- 4247 - URANUS - new discoveries? Uranus is the coldest planet in the solar system. It is the seventh planet from the sun, orbiting in the outer solar system, about two billion miles from Earth. It is an enormous world, quadruple the diameter of Earth, with 15 times the mass and 63 times the volume.
-------------------------- 4247 - URANUS - new discoveries?
- Unvisited by
spacecraft for more than 35 years, Uranus inhabits one of the least explored
regions of our solar system. Although scientists have learned some things about
it from telescopic observations and theoretical work since the Voyager 2 flyby
in 1986, the planet remains an enigma.
-
- It's easy to
divide the solar system into two large groups: an inner zone with four rocky
planets and an outer zone with four giant planets. But nature is, as usual,
more complicated. Uranus and Neptune, the eighth planet from the sun, are
vastly different from the others. Both are ice giants, composed largely of
compounds such as water, ice, ammonia and methane. They are places where the average temperature
is minus 320 to minus 350 degrees Fahrenheit.
-
- Through recent
discoveries of exoplanets, worlds outside our solar system that are trillions
of miles away, astronomers have learned that ice giants are common throughout
the galaxy. They challenge our understanding of planetary formation and
evolution. Uranus, comparatively close to us, is our cornerstone for learning
about these far away worlds.
-
- The space
community is urging NASA to launch a robotic spacecraft to explore Uranus. The 2023 decadal survey of planetary
scientists ranked such a journey as the single highest priority for a new NASA
flagship mission.
-
- This time, the
spacecraft would not simply fly by Uranus on its way somewhere else, as Voyager
2 did. Instead, the probe would spend years orbiting and studying the planet,
its 27 moons and its 13 rings.
-
- Why send a
spacecraft to Uranus and not Neptune. It's a matter of orbital architecture.
Because of the positions of both planets over the next two decades, a
spacecraft from Earth will have an easier trajectory to follow to reach Uranus
than Neptune. Launched at the right time, the orbiter would arrive at Uranus in
about 12 years.
-
- Here are just a
few of the basic questions a Uranus orbiter would help answer: What, exactly,
is Uranus made of? Why is Uranus tilted on its side, with its poles pointed
almost directly toward the sun during summer, which is different from all the
other planets in the solar system? What is generating Uranus' strange magnetic
field, shaped differently than Earth's and misaligned with the direction the
planet spins? How does atmospheric circulation work on an ice giant? What do
the answers to all these questions tell us about how ice giants form?
-
- The rings around
Uranus, probably made of dirty ice, are thinner and darker than those around
Saturn. A Uranus orbiter would look for "ripples" in them, akin to
waves on a lake. Finding them would let scientists use the rings as a giant seismometer
to help us learn about the interior of Uranus.
-
- The moons are
primarily made of frozen mixes of ice and rock. Five of the moons, Miranda,
Ariel, Umbriel, Titania and Oberon are all big enough to be spherical and
treated as miniature worlds in their own right.
-
- During its flyby,
Voyager 2 took low-resolution images of the moons' southern hemispheres. Their northern hemispheres, still unseen,
remain one of the major unexplored frontiers of our solar system. Those images include photos of ice volcanoes
on Ariel, a tantalizing hint of past geological and tectonic activity and,
possibly, subsurface water.
-
- Many planetary
scientists theorize that Ariel, and perhaps most or all of the other five
moons, may be an ocean world harboring large, underground bodies of liquid
water miles beneath the solid, icy surface. Finding out whether any of the
moons have oceans is one of the major goals of the mission.
-
- This is one reason
why an orbiter would carry a magnetometer to detect the electromagnetic
interactions of an underground ocean as one of its moons travels through
Uranus' magnetic field. Also instruments to measure the moons' gravitational
fields and cameras to study their surface geology.
-
- Liquid water is
an essential requirement for life as we know it. If oceans are detected,
scientists will then want to look for other ingredients for life on the moons
such as energy, nutrients and organic matter.
-
- One critical
factor to consider is that the cosmos operates on its own timetable, and those
spacecraft trajectories to Uranus will change over the years as the planets
move along their orbits. Ideally, NASA would launch a mission in 2031 or 2032
to maximize trajectory convenience and minimize travel time.
-
- That time span is
less than it may seem; it takes years of planning and years more of
constructing the spacecraft to be ready for launch. That's why the time is now
to start the process and fund a mission to this fascinating world.
-
-
November 30, 2023
URANUS - new
discoveries? 4247
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