Where Does Earth's Water Come From?

The water cycle brings Earth's water from the clouds to the ground and back again -- but how did it get here in the first place? Learn about the leading theories in this episode of BrainStuff, based on this article: https://science.howstuffworks.com/environmental/earth/geophysics/water-come-from.html

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeartRadio, Hey brain
Stuff Lauren vogelbom Here. A water surrounds us, falling from
rain clouds, rushing down river beds, and pouring from faucets,
and yet many of us have never stopped to wonder
where does water come from? The answer is a complicated one,

(00:24):
stretching way beyond the water cycle and all the way
back to the very origins of the universe. It's essential
to understand that water isn't just a liquid that happens
to cover our planet. It's a medium for pretty much
all life as we know it. A water's unique properties,
such as its ability to dissolve many substances and its

(00:45):
solid state being less dense than its liquid state, which
is why ice expands as it freezes and floats in
liquid water, make it invaluable. A water acts as a solvent,
a temperature regulator, and a means of transportation for new
tents and waste. And devoid of the water cycle, the
complex chain of life on Earth from microbes to mammals

(01:06):
would cease to exist. But let's go back, like way back.
Shortly after the Big Bang, neutrons and electrons swarmed in
ten billion degree heat within minutes, hydrogen and then helium
unknown as the lighter elements had taken shape from these
atomic building blocks in a process called nucleosynthesis. Lithium made

(01:29):
a cameo as well, but generally the heavier elements didn't
appear until much later, when the lighter elements underwent fusion
inside of stars and during supernova Over time, stars sent
wave after wave of these heavier elements, including oxygen, out
into space, where they mixed with the lighter elements. Of course,

(01:50):
the mixing of hydrogen and oxygen atoms and the subsequent
formation of water are two different things. That's because even
when hydrogen and oxygen atoms get together, they still need
a spark of energy to form water. The process is
a violent one, and so far nobody has found a
way to safely create water on Earth. So how did

(02:13):
our planet come to be covered with the stuff. The
simple answer is we still don't know, but we have
a few ideas. One theory states that nearly four billion
years ago, the early Solar System was overrun by millions
of asteroids and comets, which slammed into the surface of
our relatively young planet. A quick glance at the Moon's

(02:34):
crater pocked surface gives us an idea of what conditions
of early Earth might have been. The theory goes that
these crash landing celestial bodies weren't solid rock, but rather
the equivalent of cosmic sponges, loaded with water that was
released on impact. While astronomers have confirmed that water rich

(02:54):
asteroids and comets exist, some scientists think that the theory
doesn't hold water huh. They question whether enough collisions could
have taken place to account for all of Earth's water. Also,
a researchers from the California Institute of Technology found that
water from the comet hail Bop is different from normal

(03:15):
Earth water. Ours has the chemical formula H two OH.
It's one atom of oxygen linked together with two atoms
of the common hydrogen one isotope, which has in its
nucleus only one proton a butt. Most of the water
on the hail Bop is what's called semi heavy water,
a form of water in which there's still one atom

(03:38):
of oxygen, but one of the atoms of hydrogen is
a different isotope called hydrogen two or deuterium. It has
a proton and a neutron in its nucleus. The semi
heavy water's chemical formula is h DO, and its higher
mass gives it slightly different chemical and physical properties. So

(03:59):
either the comets asteroids that hit Earth were very different
from the hail BOP or Earth got its H two
oh some other way. More recently, astronomers may have revealed
that the former may actually be true. Using observations from
the Stratospheric Observatory for Infrared Astronomy or SOPHIA, which is

(04:19):
a converted seven to forty seven aircraft that flies at
high altitude with an infrared telescope sticking out of the
tail section. A researchers found that when the comet Wordinin
made its closest approach with Earth in December of twenty eighteen,
it was venting very ocean like water vapor into space.
Wordenin belongs to a specific family of comets called hyperactive

(04:40):
comets that vent more water vapor into space than others.
The researchers deduced that its water is ocean like by
comparing the ratio of observed H two O and HDO
in that water vapor. Earth's oceans have a very specific
ratio of those two hydrogen isotopes. And here's that wordinan

(05:01):
shares that same ratio as Observing infrared wavelengths from the
ground is impossible because Earth's atmosphere blocks these wavelengths. Only
space telescopes and Sophia, which flies above most of the atmosphere,
can make reliable observations of comets. Another theory states that
a young Earth was bombarded by oxygen and other heavy

(05:23):
elements produced within the Sun. The idea is that the
oxygen combined with hydrogen and other gases released from the
Earth itself in a process known as degassing, thus forming
Earth's oceans and atmosphere along the way. And a team
of scientists from Japan's Tokyo Institute of Technology has devised
yet another theory, which states that a thick layer of

(05:46):
hydrogen may have once covered Earth's surface, eventually interacting with
oxides in the crust to form our planet's oceans. Finally,
computer simulations reported on in twenty seventeen suggested a closer
origin or at least some water on our planet. This
theory states that water could develop deep inside Earth's mantle

(06:07):
and eventually escape via earthquakes or other geological processes. Water
is so essential to life on Earth that a lot
of research is devoted to finding it on other planets
and moons, because where we find it, we may find
alien life. However, here on our planet, a water's availability

(06:28):
and quality are under threat. Pollution, over extraction, and climate
change are just some of the challenges facing our planet's
water resources. Addressing these issues is not only a scientific endeavor,
but also a societal one. After all, while we can't
say with certainty how water came to Earth, we are

(06:48):
fortunate it did. Today's episode is based on the article
where does water come From? On howstiffworks dot com, written
by job An Adabury and Ian O'Neil. Brain Stuff is
production of iHeartRadio in partnership with ho stuffworks dot Com
and was produced by Tyler Klang. For four more podcasts
from my heart Radio, visit the iHeartRadio app, Apple Podcasts,

(07:11):
or wherever you listen to your favorite shows.