Saturday, December 5, 2009

Earth May Not Be a "Class M" Planet

"Super Earths May Be Superior at Fostering Life" (December 1, 2009)

"Astronomers have discovered hundreds of Jupiter-like planets in our galaxy. However, a handful of the planets found orbiting distant stars are more Earth-sized. This gives hope to astrobiologists, who think we are more likely to find life on rocky planets with liquid water.

"The rocky planets found so far are actually more massive than our own. Dimitar Sasselov, professor of astronomy at Harvard University, coined the term 'Super-Earths' to reflect their mass rather than any superior qualities.

"But Sasselov says that these planets – which range from about 2 to 10 Earth masses – could be superior to the Earth when it comes to sustaining life.

"On Shaky Ground

"It is said that 99 percent of all species that ever lived have gone extinct. Earth, it seems, is a tough place to call home. Our planet has gone through Ice Ages and global warming trends, it has been hit by comets and asteroids (leading, in one case, to a mass extinction that felled the mighty dinosaurs), and the amount of oxygen in the atmosphere has risen and fallen over time. Our planet is always in a state of flux, and life must adapt to these changes or die...."

The article points out that earthquakes and volcanic eruptions, although unarguably inconvenient-to-disastrous, are a big part of why Earth is habitable. Without plate tectonics sucking the lithosphere down along the oceanic trenches, recycling it up through volcanoes, many of the elements needed for life would be chemically locked into the rocks. Which may be what happened to Mars. The planet has some whacking great volcanoes - which may have been active in cosmically recent periods - but no mechanism for pulling the crust down for recycling.

Venus? It's almost as massive as Earth, and has (small) continents, but no sign of the sort of hectic re-organization of the surface that we're used to. And extreme pressures and temperatures on the surface.

We don't know enough - yet - to be sure, but there's speculation that Earth is just barely massive enough to support plate tectonics - and hence, life. Venus didn't quite make the grade.

Which brings up those "super-Earths." There are quite a few planets, orbiting other stars, that appear to be mostly rock and metal, like Earth - but much more massive. Applying what we're pretty sure about when it comes to planetary physics, these oversize analogues to Earth would have thinner crusts and (much) more active plate tectonics.

And, might therefore be much better suited for life than Earth is.

Back to the article:

"...Superior Alien Civilizations

"Missions like the Kepler space telescope, launched just this year, could help astronomers find many Earth-like planets in the years to come. Sasselov estimates there could be a hundred million habitable Super Earth planets just in our Milky Way galaxy. He predicts we'll find 50 to 100 Super Earth planets in the next 5 years.

"The existence of so many Super Earths could explain the "Fermi Paradox" of why aliens have not contacted us. If our lower mass planet does not have the ideal conditions for life, alien explorers would be less likely to look to us, choosing instead to target the many Super Earths in the galaxy.

" 'Earth is a marginal planet when it comes to conditions we would like to see for complex life to sustain itself,' Sasselov notes. 'In the family of Earth-like planets, the sweet spot for complex chemistry and biochemistry to emerge and sustain itself lies in planets larger than the Earth.'

"If aliens on Super Earths ever decided to investigate Earth to see if such a tiny world could harbor life, they would have a harder time sending rockets into space because of the higher gravity on their planet. 'This could be another answer to the Fermi Paradox,' says Sasselov, 'but it's not an insurmountable problem.' It could even be that because of their deeper gravity well, aliens living on Super Earths would have to develop a technology superior to our chemical rockets in order to explore the universe...."

One of the assumptions that people who create science fiction stories like the various "Star Trek" series make is that
  • There are space aliens all over
  • Who come from planets a whole lot like Earth
  • Aren't all that far from human in
    • Shape
    • Size
    • Technology
      • Often as not
And, very often, the space aliens even think the same way we do, and are just about as interested in visiting strange new worlds, seeking out new life and new civilizations, and rushing in where angels fear to tread.

Funny thing, though: flying saucer enthusiasts notwithstanding, there's precious little indication that anybody from the galactic community has been here in the last several thousand years.

If there really were Vulcans, Klingons, Romulans, Ferengi, and all the rest out there, I'd expect us to be finding uses for the space-alien equivalent of 50-gallon drums. (See "Brief Historical Background of Steel Drums," Jeannine Remy, Idaho State University) And, of course, selling genuine Earther trinkets and performing authentic dances. Like dis-ko.

Doesn't Everybody Dream of Flying?

Maybe there's nobody else out there, or maybe most people live on planets where it's really, really hard to get into orbit. Or maybe we live on a planet where, for the last few million years, the environment favored creatures with a bit more brains than usual: who were willing to take insane risks.

Like flying.

Or riding a tower of explosives to an airless hell of barren rock. Several times.

Across the galaxy, most people may be staying quietly at home, playing the local equivalent of pinochle or Mahjong, or whatever: and shuddering at the memory of crazy Uncle Eddy, who once made something he called a "raft," but - thankfully - never tried using it himself.

I've wondered, first, if there's anybody else in the universe. And, if there is, how they're like us - and, more interestingly, how they're not. It has occurred to me that Homo sapiens sapiens may be - odd.

Look at it this way: compared to just about every other animal, we're huge. Sure, there are a few creatures bigger than us: elephants, hippos, whales, for example. But most species are smaller. Much smaller.

Being big has its advantages, but not for flying creatures. Which is why birds are almost all smaller than we are. And the ostrich, that's big enough for us to ride, doesn't fly. At all.

Face it: human beings just aren't made with flying in mind. But we've dreamed about flying for a long, long time. Think Daedalus and Icarus. And as soon as we developed materials that were light and strong enough to make wings big enough to support our mass, we literally took off. One of my memories of San Francisco is the sight of hang-gliders, wheeling above the cliffs by the Pacific.

Big, heavy, sincerely ground-bound creatures: that want to fly? And, once they're given wings, have all the circuits needed to handle soaring flight?'

And are crazy enough to try? When generations of experience demonstrated that trying to fly resulted - best-case scenario - in a swift death?

That may not be as "natural" as we think.

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