Starship Asterisk*

https://www2.jpl.nasa.gov/adv_tech/balloons/outer_jupisat.htm wrote:

[img3="Hot "Air" SIRMAs balloon"]https://www2.jpl.nasa.gov/adv_tech/ball ... pibaln.jpg[/img3]

Balloons Technology for Jupiter and Saturn

<<Solar Infrared Mongolfiere Aerobots (SIRMAs) use a combination to lower planetary infrared heating during the night and solar heating during the day. A detailed study performed on the use of SIRMA-type balloons at Jupiter indicates that about 112 kg of total floating mass would be required to support a ten-kg payload. The balloon would float at about 10,000 Pa [the cold 50 km tropopause level] during the day and descends to about 20,000 Pa at night, using isentropic compression heating to help slow the nightly descent rate. The total delivered mass would be about ten times lighter than for comparable pure hydrogen balloon systems at Jupiter. A similar SIRMA for Saturn would weigh about 220 kg and may also be viable. SIRMAs for Uranus and Neptune, however, are less mass-competitive than ambient gas balloons that are filled with low molecular weight gas from these planets upper atmospheres. In order to obtain data from the lower atmosphere regions of Jupiter and Saturn, it appears quite feasible to drop lightweight, deep atmosphere sondes from the balloon as it passes over areas of scientific interest. Results can then be relayed to the stratosphere-floating Montgolfiere.>>

Nitpicker wrote:

BDanielMayfield wrote:
I wonder, at what barometric pressure range are Jupiter's cloud tops? (In case we want to build a floating station inside the Jovian atmosphere.)

It is roughly 1 bar at the top of the clouds and about 10 bars some 90 km below.

BDanielMayfield wrote:I wonder, at what barometric pressure range are Jupiter's cloud tops? (In case we want to build a floating station inside the Jovian atmosphere.)

Chris Peterson wrote:They're semi-stable storm systems.

owlice wrote:The five white spots at the top/top right here (screenshot from the video) appear to be pretty evenly spaced. Are these impact scars?
juno.JPG

jbelfiore wrote:Hello. What are the approximately equally spaced horizontal black dots at the top and the bottom of the video? Are they moons of Jupiter? (and if so, do you know which moons?) Thank you so much. (This is a fantastic video - beautiful!!!)

Nitpicker wrote:

Chris Peterson wrote:

Nitpicker wrote:
The flow in the Jovian atmosphere is highly turbulent.

It's also highly laminar- certainly across latitudes, and probably with height, as well. There is turbulence in places (particularly across boundaries), but large scale structure is not destroyed, because the turbulence is local.

Technically, it is not highly laminar, but less turbulent. The technical basis for determining whether flow is laminar or turbulent is Reynolds number (Re), and the Re values characterizing the flows in the visible cloud formations, are too high to be considered laminar. But there is certainly a wide range in the degree of turbulence. I may be arguing a technical point, but laminar flow is fairly unusual and requires small scales and/or low velocities and/or high viscosities.

https://en.wikipedia.org/wiki/Rossby_number wrote:
<<The Rossby number (Ro) named for Carl-Gustav Arvid Rossby, is a dimensionless number used in describing fluid flow. The Rossby number is the ratio of inertial force to Coriolis force. It is commonly used in geophysical phenomena in the oceans and atmosphere, where it characterizes the importance of Coriolis accelerations arising from planetary rotation.

The Rossby number (Ro) is defined as:

---

where U and L are, respectively, characteristic velocity and length scales of the phenomenon and f = 2 Ω sin φ is the Coriolis frequency, where Ω is the angular frequency of planetary rotation and φ the latitude.

A small Rossby number signifies a system which is strongly affected by Coriolis forces, and a large Rossby number signifies a system in which inertial and centrifugal forces dominate.>>

Nitpicker wrote:

Chris Peterson wrote:

Nitpicker wrote:
I don't think laminar is the correct word here. The flow in the Jovian atmosphere is highly turbulent.

It's also highly laminar- certainly across latitudes, and probably with height, as well. There is turbulence in places (particularly across boundaries), but large scale structure is not destroyed, because the turbulence is local.

Technically, it is not highly laminar, but less turbulent. The technical basis for determining whether flow is laminar or turbulent is Reynolds number (Re), and the Re values characterizing the flows in the visible cloud formations, are too high to be considered laminar. But there is certainly a wide range in the degree of turbulence. I may be arguing a technical point, but laminar flow is fairly unusual and requires small scales and/or low velocities and/or high viscosities.

Chris Peterson wrote:

Nitpicker wrote:

Chris Peterson wrote: I don't believe there is any need to invoke some sort of solid surface below the clouds to explain the persistence of atmospheric disturbances caused by impacts. It can simply be a matter of scale and the fact that the atmospheric flow is substantially laminar over large areas.

I don't think laminar is the correct word here. The flow in the Jovian atmosphere is highly turbulent.

It's also highly laminar- certainly across latitudes, and probably with height, as well. There is turbulence in places (particularly across boundaries), but large scale structure is not destroyed, because the turbulence is local.

Nitpicker wrote:

Chris Peterson wrote: I don't believe there is any need to invoke some sort of solid surface below the clouds to explain the persistence of atmospheric disturbances caused by impacts. It can simply be a matter of scale and the fact that the atmospheric flow is substantially laminar over large areas.

I don't think laminar is the correct word here. The flow in the Jovian atmosphere is highly turbulent.

Chris Peterson wrote: I don't believe there is any need to invoke some sort of solid surface below the clouds to explain the persistence of atmospheric disturbances caused by impacts. It can simply be a matter of scale and the fact that the atmospheric flow is substantially laminar over large areas.

Chris Peterson wrote:

othermoons wrote:
Relative to Earth, Jupiter is much further away therefore much colder yet the core temperature is much much hotter. The dense clouds totally and ominously cover the surface; however, is there a chance that the surface area may not be as hot as we thought?

The interior temperature of the planets is largely unrelated to the distance from the Sun. Interior temperature is determined by residual heat of formation and by radioactive decay.

https://en.wikipedia.org/wiki/Saturn#Internal_structure wrote:
<<Saturn has a hot interior, reaching 11,700 °C at its core, and it radiates 2.5 times more energy into space than it receives from the Sun. Jupiter's thermal energy is generated by the Kelvin–Helmholtz mechanism of slow gravitational compression, but this alone may not be sufficient to explain heat production for Saturn, because it is less massive. An alternative or additional mechanism may be generation of heat through the "raining out" of droplets of helium deep in Saturn's interior. As the droplets descend through the lower-density hydrogen, the process releases heat by friction and leaves Saturn's outer layers depleted of helium. These descending droplets may have accumulated into a helium shell surrounding the core.>>

https://en.wikipedia.org/wiki/Neptune#Internal_heating wrote:
<<Uranus only radiates 1.1 times as much energy as it receives from the Sun; whereas Neptune radiates about 2.61 times as much energy as it receives from the Sun. Neptune is the farthest planet from the Sun, yet its internal energy is sufficient to drive the fastest planetary winds seen in the Solar System. Depending on the thermal properties of its interior, the heat left over from Neptune's formation may be sufficient to explain its current heat flow, though it is more difficult to simultaneously explain Uranus's lack of internal heat while preserving the apparent similarity between the two planets.

Note: At a depth of 7,000 km, the conditions may be such that methane decomposes into diamond crystals that rain downwards like hailstones. Very-high-pressure experiments at the Lawrence Livermore National Laboratory suggest that the base of the mantle may be an ocean of liquid carbon with floating solid 'diamonds'.>>

othermoons wrote:Relative to Earth, Jupiter is much further away therefore much colder yet the core temperature is much much hotter. The dense clouds totally and ominously cover the surface; however, is there a chance that the surface area may not be as hot as we thought?

Nitpicker wrote:Magnificent! Thank you.

SeedsofEarth wrote:I must ask you, why do we see no cloud movement during this pass? Surely the Juno craft is not moving as fast as the video implies. It would not take it six weeks to complete an orbit if that were the case, would it? I really expected to see the clouds moving around, swirling and sweeping across the planet as they do on older videos sent back from other crafts approachiong and passing by Jipiter? In this video, the clouds appear to be static, as if the planet were merely a plastic globe with a photograph of Jupiter superimposed over it.