DNA Components, an Asteroid, and Life on a Wobbling World

Last Monday's close approach by asteroid 2000 EM26 started me thinking about impact events, and what we can do about them. In a less grimly practical vein, finding life on other planets may not be as unlikely as some thought.

1. Adenine, Guanine: DNA Components Found in a Meteorite
2. Good News, the Asteroid Didn't Hit Earth — Not-So-Good News: Some Do
3. The Moon, Tides, and Searching for Life in the Universe
   • Time and Tides
   • Life on a Double Planet
   • Living With Wobbles
   • Scorpions, cockroaches: and Humans
   • Getting a Grip About "Class M" Planets

Now, why I think we need a planetary defense system.

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Barringer Crater; Shanxi Province; and, Maybe, Atlantis

(From Frederic Edwin Church; via www.newscientist.com, Judith Filenbaum Hernstadt, and Wikimedia Commons; used w/o permission.)

Cosmic debris hits Earth every day, but so far nobody's been killed: Except for folks living in Shanxi Province about 524 years ago; and maybe others who were too close when the Tunguska event happened.

Places like Barringer and Kaali craters are of more interest to tourists than mourners: partly because the impacts happened a few thousand years back; partly because we have no written records from those days.

We know that the Minoan civilization went out of business very abruptly at about the same time as a massive explosion ripped Santorini into today's circular archipelago.

Since the Minoans lived perilously close to that volcanic cataclysm, it's quite possible that they didn't recover from the massive tsunami. Plato's Atlantis, which disappeared after "portentous earthquakes and floods, and one grievous day and night," might be a heavily-fictionalized retelling of the Minoans' last days. (Apathetic Lemming of the North (April 20, 2012))

I don't "believe in" Atlantis, or assume that all rousing stories are true. But I do accept the idea that folks like to tell stories about their experiences: and often pass along tales their ancestors told.

It's (very) remotely possible that the Atlantis described in Plato's "Critas" is based on oral traditions about a once-great civilization that built its major city a little too close to what would be an impact site.

Greenwich Village Impact: A Cautionary Tale

(Copyright M. Ahmetvaleev, via NASA News, used w/o permission.)

When the asteroid 99942 Apophis whipped past Earth last year, I outlined what could happen if something that size hit New York City's Greenwich Village.

Briefly, the New York neighborhood would disappear, at least part of Hoboken would slide into a two-mile-wide crater, and pieces of Manhattan would start raining on Atlantic City just over three minutes later.

Folks who weren't in New York City or its environs would survive, except for those who got in the way of those pieces of Manhattan Island. I'm pretty sure that somebody would eventually rebuild a port city near the mouth of the Hudson River, although that would take time.

As I said in a Google Plus post last Tuesday, I don't have much time for sensationalism, but I think the time to develop an asteroid-deflection system is before a mountain falls out of the sky: not after.

Is Saving Lives Ethical?

I've seen Western civilization's silly notion that science and technology will solve all our problems morph into the equally-silly notion that science and technology will kill us all.

Since quite a few folks still seem ambivalent, at best, about newfangled gadgets and science: here's why I think using our brains is okay. Provided, of course, that we don't do something stupid.

I think that God didn't make a horrible mistake by creating us, and putting us in charge of this world. (Genesis 1:27-31)

We don't own the world: we're stewards, with the daunting job of maintaining it. Science and technology are wonderful tools we're expected to use: wisely and ethically. (Catechism of the Catholic Church, 2402, 2293, 2293, 2415)

Technology, like science, isn't 'good' or 'bad' by itself. What we decide to do with these tools is what makes a difference. Ethics always matter. (Catechism, 2294)

I hope that we've learned a little since the 18th century, when some tightly-wound preachers warned that God would punish us for trying to cure smallpox. However, I'd be mildly surprised if someone doesn't get 15 minutes of fame by denouncing efforts to intercept an incoming asteroid as "sinful."

I'm more inclined to follow the lead of folks like Cotton Mather, Louis Pasteur, and Pope Pius VII, who thought saving lives was a good idea. (February 12, 2014)

Planetary Defense: A Work in Progress

We don't have the technology needed for planetary defense against asteroids and comets: yet. But serious discussion of asteroid impact avoidance has been going on since 1992: and more hypothetical discussions go back several decades.

If astronomers tracked an asteroid today, noting that it would impact somewhere between London and Berlin in six months: I don't think we could do much except start evacuating southeastern England, the Netherlands, and northern Germany. We probably couldn't get everyone out of the way, but millions of lives could be saved.

If we had six years, I think that maybe — just maybe — we could cobble together a space tug powerful and accurate enough to push the asteroid into a less lethal orbit.

If someone spots an asteroid bound for Earth a few decades from now: I strongly suspect that averting catastrophe will be a matter of deciding which mining company gets the contract. (September 29, 2013)

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1. Adenine, Guanine: DNA Components Found in a Meteorite

(From Michael Callahan, via Space.com, used w/o permission.)
"Life's building blocks were found in a much smaller sample of the so-called 'Murchison meteorite' than before, as this diagram shows."

"Space Dust Is Filled with Building Blocks for Life"
Elizabeth Howell, Space.com (February 17, 2014)

"A study of teeny-tiny meteorite fragments revealed that two essential components of life on Earth as we know it, could have migrated to our planet on space dust.

"Researchers discovered DNA and amino acids components [!] in a smidgen of a space rock that fell over Murchison, Victoria, in Australia in September 1969. Previous studies of the meteorite revealed organic material, but the samples examined then were much larger. This study would lend more credence to the idea that life arose from outside of our planet, researchers said in a statement.

" 'Despite their small size, these interplanetary dust particles may have provided higher quantities and a steadier supply of extraterrestrial organic material to early Earth,' said Michael Callahan, a research physical scientist at NASA's Goddard Space Flight Center in Greenbelt, Md...."

The DNA components these researchers found in the Murchison sample are adenine and guanine, nucleobases. (NASA (August 8, 2008))

Only about 5% of all meteorites are like the Murchison meteorite, carbonaceous chondrites. On top of that, these DNA parts and amino acids make up a tiny fraction of the Murchison's material. That's why some scientists aren't at all sure that carbon-rich rocks falling from the sky had much to do with life's beginnings here on Earth.

On the other hand, a whole lot of rocks have gotten splashed from one planet to another: particularly in the Solar system's hectic youth. It's possible that at least some of the material for life here came from elsewhere.

I think there's another implication to finding parts of a 'DNA kit' in a meteorite. It looks like organic material, including complex molecules used by life, is spread throughout the Solar system: and beyond.

As I wrote in another blog, "since our star isn't all that far off the 50th percentile, other stars may have had the same 'heat and stir' mix for growing life, too." (Apathetic Lemming of the North (February 16, 2010))

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2. Good News, the Asteroid Didn't Hit Earth — Not-So-Good News: Some Do

(From Slooh, via Space.com, used w/o permission.)
"This graphic shows the location of the asteroid 2000 EM26 in the night sky on Feb. 17, 2014 during a live skywatching webcast by the online stargazing venture Slooh." (detail)

"Huge Asteroid to Fly Safely By Earth Monday: Watch It Live"
Miriam Kramer, Space.com (February 15, 2014)

"An asteroid the size of three football fields is set to make a close brush of Earth on Monday (Feb. 17), and you can watch the flyby in a live webcast.

"Near-Earth asteroid 2000 EM26 poses no threat of actually hitting the planet, but the online Slooh Space Camera will track the asteroid as it passes by Earth on Monday. The live Slooh webcast will start at 9 p.m. EST (0200 Feb. 18 GMT), and you can also watch the webcast directly through the Slooh website.

"You can also watch the asteroid broadcast live on Space.com. Scientists estimate that 2000 EM26 is about 885 feet (270 meters) in diameter, and it is whizzing through the solar system at a break-neck 27,000 mph (12.37km/s), according to Slooh. During its closest approach, the asteroid will fly about 8.8 lunar distances from Earth...."

Something nearly nine times as far from Earth as our moon is "close" only on an astronomical scale. This asteroid's flyby is notable partly because it happened almost exactly a year after a much smaller bit of debris exploded over Chelyabinsk, Russia.

Only a thousand or so folks were injured that time, and nobody died. Property damage included a lot of broken windows, and at least one broken building.


(Reuters//Yevgeni Yemeldinov, used w/o permission)
"Workers repair damage caused after a meteorite passed above the Urals city of Chelyabinsk February 15, 2013." (Reuters)

It's really remarkable that nobody got killed.

The Chelyabinsk meteorite was about 65 feet across: 20 meters. Monday's asteroid is more than ten times wider. When something that size hits Earth, much more energy gets released. The good news is that bigger meteorites come less often than smaller ones.

The bad news is that bigger meteorites, and asteroids, cause more damage. About a month before the Russian meteorite hit, I'd described what might happen if something a quarter-mile across hit New York City's Greenwich Village: with more detail than in this post. (Apathetic Lemming of the North (January 11, 2013))

Briefly, there'd be a crater a bit over two miles across where Greenwich Village had been: and pieces of Manhattan Island would start falling on Atlantic City just over three minutes later. Not very big pieces: only about a quarter inch across, on average.

Even so, something like that would have a bad effect on land value near the mouth of the Hudson. I think folks would build a another city there, eventually: but on the whole, avoiding that sort of catastrophe seems prudent.

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3. The Moon, Tides, and Searching for Life in the Universe

(From Mike Neal, via Space.com, used w/o permission.)
"Astrophotographer Mike Neal sent in a photo of the Harvest Moon taken on Sept. 18, 2013, in Maui, HI." (Mike Neal, nealstudios.net)

"Alien Planets May Not Need Big Moons to Support Life"
Mike Wall, Space.com (February 3, 2014)

"Alien planets without big, climate-stabilizing moons like the one that orbits Earth may still be capable of supporting life, a new study reports.

"Previous modeling work had suggested that Earth's axial tilt, or obliquity, would vary wildly over long time spans without the moon's steadying gravitational influence, creating huge climate swings that would make it tough for life to get a foothold on our planet.

"But that's not necessarily the case, said Jack Lissauer of NASA's Ames Research Center in Moffett Field, Calif...."

Earth's axis of rotation is about 23.4°. In other words, a plane running through Earth's equator is tilted that may degrees away from the plane of Earth's orbit around the sun. Thanks to this tilt, the northern and southern parts of our planet go through an annual cycle of seasons.

If Earth didn't tilt at all, winter and summer wouldn't be nearly as dramatic. Oddly enough, Earth is slightly closer to the sun during the northern hemisphere's winter: today. (NASA's Space Place)

That'll be different 13,000 years from now, as Earth's pole twists around, and that's another topic. (Wikipedia)

We've known about Earth's traveling poles for about two millennia, although it wasn't until the last several centuries that  we started learning about the physics involved.

Then someone named Milankovitch started comparing about a half-dozen orbital parameters with changes in Earth's weather and climate.

That was less than a hundred years back. I think we're not even close to noticing, let alone understanding, all of Earth's long-term cycles.

But we're learning.

Time and Tides

Seashore tides wouldn't be nearly as noticeable without the moon, but we'd still have them. The sun's effect on Earth's oceans isn't nearly as great, and that's yet another topic.

The same forces that cause tides and keep Earth's poles swinging around in a 26,000-year cycle apparently keep our planet's axis of rotation very close to the 23.4° we're used to.

As the Space.com article points out, astronomers are still working out how much Earth's axis would wobble without our moon. Until a few years ago, it looked like Earth's tilt would go from zero to 90° and back over a span of a few million years.

Compared to the duration of most television series, that's a very long time. On a geologic or evolutionary scale, it doesn't give critters much time to adjust.

Life on a Double Planet

Luna, Earth's moon, is huge: 27% Earth's diameter. It's roughly 71% as wide as Mercury, and larger than Pluto. The European Space Agency called it a double planet back in 2003, and I think they have a point.

Since Earth is the only planet where we know life exists, using our home to define what's required for life makes sense. If life can only develop on a double planet like ours, we may very well be alone: if not in the universe, then in this galaxy.

Some of the thousand-plus planets orbiting other stars that we've cataloged so far are odd: but not one is a double planet like Earth.

Living With Wobbles

Lissauer's team used more refined math, and today's number-crunching machines, for simulations of Earth without the moon over long periods: up to 4,000,000,000 years.

Sure enough, Earth wobbled more: but not nearly as much as earlier math predicted. For shorter periods, like 100,000,000 years simulation runs, Earth's tilt never exceeded 40° or dropped below 10°.

Life on Earth might look different if we'd gone through the wider seasonal changes: but I strongly suspect that life would have gone on.

Today's climate isn't what it used to be: and never was. At the moment, we're in an interglacial period with another round of continental glaciation on the way: or at the end of the latest ice age cycle. Either way, Earth is cooler than "normal:" by Eocene standards. (January 10, 2014)

Scorpions, Cockroaches: and Humans

(From MIT News Office, used w/o permission.)

Life had endured through several billion years of hard times before the on-again, off-again ice age that started about 2,580,000 years ago.

Massive volcanic eruptions triggered rain with the acidity of lemon juice, killing a breathtaking variety of plants and animals 252,000,000 years back.

Asteroid impacts reset Earth's climate every hundred million years or so; and a 10,000,000-plus year winter sent glaciers down to the equator. Three times. (Cryogenian period, Wikipedia) (November 29, 2013, September 29, 2013, August 30, 2013)

Critters like the saiga antelope, giant pandas and the kakapo might not survive another major ice age. Not on their own. Giant pandas and the kakapo are cute, though, so I suspect that they'd keep going: in zoos.

As for humanity, we'll probably look a little different 1,000,000 years from now: but I think we'll prove at least as durable as scorpions, cockroaches, and rats. (November 29, 2013)

Getting a Grip About "Class M" Planets

(from Beau.TheConsortium, via Space.com, used w/o permission)

The old Star Trek series added "class M planet" to the language. Most of those "strange new worlds" bore a strong resemblance to either southern California or the Desilu Studios Backlot: but considering the show's budget and 1960s technology, I think they did a pretty good job.

Folks who were serious about science, or speculative fiction for that matter, realized that we weren't likely to find that many planets where conditions were so very much like one of Earth's more hospitable spots.

A few years back, when we'd learned more about plate tectonics and were cataloging nearly-Earth-size exoplanets, some scientists suggested that Earth might not be a typical life-supporting world.

Earth may be about as small as a planet can be, and keep recycling ocean basin crust as the eons roll by. (Apathetic Lemming of the North (December 5, 2009))

Others crunched numbers and decided that "uninhabitable" planets circling red dwarfs, although not "Earth-like" in the Star Trek sense, might have habitable zones. (May 10, 2013)

If we do discover life on other worlds, I'm pretty sure that much of what we find will be at least as odd as critters from Earth: worms living in near-boiling water; animals that die if exposed to oxygen; and bombardier beetles. (January 31, 2014; Apathetic Lemming of the North (April 9, 2010))

If we meet people who aren't human: we may learn that Earth was listed as uninhabitable. Their probes had found our double planet: but nobody imagined that life could survive, let alone thrive, on a world with our violent tides.

And that's yet again another topic.

Related posts:

• Living with risk
  • "Tunguska and Chelyabinsk Airbursts: Risk, Rocks, and Readiness"
    (November 8, 2013)
    Particularly
    • Earth: A Nice Place to Live, But - - -
    • Time for an Early Warning System
  • "Asteroids, Comets, and Doing Our Job"
    (September 29, 2013)
  • "A Russian Meteor, Ancient Craters, and Coming Events"
    (July 26, 2013)
    Particularly
    • A Bad Day for Dinosaurs
    • Asteroids, Spaceships, and a Little History
  • "Ethics and Asteroids"
    (February 20, 2013)
    Particularly
    • An Asteroid
    • A Meteor
    • Asteroid 99942Apophis, Greenwich Village, and Atlantic City
  • "Asteroid Apophis: No 'Earth Shattering Kaboom' "
    Apathetic Lemming of the North (January 11, 2013)
    Particularly
    • Asteroid Impact: 'What If?'
• Searching for life
  • "Planets, Creation's Afterglow, and Double Stars"
    (February 7, 2014)
    Particularly
    • Life on Earth and, Maybe, Elsewhere
    • God and the Universe, Faith and Science
    • Planets and Double Stars
  • "Strange New Worlds; Getting a Grip about Space Aliens; and a Fossil Fish"
    (January 17, 2014)
    Particularly
    • Little Green Men and the Almighty Buck
    • Rungs on the Ladder of Creation
    • A Sense of Scale
  • "Life in the Universe, God, and Getting a Grip"
    (October 17, 2013)
    Particularly
    • Increasingly Informed Speculation
  • "Three Es: Exoplanets, Exobiology, and Evolution"
    (October 4, 2013)
    Particularly
    • Science and Me
    • Evolution: Real and Imagined
    • Life in the Universe?
  • "Robots, a Martian Dune, and Mapping a Billion Stars"
    (May 10, 2013)
    Particularly
    • Nifty Name, Oldish Idea
• Being human
  • "Smallpox, Science, and Silliness"
    (February 12, 2014)
    Particularly
    • Beware the Tiny Cows!
    • Fear and Weirdness, 1722
    • Preachers, Priests, and the Pope, 1814
  • "Scorpions, Acid Rain, and the Great Dying "
    (November 29, 2013)
    Particularly
    • Prophets of Doom
    • Manure, Killer Fog, Smog, ...
    • Humans: Doing Our Job
  • "Fusion Power, Terraforming, and Old Dutch Windmills"
    (October 11, 2013)
    Particularly
    • Terraforming and Windmills
    • Fusion Power Plants: Another Step Closer
    • One Step at a Time
  • "Designed as Stewards"
    (March 17, 2013)
    Particularly
    • Made in the Image of God: A Scary Thought
    • "With Great Power ..."
  • " '...The Man With the X-Ray Eyes,' the Tuskegee Experiment, and Seeking God"
    (February 10, 2013)
    Particularly
    • Powerful, Yes; All-Powerful, No
    • Technology and Responsibility