[meteorite-list] The Solar System and Beyond is Awash in Water

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 7 Apr 2015 16:08:50 -0700 (PDT)
Message-ID: <201504072308.t37N8ovp021412_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?feature=4541

The Solar System and Beyond is Awash in Water
Jet Propulsion Laboratory
April 7, 2015

As NASA missions explore our solar system and search for new worlds, they
are finding water in surprising places. Water is but one piece of our
search for habitable planets and life beyond Earth, yet it links many
seemingly unrelated worlds in surprising ways.

"NASA science activities have provided a wave of amazing findings related
to water in recent years that inspire us to continue investigating our
origins and the fascinating possibilities for other worlds, and life,
in the universe," said Ellen Stofan, chief scientist for the agency. "In
our lifetime, we may very well finally answer whether we are alone in
the solar system and beyond."

The chemical elements in water, hydrogen and oxygen, are some of the most
abundant elements in the universe. Astronomers see the signature of water
in giant molecular clouds between the stars, in disks of material that
represent newborn planetary systems, and in the atmospheres of giant planets
orbiting other stars.

There are several worlds thought to possess liquid water beneath their
surfaces, and many more that have water in the form of ice or vapor. Water
is found in primitive bodies like comets and asteroids, and dwarf planets
like Ceres. The atmospheres and interiors of the four giant planets --
Jupiter, Saturn, Uranus and Neptune -- are thought to contain enormous
quantities of the wet stuff, and their moons and rings have substantial
water ice.

Perhaps the most surprising water worlds are the five icy moons of Jupiter
and Saturn that show strong evidence of oceans beneath their surfaces:
Ganymede, Europa and Callisto at Jupiter, and Enceladus and Titan at Saturn.

Scientists using NASA's Hubble Space Telescope recently provided powerful
evidence that Ganymede has a saltwater, sub-surface ocean, likely sandwiched
between two layers of ice.

Europa and Enceladus are thought to have an ocean of liquid water beneath
their surface in contact with mineral-rich rock, and may have the three
ingredients needed for life as we know it: liquid water, essential chemical
elements for biological processes, and sources of energy that could be
used by living things. NASA's Cassini mission has revealed Enceladus as
an active world of icy geysers. Recent research suggests it may have hydrothermal
activity on its ocean floor, an environment potentially suitable for living
organisms.

NASA spacecraft have also found signs of water in permanently shadowed
craters on Mercury and our moon, which hold a record of icy impacts across
the ages like cryogenic keepsakes.

While our solar system may seem drenched in some places, others seem to
have lost large amounts of water.

On Mars, NASA spacecraft have found clear evidence that the Red Planet
had water on its surface for long periods in the distant past. NASA's
Curiosity Mars Rover discovered an ancient streambed that existed amidst
conditions favorable for life as we know it.

More recently, NASA scientists using ground-based telescopes were able
to estimate the amount of water Mars has lost over the eons. They concluded
the planet once had enough liquid water to form an ocean occupying almost
half of Mars' northern hemisphere, in some regions reaching depths greater
than a mile (1.6 kilometers). But where did the water go?

It's clear some of it is in the Martian polar ice caps and below the surface.
We also think much of Mars' early atmosphere was stripped away by the
wind of charged particles that streams from the sun, causing the planet
to dry out. NASA's MAVEN mission is hard at work following this lead from
its orbit around Mars.

The story of how Mars dried out is intimately connected to how the Red
Planet's atmosphere interacts with the solar wind. Data from the agency's
solar missions -- including STEREO, Solar Dynamics Observatory and the
planned Solar Probe Plus -- are vital to helping us better understand
what happened.

Understanding the distribution of water in our solar system tells us a
great deal about how the planets, moons, comets and other bodies formed
4.5 billion years ago from the disk of gas and dust that surrounded our
sun. The space closer to the sun was hotter and drier than the space farther
from the sun, which was cold enough for water to condense. The dividing
line, called the "frost line," sat around Jupiter's present-day orbit.
Even today, this is the approximate distance from the sun at which the
ice on most comets begins to melt and become "active." Their brilliant
spray releases water ice, vapor, dust and other chemicals, which are thought
to form the bedrock of most worlds of the frigid outer solar system.

Scientists think it was too hot in the solar system's early days for water
to condense into liquid or ice on the inner planets, so it had to be delivered
-- possibly by comets and water-bearing asteroids. NASA's Dawn mission
is currently studying Ceres, which is the largest body in the asteroid
belt between Mars and Jupiter. Researchers think Ceres might have a water-rich
composition similar to some of the bodies that brought water to the three
rocky, inner planets, including Earth.

The amount of water in the giant planet Jupiter holds a critical missing
piece to the puzzle of our solar system's formation. Jupiter was likely
the first planet to form, and it contains most of the material that wasn't
incorporated into the sun. The leading theories about its formation rest
on the amount of water the planet soaked up. To help solve this mystery,
NASA's Juno mission will measure this important quantity beginning in
mid-2016.

Looking further afield, observing other planetary systems as they form
is like getting a glimpse of our own solar system's baby pictures, and
water is a big part of that story. For example, NASA's Spitzer Space Telescope
has observed signs of a hail of water-rich comets raining down on a young
solar system, much like the bombardment planets in our solar system endured
in their youth.

With the study of exoplanets -- planets that orbit other stars -- we are
closer than ever to finding out if other water-rich worlds like ours exist.
In fact, our basic concept of what makes planets suitable for life is
closely tied to water: Every star has a habitable zone, or a range of
distances around it in which temperatures are neither too hot nor too
cold for liquid water to exist. NASA's planet-hunting Kepler mission was
designed with this in mind. Kepler looks for planets in the habitable
zone around many types of stars.

Recently verifying its thousandth exoplanet, Kepler data confirm that
the most common planet sizes are worlds just slightly larger than Earth.
Astronomers think many of those worlds could be entirely covered by deep
oceans. Kepler's successor, K2, continues to watch for dips in starlight
to uncover new worlds.

The agency's upcoming TESS mission will search nearby, bright stars in
the solar neighborhood for Earth- and super-Earth-sized exoplanets. Some
of the planets TESS discovers may have water, and NASA's next great space
observatory, the James Webb Space Telescope, will examine the atmospheres
of those special worlds in great detail.

It's easy to forget that the story of Earth's water, from gentle rains
to raging rivers, is intimately connected to the larger story of our solar
system and beyond. But our water came from somewhere -- every world in
our solar system got its water from the same shared source. So it's worth
considering that the next glass of water you drink could easily have been
part of a comet, or an ocean moon, or a long-vanished sea on the surface
of Mars. And note that the night sky may be full of exoplanets formed
by similar processes to our home world, where gentle waves wash against
the shores of alien seas.

For more information about NASA's exploration of the solar system and
beyond, visit:

http://www.nasa.gov


Media Contact

Preston Dyches
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-7013
preston.dyches at jpl.nasa.gov

Felicia Chou
NASA Headquarters, Washington
202-358-0257
Felicia.chou at nasa.gov

2015-119
Received on Tue 07 Apr 2015 07:08:50 PM PDT