Author Topic: NASA - Cassini updates  (Read 226931 times)

Offline AS_501

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Re: NASA - Cassini updates
« Reply #740 on: 09/15/2017 04:25 PM »
Atoms and molecules from Earth now part of Saturn's atmosphere....

Offline Star One

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Re: NASA - Cassini updates
« Reply #741 on: 09/15/2017 04:53 PM »

Online ugordan

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Re: NASA - Cassini updates
« Reply #742 on: 09/15/2017 05:15 PM »
End of mission recap briefing:


Online FutureSpaceTourist

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Re: NASA - Cassini updates
« Reply #743 on: 09/15/2017 05:52 PM »

Offline Star One

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Re: NASA - Cassini updates
« Reply #744 on: 09/15/2017 06:59 PM »
Cassini: The dying of the light

Quote
But a light has gone out. We haven’t traveled to Uranus and Neptune since the 1980s. Our horizon has now contracted again, to the distance of Jupiter’s orbit. (I’m not forgetting New Horizons, but its fast flyby of a small Kuiper belt object will be a brief and welcome flash illuminating an otherwise very dark region of the solar system.) That’s the kernel of my sadness. Out there, Saturn and its rings and moons will go on being awe-inspiring places. So will Uranus and Neptune and their rings and moons. Every image from Cassini and the Voyagers before it have been wonderful, and I’m sad about the loss of our window into the life of a giant planetary system.

http://www.planetary.org/blogs/emily-lakdawalla/2017/0915-cassini-the-dying-of-the-light.html

Offline david1971

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Re: NASA - Cassini updates
« Reply #745 on: 09/15/2017 07:38 PM »
I can't have been the only person thinking about Blade Runner.


Offline jgoldader

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Re: NASA - Cassini updates
« Reply #746 on: 09/15/2017 08:25 PM »
What a mission it was, with Jupiter, Phoebe, Titan, Enceladus, Mimas, Iapetus, the rings, and everything else.  The team did an outstanding job communicating with the public, letting us ride along.  Well done, and thanks, to all involved.
Recovering astronomer

Offline Blackstar

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Re: NASA - Cassini updates
« Reply #747 on: 09/15/2017 10:06 PM »


Online MATTBLAK

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Re: NASA - Cassini updates
« Reply #748 on: 09/16/2017 06:33 AM »
They should set Gustav Holst's Saturn to a good slideshow of Cassini images!
"Those who can't, Blog".   'Space Cadets' of the World - Let us UNITE!! (crickets chirping)

Online vandersons

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Re: NASA - Cassini updates
« Reply #749 on: 09/16/2017 12:26 PM »
Farewell Cassini-Huygens and a huge thank you for the wealth of discoveries and science. I'm certain there will be many more discoveries made with all that data.

Massive kudos and congrats to everyone involved on a phenominally successfull mission!

Have been following Cassini well before it reached Saturn, bit sad now that it's gone.

Offline dawei

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Re: NASA - Cassini updates
« Reply #750 on: 09/16/2017 01:59 PM »
I have been following Cassini since long before she launched.  It was a bit laborious downloading weekly updates with a  dialup modem whenever I could borrow a computer and not hog up a phone line ... but it was worth it.  I'm so sad to see her go but thankful for all the memories.  Kudos to all who made it possible.   

Online eeergo

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Re: NASA - Cassini updates
« Reply #751 on: 09/28/2017 11:08 AM »
Very cool paper simulating a possible mechanism for ring formation: energetic impact of a comet against a proto-Mimas, tidally-locked (with Enceladus and Dione, close to the Roche radius) icy moon, which causes its disruption into pulverized mantle and a small core, onto which some of the ejected material later accretes, forming Mimas. The tidal locking constraint interestingly gives Enceladus a large tidal heating whose remnants we might be witnessing now.

https://arxiv.org/pdf/1709.08768.pdf

Even more interesting is that this can be quickly disproven through Cassini's gravitational measurements of the rings during the Grand Finale phase: if the rings' mass is much larger than the current Mimas mass this scenario would be unlikely (and this is the favored option according to the current estimates) -but conversely it gives strong constraints as to how the mechanism must have taken place if the rings' mass is smaller or about Mimas' mass.
-DaviD-

Offline catdlr

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Re: NASA - Cassini updates
« Reply #752 on: 10/04/2017 03:08 AM »
Cassini's Grand Finale at Saturn:  Oct 3, 2017 Lecture

Hubble Space Telescope
Streamed live (1 hr 28 min duration)


Space Telescope Public Lecture Series


Topic:  Cassini's Grand Finale at Saturn

Speaker:  Bonnie Meinke, Space Telescope Science Institute

Date:  Tuesday, October 3, 2017, at 8 PM

Place:  Space Telescope Science Institute Auditorium

https://www.youtube.com/watch?v=QCo7OoPac_s?t=001

« Last Edit: 10/04/2017 03:08 AM by catdlr »
Tony De La Rosa

Offline Star One

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Re: NASA - Cassini updates
« Reply #753 on: 10/15/2017 07:40 PM »
Intense storms batter Saturn’s largest moon, scientists report

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Titan, the largest of Saturn’s more than 60 moons, has surprisingly intense rainstorms, according to research by a team of UCLA planetary scientists and geologists. Although the storms are relatively rare — they occur less than once per Titan year, which is 29 and a half Earth years — they occur much more frequently than the scientists expected.

“I would have thought these would be once-a-millennium events, if even that,” said Jonathan Mitchell, UCLA associate professor of planetary science and a senior author of the research, which was published Oct. 9 in the journal Nature Geoscience. “So this is quite a surprise.”

The storms create massive floods in terrain that are otherwise deserts. Titan’s surface is strikingly similar to Earth’s, with flowing rivers that spill into great lakes and seas, and the moon has storm clouds that bring seasonal, monsoon-like downpours, Mitchell said. But Titan’s precipitation is liquid methane, not water.

“The most intense methane storms in our climate model dump at least a foot of rain a day, which comes close to what we saw in Houston from Hurricane Harvey this summer,” said Mitchell, the principal investigator of UCLA’s Titan climate modeling research group.

Sean Faulk, a UCLA graduate student and the study’s lead author said the study also found that the extreme methane rainstorms may imprint the moon’s icy surface in much the same way that extreme rainstorms shape Earth’s rocky surface.

https://astronomynow.com/2017/10/14/intense-storms-batter-saturns-largest-moon-scientists-report/

Offline catdlr

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Re: NASA - Cassini updates
« Reply #754 on: 10/16/2017 07:11 PM »
Fresh Findings From Cassini

https://www.jpl.nasa.gov/news/news.php?feature=6976

Photo Credit and details: Saturn looms in the foreground of this mosaic of Cassini images, taken by the spacecraft on May 28, 2017. Image credit: NASA/JPL-Caltech/Space Science Institute
Inside-Out Rings: Over the Limb

https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA21897
Tony De La Rosa

Offline Star One

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Re: NASA - Cassini updates
« Reply #755 on: 10/25/2017 07:25 PM »
What confines the rings of Saturn?

Quote
The viscous spreading of planetary rings is believed to be counteracted by satellite torques, either through an individual resonance or through overlapping resonances. For the A ring of Saturn, it has been commonly believed that the satellite Janus alone can prevent the ring from spreading via its 7:6 Lindblad resonance. We discuss this common misconception and show that, in reality, the A ring is confined by the contributions from the group of satellites Pan, Atlas, Prometheus, Pandora, Janus, Epimetheus, and Mimas, whose cumulative torques from various resonances gradually decrease the angular momentum flux transported outward through the ring via density and bending waves. We further argue that this decrease in angular momentum flux occurs through 'flux reversal'.
Furthermore, we use the magnitude of the satellites' resonance torques to estimate the effective viscosity profile across the A ring, showing that it decreases with radius from ~50 cm2 s-1 to less than ~10 cm2 s-1. The gradual estimated decrease of the angular momentum flux and effective viscosity are roughly consistent with results obtained by balancing the shepherding torques from Pan and Daphnis with the viscous torque at the edges of the Encke and Keeler gaps, as well as the edge of the A ring.
On the other hand, the Mimas 2:1 Lindblad resonance alone seems to be capable of confining the edge of the B ring, and contrary to the situation in the A ring, we show that the effective viscosity across the B ring is relatively constant at ~24-30 cm2 s-1.

https://arxiv.org/abs/1710.08462

Offline Helodriver

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Re: NASA - Cassini updates
« Reply #756 on: 11/01/2017 04:10 AM »
Every year I carve a unique Jack O Lantern for Halloween and this year's was in honor of the Cassini mission, launched 20 years ago this month.

Inspired by the "Saturn in Infrared" image shot by the Keck telescope in 2013.

https://futurism.com/astronomy-picture-of-the-day-121313.../

Offline Star One

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Re: NASA - Cassini updates
« Reply #757 on: 11/07/2017 04:53 PM »
HEATING OCEAN MOON ENCELADUS FOR BILLIONS OF YEARS

Enough heat to power hydrothermal activity inside Saturn’s ocean moon Enceladus for billions of years could be generated through tidal friction if the moon has a highly porous core, a new study finds, working in favour of the moon as a potentially habitable world.

A paper published in Nature Astronomy today presents the first concept that explains the key characteristics of 500 km-diameter Enceladus as observed by the international Cassini spacecraft over the course of its mission, which concluded in September.

This includes a global salty ocean below an ice shell with an average thickness of 20–25 km, thinning to just 1–5 km over the south polar region. There, jets of water vapour and icy grains are launched through fissures in the ice. The composition of the ejected material measured by Cassini included salts and silica dust, suggesting they form through hot water – at least 90ºC – interacting with rock in the porous core.
 
These observations require a huge source of heat, about 100 times more than is expected to be generated by the natural decay of radioactive elements in rocks in its core, as well as a means of focusing activity at the south pole.

The tidal effect from Saturn is thought to be at the origin of the eruptions deforming the icy shell by push-pull motions as the moon follows an elliptical path around the giant planet. But the energy produced by tidal friction in the ice, by itself, would be too weak to counterbalance the heat loss seen from the ocean – the globe would freeze within 30 million years.

As Cassini has shown, the moon is clearly still extremely active, suggesting something else is happening.

“Where Enceladus gets the sustained power to remain active has always been a bit of mystery, but we've now considered in greater detail how the structure and composition of the moon's rocky core could play a key role in generating the necessary energy,” says lead author Gaël Choblet from the University of Nantes in France.

In the new simulations the core is made of unconsolidated, easily deformable, porous rock that water can easily permeate. As such, cool liquid water from the ocean can seep into the core and gradually heat up through tidal friction between sliding rock fragments, as it gets deeper.

Water circulates in the core and then rises because it is hotter than the surroundings. This process ultimately transfers heat to the base of the ocean in narrow plumes where it interacts strongly with the rocks. At the seafloor, these plumes vent into the cooler ocean.

One seafloor hotspot alone is predicted to release as much as 5 GW of energy, roughly corresponding to the annual geothermal power consumed in Iceland.

Such seafloor hotspots generate ocean plumes rising at a few centimetres per second. Not only do the plumes result in strong melting of the ice crust above, but they can also carry small particles from the seafloor, over weeks to months, which are then released into space by the icy jets.

Moreover, the authors’ computer models show that most water should be expelled from the moon’s polar regions, with a runaway process leading to hot spots in localised areas, and thus a thinner ice shell directly above, consistent with what was inferred from Cassini.

“Our simulations can simultaneously explain the existence of an ocean at a global scale due to large-scale heat transport between the deep interior and the ice shell, and the concentration of activity in a relatively narrow region around the south pole, thus explaining the main features observed by Cassini,” says co-author Gabriel Tobie, also from the University of Nantes.

The scientists say that the efficient rock–water interactions in a porous core massaged by tidal friction could generate up to 30 GW of heat over tens of millions to billions of years.

“Future missions capable of analysing the organic molecules in the Enceladus plume with a higher accuracy than Cassini would be able to tell us if sustained hydrothermal conditions could have allowed life to emerge,” says Nicolas Altobelli, ESA’s Cassini project scientist.

A future mission equipped with ice-penetrating radar would also be able to constrain the ice thickness, and additional flybys – or an orbiting craft – would improve models of the interior, further verifying the presence of active hydrothermal plumes.

“We’ll be flying next-generation instruments, including ground-penetrating radar, to Jupiter’s ocean moons in the next decade with ESA’s Juice mission, which is specifically tasked with trying to understand the potential habitability of ocean worlds in the outer Solar System,” adds Nicolas.

http://m.esa.int/Our_Activities/Space_Science/Cassini-Huygens/Heating_ocean_moon_Enceladus_for_billions_of_years
« Last Edit: 11/07/2017 04:54 PM by Star One »

Offline Star One

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Re: NASA - Cassini updates
« Reply #758 on: 12/15/2017 10:19 PM »
Dinosaurs Were Around Before Saturn Had Rings

Data from the Cassini space probe suggests that the rings may be as young as 150 million years old


Read more: http://www.smithsonianmag.com/smart-news/dinosaurs-probably-older-saturns-rings-180967565/

Re: NASA - Cassini updates
« Reply #759 on: 12/16/2017 07:30 PM »

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