Author Topic: NASA - Cassini updates  (Read 281599 times)

Offline deruch

  • Senior Member
  • *****
  • Posts: 2426
  • California
  • Liked: 1990
  • Likes Given: 5506
Re: NASA - Cassini updates
« Reply #760 on: 04/02/2018 02:42 am »



https://www.youtube.com/watch?v=z7P5bsmVuqo?t=001s

Planning Cassini’s Grand Finale

NASA Jet Propulsion Laboratory
Streamed live on Mar 22, 2018
Original air date: March 22 at 7 p.m. PT (10 p.m. ET, 0200 UTC)
 
Mission planning is a core strength of JPL engineering, along with deep space communications and navigation. This talk looks back at the various scenarios and contingency plans the Cassini team made as they steered the spacecraft into unexplored space during its 2017 Grand Finale at Saturn. Sturm discussed how the possible scenarios -- some of which could have been mission-ending -- compared to the mission as it was actually flown, along with some science highlights from the finale.
 
Erick Sturm, JPL Systems Engineer
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline Star One

  • Senior Member
  • *****
  • Posts: 10328
  • UK
  • Liked: 2098
  • Likes Given: 208
NASA - Cassini updates
« Reply #761 on: 07/13/2018 07:33 pm »
NASA’s Cassini Coverage Lands an Emmy Nomination

The Academy of Television Arts & Sciences nominated NASA's Jet Propulsion Laboratory in Pasadena, California, for Outstanding Original Interactive Program for its coverage of the Cassini mission's Grand Finale at Saturn, including news, web, education, television and social media efforts.

In 2017, after nearly 20 years in space and 13 years revealing the wonders of Saturn, NASA’s Cassini orbiter was running out of fuel. As a final act, Cassini began a whole new mission -- its Grand Finale. This journey into the unknown would end with a spectacular plunge into the planet. JPL created a multi-month digital campaign to celebrate the mission’s science and engineering accomplishments and communicate why the spacecraft must meet its end in the skies of Saturn.



Cassini’s first, daring dive into the unexplored space between the giant planet and its rings kicked off the campaign on April 26, 2017. It culminated on Sept. 15, 2017, with live coverage of Cassini’s plunge into Saturn’s atmosphere, with the spacecraft sending back science to the very last second.

The multi-faceted campaign included regular updates on Twitter, Facebook, Snapchat, Instagram and the Cassini mission website; multiple live social, web and TV broadcasts during which reporter and public questions were answered; a dramatic short film to communicate the mission’s story and preview its endgame; multiple 360-degree videos, including NASA’s first 360-degree livestream of a mission event from inside JPL mission control; an interactive press kit; a steady drumbeat of articles to keep fans updated with news and features about the people behind the mission; state-standards aligned educational materials; a celebration of art by amateur space enthusiasts; and software to provide real-time tracking of the spacecraft, down to its final transmission to Earth.

The Primetime Emmys will be awarded by the Academy of Television Arts & Sciences in Los Angeles on Sept. 17. The Creative Arts Emmys, which includes interactive awards, will be presented during a separate ceremony on Saturday, Sept. 15, at the Microsoft Theatre in Los Angeles.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

More information about Cassini:

https://www.nasa.gov/cassini

https://saturn.jpl.nasa.gov
« Last Edit: 07/13/2018 07:34 pm by Star One »

Offline bolun

  • Senior Member
  • *****
  • Posts: 2889
  • Europe
  • Liked: 266
  • Likes Given: 72
Re: NASA - Cassini updates
« Reply #762 on: 09/05/2018 06:24 pm »
SATURN'S FAMOUS HEXAGON MAY TOWER ABOVE THE CLOUDS

04 September 2018

The long-lived international Cassini mission has revealed a surprising feature emerging at Saturn's northern pole as it nears summertime: a warming, high-altitude vortex with a hexagonal shape, akin to the famous hexagon seen deeper down in Saturn's clouds. This suggests that the lower-altitude hexagon may influence what happens up above, and that it could be a towering structure spanning hundreds of kilometres in height.

http://sci.esa.int/cassini-huygens/60589-saturn-s-famous-hexagon-may-tower-above-the-clouds/

Image credit: NASA/JPL-Caltech/University of Leicester/GSFC/ L.N. Fletcher et al. 2018

Online Robotbeat

  • Senior Member
  • *****
  • Posts: 28854
  • Minnesota
  • Liked: 9047
  • Likes Given: 5798
Re: NASA - Cassini updates
« Reply #763 on: 09/09/2018 04:19 am »
Erik Wernquist's animation of NASA Cassini's Grand Finale just won an Emmy:
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online Robotbeat

  • Senior Member
  • *****
  • Posts: 28854
  • Minnesota
  • Liked: 9047
  • Likes Given: 5798
Re: NASA - Cassini updates
« Reply #764 on: 09/09/2018 04:46 am »
Oddly enough, there's no mention of the actual person who made this draw-dropping animation (Erik Wernquist) in any of the English news articles about the Emmy nomination or award. I'm a little miffed that JPL seems to be taking all the credit for Erik Wernquist's FANTASTIC work.

The award is for the animation, which is why "YouTube" is listed as the medium on www.emmys.com, but no mention of him is given. This is really disappointing.
« Last Edit: 09/09/2018 04:49 am by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 11669
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 8798
  • Likes Given: 7392
Re: NASA - Cassini updates
« Reply #765 on: 09/09/2018 09:49 pm »
Oddly enough, there's no mention of the actual person who made this draw-dropping animation (Erik Wernquist) in any of the English news articles about the Emmy nomination or award. I'm a little miffed that JPL seems to be taking all the credit for Erik Wernquist's FANTASTIC work.

The award is for the animation, which is why "YouTube" is listed as the medium on www.emmys.com, but no mention of him is given. This is really disappointing.
Thanks for ferreting this out. It's kind of pathetic that proper credit wasn't given
« Last Edit: 09/10/2018 04:11 am by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Online catdlr

  • Member
  • Senior Member
  • *****
  • Posts: 6028
  • Viewed launches since the Redstones
  • Marina del Rey, California, USA
  • Liked: 2527
  • Likes Given: 1909
Re: NASA - Cassini updates
« Reply #766 on: 09/11/2018 01:38 am »
And the Emmy goes to: Cassini's Grand Finale

article:  https://www.jpl.nasa.gov/news/news.php?feature=7232

Photo Credit:
Quote
Members of the JPL Media Relations and Public Engagement offices, and leaders of the Cassini Mission received an Emmy for Outstanding Original Interactive Program at the Television Academy's 2018 Creative Arts Emmy Awards at the Microsoft Theater on Saturday, Sept. 8, 2018, in Los Angeles. L to R:Alice Wessen, Jia-Rui Cook, Preston Dyches, Phil Davis, Linda Spilker (holding the Emmy), Gay Hill, Veronica McGregor, Stephanie L. Smith, Bill Dunford, Earl Maize, Julie Webster, Jess Doherty.Credit: NASA/JPL-Caltech
Tony De La Rosa

Offline Star One

  • Senior Member
  • *****
  • Posts: 10328
  • UK
  • Liked: 2098
  • Likes Given: 208
Re: NASA - Cassini updates
« Reply #767 on: 12/17/2018 08:40 pm »
NASA Research Reveals Saturn is Losing Its Rings at “Worst-Case-Scenario” Rate

New NASA research confirms that Saturn is losing its iconic rings at the maximum rate estimated from Voyager 1 & 2 observations made decades ago. The rings are being pulled into Saturn by gravity as a dusty rain of ice particles under the influence of Saturn’s magnetic field.



“We estimate that this ‘ring rain’ drains an amount of water products that could fill an Olympic-sized swimming pool from Saturn’s rings in half an hour,” said James O’Donoghue of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “From this alone, the entire ring system will be gone in 300 million years, but add to this the Cassini-spacecraft measured ring-material detected falling into Saturn’s equator, and the rings have less than 100 million years to live. This is relatively short, compared to Saturn’s age of over 4 billion years.” O’Donoghue is lead author of a study on Saturn’s ring rain appearing in Icarus December 17.

Cassini image of Saturn and its rings
This image was made as the Cassini spacecraft scanned across Saturn and its rings on April 25, 2016, capturing three sets of red, green and blue images to cover this entire scene showing the planet and the main rings. The images were obtained using Cassini's wide-angle camera at a distance of approximately 1.9 million miles (3 million kilometers) from Saturn and at an elevation of about 30 degrees above the ring plane.

Scientists have long wondered if Saturn was formed with the rings or if the planet acquired them later in life. The new research favors the latter scenario, indicating that they are unlikely to be older than 100 million years, as it would take that long for the C-ring to become what it is today assuming it was once as dense as the B-ring. “We are lucky to be around to see Saturn’s ring system, which appears to be in the middle of its lifetime. However, if rings are temporary, perhaps we just missed out on seeing giant ring systems of Jupiter, Uranus and Neptune, which have only thin ringlets today!” O’Donoghue added.

Various theories have been proposed for the ring’s origin. If the planet got them later in life, the rings could have formed when small, icy moons in orbit around Saturn collided, perhaps because their orbits were perturbed by a gravitational tug from a passing asteroid or comet.

Artist's impression of Saturn losing its rings over millions of years

The first hints that ring rain existed came from Voyager observations of seemingly unrelated phenomena: peculiar variations in Saturn’s electrically charged upper atmosphere (ionosphere), density variations in Saturn’s rings, and a trio of narrow dark bands encircling the planet at northern mid-latitudes. These dark bands appeared in images of Saturn’s hazy upper atmosphere (stratosphere) made by NASA’s Voyager 2 mission in 1981.

In 1986, Jack Connerney of NASA Goddard published a paper in Geophysical Research Letters that linked those narrow dark bands to the shape of Saturn’s enormous magnetic field, proposing that electrically charged ice particles from Saturn’s rings were flowing down invisible magnetic field lines, dumping water in Saturn’s upper atmosphere where these lines emerged from the planet. The influx of water from the rings, appearing at specific latitudes, washed away the stratospheric haze, making it appear dark in reflected light, producing the narrow dark bands captured in the Voyager images.

Saturn’s rings are mostly chunks of water ice ranging in size from microscopic dust grains to boulders several yards (meters) across. Ring particles are caught in a balancing act between the pull of Saturn’s gravity, which wants to draw them back into the planet, and their orbital velocity, which wants to fling them outward into space. Tiny particles can get electrically charged by ultraviolet light from the Sun or by plasma clouds emanating from micrometeoroid bombardment of the rings. When this happens, the particles can feel the pull of Saturn’s magnetic field, which curves inward toward the planet at Saturn’s rings. In some parts of the rings, once charged, the balance of forces on these tiny particles changes dramatically, and Saturn’s gravity pulls them in along the magnetic field lines into the upper atmosphere.

Once there, the icy ring particles vaporize and the water can react chemically with Saturn’s ionosphere. One outcome from these reactions is an increase in the lifespan of electrically charged particles called H3+ ions, which are made up of three protons and two electrons. When energized by sunlight, the H3+ ions glow in infrared light, which was observed by O’Donoghue’s team using special instruments attached to the Keck telescope in Mauna Kea, Hawaii.

Their observations revealed glowing bands in Saturn’s northern and southern hemispheres where the magnetic field lines that intersect the ring plane enter the planet. They analyzed the light to determine the amount of rain from the ring and its effects on Saturn’s ionosphere. They found that the amount of rain matches remarkably well with the astonishingly high values derived more than three decades earlier by Connerney and colleagues, with one region in the south receiving most of it.

The team also discovered a glowing band at a higher latitude in the southern hemisphere. This is where Saturn’s magnetic field intersects the orbit of Enceladus, a geologically active moon that is shooting geysers of water ice into space, indicating that some of those particles are raining onto Saturn as well. “That wasn’t a complete surprise,” said Connerney. “We identified Enceladus and the E-ring as a copious source of water as well, based on another narrow dark band in that old Voyager image.” The geysers, first observed by Cassini instruments in 2005, are thought to be coming from an ocean of liquid water beneath the frozen surface of the tiny moon. Its geologic activity and water ocean make Enceladus one of the most promising places to search for extraterrestrial life.

Cassini image of Enceladus and Saturn's rings
Saturn’s moon Enceladus drifts before the rings and the tiny moon Pandora in this view that NASA’s Cassini spacecraft captured on Nov. 1, 2009. The entire scene is backlit by the Sun, providing striking illumination for the icy particles that make up both the rings and the jets emanating from the south pole of Enceladus, which is about 314 miles (505 km) across. Pandora, which is about (52 miles, 84 kilometers) wide, was on the opposite side of the rings from Cassini and Enceladus when the image was taken. This view looks toward the night side on Pandora as well, which is lit by dim golden light reflected from Saturn.

The team would like to see how the ring rain changes with the seasons on Saturn. As the planet progresses in its 29.4-year orbit, the rings are exposed to the Sun to varying degrees. Since ultraviolet light from the Sun charges the ice grains and makes them respond to Saturn’s magnetic field, varying exposure to sunlight should change the quantity of ring rain.

The research was funded by NASA and the NASA Postdoctoral Program at NASA Goddard, administered by the Universities Space Research Association. The W.M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and the data in the form of its files are available from the Keck archive. The authors wish to recognize the significant cultural role and reverence that the summit of Mauna Kea has within the indigenous Hawaiian community; they are fortunate to have the opportunity to conduct observations from this mountain.

Bill Steigerwald / Nancy Jones

NASA Goddard Space Flight Center, Greenbelt, Maryland

301-286-8955 / 301-286-0039

[email protected] / [email protected]

Offline jacqmans

  • Moderator
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 18254
  • Houten, The Netherlands
  • Liked: 3909
  • Likes Given: 212
Re: NASA - Cassini updates
« Reply #768 on: 01/14/2019 12:56 pm »
Seeing Titan with infrared eyes

Saturn’s moon Titan is enveloped in a thick atmosphere, but through the infrared eyes of the international Cassini mission, the moon’s myriad surface features are revealed in this exquisite global mosaic.

Observing the surface of Saturn’s largest moon, Titan, in visible light is difficult due to the globe-enshrouding haze that envelops the moon. On 14 January 2005, the mystery as to what lay beneath the thick atmosphere was revealed as ESA’s Huygens probe – carried to Titan by Cassini – made the first successful landing on a world in the outer Solar System. During the two-and-a-half hour descent under parachute, features that looked remarkably like shore lines and river systems on Earth appeared from the haze. But rather than water, with surface temperatures of around –180ºC, the fluid involved here is methane, a simple organic compound that also contributes to the moon’s obscuring atmosphere.

Thanks to Cassini, which studied Saturn and its rings and moons for thirteen years, Titan was extensively mapped and analysed. One result is this stunning sequence of images created using data acquired by Cassini’s Visual and Infrared Mapping Spectrometer (VIMS), whose infrared observations peered through Titan’s atmosphere, complementing the views obtained by Huygens during descent and on the surface. The maps combine data from the multitude of different observations made under a wide variety of illumination and viewing conditions over the course of the mission, stitched together in a seamless mosaic to provide the best representation of Titan’s surface to date.

The colours reflect variations in materials on the moon’s surface. For example, the moon’s equatorial dune fields appear a consistent brown colour, while bluish and purple hues may indicate materials enriched in water ice.

The image was first published in July 2018 – read more here about how the image was created, and enjoy a video featuring further stunning visuals here. The complete Cassini VIMS data archive of Saturn’s satellites is available here.

The Cassini mission is a cooperative project of NASA, ESA and Italy’s ASI space agency. The mission concluded in September 2017.
 
Credits: NASA/JPL-Caltech/University of Nantes/University of Arizona

Offline ugordan

  • Senior Member
  • *****
  • Posts: 7778
    • My mainly Cassini image gallery
  • Liked: 2014
  • Likes Given: 468
Re: NASA - Cassini updates
« Reply #769 on: 01/14/2019 01:06 pm »
The image was first published in July 2018 – read more here about how the image was created, and enjoy a video featuring further stunning visuals here.

Link?

Offline Sam Ho

  • Full Member
  • ****
  • Posts: 585
  • Liked: 248
  • Likes Given: 66
Re: NASA - Cassini updates
« Reply #770 on: 01/15/2019 02:38 am »
The image was first published in July 2018 – read more here about how the image was created, and enjoy a video featuring further stunning visuals here.

Link?
Article, with working links, is here:
http://www.esa.int/spaceinimages/Images/2019/01/Seeing_Titan_with_infrared_eyes

Offline Star One

  • Senior Member
  • *****
  • Posts: 10328
  • UK
  • Liked: 2098
  • Likes Given: 208
Re: NASA - Cassini updates
« Reply #771 on: 01/17/2019 09:22 pm »
NASA's Cassini Data Show Saturn's Rings Relatively New

The rings of Saturn may be iconic, but there was a time when the majestic gas giant existed without its distinctive halo. In fact, the rings may have formed much later than the planet itself, according to a new analysis of gravity science data from NASA's Cassini spacecraft.

The findings indicate that Saturn's rings formed between 10 million and 100 million years ago. From our planet's perspective, that means Saturn's rings may have formed during the age of dinosaurs.

The conclusions of the research - gleaned from measurements collected during the final, ultra-close orbits Cassini performed in 2017 as the spacecraft neared the end of its mission - are the best answer yet to a longstanding question in solar system science. The findings were published online Jan. 17 in Science.

Saturn formed 4.5 billion years ago, in the early years of our solar system. There have been clues that its ring system is a young upstart that attached to Saturn years afterward. But how long afterward?

To figure out the age of the rings, scientists needed to measure something else: the mass of the rings, or how much material they hold. Researchers had the remote-sensing measurements from Cassini and both of NASA's Voyager spacecraft in the early 1980s. Then came Cassini's unprecedented, up-close data from its final orbits. As the spacecraft was running out of fuel, it performed 22 dives between the planet and the rings.

The dives allowed the spacecraft to act as a probe, falling into Saturn's gravity field, where it could feel the tug of the planet and the rings. Radio signals sent to Cassini from the antennas of NASA's Deep Space Network and the European Space Agency relayed the spacecraft's velocity and acceleration.

Once scientists knew how much gravity was pulling on Cassini, causing it to accelerate - down to a fraction of a millimeter per second - they could determine how massive the planet is and how massive the rings are.

"Only by getting so close to Saturn in Cassini's final orbits were we able to gather the measurements to make the new discoveries," said Cassini radio science team member and lead author Luciano Iess, of Sapienza University of Rome. "And with this work, Cassini fulfills a fundamental goal of its mission: not only to determine the mass of the rings, but to use the information to refine models and determine the age of the rings."

Iess' paper builds on a connection scientists previously made between the mass of the rings and their age. Lower mass points to a younger age, because the rings, which are bright and mostly made of ice, would have been contaminated and darkened by interplanetary debris over a longer period. With a better calculation of ring mass, scientists were better able to estimate the rings' age.

Saturn scientists will continue work to figure out how the rings formed. The new evidence of young rings lends credence to theories that they formed from a comet that wandered too close and was torn apart by Saturn's gravity - or by an event that broke up an earlier generation of icy moons.

Rotating Layers Go Deep

From Cassini's super-close vantage point, immersed in Saturn's gravity field, the spacecraft relayed measurements that led scientists to another surprising discovery.

It's long been known that Saturn's equatorial atmosphere rotates around the planet faster than its inner layers and core. Imagine a set of nested cylinders, rotating at different speeds. Eventually, toward the center of the planet, the layers move in synchrony and rotate together.

Jupiter's atmosphere behaves like this, too. But the new findings show that Saturn's layers start rotating in synchrony much deeper into the planet - at least 5,600 miles (9,000 kilometers) in. That's three times deeper than the same phenomenon at Jupiter. It's a depth that equals 15 percent of Saturn's entire radius.

"The discovery of deeply rotating layers is a surprising revelation about the internal structure of the planet," said Cassini Project Scientist Linda Spilker of JPL. "The questions are what causes the more rapidly rotating part of the atmosphere to go so deep, and what does that tell us about Saturn's interior?"

At the same time, the measurement of Saturn's gravity solved yet another unknown: the mass of the core. Models of the interior developed by Burkhard Militzer, a UC Berkeley professor and a co-author of the paper, indicate that it is 15 to 18 Earth masses.

Cassini's mission ended in September 2017, when it was low on fuel and deliberately plunged into Saturn's atmosphere to protect the planet's moons. More science from the last orbits, known as the Grand Finale, will be published in the coming months.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency (ESA) and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. JPL designed, developed and assembled the Cassini orbiter. The radio science instrument was built by JPL and the Italian Space Agency, working with team members from the U.S. and Italy.

For more information about Cassini, go to:

https://solarsystem.nasa.gov/cassini

Offline vjkane

  • Full Member
  • ****
  • Posts: 723
  • Liked: 158
  • Likes Given: 3
Re: NASA - Cassini updates
« Reply #772 on: 01/18/2019 01:52 pm »

Saturn scientists will continue work to figure out how the rings formed. The new evidence of young rings lends credence to theories that they formed from a comet that wandered too close and was torn apart by Saturn's gravity - or by an event that broke up an earlier generation of icy moons.

If the rings are young, could the innermost moons, including Enceladus also be new?

Offline Alpha_Centauri

  • Full Member
  • ****
  • Posts: 654
  • England
  • Liked: 235
  • Likes Given: 137
Re: NASA - Cassini updates
« Reply #773 on: 01/18/2019 04:40 pm »
Yes, evidence has been growing in recent years that both the rings and inner moons were formed in a relatively young event.  That the estimated age for both happens to coincide is probably not an accident.

E.g, https://www.seti.org/seti-institute/press-release/moons-saturn-may-be-younger-dinosaurs

This is part of the astrobiological preference for Europa. We may be too early for recognisable life on Enceladus...
« Last Edit: 01/18/2019 04:54 pm by Alpha_Centauri »

Offline Star One

  • Senior Member
  • *****
  • Posts: 10328
  • UK
  • Liked: 2098
  • Likes Given: 208
NASA - Cassini updates
« Reply #774 on: 01/18/2019 04:57 pm »
Yes, evidence has been growing in recent years that both the rings and inner moons were formed in a relatively young event.  That the estimated age for both happens to coincide is probably not an accident.

E.g, https://www.seti.org/seti-institute/press-release/moons-saturn-may-be-younger-dinosaurs

This is part of the astrobiological preference for Europa. We may be too early for recognisable life on Enceladus...

Well if Enceladus is only 10 millions years old it’s highly unlikely to have life. And if this other study on icy moons (see below) is to believed in general it looks like they all maybe dead.

Ocean Moons, Promising Targets in Search for Alien Life, Could Be Dead Inside

Quote
The interiors of Europa and other watery moons in the outer solar system might be too geologically inactive to support life
« Last Edit: 01/18/2019 04:59 pm by Star One »

Offline Phil Stooke

  • Full Member
  • ****
  • Posts: 581
  • Canada
  • Liked: 386
  • Likes Given: 0
Re: NASA - Cassini updates
« Reply #775 on: 01/18/2019 05:07 pm »
The cratering history of the moons might argue against this.  I would be dubious about the results of modelling based on these assumptions:

"Assuming that the energy powering these geysers comes directly from tidal interactions, and that Enceladus’ level of geothermal activity is more or less constant, then the tides within Saturn are quite strong."

We don't know either of those assumptions is correct. 

Offline Alpha_Centauri

  • Full Member
  • ****
  • Posts: 654
  • England
  • Liked: 235
  • Likes Given: 137
Re: NASA - Cassini updates
« Reply #776 on: 01/18/2019 05:46 pm »
I don't see how those assumptions are unreasonable given what we know about Enceladus.  What alternative seems likely?

More to the point crater counting has many assumptions required which are little better than throwing darts at a dartboard blindfolded.  We have no idea of the actual historical impact rate, especially if there was a huge breakup event in the system in recent history as Saturn's rings suggest.
« Last Edit: 01/18/2019 11:30 pm by Alpha_Centauri »

Offline Star One

  • Senior Member
  • *****
  • Posts: 10328
  • UK
  • Liked: 2098
  • Likes Given: 208
NASA - Cassini updates
« Reply #777 on: 01/19/2019 08:50 am »
I don't see how those assumptions are unreasonable given what we know about Enceladus.  What alternative seems likely?

More to the point crater counting has many assumptions required which are little better than throwing darts at a dartboard blindfolded.  We have no idea of the actual historical impact rate, especially if there was a huge breakup event in the system in recent history as Saturn's rings suggest.

Is it possible that Saturn ‘recycles’ its moons on a regular basis? Also that this isn’t the first time that Saturn has had rings?
« Last Edit: 01/19/2019 08:50 am by Star One »

Offline Chris Bergin

Re: NASA - Cassini updates
« Reply #778 on: 01/25/2019 05:56 pm »
FEATURE ARTICLE: Cassini still reveals Saturn’s secrets more than a year after its mission’s end -

https://www.nasaspaceflight.com/2019/01/cassini-reveals-saturns-secrets-year-missions-end/ - By Chris Gebhardt

Render by Nathan Koga for NSF/L2

https://twitter.com/NASASpaceflight/status/1088872966287446016

Offline Star One

  • Senior Member
  • *****
  • Posts: 10328
  • UK
  • Liked: 2098
  • Likes Given: 208
Re: NASA - Cassini updates
« Reply #779 on: 03/30/2019 10:19 am »
NASA's Cassini Finds Saturn's Rings Coat Tiny Moons

New findings have emerged about five tiny moons nestled in and near Saturn's rings. The closest-ever flybys by NASA's Cassini spacecraft reveal that the surfaces of these unusual moons are covered with material from the planet's rings - and from icy particles blasting out of Saturn's larger moon Enceladus. The work paints a picture of the competing processes shaping these mini-moons.

"The daring, close flybys of these odd little moons let us peer into how they interact with Saturn's rings," said Bonnie Buratti of NASA's Jet Propulsion Laboratory in Pasadena, California. Buratti led a team of 35 co-authors that published their work in the journal Science on March 28. "We're seeing more evidence of how extremely active and dynamic the Saturn ring and moon system is."

The new research, from data gathered by six of Cassini's instruments before its mission ended in 2017, is a clear confirmation that dust and ice from the rings accretes onto the moons embedded within and near the rings.

Scientists also found the moon surfaces to be highly porous, further confirming that they were formed in multiple stages as ring material settled onto denser cores that might be remnants of a larger object that broke apart. The porosity also helps explain their shape: Rather than being spherical, they are blobby and ravioli-like, with material stuck around their equators.

"We found these moons are scooping up particles of ice and dust from the rings to form the little skirts around their equators," Buratti said. "A denser body would be more ball-shaped because gravity would pull the material in."

"Perhaps this process is going on throughout the rings, and the largest ring particles are also accreting ring material around them. Detailed views of these tiny ring moons may tell us more about the behavior of the ring particles themselves," said Cassini Project Scientist Linda Spilker, also at JPL.

Of the satellites studied, the surfaces of those closest to Saturn - Daphnis and Pan - are the most altered by ring materials. The surfaces of the moons Atlas, Prometheus and Pandora, farther out from Saturn, have ring material as well - but they're also coated with the bright icy particles and water vapor from the plume spraying out of Enceladus. (A broad outer ring of Saturn, known as the E ring, is formed by the icy material that fans out from Enceladus' plume.)

The key puzzle piece was a data set from Cassini's Visible and Infrared Mapping Spectrometer (VIMS), which collected light visible to the human eye and also infrared light of longer wavelengths. It was the first time Cassini was close enough to create a spectral map of the surface of the innermost moon Pan. By analyzing the spectra, VIMS was able to learn about the composition of materials on all five moons.

VIMS saw that the ring moons closest to Saturn appear the reddest, similar to the color of the main rings. Scientists don't yet know the exact composition of the material that appears red, but they believe it's likely a mix of organics and iron.

The moons just outside the main rings, on the other hand, appear more blue, similar to the light from Enceladus' icy plumes.

The six uber-close flybys of the ring moons, performed between December 2016 and April 2017, engaged all of Cassini's optical remote sensing instruments that study the electromagnetic spectrum. They worked alongside the instruments that examined the dust, plasma and magnetic fields and how those elements interact with the moons.

Questions remain, including what triggered the moons to form. Scientists will use the new data to model scenarios and could apply the insights to small moons around other planets and possibly even to asteroids.

"Do any of the moons of the ice giant planets Uranus and Neptune interact with their thinner rings to form features similar to those on Saturn's ring moons?" Buratti asked. "These are questions to be answered by future missions."

Cassini's mission ended in September 2017, when it was low on fuel. Mission controllers deliberately plunged Cassini into Saturn's atmosphere rather than risk crashing the spacecraft into the planet's moons. More science from the last orbits, known as the Grand Finale, will be published in the coming months.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's JPL, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the U.S. and several European countries.

More information about Cassini can be found here:

https://solarsystem.nasa.gov/cassini


Tags: