New science with old data, Atmospheric confinement of jet streams on Uranus and Neptune Options

[MarcF]

A paper published today in the journal Nature:
http://www.nature.com/nature/journal/v497/...ature12131.html

"An analysis of data collected by the Voyager 2 spacecraft and by ground-based telescopes limits the depths to which winds penetrate into Uranus and Neptune to the outermost 0.15 per cent of the total mass of Uranus and the outermost 0.2 per cent of the total mass of Neptune. This provides a stronger limit to the depth of the dynamical atmosphere than previously suggested, and shows that the dynamics are confined to a thin weather layer no more than about 1,000 kilometres deep on both planets."

"The confinement of the strong jets on Uranus and Neptune to a shallow weather layer implies that the dynamics controlling zonal jets are likely to come from shallow processes, rather than from deep columnar structures that penetrate through the planet. Nevertheless, internal heat may be significant in driving these jets, particularly on Neptune where the internal heat flux is 1.6 times stronger than the heating from the Sun."

Best regards,
Marc.

[MarcF]

For those who have no access to Nature:
http://www.space.com/21157-uranus-neptune-...s-revealed.html

[Gerald]

Can a thicker dynamic atmosphere than 1000 km make sense?
Due to a Neptun entry in Wikipedia the scale height of Neptune is around 19.7 km. This means about 22 orders of magnitude (factor 10e22) for the pressure between the top and the bottom of those 1000 km as an estimate by the barometric formula.
So, either we have an almost-vacuum at the top or an ocean/crust of hydrogen and helium at the bottom.
Phase diagram for hydrogen.

[MarcF]

Some other nice new results with old data:

For the first time, the mass of one of the uranian inner satellites has been determined. The dynamics of Uranus' highly packed inner moons is really interesting.

https://www.rt.com/news/401852-uranus-moon-density-voyager/

"The team found that the density of the moon is only 0.86 grams per cubic centimeter while its total mass is around 250 exagrams ( 2.5 x 10^17 kilograms). This suggests the moon is made of water ice with some contamination by a dark material...
The researchers say getting a better grasp of inner Uranian satellite masses and what they are made of will provide a better understanding of the tightly packed system of small moons and their fate after a collision. Chancia and his team have been studying Voyager 2’s old data for some time looking for patterns and structures in Uranus’ rings that would help uncover the planet’s secrets."

Link to the article:
https://arxiv.org/abs/1708.07566

Regards,
Marc.

[MarcF]

Revisiting decades-old Voyager 2 data, scientists find one more secret:
https://www.nasa.gov/feature/goddard/2020/r...one-more-secret

"Unbeknownst to the entire space physics community, 34 years ago Voyager 2 flew through a plasmoid, a giant magnetic bubble that may have been whisking Uranus’s atmosphere out to space. The finding, reported in Geophysical Research Letters, raises new questions about the planet’s one-of-a-kind magnetic environment."

These old data still contain many treasures !
Best regards,
Marc.

[titanicrivers]

While the data is not THAT old, a new paper published yesterday https://agupubs.onlinelibrary.wiley.com/doi...29/2020JA028739 evaluates X-ray data from Chandra telescope observations of Uranus obtained in 2002 and 2017. The data is mapped to a nice image of Uranus and its rings obtained by the Keck-I telescope (from 2004). A summary from NASA.gov is available here: https://www.nasa.gov/mission_pages/chandra/...discovered.html

[titanicrivers]

Another article https://physicsworld.com/a/x-ray-emissions-...the-first-time/ concerning X-ray detection from Uranus. This is basically Physicsworld's Planetary Science comments on the Dunn paper noted in the previous post. The Physicsworld article does add that 'future observations will be greatly improved by upcoming missions including ESA’s ATHENA X-ray Observatory, and NASA’s Lynx X-ray Observatory – both planned for launch in the 2030s. The team’s results could one day provide valuable guidance for these future observations'.

[MarcF]

It seems that at least one (if not two) Uranian mains moons is/are still active... Plumes and oceans everywhere in the solar system ?

https://www.jhuapl.edu/news/news-releases/2...has-ocean-moons

"In a new study led by the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, researchers reanalyzed nearly 40-year-old energetic particle and magnetic field data taken by NASA’s Voyager 2 spacecraft — the only spacecraft so far to have gone to Uranus. Their results, recently accepted for publication in the journal Geophysical Research Letters, suggest that one or two of Uranus’ 27 moons — Ariel and/or Miranda — are adding plasma into the space environment through an unknown and mysterious mechanism. One tantalizing explanation is that one or both moons have oceans beneath their icy surfaces and are actively spewing material, possibly through plumes."

I always thought that the surface s of Miranda and Ariel looked very young.
I hope the mission to the Uranian System (Uranus Orbiter and Probe) will indeed take place and that I will still be alive to see the data.
Best regards,
Marc.

[Antdoghalo]

Miranda looks like it had been dead for the past billion years, but Ariel looks a lot like Enceladus. I wonder would would cause either of these moons to be active. We know Dione has a resonance with Enceladus which would give it energy but Uranus doesn't have known resonances between the larger moons.

[MarcF]

"Re-analysis of data from NASA’s Voyager spacecraft, along with new computer modeling, has led NASA scientists to conclude that four of Uranus’ largest moons likely contain an ocean layer between their cores and icy crusts. Their study is the first to detail the evolution of the interior makeup and structure of all five large moons: Ariel, Umbriel, Titania, Oberon, and Miranda. The work suggests four of the moons hold oceans that could be dozens of miles deep."

https://www.nasa.gov/feature/jpl/new-study-...-may-hold-water

[Stefan]

"Re-analysis of data from NASA’s Voyager spacecraft, along with new computer modeling, has led NASA scientists to conclude that four of Uranus’ largest moons likely contain an ocean layer between their cores and icy crusts. Their study is the first to detail the evolution of the interior makeup and structure of all five large moons: Ariel, Umbriel, Titania, Oberon, and Miranda. The work suggests four of the moons hold oceans that could be dozens of miles deep."

This is a pure modeling paper that did not involve any re-analysis of data from NASA’s Voyager spacecraft. The authors even point out that "there is potential room for improving the analysis of the Voyager data." Weird to start the press release like that. Great paper, of course.