We are stardust, or so they say.
Long ago, giant exploding stars spread clouds of cosmic dust.
Some of the dust coalesced into our solar system.
Over time, on this planet, Nature put it to use in an increasingly complex experiment
called life.
We've been using components of the dust cloud - iron, aluminum, and silicon -
to look back out into space.
What we've learned has only deepened the mystery of our place in the universe.
Scientists and philosophers alike want to know: Is life a fluke,
a lucky ro ll of cosmic dice?
Or is the universe somehow fine-tuned to allow life to arise, and flourish
throughout the cosmos?
We are living in an age of precision cosmology. With new generations of giant telescopes on
land, and specialized instruments in space,
astronomers are probing the forces that shaped our universe.
They are documenting its behavior on the largest of scales
going back to the first micro-moments of its existence.
They are charting its evolution hundreds of billions of years into the future.
For all we have learned about the universe as a whole, profound questions remain:
what does it all add up to? How do you explain this rise of complex life, intelligent life?
Some scientists point to the finely tuned interactions of gravity, electromagnetism,
and the strong and weak nuclear forces within the atom.
If the strength of any these forces had varied only slightly, the universe might after
have flown apart and dissipated moments it was born.
Or gravity might have reined it in, forming one giant black hole.
In either case, the universe would have no galaxies, stars, planets, or life.
Was the basic layout of physical laws a coincidence? Or was it somehow meant to be?
One answer, from what's often known as the Anthropic principle, holds that the universe
is uniquely suited to spawn life.
To some, this implies that the universe is imbued with purpose. We, who are able to observe
the universe and document its workings, are proof that this is so.
But that conclusion, which can't be falsified, is more of a religious or philosophical concept
than a scientific one.
Consider the broad arc of cosmic history. Trillions upon trillions of years from now,
all the stars in the universe will slowly burn out. Much of the matter we see in galaxies
will gradually drift in toward their centers and be swallowed by black holes.
All will go dark, eventually fading into the dark reaches of infinity.
Overall, the evolution of life, and intelligent life, is a minor event, probably confined
to a relatively narrow window of time.
There's another way to ask the question. Are the processes that give rise to life central
to the way the universe works?
In search of answers, we'll explore the origin of two of life's most important components:
water and dust.
Our story begins in the earliest moments of time, when the universe was awash
in hydrogen gas.
Gravity drew it into denser and denser regions, where the earliest stars were born.
Generation after generation of stars formed and died.
In the larger ones, fusion produced the elements carbon and oxygen.
They became, by mass, the third and fourth most abundant elements in the universe.
Heavier elements followed, including those created in the violent death of large stars.
This animation depicts a supernova spotted by Chinese astronomers in the year 1054 AD.
The star was utterly destroyed, except for a spinning ultra-dense core the size of a
city, a neutron star, and an expanding cloud of gas and dust.
Astronomers have been poring over the Crab nebula, still growing at a rate of a thousand
kilometers a second.
What they found is that the filaments of matter that roared out of the blast contain large
volumes of dust, an array of mostly carbon or silicate compounds that absorb visible
light.
These solid particles are crucial for the formation of solar systems. Within the Crab
nebula, there is enough dust to make some 30 to 40,000 Earths.
Over time, and after countless stellar explosions, dust has collected in dense pockets throughout
our galaxy.
But dust grains can be found throughout intergalactic space as well.
Some might have come from the earliest supernovas.
There is another source as well.
Since the 1960s, astronomers have been studying bright beacons of light that shine from the
centers of distant galaxies.
A quasar's power source, they've found, is a black hole that has grown to millions, even
billions, of times the mass of our own sun.
The thinking is that magnetic fields leap off a disk of matter that's spiraling into
the black hole, drawn by its extreme gravity. These fields channel a portion of the inflowing
matter out into powerful particle beams.
The jet is part of a larger rush of matter away from the black hole.
You can see it in a large spiral galaxy called NGC 3783, 30 million light years from earth.
Astronomers used the Very Large Telescope array in Chile's Atacama Desert to peer into
the core of this galaxy to study the environment of a supermassive black hole.
From a disk of matter flowing into the black hole, intense radiation had created a dusty
wind that is moving up and away from the black hole.
The source of the dust is likely generations of giant stars that lived and died in the
galaxy's central region.
Black hole winds are now thought to have had a major impact on the universe at large.
You can see it in a simulation of early cosmic evolution.
It starts 12 million years after time zero, and evolves within a volume 350 million light
years across.
Not everything is known, including the nature of a dominant substance known as dark matter.
Gravity draws matter into filaments, where it heats up, forming a vast luminous web.
In time, tens of thousands of galaxies take shape.
The action heats up where filaments meet.
Giant bubbles of hot gas form and expand outward, pushing well beyond the central galaxies.
This happens when galaxies merge, sending streams of matter into black holes that lie
in their centers. These monsters, in turn, blast inflowing matter out in jets and winds.
This seeds the wider universe with dust and gas.
In our galaxy, dust has collected in star-forming regions, like the Orion Nebula, 1500 light
years from Earth.
At its heart is a star cluster called the Trapezium, a brilliant formation first discovered
by Galileo. It pumps out a wind of ultraviolet radiation that clears the surrounding region
and makes the gas glow.
In its midst, perhaps a thousand hot young stars are being born. Some are blasting out
jets of radiation that carve out ghostly red shapes in their surroundings.
Around young stars like these, enshrouded in dust, nature sets the stage for the alchemy
of life.
Within these solar nebulae, gravity can build an array of bodies, from rocks to asteroids
and planets.
But the deck is stacked against it. As small objects merge into larger ones, they can collide
with one another at high speed, and smash into smaller pieces.
If one does grow larger, friction with gas and dust can slow it down and send it spiraling
toward the star.
It takes a special set of circumstances to get the process going.
Astronomers saw it with a millimeter wave telescope called Alma. They used it to peer
into the light of one newly formed star 400 light years from earth.
They found an odd feature within the ring of dust surrounding the star.
It's a large vortex perhaps created by a planet or a companion star circulating through the
clouds.
The region acts like a trap, holding the dust grains in place and allowing them to form
larger objects.
If planets can form, their dusty environment may play a more direct roll in spawning life.
Some 40,000 tons of dust and rocks rain down onto the Earth each year, leftovers from the
birth of the solar system four to five billion years ago.
Interplanetary dust has long been known to carry organic, or carbon, compounds able to
survive the journey through Earth's atmosphere.
Scientists recently found something else, on the dust particles themselves.
Hydrogen ions, or protons, from the solar wind strike these particles.
When these protons interact with oxygen in silicate mineral grains, they form H20 molecules,
which then cling to the particles.
This process was documented in lunar dust grains picked up by Apollo astronauts. It
may be the source of water ice that has collected in the bottom of some lunar craters, and is
strewn about lunar landscapes.
In addition to watery dust raining down onto the earth, this may explain how comets and
asteroids were able to generate stores of water, and to bring them down to Earth.
This process happens one grain at a time, as solar particles race through clouds of
dust or strafe the surface of solid bodies.
It takes place in regions where stars are being born, where dust is prevalent and solar
winds are fierce.
That's only one source of water.
Out in the constellation of Perseus, about 750 light years from Earth, astronomers have
spotted a proto star called L1448-MM. It is shooting matter out of its poles in high-speed
jets containing oxygen and hydrogen.
When these molecules reach a cooler environment, they combined to form water, at a rate of
one hundred million times the flow of the Amazon River.
To get an idea of how much water the universe makes, check out a quasar known as APM08279+5255.
At 12 billion light years away, it's one of the most luminous objects known in our universe.
Astronomers were already amazed to find that it's spewing out large amounts of iron.
Now they have found that its center is literally saturated in water, about 140 trillion times
the amount of water found on Earth.
Given that water is created and spread so readily, it�s not surprising that it pervades
our own solar system. At its edges, Pluto and its moon Charon are lined with a thick
layer of frozen methane and water ice.
The blue planets Neptune and Uranus get their color from the methane clouds that make up
their frigid atmospheres.
Within, charged particles circulate in a sea of liquid water, producing electrical currents
and magnetic fields.
Within the folds of Saturn's rings are countless particles of ice.
Hovering just above them is the moon, Enceladus, with an icy surface that makes it one of the
brightest objects in the entire solar system.
The Cassini spacecraft detected jets of water ice shooting out of its south pole. Scientists
believe they are coming from an interior ocean, launched by the squeezing action of Saturn's
gravity.
The largest planet, Jupiter, harbors its own storehouse of water. The storms that drift
along its surface are the result of water vapor rising and falling like thunderstorms.
Beyond Jupiter's roiling atmosphere, lies a water world: Jupiter's second moon, Europa.
Its bright, smooth surface is crisscrossed by channels and grooves carved out by shifts
in an ocean of liquid water or slushy ice that lies below.
The faint emissions of water jets, illustrated here, were recently picked up by the Hubble
Space Telescope.
On our own moon, water ice is tucked into polar craters. There may well be additional
stores in rocks below the surface.
Mars, its surface etched by ancient dry riverbeds. If there's any water left, it too is most
likely hidden below the surface.
Then there's Venus. A thick carbon dioxide atmosphere has trapped enough solar energy
to turn it into the hottest planet in the solar system. There's no water here.
Earth, in contrast, is a water planet.
Vast interconnected bodies of water, the oceans, cover 71% of its surface.
Now scientists have detected whole oceans of water hidden in rocks deep inside the planet.
The story of dust and water is central to understanding how life arose on this planet.
As far as we know, these two components can be found throughout the galaxy.
One recent estimate, based on data from the planet-finding Kepler Space Telescope, says
our galaxy has around 8.8 billion stars with planets nearly the size of Earth, with surface
temperatures conducive to the development of life.
This means that in our galaxy, Nature has had as many as 40 billion chances to get life
started and evolve it from there.
But with Earth as our only data point, we know that this process must survive a host
of crushing threats.
Planet shattering impacts.
Massive volcanic eruptions.
Global ice ages.
So is the presence of life in our universe a fact guided more by destiny, or more by
chance?
We'll scan the heavens for evidence, a sign, or new ways to ask the question:
What does it all add up to?
7