"We've used Titan's gravity throughout the mission to sling Cassini around the Saturn system," said Earl Maize, Cassini project manager at JPL. "Now Titan is coming through for us once again, providing a way for Cassini to get into these completely unexplored regions so close to the planet."

The spacecraft to leap over the rings with a single (and final) Titan flyby in April, 2017 to begin its Grand Finale.

After more than 12 years studying Saturn, its rings and moons, NASA's Cassini spacecraft has entered the final year of its epic voyage. The conclusion of the historic scientific odyssey is planned for September 2017, but not before the spacecraft completes a daring two-part endgame.

Beginning on November 30, Cassini's orbit will send the spacecraft just past the outer edge of the main rings. These orbits, a series of 20, are called the F-ring orbits. During these weekly orbits, Cassini will approach to within 4,850 miles (7,800 kilometers) of the center of the narrow F ring, with its peculiar kinked and braided structure.

"During the F-ring orbits we expect to see the rings, along with the small moons and other structures embedded in them, as never before," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California. "The last time we got this close to the rings was during arrival at Saturn in 2004, and we saw only their backlit side. Now we have dozens of opportunities to examine their structure at extremely high resolution on both sides."

Cassini's final phase—called the Grand Finale—begins in earnest in April 2017. A close flyby of Saturn's giant moon Titan will reshape the spacecraft's orbit so that it passes through the gap between Saturn and the rings - an unexplored space only about 1,500 miles (2,400 kilometers) wide.

The spacecraft is expected to make 22 plunges through this gap, beginning with its first dive on April 27.

During the Grand Finale, Cassini will make the closest-ever observations of Saturn, mapping the planet's magnetic and gravity fields with exquisite precision and returning ultra-close views of the atmosphere.

Scientists also hope to gain new insights into Saturn's interior structure, the precise length of a Saturn day, and the total mass of the rings—which may finally help settle the question of their age. The spacecraft will also directly analyze dust-sized particles in the main rings and sample the outer reaches of Saturn's atmosphere—both first-time measurements for the mission.

"It's like getting a whole new mission," said Spilker. "The scientific value of the F ring and Grand Finale orbits is so compelling that you could imagine a whole mission to Saturn designed around what we're about to do."

Since the beginning of 2016, mission engineers have been tweaking Cassini's orbital path around Saturn to position the spacecraft for the mission's final phase. They have sent the spacecraft on a series of flybys past Titan that are progressively raising the tilt of Cassini's orbit with respect to Saturn's equator and rings.

The Grand Finale will come to a dramatic end on Sept. 15, 2017, as Cassini dives into Saturn's atmosphere, returning data about the planet's chemical composition until its signal is lost. Friction with the atmosphere will cause the spacecraft to burn up like a meteor soon afterward.

To celebrate the beginning of the final year and the adventure ahead, the Cassini team is releasing a new movie of the rotating planet, along with a color mosaic, both taken from high above Saturn's northern hemisphere. The movie covers 44 hours, or just over four Saturn rotations.

"This is the sort of view Cassini will have as the spacecraft repeatedly climbs high above Saturn's northern latitudes before plunging past the outer—and later the inner—edges of the rings," said Spilker.

And so, although the mission's end is approaching—with a "Cassini Final Plunge" clock already counting down in JPL mission control—an extremely important phase of the mission is still to come.

"We may be counting down, but no one should count Cassini out yet," said Curt Niebur, Cassini program scientist at NASA Headquarters in Washington. "The journey ahead is going to be a truly thrilling ride."

The Daily Galaxy via JPL/NASA

Related articles

A Moment of Zen --Titan Beyond Saturn's Rings

Cassini Spacecraft Tracks Mystery Object in a Titan Sea

Supermassive black holes, millions to billions of times the mass of our Sun, are found at the centers of galaxies. Many of these galactic behemoths are hidden within a thick doughnut-shape ring of dust and gas known as a torus. Previous observations suggest these cloaking, tire-like structures are formed from the native material found near the center of a galaxy.

New data from the Atacama Large Millimeter/submillimeter Array (ALMA), however, reveal that the black hole at the center of a galaxy named NGC 1068 is actually the source of its own dusty torus of dust and gas, forged from material flung out of the black hole's accretion disk.

This newly discovered cosmic fountain of cold gas and dust could reshape our understanding of how black holes impact their host galaxy and potentially the intergalactic medium.

"Think of a black hole as an engine. It's fueled by material falling in on it from a flattened disk of dust and gas," said Jack Gallimore, an astronomer at Bucknell University in Lewisburg, Pennsylvania, and lead author on a paper published in Astrophysical Journal Letters. "But like any engine, a black hole can also emit exhaust." That exhaust, astronomers discovered, is the likely source of the torus of material that effectively obscures the region around the galaxy's supermassive black hole from optical telescopes.

NGC 1068 (also known as Messier 77) is a barred spiral galaxy approximately 47 million light-years from Earth in the direction of the constellation Cetus. At its center is an active galactic nucleus, a supermassive black hole that is being fed by a thin, rotating disk of gas and dust known as an accretion disk. As material in the disk spirals toward the central black hole, it becomes superheated and blazes bright with ultraviolet radiation. The outer reaches of the disk, however, are considerably cooler and glow more appreciably in infrared light and the millimeter-wavelength light that ALMA can detect.

Using ALMA, an international team of astronomers peered deep into this region and discovered a sprinkling of cool clouds of carbon monoxide lifting off the outer portion of the accretion disk. The energy from the hot inner disk partially ionizes these clouds, enabling them to adhere to powerful magnetic field lines that wrap around the disk.

ALMA image at the top of the page shows the central region of galaxy NGC 1068. The torus of material harboring the supermassive black hole is highlighted in the pullout box. This region, which is approximately 40 light-years across, is the result of material flung out of the black hole's accretion disk. The colors in this image represent the motion of the gas: blue is material moving toward us, red moving away.

The areas in green are low velocity and consistent with rotation around a black hole. The white in the central region means the gas is moving both toward and away at very high speed, the conditions illustrated in the artist impression. The outer ring area is unrelated to the black hole and is more tied to the structure of the central 1,000 light-years of the host galaxy.

Like water being flung out of a rapidly rotating garden sprinkler, the clouds rising above the accretion disk get accelerated centrifugally along the magnetic field lines to very high speeds—approximately 400 to 800 kilometers per second (nearly 2 million miles per hour). This is up to nearly three times faster than the rotational speed of the outer accretion disk, fast enough to send the clouds hurtling further out into the galaxy.

"These clouds are traveling so fast that they reach 'escape velocity' and are jettisoned in a cone-like spray from both sides of the disk," said Gallimore. "With ALMA, we can for the first time see that it is the gas that is thrown out that hides the black hole, not the gas falling in." This suggests that the general theory of an active black hole is oversimplified, he concludes.

With future ALMA observations, the astronomers hope to work out a fuel budget for this black hole engine: how much mass per year goes into the black hole and how much is ejected as exhaust.

"These are fundamental quantities for understanding black holes that we really don't have a good handle on at this time," concludes Gallimore.

This research is presented in the paper titled "High-velocity bipolar molecular emission from an AGN torus," by J. Gallimore et al., published in Astrophysical Journal Letters on 15 September 2016. [Preprint: arxiv.org/pdf/1608.02210v1.pdf ]

The Daily Galaxy via National Radio Astronomy Observatory

Image Credit: Gallimore et al.; ALMA (ESO/NAOJ/NRAO); B. Saxton (NRAO/AUI/NSF)

Related articles

Friday's 'Galaxy' Insight --"Why the Universe Exists"

"Extreme Black Hole Jets Signal Galaxy Mergers" --Hubble/ALMA Observatories

Evidence of Enormous First Stars of the Cosmos Found in Primordial Galaxy

NASA has astronauts in training under extreme weather conditions of Antarctica to prepare them for deep space and planetary explorations such as the manned journey to Mars. The preparation includes the astronauts undergoing tests to cope with isolation, confinement and an extreme weather environment (ICE).

"You can't walk off the ice. That goes for whether you're having a health, behavioral health or a personal issue, you're not going anywhere," Lisa Spence, project manager for NASA flight analogs in the Human Research Program said in a press release. "That is very similar to spaceflight. It changes your mindset about how you are going to respond when you know you can't leave," Spence added.

"The most helpful strategy I developed was to avoid thinking about all the things I was missing out on and instead focused on the unique things in the moment that I would never get to experience again," said NASA astronaut Christina Hammock Koch.

An October, 2015 NASA study says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.

The research challenges the conclusions of other studies, including the Intergovernmental Panel on Climate Change's (IPCC) 2013 report, which says that Antarctica is overall losing land ice.

According to the new analysis of satellite data, the Antarctic ice sheet showed a net gain of 112 billion tons of ice a year from 1992 to 2001. That net gain slowed to 82 billion tons of ice per year between 2003 and 2008.

“We're essentially in agreement with other studies that show an increase in ice discharge in the Antarctic Peninsula and the Thwaites and Pine Island region of West Antarctica,” said Jay Zwally, a glaciologist with NASA Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study, which was published on Oct. 30 in the Journal of Glaciology. “Our main disagreement is for East Antarctica and the interior of West Antarctica there, we see an ice gain that exceeds the losses in the other areas.” Zwally added that his team “measured small height changes over large areas, as well as the large changes observed over smaller areas.”

Scientists calculate how much the ice sheet is growing or shrinking from the changes in surface height that are measured by the satellite altimeters. In locations where the amount of new snowfall accumulating on an ice sheet is not equal to the ice flow downward and outward to the ocean, the surface height changes and the ice-sheet mass grows or shrinks.

But it might only take a few decades for Antarctica's growth to reverse, according to Zwally. “If the losses of the Antarctic Peninsula and parts of West Antarctica continue to increase at the same rate they've been increasing for the last two decades, the losses will catch up with the long-term gain in East Antarctica in 20 or 30 years -- I don't think there will be enough snowfall increase to offset these losses.”

The study analyzed changes in the surface height of the Antarctic ice sheet measured by radar altimeters on two European Space Agency European Remote Sensing (ERS) satellites, spanning from 1992 to 2001, and by the laser altimeter on NASA's Ice, Cloud, and land Elevation Satellite (ICESat) from 2003 to 2008.

Zwally said that while other scientists have assumed that the gains in elevation seen in East Antarctica are due to recent increases in snow accumulation, his team used meteorological data beginning in 1979 to show that the snowfall in East Antarctica actually decreased by 11 billion tons per year during both the ERS and ICESat periods. They also used information on snow accumulation for tens of thousands of years, derived by other scientists from ice cores, to conclude that East Antarctica has been thickening for a very long time.

“At the end of the last Ice Age, the air became warmer and carried more moisture across the continent, doubling the amount of snow dropped on the ice sheet,” Zwally said.

The extra snowfall that began 10,000 years ago has been slowly accumulating on the ice sheet and compacting into solid ice over millennia, thickening the ice in East Antarctica and the interior of West Antarctica by an average of 0.7 inches (1.7 centimeters) per year. This small thickening, sustained over thousands of years and spread over the vast expanse of these sectors of Antarctica, corresponds to a very large gain of ice enough to outweigh the losses from fast-flowing glaciers in other parts of the continent and reduce global sea level rise.

Zwally's team calculated that the mass gain from the thickening of East Antarctica remained steady from 1992 to 2008 at 200 billion tons per year, while the ice losses from the coastal regions of West Antarctica and the Antarctic Peninsula increased by 65 billion tons per year.

“The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 millimeters per year away,” Zwally said. “But this is also bad news. If the 0.27 millimeters per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for.”

“The new study highlights the difficulties of measuring the small changes in ice height happening in East Antarctica,” said Ben Smith, a glaciologist with the University of Washington in Seattle who was not involved in Zwally's study.

"Doing altimetry accurately for very large areas is extraordinarily difficult, and there are measurements of snow accumulation that need to be done independently to understand what's happening in these places,” Smith said.

To help accurately measure changes in Antarctica, NASA is developing the successor to the ICESat mission, ICESat-2, which is scheduled to launch in 2018. “ICESat-2 will measure changes in the ice sheet within the thickness of a No. 2 pencil,” said Tom Neumann, a glaciologist at Goddard and deputy project scientist for ICESat-2. “It will contribute to solving the problem of Antarctica's mass balance by providing a long-term record of elevation changes.”

The Daily Galaxy NASA, NatureWorldNews and http://www.spacedaily.com/reports/Antarctica_Provides_ICE_to_Study_Behavior_Effects_in_Astronauts_999.html

Related articles

The Day the World's Astronomers Zoomed in On a Distant Galaxy

NASA News: Observes an Erupting Black Hole With an Orbiting Sun-Like Star

Robotic NASA Detective Discovers Planet-Destroying Electric Winds That Suck Oxygen Out of an Atmosphere

New Water Sources Observed on the Moon --Could Facilitate Future Manned Bases

When it comes to exoplanets, astronomers have realized that they only know the properties of the planets they discover as well as they know the properties of the stars being orbited. For a planet's size, precisely characterizing the host star can mean the difference in our understanding of whether a distant world is small like Earth or huge like Jupiter.

For astronomers to determine the size of an exoplanet—planets outside the solar system—depends critically on knowing not only the radius of its host star but also whether that star is single or has a close companion. About half of the stars in the sky are not one but two stars orbiting around each other, this makes knowing the binary property of a star paramount.

One particularly interesting and relatively nearby star, named TRAPPIST-1, recently caught the attention of a team of researchers at NASA's Ames Research Center. They wanted to determine if TRAPPIST-1, which is home to three small, potentially rocky planets—one of which orbits in the temperate habitable zone where liquid water might pool on the surface—was a single star like the sun, or if it had a companion star. If TRAPPIST-1 did have a companion star, the discovered planets will have larger sizes, possibly large enough to be ice giants similar to Neptune.

If an exoplanet orbits a star in a binary system but astronomers believe the starlight captured by the telescope is from a single star, the real radius of the planet will be larger than measured. The difference in the measured size of the exoplanet can be small ranging from 10 percent to more than a factor of two in size, depending on the brightness of the companion star in the system.

To confirm or deny the single star nature of TRAPPIST-1, Steve Howell, senior research scientist at Ames Research Center, led an investigation of the star. Using a specially designed camera, called the Differential Speckle Survey Instrument or DSSI, Howell and his team measured the rapid disturbances in the light emitted by the star caused by the Earth's atmosphere and corrected for them. The resultant high-resolution image revealed that the light coming from the TRAPPIST-1 system is from a single star.

With the confirmation that no other companion star resides in the vicinity of TRAPPIST-1, the research team's result validates not only that transiting planets are responsible for the periodic dips seen in the star's brightness but that they are indeed Earth-size and may likely to be rocky worlds.

“Knowing that a terrestrial-size potentially rocky planet orbits in the habitable zone of a star only 40 light-years from the Earth is an awesome finding,” said Howell. “The TRAPPIST-1 system will continue to be studied in great detail as these transiting exoplanets offer one of the best chances to characterize the atmosphere of an alien world.”

Mounted on the 8-meter Gemini Observatory South telescope in Chile, the DSSI provided astronomers with the highest resolution images available today from a single ground-based telescope. The nearness of TRAPPIST-1 allowed astronomers to peer deep into the system, looking closer than Mercury's orbit to our sun.

The four-panel graphic above illustrates the difference of measured starlight when seen through a ground-based telescope with and without (top left corner) the blurring effects caused by Earth's atmosphere. The technique to neutralize Earth's atmospheric blur is called speckle interferometry. All four images are shown at the same scale. Credits: NASA/Ames/W. Stenzel

Interest in the recently-discovered TRAPPIST-1 with its three Earth-size planets is high. Astronomically speaking, at 40 light-years from Earth, the system is a hop, skip and a jump away. The star itself is a dim M-type star, which, relative to most stars, is very small and cool, but making transit detection of small planets easier.

Further detailed measurement of the planetary transits seen in TRAPPIST-1 will begin later this year when NASA's Kepler space telescope in its K2 mission will precisely monitor minute changes in the light emitted from the star for a period of about 75 days.

The space-based observations from the Kepler spacecraft will provide extremely precise measurements of the planet transit shapes allowing for more refined radius and orbital period determination. Noting variations in the mid-time of the transit events can also help astronomers determine the planet masses. Additionally, the new observations will be searched for more transiting planets in the TRAPPIST-1 system.

Speckle interferometry, the imaging technique used by the DSSI, is a powerful asset in the astronomer's toolkit as it provides a unique capability to characterize the environment around distant stars. The technique provides ultra high-resolution images by taking multiple extremely short (40-60 millisecond) exposures of a star to capture fine detail in the received light and “freeze” the turbulence caused by Earth's atmosphere.

By combining the many thousands of exposures and using mathematical techniques to remove the momentary distortions caused by Earth's atmosphere, the final result provides a resolution equal to the theoretical limit of what the 8-meter Gemini telescope would produce if no atmosphere were present.

The Daily Galaxy via  astrobio.net

Image credit top of page: with thanks to atramateria.com

Fringe-lipped bat close-up (Alexander T. Baugh)

Former Smithsonian Tropical Research Institute intern Dylan Gomes releases a Jamaican fruit-eating bat (Artibeus jamaicensis) in Soberanía National Park, Panama, on June 6, 2014. (Photo by Sean Mattson / Smithsonian Tropical Research Institute)

Bat attacking the robotic frog setup. (Photo by Rachel Moon)

The fringe-lipped bat foraging above the forest floor. (Photo by Alex Lang)