Space Sunday: water, rockets, telescopes

Euorpa's icy, mineral-stained surface as imaged by NASA's Galileo mission - see bwlow (credit: NASA / JPL)

Euorpa’s icy, mineral-stained surface as imaged by NASA’s Galileo mission – see below (credit: NASA / JPL)

NASA have been teasing the press and pundits with news that they have a “surprising” announcement to make about Europa, one of Jupiter’s four Galilean moons (so-called as they were first recorded by Galileo Galilei).

Slightly smaller than our own Moon, Europa is covered by shell of water ice, much of it discoloured by mineral deposits and by deep cracks. This icy surface might only be relative thin, on the order of a handful of kilometres in extent, or it might be tens of kilometres thick, and sits over an ocean which is mostly likely liquid water, although some argue it might actually be an icy slush, perhaps extending to 100 km (62.5 miles) in depth.

The ocean is made possible by tidal flexing enacted by the massive gravity of Jupiter as well as from the other large Galilean moons. This generates heat within Europa, and this heat stops the water from freezing solid.

An artist's impression of what the 2012 water plume might have looked like if seen from the vicinity of Europa. Credit: NASA / ESA / M. Kornmesser.

An artist’s impression of how a huge plume of water, over 200km (125 mi) high, which erupted from Europa in 2012 and was “seen” by the Hubble Space Telescope, might have looked like if witnessed from the vicinity of Europa. Credit: NASA / ESA / M. Kornmesser.

Exactly how much heat is generated as a result of this flexing isn’t known, but it has been suggested that the ocean floor could be home to volcanic activity with hydrothermal vents and fumeroles responsible for pumping huge amounts of minerals into the water, as well as supplying energy, potentially marking Europa’s ocean as a place where basic microbial life might arise.

The discovery of life on Europa isn’t going to be the subject of the NASA press conference. It will instead reveal the findings of a Europa observation campaign using the Hubble Space Telescope linked to the potential for a liquid water ocean being present under the moon’s ice. I’ll likely have more next week.

Nor is Europa likely to be alone in harbouring a subsurface ocean among the Galilean moons of Jupiter. In 2015 data from the Hubble Space Telescope confirmed that Jupiter’s largest moon, Ganymede, has an underground ocean that contains more water than all of Earth’s combined. Hubble was used to carry out a spectrographic observation of Ganymede’s aurorae, displays of light in the atmosphere. Because aurorae are controlled by a moon or planet’s magnetic field, observing changes in how they behave offers insights into what is happening beneath the surface of the planet or moon. In Ganymede’s case, the aurorae allowed scientists to confirm a long-suspected subsurface salt water there.

Pluto’s Liquid Heart

Four images from New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with color data from the Ralph instrument to create this global view of Pluto. The images, taken when the spacecraft was 280,000 miles (450,000 kilometers) away from Pluto, show features as small as 1.4 miles (2.2 kilometers). Credits: NASA/JHUAPL/SwRI

A global mosaic of Pluto captured by New Horizons from a distance of  450,000 km (280,00 mi) from Pluto byt New Horizons on July 14th, 2015, coloured from data received by the RALPH instrument on the spacecraft, reveals the planet’s heart-shaped mark, the left “lobe” of which is formed by the massive depression dubbed “Sputnik Planum”. Credit: NASA/JPL / JHU/APL / SwRI

In June, I wrote about a paper proposing Pluto harbouring a liquid water ocean beneath its surface. The paper, by Planetary Science Institute Senior Scientist Amy C. Barr and Noah P. Hammond of Brown University, reached its conclusion after a prolonged study of Pluto’s geological features, including “Sputnik Planum”, a massive depression on the planetoid which forms one “lobe” of Pluto’s distinctive “heart”.

Barr and Hammond’s work focused on the lack of ice II on Pluto – a place where ice II should be expected to form. Had it done so, it would have caused volume contraction, resulting in the formation of compressional tectonic features on the surface of the planet. However, Barr and Hammond found no evidence for such features on Pluto in all of the images returned by the New Horizons spacecraft which flew past Pluto and its twin, Charon, in July 2015. This led them to conclude that Pluto’s interior is warmer than might be expected, which would both prevent ice II from forming and potentially give rise to a liquid ocean beneath Pluto’s frozen crust.

Now, a second paper has been published in Geophysical Research Letters, offering a suggestion as to how deep that ocean is, and its potential composition. Another research team at Brown University have been investigating the dynamics between Pluto and Charon, and the likely formation and development of the “Sputnik Planum” depression, which is thought to have been initially created by the impact of an object some 200 km (125 mi) across at some point in Pluto’s formative years.

Pluto and Charon are tidally locked with each other, so they always show each other the same face as they rotate. “Sputnik Planum” sits directly on the tidal axis linking the two worlds. This suggests the basin has what’s called a positive mass anomaly — it has more mass than average for Pluto’s icy crust. As Charon’s gravity pulls on Pluto, it would pull proportionally more on areas of higher mass, which would tilt the planet until “Sputnik Planum” became aligned with the tidal axis.

The surface ice on "Sputnik Planum" is constantly being renewed both by atmospheric deposition from above, and convection action from below, suggesting a source of heat beneath the ice, which in turn could be keeping any subsurface ocean liquid. Credit: NASA/JPL / JHU/APL / SwRI

The surface ice on “Sputnik Planum” is constantly being renewed both by atmospheric deposition from above, and convection action from below, suggesting a source of heat beneath the ice, which in turn could be keeping any subsurface ocean liquid. Credit: NASA/JPL / JHU/APL / SwRI

But why would a crater – essentially a hole in the ground – be a positive mass anomaly? Part of the answer probably lies in the huge amount of nitrogen ice which has accumulated in the basin over the aeons, adding mass to the basin.

But the ice isn’t thick enough on its own to create the amount of mass needed to make “Sputnik Planum” have positive mass. Water, however, could have sufficient mass.

An impact creates a dent on a planet’s surface, followed by a rebound. That rebound pulls material upward from deep in the planet’s interior. If that material is denser than what was blasted away by the impact, the crater ends up with the same mass as it had before the impact happened. Any material added to it after the impact and rebound would therefore add mass to it, creating a positive mass anomaly.

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Discovering an old friend for the first time in Second Life

Vecchi Amici

Vecchi Amici – click any image for full size

I recently received an invitation from Patti Peregrine to visit her quarter region holding at Serena Pirates Wells, called Vecchi Amici (“Old Friends”) Winery. As I’m familiar with Patti’s work from her time at Hestium I where she worked with my friend Boudicca Amat (and which you can read about here),  I made it a point to hop across to take a look as soon as time allowed.

Currently featured as at Editor’s Pick in the Destination Guide Vecchi Amici is a simply done but delightfully eye-catching corner of Tuscany brought to life in Second Life by someone with an eye for layout and ambience. And for those who enjoy their wine (/me moves her glass out of sight), it is just the spot to while away an afternoon.

Located atop a gentle slope on the north-east side of the region, Vecchi Amici presents a small, active vineyard before which sit a little orchard (so is cider also produced here?). A path meanders through a little grove of trees, passing the vines on one side and a large pond on the other, as it winds its way up to a converted villa.

Fronted by a low stone wall and a line of fir trees and with walled gardens shouldering it on either side, the villa offers visitors a comfortable place to sit and relax, with a small café area to one side of its large, single room and comfortable chairs and sofa on the other. Outside, water splashes in a fountain, and a bench seat is shaded by a young maple tree. A small terrace to one side of the villa offers a swing seat and access to one of the walled gardens, where butterflies weave patterns over the flowers and wooden benches offer further places to sit. The garden to the other side of the villa offers another pleasing mix of flowers, benches, butterflies and – for the hungry – a little afternoon tea set out on a dainty table.

Those with a taste for wine may well be waylaid on their way up the villa by opportunities to sample the local produce either from the bottle or – if it is ready – straight from the tap of an ageing barrel. Just across the path, the pond offers a little retreat where samples can be enjoyed while watching the local swans and dear.

Small and simple it might first appear, but there is an elegance to Vecchi Amici which more than lives up to its name; a visit is like a return to a familiar old friend of a place; there’s a refined, aged fell to the villa, and the setting lends itself to photography. Should you enjoy your visit, do please consider a donation towards the vineyard’s continued presence in Second Life.

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Of times past, times future and hauntings at Seanchai Library

It’s time to kick-off a week of story-telling in voice, brought to our virtual lives by the staff and volunteers at the Seanchai Library. As always, all times SLT, and events are held at the Library’s Second Life home at Bradley University, unless otherwise indicated.

Sunday, September 25th

13:30: Tea Time at Baker Street

Tea-time at Baker Street returns for the summer, featuring a new location – 221B Baker Street at the University of Washington iSchool in Second Life. Caledonia Skytower, John Morland and Kayden Oconnell invite you to join them as they return to what is quite possibly the most famous of Sir Arthur Conan Doyle’s works, and present their fourth reading from The Hound of the Baskervilles.

Baskervilles-1902The third full-length novel written about Sherlock Holmes, this is likely to be the one Holmesian story which – at least in outline – known to most, whether or not they have actually read any of Holmes’ adventures.

But how many of us know the story as it was originally written? Over the decades it has been adapted for film and television more than 20 times, starting as early as 1914/15 with the 4-part series, Der Hund von Baskerville, and continuing on through to Paul McGuigan’s The Hounds of Baskerville, featured in the BBC’s brilliant Sherlock series.

All of these adaptations have offered their own take on the tale. Some – such as McGuigan’s, have simply taken the title of the story and used it to weave a unique tale of their own; others have stayed true to the basics of the story whilst also adding their own twists and turns quite outside of Conan Doyle’s plot in order to keep their offering fresh and exciting to an audience.

So why not join Cale, John and Kayden as they read from the 1902 original, and discover just how Sir Arthur Conan Doyle unfolded this apparently supernatural tale of giant hounds and murder, and the pivotal role played by John Watson himself?

18:00: Magicland Storytime

It’s a Small World of Folktales at The Golden Horseshoe in Magicland Park with Caledonia Skytower.

Caledonia continues a journey around the globe, beginning with her feet wet from Pacific waters and heading west – surfing with the Sun through stories from different lands. THIS WEEK: The Americas!

Monday September 26th, 19:00: A Spectre is Haunting Texas

spectreGyro Muggins reads Fritz Leiber’s 1969 novel telling of a world in which Texas had secretly run the United States from 1845 through until the Third World War, after which the former state conquered the entire North American continent.

Of it was never given out to the general public in the states, who never had no brains or guts nohow & flustered easy, that this assumption of leadership was annexation–but it was always known to the Speaker of the House & the senators who counted in Washington that secretest treaty Texas was boss…With the coming of the 3rd World War & the atomization of Washington, New York, San Francisco & so forth, secrecy became unnecessary.

Now, Scully Christopher Crockett La Cruz an actor, fortune seeker and adventurer from the isolated orbital technocratic democracies of Circumluna & the Bubbles Congeries, has arrived in what he believes to be Canada. He’s come to reclaim family mining interests, but finds Canada is now N. Texas, ruled over by by primitive, backslapping, bigger than life anti-intellectual “good ol’ boys” convinced of their own moral superiority.

Tuesday September 27th, 19:00: Selections from The Outlander

outlanderDiana Gabaldon’s Outlander series started by accident when she decided to sit down and writer a novel “for practice” in the late 1980s, and to learn what is required to write a good book and whether she had the capacity to become a writer.

Published in 1991 as Cross Stitch in the UK and Outlander in North America, that first “practice” novel went on to spawn an entire set of novels – and a television series as well.

Caledonia Skytower reads selections from Outlander, which follows British Army Nurse Claire Randall who, after the end of World War Two goes on a second honeymoon to Scotland with her historian husband Frank.

Whilst visiting a set of standing stones, Claire hears a strange buzzing, faints, and awakes in the Scotland of the 1740s, where first she encounters Captain Jack Randall, an ancestor of her husband, and then a band of Scots which includes the dashing James Fraser, who presents Claire with an unexpected romantic attraction. Thus, whilst trying to find her way back to her own time, Claire in thrust into the turmoil of the Jacobite movement, find her self caught in Fraser’s love for her, and more besides.

Outlander will also be the subject of a Book Discussion at Community Virtual Library central, at 17:30 SLT on Wednesday, September 28th.

Wednesday September 28th, 19:00: TBA

Check the Seanchai Library blog for updates.

Thursday, September 29th, 19:00 From the Shadows – Tales that Haunt

With Shandon Loring in both Second Life and Kitely (check Seanchai Library’s Kitely event announcements for specific grid location details).


Please check with the Seanchai Library SL’s blog for updates and for additions or changes to the week’s schedule.

The featured charity for September-October is Alex’s Lemonade Stand Foundation (ALSF), a childhood cancer foundation dedicated to raising funds for research into new treatments and cures for all children battling cancer.

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SL project updates 38/2: TPVD meeting, avatar and object rendering

Revenland: the castle and town

Revenland: the castle and town – blog post

The majority of the notes in this update are taken from the TPV Developer meeting held on Friday, September 23rd. The video of that meeting is embedded at the end of this update, and references to it are indicated through the use of time stamps in the paragraphs below. My thanks as always to North for recording and providing it.

This is not intended to be a transcript of the entire meeting, which featured discussions of some situations specific to individual region rather than SL as a whole. However, key discussion points have hopefully been highlighted.

Server Deployment

There was no update on the Main (SLS) channel on Tuesday, September 20th. On Wednesday, September 21st, all three RC channels should receive the same new server maintenance package, containing further “minor internal changes”.

SL Viewer

VLC and Project Bento RC Viewer Updates

On Tuesday, September 20th The VLC media plug-in viewer updated to version 4.1.1.319856, while the Project Bento RC viewer updated to version 5.0.0.319893 on Thursday, September 22nd. In both cases, the updates were primarily intended to bring the viewers to parity with the de facto release viewer code base.

It is hopes the VLC media plug-in viewer will be promoted to the de facto release status in week #39 (week commencing Monday, September 26th).

64-bit Versions

Clarifications was given at the TPV meeting that the 64-bit version of the official viewer will be Windows, Mac and Linux, with the 32-bit version of windows continuing, Mac and Linux moving purely to 64-bit. Active development of the 64-bit viewer is expected to resume in week #39, with the intention of getting the viewer out and available sooner rather than later.

Autobuild, Public Sources and Viewer Building

Part of the 64-bit viewer work involves viewer build infrastructure changes. These include updates to how public sources should be built and to the viewer Autobuild process. In particular, these updates allow the viewer library files to all be built using the same compiler switches regardless of build system. The wiki documentation for viewer builds will be updated to reflect these changes, and there may be a presentation on things at the next TPV Developer meeting. There is a separate file for controlling the compiler switches, so if TPVs and self-compilers wish to build their viewer with different compiler settings, they can swap this file with their own.

Viewer Blocking

As per the Lab’s recent blog post, all official viewer versions older than 4.0.5 have been blocked from accessing Second Life. Users on such viewers will be required to update their viewer to a more recent version. This has been done to encourage users to keep up with the numerous changes and improvements being made to the viewer.

That same blog post indicated that the Lab are discontinuing support for Windows Vista and for Mac OSX versions below 10.9. The Lab is doings its best to maintain back compatibility wherever it can, but where the underlying technology loses support, etc., then it is not possible for the Lab to continue maintaining support either (the more recent versions of CEF, for example, do not work on Windows Vista).

Crash Rates

The recent changes to the viewer code are said to be significantly reducing the crash rate for the official viewer, and it is hoped this will continue with further improvements to the code and through the coming availability of 64-bit versions of the viewer.

Maintenance RC

The next Maintenance RC viewer could be appearing in the early part of week #39.

Avatar and Object Rendering Investigations

[12:12] Vir Linden is starting to work on a new project (concurrent with Bento) involving digging into avatar and object rendering, and land impact. The work is due to an accumulation of issues raised concerning rendering costs by users, and the investigations at this point are focused on what might be improved and what cannot be (due to issues like backwards compatibility) .

This will involve taking “a bunch” of representative / problem cases, and try to take a set of carefully defined measurements of what the real impact is during rendering on a wide range of systems. It is hoped this will allow the Lab to adjust the formulas used to make a reasonable generalisation in the rendering cost of things, and whether or not objects are being reasonably accounted for in those calculations.  At this point in time, it is not a given that anything will chance – simply because it has been a long while since the Lab took a similar “deep dive” into rendering, but there is a “good possibility” changes will result from the investigations.

Avatar Rendering Calculations

[14:54] Avatar rendering calculations were expanded upon by Oz in terms of what happens now, and what the intent was behind things.

The viewer, providing it is using LL’s code unchanged, sends to the simulator a report on what it believes is the rendering cost of all the avatars it can “see” in a region.  The simulator then averages the reports from the various viewers, with heuristics to remove excessive values at either end of the scale, back to everyone in the region.

Right now, the viewer decides how to render each avatar it its view purely on its own per-avatar calculation, using the full dataset for each avatar. However, by using the average value calculated by the simulator, it should be possible for the viewer to start making decisions on whether or not to render avatars in a field of view based on that average (compared with its own Max Complexity setting), without having to wait for the full data on each avatar to be received. The viewer-side code to allow this has yet to be written and implemented, but may form a future project.

[18:34] The other aspect of avatar complexity calculations is that the viewer sends to the simulator a single bit of information for each avatar it can “see”, on whether or not the avatar is rendered as a Jelly Doll. The Simulator then counts how many viewers are reporting on each avatar, and how many of those are rendering that avatar as a Jelly Doll. This information fed back to that avatar roughly once a minute to generate the pop-up notification we see in the top right corner of the viewer window.

Due to the nature of the system, the updates can be delayed, or include out-of-date information. For example: data on avatars who have left a region isn’t immediately discarded by the viewer, but is held for a certain amount of time. Similarly, when changing outfits, you get an immediate update on your complexity (as it is a local calculation), but the number of those who are not rendering you fully is delayed by around 90 seconds while your updated appearance is sent to other viewers and they respond to the simulator with their information on whether they are rendering you fully or as a Jelly Doll, and the simulator feeds that information back to you.

Complexity Variances

[25:15] As noted in my Avatar Complexity updates, the complexity value assigned to an avatar can differ by up to 2K in value between those looking at the avatar. There are a number of reasons for this, including differences in the rendering capabilities of the systems viewing an avatar, and level of detail seen / distance. While it is not a high priority, the Lab is considering tuning how complexity is calculated (such as removing the LOD / distance factors from the calculations).

There are two significant bug reports for issues with the current viewer-side avatar complexity calculations:

  •  BUG-37642 – an avatars complexity value can double or triple following a teleport or relog without changing its outfit. This appears to be triggered by certain outfits / attachments.
  • BUG-37631 – wearing a rigged mesh with any amount of transparency applied to it results in a 4 times higher complexity value. This appears to be due to x4 multiplier used in the Mesh/Rendering Weight calculation for an alpha being applied to the entire avatar complexity calculation, rather than just the vertices using the transparency.

BUG-37692 – llRezObject() and llRezAtRoot()

[39:30]  BUG-37692 has been raised at a number of recent UG meetings, and is seen to be causing a wide range of issues, notably for weapon systems used in combat environments.  The Lab does not currently have a response for the issue, which will be looked at during the next triage period, on Monday, September 26th.