Late Heavy Bombardment / Big Wednesday

I have a vague memory of playing a game in gym class called bombardment. You divide the class into two groups - did we ever pick teams when there was a teacher around? - and stand around throwing balls at each other. There must be more rules than this, but I recall only the joyous bombardment. 

Today in Ian Time it’s a Wednesday in mid-late January. I’m in Hawai’i visiting old friends and recording ocean sounds for a new film. All week everyone has been talking about the big swell soon to bombard the north shore of Oahu. A famous surf contest - only held when the swells hold a 40’ minimum wave face - was cancelled but it’s still expected to be big enough (25’-30’) to draw legions of surfers to Waimea Bay. Still vaguely on East Coast Time, I wake before dawn and listen to the rising roar of the dark waves. They strike the basalt shore every 10-15 seconds, each wave a liquid packet of blue-white energy unburdening itself after a long windy romp across the ocean. 

 Comet riders.

Comet riders.

Last night we watched as Comet Lovejoy slid across the zenith, not far from the Pleiades and the Hyades. My time-lapse exposures were a mite shaky, and we fancifully imagined it was the colossal waves pounding the soil just steps from the camera’s tripod. (It’s also highly possible I left the lens’ image stabilizer on, but human error is always a more stultifying explanation.)

This week, in Earth Time, it’s the Late Heavy Bombardment. We’re about 700 million years since the roiling, tumultuous formation of the planet, but the relative quiet of the Hadean Era is now interrupted by a rain of rocks from space. Many of the craters on the moon are being formed during this bombardment. (Rocks brought back by the Apollo astronauts will suggest the timeframe.) Mercury is getting some scars, too. Here on Earth it’s a cascading fireworks show of falling ice and rock, such that few corners of the planet are spared. The surface grows molten anew, pockmarked with round craters.

Eventually, traces of the bombardment on Earth will mostly be wiped clean by erosion, subduction of the plates, and other geologic processes. Old scars will be smoothed and filled by time. But geologists will find traces here and there of rocks that survived the bombardment from our earlier days. Geochemists will analyze scraps of surviving meteorites and fallout dust, counting iridium spikes in an attempt to suss out the origin of the LHB. Physicists will theorize that the orbits of the gas giants Jupiter and Saturn gravitationally perturbed asteroids and/or comets, sending them hurtling towards the wee rocky planets of the inner solar system. As if, in gym class, one of my burlier classmates had shown up with a slingshot. 

 Mischievous Jupiter!

Mischievous Jupiter!

I’ll return to terminology - what’s an asteroid, a comet, a meteor, a meteoroid, a meteorite, a bolide - later, but for now I want to say a word of thanks to my 5-year-old friend Sal, son of my friends Adam & Amanda in Vermont. Sal shares my love of planets and has agreed to illustrate a few of them (in this case, that mischievous slingshotter Jupiter, above shown with its bevy of moons) throughout my spring trek through time. Thanks Sal!