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  • richardmitnick 8:26 pm on December 15, 2014 Permalink | Reply
    Tags: , , , , , NASA Voyager   

    From JPL: “NASA Voyager: ‘Tsunami Wave’ Still Flies Through Interstellar Space” 

    JPL

    December 15, 2014

    Media Contact
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    Elizabeth.Landau@jpl.nasa.gov

    •The Voyager 1 spacecraft has experienced three shock waves

    • The most recent shock wave, first observed in February 2014, still appears to be going on

    • One wave, previously reported, helped researchers determine that Voyager 1 had entered interstellar space

    v
    NASA/Voyager

    The “tsunami wave” that NASA’s Voyager 1 spacecraft began experiencing earlier this year is still propagating outward, according to new results. It is the longest-lasting shock wave that researchers have seen in interstellar space.

    “Most people would have thought the interstellar medium would have been smooth and quiet. But these shock waves seem to be more common than we thought,” said Don Gurnett, professor of physics at the University of Iowa in Iowa City. Gurnett presented the new data Monday, Dec. 15 at the American Geophysical Union meeting in San Francisco.

    A “tsunami wave” occurs when the sun emits a coronal mass ejection, throwing out a magnetic cloud of plasma from its surface. This generates a wave of pressure. When the wave runs into the interstellar plasma — the charged particles found in the space between the stars — a shock wave results that perturbs the plasma.

    cme
    CME (Photo: NASA/GSFC/SDO)

    “The tsunami causes the ionized gas that is out there to resonate — “sing” or vibrate like a bell,” said Ed Stone, project scientist for the Voyager mission based at California Institute of Technology in Pasadena.

    This is the third shock wave that Voyager 1 has experienced. The first event was in October to November of 2012, and the second wave in April to May of 2013 revealed an even higher plasma density. Voyager 1 detected the most recent event in February, and it is still going on as of November data. The spacecraft has moved outward 250 million miles (400 million kilometers) during the third event.

    “This remarkable event raises questions that will stimulate new studies of the nature of shocks in the interstellar medium,” said Leonard Burlaga, astrophysicist emeritus at NASA Goddard Spaceflight Center in Greenbelt, Maryland, who analyzed the magnetic field data that were key to these results.

    It is unclear to researchers what the unusual longevity of this particular wave may mean. They are also uncertain as to how fast the wave is moving or how broad a region it covers.

    The second tsunami wave helped researchers determine in 2013 that Voyager 1 had left the heliosphere, the bubble created by the solar wind encompassing the sun and the planets in our solar system. Denser plasma “rings” at a higher frequency, and the medium that Voyager flew through, was 40 times denser than what had been previously measured. This was key to the conclusion that Voyager had entered a frontier where no spacecraft had gone before: interstellar space.

    “The density of the plasma is higher the farther Voyager goes,” Stone said. “Is that because the interstellar medium is denser as Voyager moves away from the heliosphere, or is it from the shock wave itself? We don’t know yet.”

    Gurnett, principal investigator of the plasma wave instrument on Voyager, expects that such shock waves propagate far out into space, perhaps even to twice the distance between the sun and where the spacecraft is right now.

    Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft and is expected to enter interstellar space in a few years.

    JPL, a division of Caltech, built the twin Voyager spacecraft and operates them for the Heliophysics Division within NASA’s Science Mission Directorate in Washington.

    For more information on the Voyager mission, visit:

    http://voyager.jpl.nasa.gov

    See the full article here.

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 10:11 am on November 29, 2014 Permalink | Reply
    Tags: , , , , NASA Voyager, , Triton   

    From NYT: “A Captured Ice Moon | Out There | The New York Times “ 

    New York Times

    The New York Times

    temp
    Global Color Mosaic of Triton, taken by Voyager 2 in 1989

    NASA Voyager 2

    Neptune’s moon Triton was the last stop on Voyager 2’s tour of the outer planets. It is one of the coldest objects in the solar system and a big brother of Pluto, which NASA will visit next year.

    Produced by: Dennis Overbye, Jason Drakeford and Jonathan Corum

    Watch, enjoy learn.

    See the full article here.

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  • richardmitnick 9:54 am on November 21, 2014 Permalink | Reply
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    From SPACE.com: “Planet Uranus: Facts About Its Name, Moons and Orbit” 

    space-dot-com logo

    SPACE.com

    November 18, 2014
    Charles Q. Choi

    Uranus is the seventh planet from the sun and the first to be discovered by scientists. Although Uranus is visible to the naked eye, it was long mistaken as a star because of the planet’s dimness and slow orbit. The planet is also notable for its dramatic tilt, which causes its axis to point nearly directly at the sun.

    ur

    British astronomer William Herschel discovered Uranus accidentally on March 13, 1781, with his telescope while surveying all stars down to those about 10 times dimmer than can be seen by the naked eye. One “star” seemed different, and within a year Uranus was shown to follow a planetary orbit.

    Uranuswas named after the Greek sky deity Ouranos, the earliest of the lords of the heavens. It is the only planet to be named after a Greek god rather than a Roman one. Before the name was settled on, many names had been proposed for the new planet, including Hypercronius (“above Saturn”), Minerva (the Roman goddess of wisdom), and Herschel, after its discoverer. To flatter King George III of England, Herschel himself offered Georgium Sidus (“The Georgian Planet”) as a name, but that idea was unpopular outside of England and George’s native Hanover. German astronomer Johann Bode, who detailed Uranus’ orbit, gave the planet its ultimate name.

    Physical characteristics

    Uranusis blue-green in color, the result of methane in its mostly hydrogen-helium atmosphere. The planet is often dubbed an ice giant, since 80 percent or more of its mass is made up of a fluid mix of water, methane, and ammonia ices.

    Unlike the other planets of the solar system, Uranus is tilted so far that it essentially orbits the sun on its side, with the axis of its spin nearly pointing at the star. This unusual orientation might be due to a collision with a planet-size body, or several small bodies, soon after it was formed.

    This unusual tilt gives rise to extreme seasons roughly 20 years long, meaning that for nearly a quarter of the Uranian year, equal to 84 Earth-years, the sun shines directly over each pole, leaving the other half of the planet to experience a long, dark, cold winter.

    The magnetic poles of most planets are typically lined up with the axis along which it rotates, but Uranus’ magnetic field is tilted, with its magnetic axis tipped over nearly 60 degrees from the planet’s axis of rotation. According to Norman F. Ness, et al, in an article in the journal Science, this leads to a strangely lopsided magnetic field for Uranus, with the strength of the field at the northern hemisphere’s surface being up to more than 10 times that of the strength at the southern hemisphere’s surface, affecting the formation of the auroras.

    Orbital characteristics

    Average distance from the sun: 1,783,939,400 miles (2,870,972,200 kilometers). By comparison: 19.191 times that of Earth

    Perihelion (closest approach to the sun): 1,699,800,000 miles (2,735,560,000 km). By comparison: 18.60 times that of Earth

    Aphelion (farthest distance from sun): 1,868,080,000 miles (3,006,390,000 km). By comparison: 19.76 times that of Earth
    The planet Uranus, seventh planet from the sun, is a giant ball of gas and liquid and was the first planet discovered with a telescope.

    ur
    Credit: Karl Tate, SPACE.com

    Composition & structure

    Atmospheric composition (by volume): 82.5 percent hydrogen, 15.2 percent helium, 2.3 percent methane

    Magnetic field: Magnetic pole tilt compared to rotational axis: 58.6 degrees

    Composition: The overall composition of Uranus is, by mass, thought to be about 25 percent rock, 60 to 70 percent ice, and 5 to 15 percent hydrogen and helium.

    Internal structure: Mantle of water, ammonia and methane ices; core of iron and magnesium-silicate
    Orbit & rotation

    Axial tilt: 97.77 degrees, compared to Earth’s 23.5 degrees

    Seasonal cycle & length: Approximately 21 years per season

    Orbital period: Approximately 84 Earth years
    Uranus’ climate

    The extreme axial tilt Uranus experiences can give rise to unusual weather. As sunlight reaches some areas for the first time in years, it heats up the atmosphere, triggering gigantic springtime storms roughly the size of North America, according to NASA.

    Ironically, when Voyager 2 first imaged Uranus in 1986 at the height of summer in its south, it saw a bland-looking sphere with only about 10 or so visible clouds, leading to it to be dubbed “the most boring planet,” writes astronomer Heidi Hammel in The Ice Giant Systems of Uranus and Neptune, a chapter in Solar System Update (Springer, 2007). It took decades later, when advanced telescopes such as Hubble came into play and the seasons changed, to see extreme weather on Uranus, where fast-moving winds can reach speeds of up to 560 miles (900 kilometers) per hour.

    NASA Voyager 2
    NASA/Voyager 2

    NASA Hubble Telescope
    NASA/ESA Hubble

    The rings of Uranus

    The rings of Uranus were the first to be seen after Saturn’s. They were a significant discovery, because it helped astronomers understand that rings are a common feature of planets, not merely a peculiarity of Saturn.

    Uranus possesses two sets of rings. The inner system of rings consists mostly of narrow, dark rings, while an outer system of two more-distant rings, discovered by the Hubble Space Telescope, are brightly colored, one red, one blue. Scientists have now identified 13 known rings around Uranus.
    Uranus’ moons

    Uranus has 27 known moons. Instead of being named after figures from Greek or Roman mythology, its first four moons were named after magical spirits in English literature, such as William Shakespeare’s “A Midsummer Night’s Dream” and Alexander Pope’s “The Rape of the Lock.” Since then, astronomers have continued this tradition, drawing names for the moons from the works of Shakespeare or Pope.

    Oberon and Titania are the largest Uranian moons, and were the first to be discovered, by Herschel in 1787. William Lassell, who was the first to see a moon orbiting Neptune, discovered the next two, Ariel and Umbriel. Then nearly a century passed before Miranda was found in 1948.

    Then, Voyager 2 visited the Uranian system in 1986 and found an additional 10, all just 16 to 96 miles (26-154 km) in diameter — Juliet, Puck, Cordelia, Ophelia, Bianca, Desdemona, Portia, Rosalind, Cressida and Belinda — and each roughly made half of water ice and half of rock. Since then, astronomers using the Hubble Space Telescope and ground-based observatories have raised the total to 27 known moons, and spotting these was tricky — they are as little as 8 to 10 miles (12 to 16 km) across, blacker than asphalt, and nearly 3 billion miles (4.8 billion km) away.

    Between Cordelia, Ophelia and Miranda is a swarm of eight small satellites crowded together so tightly that astronomers don’t yet understand how the little moons have managed to avoid crashing into each other. Scientists suspect there might still be more moons, closer to Uranus than any known.

    In addition to moons, Uranus may also have a collection of Trojan asteroids — objects that share the same orbit as the planet — in a special region known as a Lagrangian point. The first was discovered in 2013, despite claims that the planet’s Langrangian point would be too unstable to host such bodies.

    Research & exploration

    NASA’s Voyager 2 was the first and as yet only spacecraft to visit Uranus. It discovered 10 previously unknown moons, and investigated its unusually tilted magnetic field.

    In 2013, the Planetary Science Decadal Survey recommended NASA consider a mission to the icy planet.

    See the full article here.

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  • richardmitnick 9:27 am on September 17, 2014 Permalink | Reply
    Tags: , , , , , NASA Voyager,   

    From NOVA: “Chasing the Edge of the Solar System” Old But Worth a Look 

    PBS NOVA

    NOVA

    Tue, 09 Apr 2013
    David McComas

    For most of its lifetime, Voyager 1 has been traveling through uncharted territory. Initially launched to study the outer planets, Voyager 1 has soldiered on past Jupiter and Saturn and on to the outer edges of the solar system. It’s currently the farthest human-made object from Earth, but when will it be the first spacecraft to travel between the stars? Well, we won’t know until we answer two more fundamental questions: Where does our solar system end and the rest of the space between the stars begin? And if you were at the “edge” of our solar system, how would you know you had left? Recent scientific discussions on the Voyager spacecraft missions have captivated many people. And as the scientific debate swirled around the internet in near-real time, it became clear that these questions are not easy to answer. Voyager spacecraft
    The identical Voyager 1 and Voyager 2 are currently probing the farthest reaches of the solar system.

    NASA Voyager 2
    NASA/Voyager 2

    As the Principal Investigator for NASA’s Interstellar Boundary Explorer, or IBEX, spacecraft, I lead a team that is also studying this last frontier of our solar system. Data from IBEX complements the Voyager spacecraft—both missions are working together to find the very farthest reaches of the solar system. Unlike the Voyager spacecraft, which are careening out into interstellar space, IBEX orbits the Earth, collecting particles that have traveled in from the solar system’s boundary region and beyond. From those particles, we can determine many things, including what the boundary is like and what, exactly, is happening out there.

    NASA IBEX
    NASA/IBEX

    More Than Planets

    Most everyone knows our solar system is composed of small solid objects orbiting the Sun—planets, comets, and asteroids. But there’s more to it than that. Our Sun continuously emits a “wind” of material outward in all directions, typically at speeds of about a million miles per hour (1.6 million kilometers per hour). The solar wind is composed mostly of charged particles, such as electrons and protons. It also carries the Sun’s magnetic field. As the solar wind streams away from the Sun, it races out past all the planets, past Pluto, and toward the space between the stars more than 10 billion miles away. We tend to think of that space as empty, but it’s not. Rather, it contains cold hydrogen gas, dust, ionized gas, and traces of other material. Called the interstellar medium, it’s a very thin mix that comes from exploded stars and the stellar wind of other stars. When the magnetic fields of the solar wind hit the magnetic fields of the interstellar medium, they do not intermix. The expanding solar wind pushes against the interstellar medium, clearing out a cavity in interstellar space known as the heliosphere. The boundary of that bubble is where the solar wind’s strength exactly matches the pressure of the interstellar medium. We call it the heliopause, and it’s often considered to be the very outer edge of our solar system.

    The Heliopause.

    A few things about the heliopause: It isn’t an impermeable wall. Instead, it’s more like the edge of a forest clearing—the boundary is well defined, but easily negotiated. It’s also shaped more like a drop of water than a uniform sphere. That’s because our entire heliosphere, which contains our Sun, the planets, and everything else in our solar system, is moving through the interstellar medium at about 50,000 miles per hour (80,000 kilometers per hour). That motion creates a wake in the interstellar medium, much like a boat moving through water. As the solar system travels through the interstellar medium the heliopause is closest at the “front,” or the foremost point in the direction in which our solar system is traveling. At that point, the heliopause is still over 10 billion miles, or 16 billion kilometers, from the Sun.

    hh
    Heliosphere and heliopause

    As solar wind pushes out against the interestellar medium, it creates a bubble known as the heliosphere; the boundary between the two is known as the heliopause. The termination shock is where the solar wind slows as it presses against more of the interstellar medium, which also raises the plasma’s temperature. The bow wave is where the interstellar medium material piles up in front of our heliosphere, similar to water in front of a moving boat
    At least, that’s our best guess. We don’t know exactly where the boundary is or what it’s like. That’s what the IBEX and Voyager missions are trying to find out. IBEX lets us peer into the boundaries of our solar system to get a better idea of what it’s like and what’s happening there. However, because IBEX orbits the Earth, we cannot use it to mark where the boundary is located. That’s where Voyager 1 and 2 come in. Currently, they are directly sampling the boundary region. Several of the instruments on Voyager 1 and 2 are no longer working, including the cameras used to snap the stunning fly-by photos of Jupiter, Saturn, Uranus, and Neptune, but others that detect charged particles and magnetic fields are still gathering data. Both Voyagers are traveling in roughly the same direction as our solar system through the interstellar medium. We expect Voyager 1, the quicker and farther out of the two, to reach the heliopause first. Currently, it’s just over 11 billion miles, or 18 billion kilometers, from the Sun. This is so distant that radio signals from Voyager 1, which are traveling at the speed of light, take 17 hours to reach Earth.

    Three Criteria

    Before we can declare that Voyager 1 has crossed the heliopause, we are waiting to observe three main changes:

    A decrease in highly energetic charged particles from inside our heliosphere,
    An increase in highly energetic charged particles from outside our heliosphere,
    And a change in the strength and direction of the magnetic field, matching that outside the heliosphere.

    Voyager 1 observed the first two in late 2012, and IBEX has provided what are likely the best observations of the third. By using IBEX to look at particles that have traveled in from outside the heliosphere, we have an idea of the direction of the magnetic field beyond the solar system, and it’s very different from the Sun’s, which is carried out by the solar wind. So far Voyager 1 hasn’t observed this change direction of the magnetic field. That’s why we don’t think that Voyager 1 has crossed the heliopause—yet.

    The IBEX satellite orbits the Earth, capturing particles that have traveled into the solar system from beyond the heliosphere.
    Now, Voyager 1 has clearly passed into a new region of space, one that we have not detected before. Every new bit of data coming from the venerable spacecraft is teaching us more about this uncharted territory. All of this information is new, and we are learning more every day. So, do we know when Voyager 1 will cross the heliopause? We really have no idea. And that’s part of the fun. But learning about the edge of space is more than just an esoteric pursuit. Our heliosphere is a protective cocoon, a crucial layer of shielding against dangerous charged particles, known as galactic cosmic rays, that are harmful to living things. Understanding it will help us understand how the heliosphere has protected our solar system, enabling life to flourish on this planet we call home. And someday, that knowledge will help us prepare for our first voyage beyond the protective cocoon of the solar system, when we step across the threshold and venture into deep space.

    See the full article here.

    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

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  • richardmitnick 8:51 am on July 31, 2014 Permalink | Reply
    Tags: , , , , , NASA Voyager   

    From SPACE.com: “How Far Away is Neptune?” 

    SpacedotcomHeader
    SPACE.com

    December 14, 2012
    Nola Taylor Redd

    The ice giant Neptune is the eighth and most distant planet from the sun. Since its discovery, only one Neptunian year has passed.

    neptune
    On June 25, 2011, Neptune arrived at the same location in space where it was discovered 165 years earlier. To commemorate the event, NASA’s Hubble Space Telescope took “anniversary pictures” of the blue-green giant planet.
    Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

    How far is Neptune from Earth?

    The distance from one planet to another is constantly shifting because both bodies are moving through space. When Neptune and Earth line up on the same side of the sun, at their closest, they are only 2.7 billion miles (4.3 billon kilometers) apart. But when the planets are on opposite sides of the sun, they can put as many as 2.9 billion miles (4.7 billion km) between them.

    Neptune’s extreme distance made it the last full-size planet to be discovered. Unlike Uranus, it was found primarily by pouring over mathematical formulas rather than peering through a telescope. Astronomers had noticed that the recently-discovered Uranus had some orbital oddities that could not be explained. John Couch Adams and Urbain Le Verrier independently calculated the planet’s orbit between 1845 and 1846, and several astronomers began to search for the proposed planet. On September 23, 1846, the icy body was found within one degree of Le Verrier’s predictions and 12 degrees from where Adams suggested it would travel. This prompted discussion over who should be credited with the discovery, but ultimately both men were recognized for their roles.

    The planet was spotted in 1612 and 1613 by Galileo Galilei. Unfortunately, the Italian astronomer made his observations when Neptune had just begun its backward, or retrograde, motion across the sky. Planets that lie farther from Earth occasionally appear to move backward when our planet passes them in their orbit. The enormous distance to Neptune meant that the motion was too small to record in Galileo’s early telescope, resulting in his mischaracterization.

    How far is Neptune from the sun?

    Like all planets, Neptune orbits the sun in a stretched-out circle known as an ellipse. This means that its distance from the star is constantly changing. When the icy planet is closest to the sun, it lies “only” 2.77 billion miles (4.46 billion km). At its farthest, it passes 2.82 billion miles (4.54 billion km) from the star.

    Although Neptune is the eighth most distant planet, it was not always. The dwarf planet Pluto occasionally dips inside of Neptune’s orbit. Thus, when Pluto was classified as a planet, it was sometimes the eighth most distant planet while Neptune was the ninth. The two bodies will never collide, however, because for every three trips Neptune makes around the sun, Pluto takes exactly two, which keeps them from every traveling through the same area at the same time.

    Neptune takes 164.79 Earth-years to travel around the sun. On July 11, 2011, Neptune had completed one full orbit since its discovery. It was not in the same spot in the sky, however, because Earth lay at a different point in its orbit.

    Although the most distant planet now, it is possible the Neptune was not always so far away. The amount of gas and ice needed to form the giant planet is greater than fits current models. Some scientists suggest that Neptune may have formed closer to the sun, then migrated out to its present location over time.

    How long does it take to reach Neptune?

    The constant motion of Neptune and Earth is the biggest force that determines how long it takes to travel between the two planets. It would take a satellite longer to reach Neptune if it was launched when the two planets were on opposite sides of the sun instead of the same time.

    The only spacecraft to visit Neptune was Voyager 2. Launched on August 20, 1977, it made its closest approach to the planet on August 25, 1989, after a dozen years of travel. Voyager 2 observed Neptune’s “Great Dark Spot,” a series of short-term storms in Neptune’s atmosphere. The dark spot is approximately the same size as Earth, and is thought to be a hole in Neptune’s methane clouds.

    NASA Voyager 2
    NASA/Voyager 2

    No other craft has traveled to the planet. However, NASA’s New Horizons, launched January 19, 2006, will pass through Neptune’s orbit on its way to visit Pluto and the Kuiper Belt. The spacecraft will travel through the planet’s orbit in August of 2014, after eight years of traveling.

    NASA New Horizons spacecraft

    kuiper belt
    Kuiper Belt

    See the full article here.


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  • richardmitnick 10:11 am on February 13, 2014 Permalink | Reply
    Tags: , , , , , , NASA Voyager   

    From NASA/JPL at Caltech: “Largest Solar System Moon Detailed in Geologic Map” 

    February 12, 2014
    Jia-Rui Cook 818-354-0850
    Jet Propulsion Laboratory, Pasadena,
    Calif. jccook@jpl.nasa.gov

    More than 400 years after its discovery by astronomer Galileo Galilei, the largest moon in the solar system – Jupiter’s moon Ganymede – has finally claimed a spot on the map.

    Ganymede
    To present the best information in a single view of Jupiter’s moon Ganymede, a global image mosaic was assembled, incorporating the best available imagery from NASA’s Voyager 1 and 2 spacecraft and NASA’s Galileo spacecraft. USGS Astrogeology Science Center/Wheaton/NASA/JPL-Caltech

    A group of scientists led by Geoffrey Collins of Wheaton College has produced the first global geologic map of Ganymede, Jupiter’s seventh moon. The map combines the best images obtained during flybys conducted by NASA’s Voyager 1 and 2 spacecraft (1979) and Galileo orbiter (1995 to 2003) and is now published by the U. S. Geological Survey as a global map. It technically illustrates the varied geologic character of Ganymede’s surface and is the first global, geologic map of this icy, outer-planet moon. The geologic map of Ganymede is available for download at: http://www.jpl.nasa.gov/spaceimages/details.php?id=pia17902 ).

    NASA Galileo
    Galileo

    NASA Voyager
    Voyager

    “This map illustrates the incredible variety of geological features on Ganymede and helps to make order from the apparent chaos of its complex surface,” said Robert Pappalardo of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “This map is helping planetary scientists to decipher the evolution of this icy world and will aid in upcoming spacecraft observations.”

    The European Space Agency’s Jupiter Icy Moons Explorer mission is slated to be orbiting Ganymede around 2032. NASA is contributing a U.S.-led instrument and hardware for two European-led instruments for the mission.

    Since its discovery in January 1610, Ganymede has been the focus of repeated observation, first by Earth-based telescopes, and later by the flyby missions and spacecraft orbiting Jupiter. These studies depict a complex, icy world whose surface is characterized by the striking contrast between its two major terrain types: the dark, very old, highly cratered regions, and the lighter, somewhat younger (but still very old) regions marked with an extensive array of grooves and ridges.

    According to the scientists who have constructed this map, three major geologic periods have been identified for Ganymede that involve the dominance of impact cratering, then tectonic upheaval, followed by a decline in geologic activity. The map, which illustrates surface features, such as furrows, grooves and impact craters, allows scientists to decipher distinct geologic time periods for an object in the outer solar system for the first time.

    “The highly detailed, colorful map confirmed a number of outstanding scientific hypotheses regarding Ganymede’s geologic history, and also disproved others,” said Baerbel Lucchitta, scientist emeritus at the U.S. Geological Survey in Flagstaff, Ariz., who has been involved with geologic mapping of Ganymede since 1980. “For example, the more detailed Galileo images showed that cryovolcanism, or the creation of volcanoes that erupt water and ice, is very rare on Ganymede.”

    The Ganymede global geologic map will enable researchers to compare the geologic characters of other icy satellite moons, because almost any type of feature that is found on other icy satellites has a similar feature somewhere on Ganymede.

    “The surface of Ganymede is more than half as large as all the land area on Earth, so there is a wide diversity of locations to choose from,” Collins said. “Ganymede also shows features that are ancient alongside much more recently formed features, adding historical diversity in addition to geographic diversity.”

    Amateur astronomers can observe Ganymede (with binoculars) in the evening sky this month, as Jupiter is in opposition and easily visible.

    See the full article here.

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

    Caltech Logo
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