Starship Asterisk*

Pedr Fawr wrote:
That should be "mesospheric" not "mesopheric".

geckzilla wrote:
I love the title metaphor.

Psnarf wrote:How does water get up there? I recall that after the Space Shuttle drops the external solid fuel rockets, liquid hydrogen and oxygen take over. That leaves a water vapor trail. Does that water vapor then disperse to become condensed by meteor dust?

Chris Peterson wrote:

Psnarf wrote:
How does water get up there? I recall that after the Space Shuttle drops the external solid fuel rockets, liquid hydrogen and oxygen take over. That leaves a water vapor trail. Does that water vapor then disperse to become condensed by meteor dust?

All parts of the atmosphere contain all the gases found anywhere in it. The amount of mixing that occurs vertically is determined by various factors, and in the case of water, much is trapped at the tropopause, and much of what passes that is condensed out in the stratosphere. But some still makes it to the mesosphere. Most of this water originally evaporated off the oceans. It's unlikely that human activities like spaceflight are significantly impacting the upper atmospheric water mass.

http://en.wikipedia.org/wiki/Noctilucent_cloud wrote:
<<Nioctilucent clouds are composed of tiny crystals of water ice up to 100 nm in diameter and exist at a height of about 76 to 85 km, higher than any other clouds in Earth's atmosphere. Clouds in the Earth's lower atmosphere form when water collects on particles, but mesospheric clouds may form directly from water vapour in addition to forming on dust particles. The sources of both the dust and the water vapour in the upper atmosphere are not known with certainty. The dust is believed to come from micrometeors, although particulates from volcanoes and dust from the troposphere are also possibilities. The moisture could be lifted through gaps in the tropopause, as well as forming from the reaction of methane with hydroxyl radicals in the stratosphere.

The exhaust from Space Shuttles, which was almost entirely water vapour after the detachment of the Solid Rocket Booster at a height of about 46 km, was found to generate minuscule individual clouds. About half of the vapour was released into the thermosphere, usually at altitudes of 103 to 114 km. The exhaust can be transported to the Arctic region in little over a day, although the exact mechanism of this very high-speed transport is unknown. As the water migrates northward, it falls from the thermosphere down into the colder mesosphere, which occupies the region of the atmosphere just below. Although this mechanism is the cause of individual noctilucent clouds, it is not thought to be a major contributor to the phenomenon as a whole.

As the mesosphere contains very little moisture the ice crystals can form only at temperatures below about −120 °C. This means that noctilucent clouds form predominantly during summer when, counterintuitively, the mesosphere is coldest, therefore they can't be observed (even if they are present) inside the Polar circles because the Sun is never low enough under the horizon at this season at these latitudes. Noctilucent clouds form mostly near the polar regions, because the mesosphere is coldest there.

Ultraviolet radiation from the Sun breaks water molecules apart, reducing the amount of water available to form noctilucent clouds. The radiation is known to vary cyclically with the solar cycle and satellites have been tracking the decrease in brightness of the clouds with the increase of ultraviolet radiation for the last two solar cycles. It has been found that changes in the clouds follow changes in the intensity of ultraviolet rays by about a year.>>

Psnarf wrote:Noctilucent clouds are lit by sunlight scattered by ice crystals. That's why you can see them only a short time after the sun sets. In the land of perpetual sunlight, whenever the sun sinks below a particular degree below the horizon, voila!

To calculate the degrees below the horizon, draw a tangent to Earth from the Sun to 80km, then a tangent to the horizon? Then see where they intersect?

DavidLeodis wrote:I wonder what the actual date/time was?

Case wrote:

DavidLeodis wrote:I wonder what the actual date/time was?

The photographer only specifies “Date: July 2014” on the TWAN page.
The exif data also shows two modifications by Photoshop at 2014:07:17 23:31:04+02:00 and 2014:07:17 23:37:07+02:00. These are based on a pc clock, thus more likely accurate than date and time from the camera.
There are some stars faintly visible (Ursa Major, Perseus), that should't be in those positions yet at the date and time for the modification, which leads me to believe the photo was taken on the previous day or earlier. If the photo was taken on the 16th, it would be around 01:30 am, roughly toward the north. If it was taken earlier, it would be about 4 minutes later per day.