NASA is exploring our solar system and beyond to understand the workings
of the universe, searching for water and life among the stars.
Image credit: NASA. › Larger image | › Standard Podcast: Play animation
Image credit: NASA. › Larger image | › Standard Podcast: Play animation
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.
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.
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@jpl.nasa.gov
Felicia Chou
NASA Headquarters, Washington
202-358-0257
Felicia.chou@nasa.gov
Media Contact
Preston Dyches
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-7013
preston.dyches@jpl.nasa.gov
Felicia Chou
NASA Headquarters, Washington
202-358-0257
Felicia.chou@nasa.gov
Source: JPL-Caltech