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

[Ron Baalke]

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