet pushed southward then left in place, much like the pile of snow left when a snowplow backs up (explaining its long, narrow shape).

So I shouldn't complain about the cold.  The era of the Laurentide Glaciation was a lot colder.  And in fact, there have been periods in Earth's history where everyone, not just people like who live in the frozen north, would have been in the icebox.

Our knowledge of this rather miserable time in the far distant past has, like so many discoveries, built by accretion.  In the 1870s and 1880s geologists found evidence of widespread glaciation in strata in Scotland -- then, more puzzlingly, in Australia and India.  Any deep understanding of this was hampered by the fact that back then, scientists thought the continents were firmly fixed in place; continental drift wasn't even first proposed until 1912, and then was soundly rejected until magnetometer data proved in 1958 that the tectonic plates were in constant motion.  The first evidence of a worldwide glaciation -- not just a big one, like the Laurentide -- was uncovered in 1964 by Cambridge University geologist W. Brian Harland, who showed that glacial strata in Svalbard and Greenland had been deposited in tropical latitudes.  Thus demonstrating two rather amazing conclusions in one fell swoop; first, that Svalbard and Greenland had moved a long way, and second, that at the time when they were near the equator, the whole world was covered with ice.

This "Snowball Earth" model has since been demonstrated as accurate in multiple ways.  More than once, but most significantly between 720 and 580 million years ago (i.e. the end of the Precambrian Era), the whole planet was covered with a kilometers-thick sheet of ice.  Picturing what this was like is a little mind-boggling.  The glaciers covered not only the land, but the entire ocean.  Because the liquid water underneath was moving, the ice sheets broke up and ground together, much like the rocky tectonic plates do today, floating on the liquid mantle of the Earth.  Any organisms caught in the cracks of the ice sheet, or between the glaciers and the seafloor, would have been pulverized.  "It’s basically like having a giant bulldozer," said Huw Griffiths, of the British Antarctic Survey, in an interview with Eos.  "The next glacial expansion would have just erased all [traces of life] and turned it into mush, basically."

Griffiths is the reason the topic comes up, actually; he, Rowan Whittle (also of the British Antarctic Survey), and Emily Mitchell (of the University of Cambridge) are the authors of a paper in The Journal of Geophysical Research that looked at the rare fossils that have survived since that time, and have drawn some fascinating parallels to species who survive today in similar conditions -- on the seafloor beneath the Antarctic Ice Sheets:

The timing of the first appearance of animals is of crucial importance for understanding the evolution of life on Earth.  Although the fossil record places the earliest metazoans at 572–602 Ma, molecular clock studies suggest a far earlier origination, as far back as ~850 Ma.  The difference in these dates would place the rise of animal life into a time period punctuated by multiple colossal, potentially global, glacial events...  The history of recent polar biota shows that organisms have found ways of persisting on and around the ice of the Antarctic continent throughout the Last Glacial Maximum (33–14 Ka), with some endemic species present before the breakup of Gondwana (180–23 Ma)...  [D]espite the apparent harshness of many ice covered, sub-zero, Antarctic marine habitats, animal life thrives on, in and under the ice.  Ice dominated systems and processes make some local environments more habitable through water circulation, oxygenation, terrigenous nutrient input and novel habitats...  The recent glacial cycle has driven the evolution of Antarctica's unique fauna by acting as a “diversity pump,” and the same could be true for the late Proterozoic and the evolution of animal life on Earth, and the existence of life elsewhere in the universe on icy worlds or moons.

One group of weird animals they looked at, which apparently thrived in these harsh conditions, were frondomorphs (Phylum Petalonamae), which are thought to have left no descendants whatsoever, and whose alliances to other animals are uncertain at best.

Fossil of a Precambrian frondomorph, Charniodiscus arboreus, from the Flinders Range in Australia [Image licensed under the Creative Commons tina negus from UK, Charniodiscus arboreus, CC BY 2.0]

These peculiar beasts were apparently anchored to the seafloor and absorbed nutrients and oxygen from the frigid waters through the feathery bits, but honestly, we know barely anything about how they made a living.  Some may have -- as many Antarctic sponges and sea anemones do today -- been affixed upside-down from the underside of the ice sheet.

These animals, nicknamed "extremophiles" for obvious reasons, just about all died out when things warmed up and the ice finally melted.  But it bears mentioning how long the Snowball Earth conditions persisted -- around 140 million years.  In other words, about the same amount of time as between the end of the Jurassic Period and now.   During that time, there were minor ups and downs, temperature-wise, but that's still a huge expanse of time during which the Earth was an ice-covered wasteland.

When the snowball finally did melt, and the cold-loving extremophiles such as Charniodiscus went extinct, it opened the door for one of the major events in the history of life on Earth -- the Cambrian explosion, when all of the main phyla of animals evolved in a relative flash.  But even when conditions were at their worst, life still survived, somehow.  The fact that life can thrive in apparently hostile conditions improves our chances of finding it elsewhere in the universe, and cheers me up significantly with regards to the weather we're currently having here.

It's also further support for the famous line from the inimitable Ian Malcolm in Jurassic Park: "Life, uh, finds a way."

****************************************

Life in the shadows

In Michael Ray Taylor's brilliant1999 book Dark Life, the author looks at some of the strangest forms of life on Earth -- extremophiles, organisms (mainly bacteria) that thrive in places where nothing else does.  Surrounding hydrothermal vents under crushing pressures and temperatures over 100 C, buried underground below the deepest mines, frozen in Antarctic ice, floating in boiling, acidic hot springs.  Taylor himself is a veteran spelunker and got interested in the topic after running into the aptly-named snottites -- biofilms found in caves that hang downward from the ceiling and are the consistency of, well, snot.

The brilliant colors of Grand Prismatic Spring in Yellowstone National Park are due, in part, to extremophilic bacteria [Image is in the Public Domain]

Taylor's contention -- that such bizarre creatures are so numerous that they outnumber all other life forms on Earth put together -- just got a boost last week from a piece of research published in the Journal of Geomicrobiology.  Written by a team from the University of Toronto -- Garnet S. Lollar, Oliver Warr, Jon Telling, Magdalena R. Osburn, and Barbara Sherwood Lollar -- it describes the discovery, 7,900 meters underground, of a thriving ecosystem of microbes in a mine 350 kilometers north of Toronto.

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."

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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!]