Friday, October 18, 2013

Oxygen, Life, and Autocells

Oxygen in another planet's atmosphere might not come from plants, and life on Earth may have started on Jupiter, of all places:
  1. Oxygen: From Plants Or Sunlight
  2. Life's Origins: Autocells?

What If We're Not Alone?

It's not likely, but next week someone might find clear, unequivocal, solid evidence that life exists on other planets.

If that happened, I'm pretty sure that some folks would be excited, others incredulous, and others upset. I'd be in the first group.

Finding people who aren't human would be even better: or worse, depending on who you ask.

I've read and heard that discovering extraterrestrial life would radically change our view of life, the universe, and everything. How true that is probably depends on who you look at.

Knowledge and Uncertainty

Faced with new information, flat-out denial is an option.

Some folks may decide that news of life on another planet is a plot: to sell newspapers; promote immorality; whatever. I don't think many will take that option, but I'm also pretty sure that folks who will not believe what's real will want, and get, attention.

Others may say that because life exists on other worlds, God can't exist. That seems as goofy as saying that God isn't there because the universe is big and old: or that God must have made a universe that's small and young because that's what Ussher said.

Me? I've been through a false alarm, back in 1996 when some scientists said they'd found fossilized microbes in a Martian meteorite. The last I heard, there's still debate over whether we're looking at nanobacteria smaller than anything on Earth: or odd mineral deposits.

That ongoing discussion didn't shatter my faith in science or anything else. Tiny features in the ALH 84001 meteorite could be evidence of extraterrestrial life, or not. If they are fossils of living creatures, they're too different from anything we're familiar with to be certain.

Their size notwithstanding, the things look too much like terrestrial microbes for me to think that NASA's David McKay is a crackpot.

It's easier when something is obviously true, or patently false. That's not always the case, and I think it's prudent to accept uncertainty as a fact of life.

Space Aliens

Looking back on attitudes that sold tickets to Close Encounters of the Third Kind, some folks might see the space aliens as celestial saviors. That seems goofy, too. On a serious note, idolatry is a bad idea and we shouldn't do it. (Catechism of the Catholic Church, 2113)

In the unlikely event that an alien spaceship lands on the White House lawn tomorrow, I'm pretty sure that we won't experience something like either "Earth vs. the Flying Saucers" or "The Day the Earth Stood Still." And that's another topic.

More of my take on science, life, and people:

1. Oxygen: From Plants Or Sunlight

(From Carnegie Institution for Science, via, used w/o permission.)
"This graphic shows the orbits of the alien planet GJ 667Cc, which takes about 28 days to orbit its parent star. The orbits of other potential planets in the system are also shown."
"Life on Alien Planets Trickier to Find Than Previously Thought"
Miriam Kramer, (October 7, 2013)

" Finding alien life on habitable planets around distant stars may be harder to identify than scientists have previously thought, a new study suggests.

"The search for inhabited and habitable exoplanets is focused on M dwarf stars - stars that are smaller than the sun but make up more than 75 percent of the stars in the sun's vicinity, scientists have said.

"But these small stars have different ultraviolet properties from the sun, however, which could further complicate the search for alien life, researchers with the new study, which was unveiled today (Oct. 7)...."
Scientists have learned that oxygen in a planet's atmosphere may come from the local equivalent of plants: or not. This makes looking for life in the universe trickier, since up to now oxygen in a planet's atmosphere was seen as a fairly certain sign that plants lived there.

Happily, we learned this before someone found a lifeless planet with oxygenated air. That would have been exciting, but also a huge disappointment as researchers learned where the oxygen came from.

Illustrations, Abbreviations, and Assumptions

Including a graphic that shows orbits of planets circling GJ677C in this article is a good idea.

Assuming that everyone will understand what the abbreviations in the graphic mean: maybe not so much. Quite a few folks probably recognized "CO2" as "carbon dioxide" immediately. Most of us grew up with carbon dioxide extinguishers in the hallways of many buildings.

"HZ" probably stands for "Habitable Zone," since "Hertz" doesn't make much sense in this context. Besides, that acronym is spelled Hz."

Small Stars, (Comparatively) Big Flares

"...'Before we can claim the discovery of life on exoplanets, we have to examine the stars harboring these planets more carefully,' study leader Feng Tian, a professor at the Center for Earth System Science at Tsinghua University in Beijing, China, said in a statement. He presented the research today in Denver, Colo., at the 45th annual meeting of the American Astronomical Society's Division for Planetary Sciences.

"The buildup of high levels of oxygen in the atmosphere of an exoplanet is the most promising indicatory for life on alien planets, officials from Tsinghua University said. The new study shows that oxygen can still build up in the atmospheres of lifeless planets, they added.

"Feng Tian and his research team used the idea of a hypothetical habitable planet orbiting GJ 876 to test this in an earlier study. 'In this case the atmosphere of a lifeless planet can be close to that of the Earth's 2.2 billion years ago, after the so called Great Oxidation Event in Earth's geological history,' he said...."
(Miriam Kramer, (October 7, 2013))
These researchers discovered at least one way that local sunlight could break compounds in an exoplanet's atmosphere apart, producing oxygen without the help of plants.

The process is the same sort of thing that produces ozone in Earth's atmosphere.

I'm not terribly surprised that these folks are the first to study what ultraviolet (UV) light from red dwarf starts does to a planet's atmosphere. Red dwarfs, spectral class M stars, are smaller and cooler than our star. On average, their sunlight has more red and infrared light, and less blue and ultraviolet than our star's.

That's "on average," though. Many red dwarfs also produce flares, like our star. The difference is that red dwarf stars are much dimmer than our sun, but their flares aren't. For example, flares on Proxima Centauri emit about as much X-ray radiation as the sun's.

We didn't notice solar flares until 1859, and they didn't matter much to us until we started building large power grids and using radio for communication.

A planet close enough to a red dwarf to have Earth-like temperatures would be close enough to experience the star's flares: up close and personal. Besides X-rays, these flares can emit UV light, which could produce oxygen in the planet's atmosphere.

Sunlight on Other Planets

A lifeless Earth-size planet in a star's habitable zone might easily have water, methane, and carbon dioxide (H2O, CH4, and CO2) in its atmosphere. Far-ultraviolet light breaks these compounds apart. That reaction releases oxygen, since two of them, H2O and CO2, contain oxygen.

A similar process changes the sort of oxygen we breathe, O2, into two O1, which promptly latch onto O2, making O3, which splits into, O2 and O1, and the dance goes on. The ozone-oxygen cycle has most likely been going on since Earth's atmosphere had enough oxygen.

Photosynthesis: Good News, Bad News

An atmosphere similar to Earth's 2,200,000,000 years back wouldn't make the place habitable by humans. Our planet's air apparently had roughly a tenth the percentage of oxygen it does today for a long time after the Great Oxygenation Event.

Oxygen is poison to some microcritters. Scientists describe them with the distinctly un-catchy phrase "obligate anerobes." Some microorganisms of that sort survive, but these days they're limited to oxygen-free environments.

There's very good evidence that cyanobacteria started producing oxygen about 200,000,000 years before the Great Oxidation Event. Oxygen from these microorganisms didn't have a chance to reach the atmosphere. It combined with iron, organic matter, or anything else dissolved in Earth's ocean that reacts with oxygen.

Eventually, with much less stuff to react with in the water, oxygen from cyanobactera got dumped into Earth's atmosphere. Good news for us, not so much for obligate anerobes.

More about:

2. Life's Origins: Autocells?

(From Van Dyke 1982, An Album of Fluid Motion, via Astrobiology Magazine, used w/o permission.)
"Convection caused by heating will generate a pattern of hexagons in a thin film of oil, showing that order can be brought to a system."
"Did Autocells Lead to Life?"
Amanda Doyle, Astrobiology Magazine (September 23, 2013)

"The origin of life on Earth is still a hotly-debated topic. There are many different theories on how life was kick-started, as well as various experiments underway attempting to understand the processes involved. For example, a reverse engineering approach can be used by stripping away cells until the simplest possible system is left. However, evolution has ultimately hampered our understanding of life's origins as it has washed away the traces of the first forms of life, making it impossible to retrace life's early steps. This means that even the simple systems left after the reverse engineering approach are still too complicated to bear a resemblance to the first forms of life.

"Life must have started simply; it couldn't be created from a complicated group of molecules already working together. There had to a step prior to this in which these molecules themselves were created. Terrence Deacon, of the University of California Berkeley, outlined in a recent talk how this step could have taken place...."
I agree that life "started simply," as the article says.

Life might have started abruptly, going straight from no energy and matter at all to Earth's current roster of biomes: from arctic wastes to tropical rainforests. But it's become increasingly obvious that this universe is "in a state of journeying."

I've given my take on God, change, and secondary causes before:

Evolution and Hungry Critters

Amanda Doyle is right about evolution hampering our efforts to understand how life started. "Reverse engineering" of today's life tells us quite a bit, but we're studying creatures that have been changing for 3,600,000,000 years. Chemical machinery inside our cells is remarkably modular, and that's almost another topic.

After at least three and two thirds billion years, not only has life changed a great deal: living creatures have eaten and recycled nearly all physical evidence of earlier eras. Still more topics:

Heat, - - -

"Life needs order

"A tricky challenge that must be overcome before life can form is that order must be generated. However, this is not as simple as it sounds because the laws of physics state that things will naturally descend into a state of disorder. For example, a book placed precariously on the edge of a shelf will probably fall - thus creating disorder - but it is highly unlikely to create order by picking itself up again.

"Order can still be created locally, even when the overall system tends to go towards disorder. Pushing heat through a system can organize it, for example a regular pattern of hexagons is created when a thin layer of oil is heated evenly to form Benard convection cells...."
(Amanda Doyle, Astrobiology Magazine)
"Things will naturally descend into a state of disorder" is true, and it is a law of physics called entropy. More specifically, it's an important part of thermodynamics and statistical mechanics.

We see an effect of entropy when an ice cube warms up as the drink it's in cools.

I'm not at all convinced that entropy applies to biological evolution. It's a very "scientific" word, though.

What's interesting, and may be important, that "pushing heat through a system can organize it." That's related to entropy, in that BĂ©nard convection cells happen when energy 'moves' through a system on its way to thermodynamic equilibrium.

- - - Catalysts and Self-Packing Molecules

(From Terrence Deacon, via Astrobiology Magazine, used w/o permission.)
"The catalysts could form enough molecules that self assembly occurs, creating a barrier around the catalysts so that they don't disperse."
"...If the container surrounding the catalysts becomes shattered, the catalysts will spill out. All is not lost, however, because they will just create another container for themselves. If the catalysts spread apart a little after the breakage, it's possible that multiple systems could then be created meaning they can effectively 'reproduce'.

"These autogenic 'cells', or autocells, are still not living cells in the traditional sense because they still lacks processes that are essential for life...."
(Amanda Doyle, Astrobiology Magazine)
I see self-assembling molecules as another fascinating example of exquisite design built into the universe. Others might see them as a threat to their faith, or as proof that God doesn't exist.

I don't hope to convince zealots. I do, however, see no problem with believing that a rational, orderly God created a rational, orderly universe.

Moving along.

Jupiter, Mars, and Life on Earth

(From NASA, via Astrobiology Magazine, used w/o permission.)
"The famous Martian meteorite ALH 84001 contains a 'fossil' that was ruled out as life because of its small size, however it could still be an autocell - a precursor to life."
"...A helping hand from the gas giants

"A huge problem lies in the fact that the autogenic process is unlikely to start on a planet such as the prebiotic Earth, as the polymers needed for life will break down in water. However, if we take our chemistry experiment to a gas giant like Jupiter, the high levels of methane and ammonia will produce hydrogen cyanide polymers. These polymers can only be produced in environments without water and have a 'backbone' identical to proteins, but with different side chains. These are called polyamidines.

"If these polyamidines hitched a ride to the Earth in earlier epochs when the Earth was being bombarded by outer Solar System material, they would come into contact with water. However, these particular polymers will resist being broken down for some time. Instead, they replace their side chains with the carbohydrates characteristic of proteins.

"In this way, they create partial proteins, and this might be a way that autogenesis based on proteins began on the early Earth. The inner planets also have the advantage of containing phosphorous, sulfur and iron which are unavailable in the outer planets, and these metals speed up catalysis...."
(Amanda Doyle, Astrobiology Magazine)
Maybe life on Earth couldn't have started without a chemical assist from Jupiter. Terrence Deacon's idea isn't as preposterous as it might seem. We've found quite a few meteorites that came from Mars, including that famous 'they're too small to be microbes' one.

It's quite possible, even likely, that stuff from Jupiter and other planets got splashed into space by large impacts in the Solar System's youth and eventually fell on Earth.

If this is, as Terrence Deacon says, the only way life could have started on Earth: we can narrow the search for life in the universe quite a bit.

I'm not entirely convinced, but this is a fascinating bit of research.

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