Impacts, extinctions and life

Asteroids, gotta love the yummy things.  For example: asteroid 5748 Davebrin made its closest approach to Earth April 4. (1.7 AU). Hey! I can see my house from here! Come on guys, it's mine so let's go melt it down and get rich.

And yes, this means it is time for one of our "look up!" postings, here on Contrary Brin!  For example...

Many of you recall the thrilling sight of Jupiter getting whacked multiple times by the comet Shoemaker-Levy 9 in 1994. Now Phil Plait reveals some video taken this month by an amateur astronomer, which appears to reveal another one smacking the King World. And hints there may have been another collision some years ago.

Yipe!  This’ll affect the statistics, for sure. No fluke, after all.  As Goldfinger said: "Three times, Mr. Bond, is enemy action."

What do we know about the asteroids out there? The website Asterank offers a scientific and economic database of over 600,000 asteroids, as well as wonderful 3D animation. This extensive database gives a perspective to the places to go within our solar system, including each asteroid’s mass and composition.. .and likely profitability for mining. You can even hitch a ride on one of the objects mapped and see where it takes you! And yet, this list is made obsolete with each day’s new discoveries. Also I wonder if the estimated profits take into account the fact that gold, silver and other metals prices will plummet when asteroid mining truly delivers its promised riches. The pursuit of a few forward looking visionaries such as Planetary Resources and Deep Space Industries. 

== Impacts and Extinctions ==

Speaking of planet smackers, we’ve known since the 1980s that asteroids and comets have had a major “impact” on the history of life on Earth, and not only the dinosaur killing and Cretaceous-ending rock that impacted the Yucatan, 66 million years ago.  Researchers such as Raup & Sepkoski have plumbed the paleontological record for exceptionally sudden die-offs of numerous species and found that it appears to happen at roughly 26 to 30 million year intervals, a possible cycle which has been studied more closely by Michael Rampino of New York University. (Keep an eye for Michael’s new book on the subject, this coming year.)

What could provoke mass extinctions at such a very long-but-regular interval? Well, decades ago Daniel Whitmire and John Matese proposed – in parallel with Luis Alvarez and his team -- the notion that this scale could represent the orbit of a distant planet X, whose rhythmic passages through the cometary Oort Cloud surrounding our sun might perturb clusters of iceballs, sending them plummeting toward hapless Earth,  This theory for mass extinctions appeared in the journal Nature in 1985.  

The notion of a Planet X was given added impetus lately when researchers Konstantin Batygan and Mike Brown from Caltech inferred its existence based on orbital anomalies seen in objects in the Kuiper Belt, a disc-shaped region of comets and other, larger bodies beyond Neptune. Though at more than 1,000 a.u., it might be very weakly bound in orbit around the sun.  

Problem.  Not all of those rhythmic mass extinctions in the past show any clear signs of being cause by impacts.  Several others evidently happened due to massive releases of volcanism from the Earth’s interior, whose traces are still seen in basaltic flow formations called the Siberian and Deccan “traps.”  

There is an astronomical phenomenon that has timing on the scale of tens of millions of years -- our solar system's orbit around the Milky Way galaxy.  While a full orbit takes more than 200 million years (at our distance from galactic center), there is a way to match intervals. In fact, back in the 1980s I had a paper suggesting we'd get this timing from some ferocious object that laps us every 30 million years or so, orbiting closer to galactic center.  See my earlier article:  "The Deadly Thing at 2.4 Kiloparsecs."

Far fetched? Okay here's another interval match. Our sun's path dips in and out of the galactic plane  - like a pleated skirt - more often. In fact, pretty much at that 30 million year interval. 

This led some to ponder whether our passage through the plane might, each time, result in collisions with gas or dust clouds that trigger comet infall from a disturbed Oort cloud. Interesting! But that theory had several problems.  
 (1) Sometimes there would be a cloud and sometimes (more often) not.  
 (2) the needed Planet X would orbit so far out that its ties to the Sun might be tenuous. And
 (3) again, some extinctions seemed more related to volcanism than rock or comet impact.

So Michael Rampino has suggested another concept -- that dark matter in the galactic rim may be a factor causing extinctions and massive volcanism. If dark matter clusters in the skirt of the galaxy, then each time we pass through, it might both disturb the Ooort Cloud a bit and fill the Earth's core with enough DM to heat it just enough to spur added volcanos.  Huh!  What an idea.

See also Lisa Randall's recent book exploring this topic - Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe.

Oh. In a possibly related item, analyses of Iron 60, a decaying isotope, in sub-ocean crustal core measurements, has revealed likely supernovae relatively nearby (within a few hundred light years) occurring 1.5 million, 2.3 million and 8 million years ago. The last of these might bear some relation to the start of the Ice Ages.  

Fascinating. And it just goes to show.  The universe is a rough neighborhood.  We may have been lucky.

== The lesson from all this? ==

We need to grasp the tiller of our destiny.  That means learning not to make the sort of big mistakes that Jared Diamond talks about in his book Collapse: How Societies Choose to Fail or Succeed, grievous blunders that brought ruin to other societies. Like eco-mismanagement. Only we may be doing it on a planet-wide scale.

And learning how to prevent all sorts of natural disasters from ending our hopes, as well.  It has been suggested that: "There are no more dinosaurs, because they lacked a space program."

Well said. 

Though of course there are still dinosaurs.  Descendants of the ones that at least learned to fly.  If you cannot prevent disaster, at least be able to ride it out.  We need both anticipation and resilience.

 Always on the lookout for such tasty aphorisms of wisdom, I perked up when a member of this community – Mike DeSimone -- offered another quotation that I intend to use:  

“Humanity has two possible destinations: stars or strata.”