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 hell

Given my near-obsessive interest in extraterrestrial life, I suppose it was inevitable that I've now been sent links to the latest research on Venus over a dozen times.

The gist, in case you haven't read about it yet, is that astronomers have identified the absorption spectrum of a rare molecule -- phosphine -- in the upper atmosphere of the planet Venus.  Phosphine is produced in vanishingly small quantities on Earth by cloud-to-ground lightning strikes and volcanic eruptions, but the amount detected in the atmosphere of Venus is a full ten thousand times too high to be accounted for by any known inorganic chemistry or geology.

Ruling out one by one all of the inorganic sources of phosphine seems to leave only one remaining possibility; there are microbes in the Venusian atmosphere that produce the stuff.  There are a handful of species of terrestrial microbes that produce phosphine (here, it's in even smaller quantities than the inorganic sources).  But if these microbes (or something like them) existed on Venus, it could easily account for the excess.

You may be wondering how anything lives on Venus.  It's a good question.  The surface of Venus is a lot like our conception of hell.  For a long time people interpreted the constant cloud layers that obscure the surface as being made of water droplets, like they are on Earth; it led to some pretty cool speculative fiction about what could be down there (C. S. Lewis's novel Perelandra and H. P. Lovecraft's outstanding short story "In the Walls of Eryx" come to mind).  But that speculation was based on nothing but an absence of evidence.  As Carl Sagan put it so eloquently:

The chain of reasoning goes something like this: I can't see a thing on the surface of Venus.  Why not?  Because it's covered with a dense layer of clouds.  Well, what are clouds made of?  Water, of course.  Therefore, Venus must have an awful lot of water on it.  Therefore, the surface must be wet.  Well, if the surface is wet, it's probably a swamp.  If there's a swamp, there's ferns.  If there's ferns, maybe there's even dinosaurs.

Observation: I can't see a thing.  Conclusion: dinosaurs.

This whole thing got shot down pretty conclusively in the 1960s when the first unmanned (fortunately) probes to Venus dropped through the atmosphere and promptly were simultaneously crushed and fried by an atmosphere with ninety times the pressure of Earth's atmosphere at sea level and temperatures that hover around 460 C.  Further exploration showed that the clouds are largely sulfuric acid, and the atmosphere is 96.5% carbon dioxide (compared to 0.04% on Earth), leading to a runaway greenhouse effect.

The surface of Venus [Image is in the Public Domain courtesy of NASA/JPL]

It's not just hot, it's wracked with turbulence the likes of which we never see on Earth.  The heat provides a huge energy source for Venusian weather, mostly in the form of violent storms and updrafts.  As dubious as he was about life on Venus, Sagan had suggested these updrafts as a key to the possible terraforming of the planet, and proposed launching rockets with payloads of blue-green bacteria spores, set to detonate in the upper clouds.  As the spores fall through the relatively mild temperatures of the upper atmosphere, they begin to photosynthesize, using up some of the carbon dioxide.  Enough are kept aloft by the updrafts to keep the process going, and ultimately, the greenhouse effect would diminish and the temperature would fall to more tolerable levels.

Well, nature may have anticipated Sagan.  If there are anaerobic microbes riding the turbulence in Venus's upper atmosphere, it would be the first unequivocal example of extraterrestrial life ever found.  The scientists are being careful about overstating their conclusion, but even given the usual caution, the excitement is palpable.  "The non-biological production of phosphine on Venus is excluded by our current understanding of phosphine chemistry in rocky planets' atmospheres," said Leonardo Testi, astronomer with the Atacama Large Millimeter/submillimeter Array in Chile, one of the most sensitive telescopes in existence.  "Confirming the existence of life on Venus's atmosphere would be a major breakthrough for astrobiology; thus, it is essential to follow-up on this exciting result with theoretical and observational studies to exclude the possibility that phosphine on rocky planets may also have a chemical origin different than on Earth."

So it's premature to say "we've discovered extraterrestrial life," but this is the best candidate for it I can recall seeing, and in one of the most inhospitable spots in the Solar System.  If this is confirmed to be of biological origin, it gives a lot of support to the contention I've had all along -- that life will turn out to be common in the the universe.  It'd boost the enthusiasm for checking out other places in the Solar System that could host life (Jupiter's moon Europa and Saturn's moon Titan come to mind), because after all, if life can exist on Venus, it could exist damn near anywhere.

Still no dinosaurs, though.  None of Lewis's floating islands made of rafts of plants, either, nor Lovecraft's evil jewel-hunting reptilian natives.  But for now, it's good enough for me, as long as the astronomers don't find some kind of exotic Venusian chemistry that explains the gas's presence.

If the whole thing pans out, it really gives new meaning to Ian Malcolm's line from Jurassic Park, doesn't it?

"Life finds a way."

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This week's Skeptophilia book-of-the-week is about one of the most terrifying viruses known to man: rabies.

In Rabid: A Cultural History of the World's Most Diabolical Virus, by Bill Wasik and Monica Murphy, we learn about the history and biology of this tiny bit of protein and DNA that has, once you develop symptoms, a nearly 100% mortality rate.  Not only that, but it is unusual amongst pathogens at having extremely low host specificity.  It's transmissible to most mammal species, and there have been cases of humans contracting rabies not from one of the "big five" -- raccoons, foxes, skunks, bats, and dogs -- but from animals like deer.

Rabid goes through not only what medical science has to say about the virus and the disease it causes, but its history, including the possibility that it gave rise to the legends of lycanthropy and werewolves.  It's a fascinating read.

Even though it'll make you a little more wary of wildlife.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]