I'm currently reading planetary scientist Sarah Stewart Johnson's wonderful book The Sirens of Mars, about the search for signs of life on Mars (and other planets in the Solar System). What strikes me whenever I read anything on this topic is that everything we've learned supports the contention that life is common in the universe. (Not necessarily intelligent life; as I've dealt with before, that's another discussion entirely.) As I learned from another great book I read a while back, Michael Ray Taylor's Dark Life: Martian Nanobacteria, Rock-Eating Cave Bugs, and Other Extreme Organisms of Inner Earth and Outer Space, every place we've looked on Earth -- however seemingly inhospitable -- we've found living things. Fissures in rocks miles underneath the Earth's surface; deep-sea hydrothermal vents under crushing pressures and sky-high temperatures; brine ponds containing water many times the salinity of seawater; alkaline and acidic hot springs; chilly, pitch-dark caves with toxic air; anaerobic, sulfur-filled mud. Teeming with life, all of them.
Not only that, but the building blocks of life are kind of everywhere. When Stanley Miller and Harold Urey did their mind-blowing experiment back in 1953, it was unclear whether they had just happened on the right formula; they'd included their best guesses as to the constituents of the early Earth's atmosphere, and used artificial lightning as an energy source, and in short order they had organic compounds in enormous quantities. It turned out, though, that the results had been not so much of a happy accident as an inevitability. As long as you have (1) a reducing atmosphere (i.e. no free oxygen), (2) inorganic sources of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur, and (3) some kind of an energy source, you end up synthesizing all twenty amino acids found in living things (plus some we don't use), DNA and RNA nucleotides, simple sugars, fatty acids, glycerol, and a host of other organic compounds.
In other words, every monomer you need to build an organism. All from off-the-shelf inorganic chemicals and some kind of power source.
What became clear after Miller and Urey published their results is that the early Earth's seas -- and by extension, the seas of any planet with a reducing atmosphere and sufficient liquid water -- might be expected to be brimming with the building blocks of life. This so-called "primordial soup" on Earth gave rise to primitive life in a relative flash, and there's no reason to expect the same wouldn't happen elsewhere.
What came as something of a shock, though, is that you don't even need warm, Earthlike conditions to generate biochemistry. Not long ago, astrophysicists started finding the characteristic signatures of organic compounds in interstellar nebulae. And just last week researchers at the University of Copenhagen announced that they'd discovered organic compounds in a cloud of gas, dust, and ice called Chameleon 1 -- one of the coldest, darkest places ever to be studied, located about six hundred light years away.
Detected by their spectroscopic fingerprints -- the characteristic frequencies of light they absorb from the ambient starlight -- these chemicals were located during a new study using the James Webb Space Telescope. "With the application of observations, e.g. from ALMA [the Atacama Large Millimeter Array, which was also used in the study], it is possible for us to directly observe the dust grains themselves, and it is also possible to see the same molecules as in the gas observed in the ice," said Lars Kristensen, who co-authored the study.
"Using the combined data set gives us a unique insight into the complex interactions between gas, ice and dust in areas where stars and planets form," added Jes Jørgensen, who also co-authored. "This way we can map the location of the molecules in the area both before and after they have been frozen out onto the dust grains and we can follow their path from the cold molecular cloud to the emerging planetary systems around young stars."
What this shows is that a great many of the compounds in the primordial soup may have formed before the coalescence of the Earth, and might already have been present when the seas formed. "This study confirms that interstellar grains of dust are catalysts for the forming of complex molecules in the very diffuse gas in these clouds, something we see in the lab as well," said Sergio Ioppolo, another co-author.
Further evidence that biochemistry -- and almost certainly life -- is plentiful in the universe.
I wonder what life is like on other worlds. Surely whatever it is, it's evolved into a host of forms completely different from what we have here, ones that have adapted to whatever the local conditions are. Different sets of environmental challenges would generate new and innovative evolutionary solutions, as would a different set of one-off occurrences (such as the Chicxulub Meteorite collision that ended the supremacy of the dinosaurs and put us mammals on the pathway to pretty much running the place). Now, take that diversity, those "endless forms most beautiful and most wonderful," as Darwin so trenchantly put it -- and multiply that by a million times.
That is what is very likely to be out there in the cosmos.
If I can be forgiven for ending a post with a quote by Carl Sagan two days in a row, the line he put in the mouth of his iconic character Ellie Arroway (from the book and the movie Contact) seems apposite: "If we're the only ones in the universe, it seems like an awful waste of space."
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