A (6)

34 AUSTRALIAN SKY & TELESCOPE JULY 2016

themasaseriesofwaypoints,eachproposedorigin

marking a different stage in the ‘hominisation’ of the

planet, with no single, correct moment of genesis.

But if geologists are going to formalise the definition,

theyneedtopinittoaspecificstageintherockrecord.

Soletmeoffermyownmodestproposalfora‘golden

spike’ to mark the Anthropocene. If we must choose one

geological deposit that announces the human presence,

I would suggest the area of Mare Tranquillitatis, where

Apollo astronauts first stepped onto another world,

leaving a flag, machines and footprints.

Those boot marks will fade in a few million years

as micrometeorites grind them into the dust, but signs

of our presence, including the alien artifacts we left,

will be detectable for as long as there is an Earth and

a Moon. These lunar landmarks could not have been

made by a species without world-changing technology.

This altered landscape also captures the moment we

first looked back and saw the unity of our home and

our common destiny with all life on our planet.

Of course, as an actual proposal for correlating

geological events on Earth, a Tranquility Base golden

spike is ridiculously impractical. But so what? There

is nothing practical about the decision to formalise

the Anthropocene Epoch. Any geologists, human or

alien, studying our time millions of years from now

will not care about our nomenclature. This is all about

symbolism and our self-image as we confront the

challenges of this new age. So, I know I’ll propbably

lose, but I vote for Tranquility Base. ✦

A

far-future geologist studying Earth history

would note that our time was one of sudden and

unprecedented changes. Could this be a type

of transition that other planets also go through, when

cognitive systems begin to influence global systems?

I’ve written before about the proposal to

formally rename our current geological epoch the

‘Anthropocene’ to acknowledge the fact that humans

have become a major force of global modification.

Within geological and other academic circles it’s

been contentious but fruitful — sparking interesting

debates about how we humans should regard, and

attempt to guide, our own planet-altering presence.

But there’s no consensus over when exactly this

humanised age began. Did it arise with the first

atomic bomb explosions in the 1940s? If there was

ever a time when we started to realise we were all in

the same boat, shooting holes in the hull, it was the

dawn of the nuclear age. We began to see what we’d

become, and it left an indelible isotopic signature. This

provides what geologists call a ‘golden spike,’ a unique

time stamp associated with an event or transition.

Others place the onset of the Anthropocene at the

beginning of the Industrial Revolution, or thousands

of years earlier when we first undertook large-scale

modification of landscapes.

These arguments are most valuable if we read

them as a protracted dialogue on how humanity has

journeyed from being just another hominid species

in East Africa to the global force we are today. I view

The golden spike

of Tranquility Base

NASA

DAVID

GRINSPOON

is an

astrobiologist,

author, and

senior scientist

at the Planetary

Science

Institute. Follow

himonTwitterat

@DrFunkySpoon.

Cosmic Relief

A modest proposal: the Anthropocene began with the lunar landings.