Earth's Satellite

Image by John Fowler

The Moon is Earth's only natural satellite.

The Moon is a prominent and receding presence in our lives. Silent and invariable, its waxing and waning phases, its visual presence and absence, imprints us with the cyclical patterns of nature.

The Moon's prominence in the evening sky, and its predictable phases, have influenced art and created mythologies since antiquity.

A full luminous Moon reveals the same face because, like the tuned gears of a watch, it is in synchronous rotation with Earth.

“Her antiquity in preceding and surviving succeeding tellurian generations: her nocturnal predominance: her satellitic dependence: her luminary reflection: her constancy under all her phases, rising and setting by her appointed times, waxing and waning: the forced invariability of her aspect: her indeterminate response to inaffirmative interrogation: her potency over effluent and refluent waters: her power to enamour, to mortify, to invest with beauty, to render insane, to incite to and aid delinquency: the tranquil inscrutability of her visage: the terribility of her isolated dominant resplendent propinquity: her omens of tempest and of calm: the stimulation of her light, her motion and her presence: the admonition of her craters, her arid seas, her silence: her splendour, when visible: her attraction, when invisible.”
― James Joyce, Ulysses

The Word

The word Moon is derived from the Old English mona, the Germanic mene, the Middle Dutch mane, the Old Saxon mano, as well as from Old Icelandic and Danish influence. Luna is the Latin word for Moon. The late Middle English word Lunar meaning ― of or related to the Moon ― is derived from the Latin luna.

Genesis

Depiction of Theia
crashing into Earth

The Moon wasn't always a satellite. The Giant Impact Hypothesis is the favored narrative for the genesis of the Moon.

Planetary scientists believe the Moon settled into its current configuration about 4,500,000,000 yeas ago. Anatomically modern humans appeared on Earth about 200,000 years ago which means the Moon is more than 20,000 times older than us.

The Giant Impact Hypothesis posits that the Moon was formed from debris caused by a glancing collision between the a protoplanet Earth and a planetoid about the size of Mars called Theia ― named after the mythical Greek Titan and mother of Selene, the goddess of the Moon.

Evidence supporting the Giant Impact Hypothesis is:

• Earth's spin and the Moon's orbit having similar orientations, and
• Stable isotope ratios of Earth and Moon rock are identical which infers a common origin.

The Moon has been Earth's tethered companion for billions of years. For thousands of years the Moon has awed and inspired artists, writers, philosophers, and natural scientists.

We all shine on...like the moon and the stars and the sun...we all shine on...come on and on and on...
― John Lennon

Moon spots in the forest, winter
Arkhip Kuindzhi (1842–1911)

REFERENCES

• Broken World by Brian Koberlein, 25 March 2014.
• Giant Impact Hypothesis, Wikipedia.
• Origin of the Moon in a giant impact near the end of the Earth's formation, Robin M. Canup & Erik Asphaug, Nature, Volume 412, 16 August 2001.
• Science Diction: The Origin Of The Word ‘Moon’, Science Friday, 20 January 2012.
• Ulysses, James Joyce, Sylvia Beach 1922.

Tangerines and String Quartets

The origin of life eludes us. The leap from organics to organisms isn't definitively understood.

I believe a leaf of grass is not less than the journey-work of the stars.
— Walt Whitman, Song of Myself

The desire for us to understand existential unknowns produces limits on the range of possibilities. The range of possibilities provide the guideposts to inquiry. Within possibilities emerge the paths of plausibility, some more fruitful than others.

The origin of life, and the nature of the living, remains elusive. Still there are established characteristics, like heredity — the self-replicating passing on of information — that links all organisms to the simplest cells and the most basic elements on the periodic chart.

What do they call it…the primordial soup? The glop? That heartbreaking second when it all got together, the sugars and the acids and the ultraviolets, and the next thing you knew there were tangerines and string quartets.
— Edward Albee, Seascape

The microcosmic gods of life seem to be nucleic acids and proteins. The earliest detectable life arrived 3.6 to 3.8 billion years ago in the form of simple cells.

Over billions of years, simple replicating cells evolved into complex organisms. This came about against the deterministic cleave of natural selection.

The one thing we have in common with all other living things is that for nearly four billions years our ancestors have managed to slip through a series of closing doors every time we needed them to.
— Bill Bryson, A Short History of Nearly Everything

Humans are comparative newcomers arriving 200,000 years ago, yet our organic and earlier inorganic ancestry, is traceable to cosmic stardust.

Years Ago	Event
4.6 billion	Earth began circling the sun
3.6 billion	Arrival of simple cells - Prokaryotes
3.4 billion	Arrival of cyanobacteria performing photosynthesis
2 billion	Arrival of complex cells - Eukaryotes
1 billion	Arrival of multicellular life
600 million	Arrival of simple animals
550 million	Arrival of bilaterians, animals with a front and a back
500 million	Arrival of fish and proto-amphibians
475 million	Arrival of land plants
400 million	Arrival of insects and seeds
360 million	Arrival of amphibians
300 million	Arrival of reptiles
200 million	Arrival of mammals
150 million	Arrival of birds
130 million	Arrival of flowers
66 million years ago	Departure of the pterosaurs and non-avian dinosaurs, in the Cretaceous–Paleogene extinction event.
60 million	Arrival of primates
20 million	Arrival of Hominidae or great apes
2.5 million	Arrival of the genus Homo - human predecessors
200,000	Arrival of anatomically modern humans

An insatiable curiosity and judicious hypothesis testing will eventually lead us to many of the answers we seek. But the satisfaction of each answer will be momentary. The side effect of each aha! moment is a set of new questions. This is the quest of science.

The Existential Ledger

On the known side of the ledger, is the precedence, preponderance and rigor of established science. On the unknown side, it must suffice that the nature of life will reveal itself in fits and starts.

We're continually pinged with incoming data. Revelations necessitate reconciling of our existential accounts. We only know what we know at a given time. What remains is pontification or poetry.

REFERENCES

• Lonely Planets: The Natural Philosophy of Alien Life, David Grinspoon, Harper Collins, November 2003.
• Timeline of evolutionary history of life, Wikipedia.

Subterranean Mystery

Journey to the Centre of the Earth Subterranean ocean illustration by Edouard Riou

In Jules Verne's science fiction novel Journey to the Centre of the Earth, a professor, his nephew and their guide descend into the Snæfellsjökull volcano in Iceland, then travel deep into the Earth before emerging from the Stromboli volcano in Italy.

Much of what Jules Verne wrote about the Earth's interior has been shown to be demonstrably fictional since Journey to the Centre of the Earth was published in 1864.

Science, my lad, is made up of mistakes, but they are mistakes that are useful to make, because they lead little by little to the truth.
— Jules Verne

Verne's tale of sub-crustal Earth adventures, lit above by an electrically charged gas, contained a vast subterranean ocean.

A subsurface ocean might seem far-fetched, but recent findings indicate there might indeed be a subsurface reservoir.

A team of scientists lead by Graham Pearson have found the hydrophilic mineral ringwoodite in Earth's mantle at a depth of 400 to 600 kilometers indicating there could be vast subterranean water repository.

Brown diamond containing a ringwoodite sample. Photo: Richard Siemens, University of Alberta

"This sample really provides extremely strong confirmation that there are local wet spots deep in the Earth in this area. That particular zone in the Earth, the transition zone, might have as much water as all the world's oceans put together."
— Graham Pearson, University of Alberta

REFERENCES

• Alberta scientists find water reservoirs deep below Earth's surface that could rival oceans, Andrea Sands, Edmonton Journal, 12 March 2014.
• Earth has a secret reservoir of water, scientists say, Richard Ingham, Sydney Morning Herald, 13 March 2014.
• Hydrous mantle transition zone indicated by ringwoodite included within diamond, D. G. Pearson, et. al., Nature, 12 March 2014.
• Journey to the Centre of the Earth, by Jules Verne 1864.

Terra Firma

Dating of the oldest rocks on Earth sheds light on how the planet cooled to a life-supportable solid crust from a nascent sphere of molten magma. A cathodoluminescence image of a 400-mm zircon crystal found in a remote part of Western Australia known as Jack Hills is dated at 4.4 billion years old.

A zircon crystal estimated to be 4.4 billion years old
John Valley, University of Wisconsin

Penetrating so many secrets, we cease to believe in the unknowable. But there it sits, nevertheless, calmly licking its chops.
― H. L. Mencken

Genesis Rock from the moon.

To date, Jack Hills zircon crystals are the oldest crystals discovered in-situ on the face of the Earth.

The Genesis Rock, collected by Apollo 15 astronauts during their moon landing, has been dated at 4.46 billion years. Although it originated on the Moon, it is one of the oldest known rocks.

Scientists hypothesize that the Earth began orbiting the sun about 4.6 billion years ago. As a molten protoplanet, the Earth needed a cooling period before a rocky crust was formed that was cool enough to support carbon-based organisms. It cooled from its molten state to solid earth. Terra firma is Latin phrase meaning solid earth. Terra translates to earth. Firma translates to solid.

"You're on Earth. There's no cure for that."
— Samuel Beckett

The dating of the Jack Hills crystal suggests that by its 200-millionth birthday, the Earth had a rocky crust.

Chemical hints in the Isua sediments found on the southwestern coast of Greenland suggest life existed as early as 3.8 billion years ago.

"What are men to rocks and mountains?"
— Jane Austen, Pride and Prejudice

REFERENCES

• 4.4 Billion-Year-Old Crystal Is Oldest Piece of Earth, Elizabeth Landau, CNN, 25 February 2014.
• 4.4 Billion-Year-Old Crystal Is Oldest Piece of the Earth’s Crust, Allison Eck, PBS, 24 Feb 2014
• At 4.4 Billion Years Old, Oz Crystals Confirmed As World's Oldest, NPR, Nell Greenfieldboyce, 24 February 2014.
• Oldest dated rocks, Wikipedia.
• Terra Firma, Wikipedia.
• The Isua Rocks, Douglas Page, 2000.

Cosmic Newcomers

Humans are cosmic newcomers.

It is commonly held that our home planet coalesced from cosmic dust and gas. Carbon-based life is a relatively recent event. Life is a viral outbreak that occurred billions of years ago on Earth.

The profundity of carbon-based life is that chemical organisms replicate and grow in complexity.

Life, and more specifically human life, is a latecomer to the existential table.

Humans are a puff, a wink, or a dream.

Men come and go, cities rise and fall, whole civilizations appear and disappear-the earth remains, slightly modified. The earth remains, and the heartbreaking beauty where there are no hearts to break....I sometimes choose to think, no doubt perversely, that man is a dream, thought an illusion, and only rock is real. Rock and sun.
― Edward Abbey, Desert Solitaire: A Season in the Wilderness

Many geologists think our atmosphere and oceans arrived on the Earth about 4 billion years ago either from a series of volcanic eruptions or from comets colliding with earth that released water and gases.

Evidence of Life

How long before life emerged from the chemical soup of oceans and atmosphere? The first evidence of life, inferred from the chemical record (e.g., Carbon isotope C-12 to C-13 ratio), dates from 3.85 to 3.65 billion years ago. The first undisputed fossils appear in rocks about 3.2 billion years ago. Human footprints appear 1,500,000 years ago. The first humans fossils known to us are from 195,000 years ago.

Artifact Years Ago Atmosphere and Ocean 4,000,000,000 Life 3,850,000,000 Fossil 3,200,000,000 Human Footprint 1,500,000 Human Fossil 195,000

I stand for what I stand on.
― Edward Abbey

REFERENCES

• Carbon-based Life, Wikipedia.
• How did our planet form?, Kate Ravilious for The Guardian, 27 April 2008.
• Oldest Human Footprints With Modern Anatomy Found, John Roach for National Geographic News 26 February 2009.
• Oldest Human Fossils Identified, Hillary Mayell for National Geographic News, 16 February 2005.
• When Did Life on Earth Begin? Ask a Rock., David Tenenbaum for Astrobiology Magazine, 14 October 2002.