Guillaume Blanchard / ESO

Comet Lovejoy streaks through the pre-dawn skies above the European Southern Observatory's Paranal Observatory in Chile on Dec. 22.

If anyone questioned whether Comet Lovejoy would become the star of the season — and a lot of people did — the pictures of the past few days have removed any doubt. In the Southern Hemisphere, the death-defying comet is truly this year's "Star of Wonder."

Not only do we have an amazing video of the long-tailed iceball rising from the horizon, as seen from the International Space Station, we also have the stunning pictures and video released today by the European Southern Observatory. Skywatchers at the ESO's Paranal Observatory in Chile captured the comet against the glittering backdrop of the Milky Way.

"For me, this comet is a Christmas present to the people who will stay at Paranal over Christmas," said Guillaume Blanchard, who snapped a picture of dawn at Paranal with the Milky Way and Lovejoy dominating the sky.

Gabriel Brammer put together a time-lapse sequence of the comet rising just before the sun. For devotees of the night sky, it's the latest must-see video. The clip also features the pencil-thin laser beam that Paranal's Very Large Telescope uses as a guide star for its astronomical observations. Expand the video to full screen to increase the awesomeness.

"With this spectacular sequence of the 2011 Christmas Comet Lovejoy, ESO would like to wish everyone a Merry Christmas and a Happy New Year," the observatory's staff says in today's image advisory.

Amen to that!

More about Comet Lovejoy:

• 'Amazing' view of comet from space
• Lovely Lovejoy! Comet shot at sunrise
• Sun rips comet's tail during close encounter
• Still more pictures from IceinSpace.com.au

One of the most enjoyable parts of Santa's job must be to see the world from on high on Christmas Eve — but thanks to the astronauts on the International Space Station, we can get a similar view on video. Over the past year, the space station's night flights have produced some fantastic pictures of city lights and auroral displays. This video puts together some of the latest clips posted to NASA's Gateway to Astronaut Photography of Earth.

You're actually looking at five time-lapse clips, strung together for a west-to-east journey:

• The first five seconds are from a trip heading up the U.S. East Coast on Dec. 11, with bright city lights strung up all the way from Boston to New York to Philadelphia to Washington. You'll notice a green auroral glow in the upper left corner.

• The northern lights are the main attraction in the clip running from 0:05 to 0:25. This was the view looking north on Dec. 11 as the station was heading from Nova Scotia to northern Italy.

• Our virtual sleigh travels over Africa, Europe and Asia from 0:25 to 0:50, with the camera pointed toward the northeast. Among the sights from Dec. 4 are the Iberian Peninsula and north Africa, England and France, the Baltic Sea, Moscow and central Russia, and atmospheric airglow that gives way to the beginnings of sunrise in the east. Once again, there's a taste of northern lights in the upper left corner.

• The next clip, from 0:50 to 1:13, chronicles an Oct. 21 pass that begins at the coast of France and heads right across Europe. A couple of lightning flashes can be seen over Italy, then the space station makes its way across Turkey and onward to the Arabian Peninsula.

• My favorite part of the trip runs from 1:13 to the end, and takes in a swath of our planet from Central Asia to South Australia. This video was assembled from pictures taken during the space station's night flight on Oct. 29. Here's how the folks at NASA's Johnson Space Center describe the view:

"The video begins just northwest of the Tibetan Plateau, where the greenish glow is from airglow. The line separating the plateau and the city lights to the right of track are the Himalaya Mountains, with cities like New Delhi, Lahore, and Islamabad standing out. Continuing down track, one can spot the brightly lit city of Calcutta just right of track before flying over Burma and Thailand. Thailand's capital city, Bangkok, is the brightest-lit city in the video. The white lights of the city can be seen nearby the green and purple lights on the Gulf of Thailand, which are fishing boats and oil rigs. Once across the Gulf of Thailand, cities like Kuala Lumpur and Singapore stand out right of track before flying over the island of Java (long, thin island downtrack from Singapore). Near the end of the video the ISS flies southeast over Australia and lightning storms, and the Milky Way can be seen rising in the sky."

There's no soundtrack for the video, but feel free to play Christmas music in the background. You could fire up some "Space Age Santa Claus," or take a listen to the first live music broadcast from orbit: "Jingle Bells." Archive.org has the audio recording from 1965's Gemini 7/6 mission. The harmonica and jingling bells come in around 2:10 in the clip.

And now for something completely different: Check out this sleigh ride over Mars:

Looking for more night flyovers? Here's a sampling:

• 'Amazing' view of comet from space
• The best of NASA's night lights
• See the world from space ... in 60 seconds
• Fly over the southern lights in the space station

And if there's anything you've missed from the Cosmic Log Space Advent Calendar, here's your chance to catch up. We'll present our final image from the calendar on Christmas Day:

• The full Cosmic Log Space Advent Calendar
• Dec. 1: An ornament in outer space
• Dec. 2: The masses in Mecca
• Dec. 3: Santa's shrinking domain
• Dec. 4: The monster of Madagascar
• Dec. 5: Antarctica stripped naked
• Dec. 6: Streaking for home
• Dec. 7: Pearl Harbor from above, 1941-2011
• Dec. 8: The rise and fall of the Dead Sea
• Dec. 9: How an eclipse dims Earth
• Dec. 10: Psychedelic storm
• Dec. 11: Beauty of the Inland Sea
• Dec. 12: Drone-spotting stirs up debate
• Dec. 13: Light up your St. Lucy's Day
• Dec. 14: Satellite spots Chinese aircraft carrier
• Dec. 15: Hooray for Hollywood
• Dec. 16: Olympics under construction
• Dec. 17: Mystery in the Gobi Desert
• Dec. 18: Glow over Miami
• Dec. 19: North Korea's dark ages
• Dec. 20: Happy Hanukkah from space
• Dec. 21: Season's tiltings
• Dec. 22: Circle of power
• Dec. 23: North Pole revealed
• Hubble calendar, from The Atlantic's In Focus
• 2011 Zooniverse Advent calendar

Gadgets are great. We're enticed to buy new ones every few years. Sometimes that's because the new features are too awesome to resist, but other times we're simply buying replacements. As cool as gadgets are, they are prone to break and hard, if not impossible, to repair.

That frustration of throwing away perfectly good technology just because it doesn't work may be history, thanks to a "self-healing" electronics developed by engineers at the University of Illinois.

This system restores electrical conductivity to a cracked circuit in less time than it takes to blink, the university reports. It does this with tiny microcapsules on top of a gold line functioning as a circuit in a chip.

"As a crack propagates, the microcapsules break open and release the liquid metal contained inside. The liquid metal fills the gap in the circuit, restoring electrical flow," reads a new release on the technology.

While this technology could find a home in gadgets, the reality is you'll still want to replace them every few years to take advantage of technological leaps. But for other uses, such a ship en route to Mars, self-healing electronics could be a life saver.

For more information, check out the news release on the study reported in the journal Advanced Materials as well as the video above with lead author Scott White, a professor of aerospace engineering.

More on self-healing tech:

• Fix scratches in a flash, literally
• Metals with memory could fix dents
• Self-healing car coating repairs scratches
• Bendy antennas could reshape electronics

John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

Antonio Calanni / AP

The Shroud of Turin bears the faded image of what appears to be a Christlike figure. Italian researchers say they've come close to the shroud's coloration by blasting strips of linen with ultraviolet laser light.

Last updated 2:15 p.m. ET Dec. 23:

Italian researchers have resurrected the idea that the Shroud of Turin's mysterious image of a Christlike figure could only have been created by a powerful flash of light — but skeptics still aren't buying it.

Scientists have tussled with believers, and with each other, over the origins of the centuries-old cloth for decades: Many believers think it's the true image of Jesus, left behind miraculously on his burial cloths after his resurrection. Analyses of the Shroud's chemical makeup, as well as radiocarbon dating of fiber samples, have led lots of researchers to conclude that the image was painted onto the cloth during the 14th century. But other researchers, sympathetic to the Shroud's cause, say those tests were faulty.

The Italian studies, conducted at the ENEA Research Center in Frascati, addresses a specific question in Shroud science: Could a burst of radiation have created the coloration seen on the linen? The answer is yes, although the results reported in the latest studies aren't a perfect match. So does that mean the Shroud image could only have been created by the flash of a miraculous resurrection? The answer is no, despite what you might read on the Web.

Five years of tests
"Sadly, we have seen many claims spread in the Web made by journalist/bloggers that discuss the content of a paper they never read," lead researcher Paolo Di Lazzaro told me today in an email. "It is obvious that a serious scientific work cannot prove any supernatural action. We have shown that the most advanced technology available today is unable to replicate all the characteristics of the Shroud image. As a consequence, we may argue it appears unlikely a forger may have done this image with technologies available in the Middle Ages or earlier. The probability the Shroud is a medieval fake is really low. In this sense, the Shroud image is still a scientific challenge."

Di Lazzaro and his colleagues based their conclusions on five years of tests, using an ultraviolet laser apparatus and strips of modern-day linen. They blasted the cloth with UV at different power levels, and reported that they "achieved a very superficial Shroud-like coloration of linen yarns in a narrow range of irradiation parameters." The best effect depended on laser pulses lasting less than 50 nanoseconds.

"These processes may have played a role in the generation of the body image on the Shroud of Turin," the researchers report.

They don't go so far as to claim a miracle. But the fact that UV laser blasters didn't exist in the 13th century, let alone in Jesus' day, strongly implies that they suspect something out of the ordinary was going on.

Di Lazzaro told me that the tests were not financed by ENEA, which is a government-sponsored research agency, and were conducted outside working hours. "The research was curiosity-driven, the attempt to replicate an image which is considered 'the impossible image' due to its very peculiar characteristics," he said.

Over the years, Di Lazzaro and his colleagues have published a long list of studies, including peer-reviewed papers (see below). The latest studies were presented at a May conference in Frascati and published in November as an ENEA technical report (with a disclaimer saying that the contents didn't necessarily express ENEA's opinion). But they didn't really get traction until this week, just in time for Christmas, thanks to a series of sensationalized British news reports.

Critiquing Shroud science
Shroud science, also known as sindology, usually percolates outside the scientific mainstream — but every once in a while a sensational claim comes into the public spotlight. Joe Nickell, an investigator for the New York-based Center for Inquiry, has been following sindology for decades. He noted that the Italian research revives a discussion going back to the 1980s, spearheaded by a group called the Shroud of Turin Research Project, or STURP.

"This is really nothing new," Nickell told me today. "This is a supposed vindication of STURP."

Nickell said Di Lazzaro and his colleagues started out with the assumption that the coloration on the Shroud couldn't have been created by applying pigment to the linen — which runs counter to the conclusions drawn by other studies. Starting out with the idea that the human figure shown on the Shroud is an "impossible image" stacks the deck in favor of a miraculous explanation, he said.

"Making the assumption of a miracle is a really, really, really, really, really big assumption," Nickell said. "That it's done in the name of science is just astonishing."

Nickell said the latest findings don't prove much of anything, even though they're dressed up in high-tech tests.

"It is made up of whole cloth," he said. "The pro-Shroud people start with the answer, and then they have to get some scientific evidence to back this up."

Some folks would suggest that the Shroud of Turin is a valuable focus for faith, whether it's real or not. What do you think? How much value is there in studying the Shroud, and how much impact do scientifico-religious debates like this one have on your own thinking? Check out the Web links below, give it some thought, and add your comments.

Update for 4:15 p.m. ET Dec. 22: Di Lazzaro sent a follow-up email calling attention to his group's publications, which I've added below, and he poses this question for Joe Nickell: "Was he (or anybody else) able to reproduce by chemical paint, acid and any other color a depth of coloration which is 0.2 micrometer thick (that is, one-fifth of a thousandth of a millimeter)? We are talking of this, because on the Shroud, the image has a coloration depth so thin that it is impossible to do with any kind of painting. I can quote peer-reviewed papers that show this is the coloration depth of the Shroud image.

"By the way, Nickell will be interested to know that using VUV photons we obtained this shallow coloration thickness," Di Lazzaro wrote.

I'll pass the question along to Nickell, who says he doesn't use email. I suspect the answer could go along two tracks: One is that it's a tough thing to try to reproduce a precise coloration depth under any circumstances. The other is that centuries of wear and tear might have had an effect that's not easily replicated by the contemporary application of pigments or other chemicals. But we'll see what Nickell has to say.

Update for 2:15 p.m. ET Dec. 23: Nickell responded to Di Lazzaro's question, and added a couple of questions of his own:

"Paolo Di Lazzaro claims the Turin 'Shroud' coloration depth is 0.2 micrometers, but surely he does not claim that that was uniformly measured throughout the cloth. The coloration indeed appears to be generally confined to the topmost fibrils (although the face image does show faintly on the back of the cloth). Using a two-part hypothesis I put forward in 1983, Italian chemist Luigi Garlaschelli has produced a replica shroud with such superficial staining. So let me ask Lazzaro a question in turn: Have you been able, using your high-intensity ultraviolet laser technique, to produce a replica shroud yourself? Until you do, shouldn’t you stop slashing carelessly with Occam’s razor?"

Here's a 2009 Reuters report about the Garlaschelli replica.

This week's chatter on the Shroud:

• ENEA: Shroud-like coloration of linen fabrics by vacuum UV radiation
• Int'l Workshop on the Scientific Approach to Acheiropoietos Images
• Telegraph: Study claims Shroud is Christ's authentic burial robe
• Daily Mail: The Turin Shroud DOES have miraculous powers
• The Independent: Scientists say Shroud is supernatural
• Center for Inquiry: Turin 'Shroud' called 'supernatural'
• Telegraph: The Turin Shroud is fake. Get over it

Earlier tales of the Shroud of Turin:

• Documentary looks at the face in the Shroud
• 'Jesus-era' cloth casts doubt on Turin Shroud 
• Could new test settle Shroud of Turin debate?
• Public gets a look at the Shroud of Turin

Journal references from Paolo Di Lazzaro:

Peer reviewed Journals:
G. Baldacchini, P. Di Lazzaro, D. Murra, G. Fanti: “Coloring linens with excimer lasers to simulate the body image of the Turin Shroud” Applied Optics vol. 47, 1278-1283 (2008).

P. Di Lazzaro, D. Murra, A. Santoni, G. Fanti, E. Nichelatti, G. Baldacchini: “Deep Ultraviolet radiation simulates the Turin Shroud image” Journal of Imaging Science and Technology vol. 54, 040302-(6) (2010).

Conference Proceedings
P. Di Lazzaro, G. Baldacchini, G. Fanti, D. Murra, E. Nichelatti, A. Santoni: “A physical hypothesis on the origin of the body image embedded into the Turin Shroud” Proceedings of the Int. Conf. on The Shroud of Turin: Perspectives on a Multifaceted Enigma, edited by G. Fanti (Edizioni Libreria Progetto Padova 2009) pp. 116 – 125. ISBN 978-88-96477-03-08 01-12.

P. Di Lazzaro, G. Baldacchini, G. Fanti, D. Murra, A. Santoni: “Colouring fabrics with excimer lasers to simulate encoded images: the case of the Shroud of Turin”, XVIII Int. Symposium on Gas Flow, Chemical Lasers, High-Power Lasers, edited by R. Vilar, Proceedings SPIE vol. 7131 (2009) pp. 71311R-1 – 71311R-6.

P. Di Lazzaro, D. Murra, A. Santoni, G.- Baldacchini: “Sub-micrometer coloration depth of linens by vacuum ultraviolet radiation”, Proc. International Workshop on the Scientific approach to the Acheiropoietos Images, edited by P. Di Lazzaro (2010) pp. 3 – 10.

D. Murra, P. Di Lazzaro: “Sight and brain, an introduction to the visually misleading images”, Proc. International Workshop on the Scientific approach to the Acheiropoietos Images, edited by P. Di Lazzaro (2010) pp. 31 – 34.

Technical Reports
G. Baldacchini, P. Di Lazzaro, D. Murra, G. Fanti: “Colorazione di tessuti di lino con laser ad eccimeri e confronto con l’immagine sindonica” ENEA RT/2006/70/FIM (2006).

P. Di Lazzaro: “Wissenschaftliche Hypothesen zur Entstehung des Bildes auf dem Turiner Grabtuch” 30Tagen n.4 (2010) pp. 63-66.

P. Di Lazzaro, D. Murra, E. Nichelatti, A. Santoni, G. Baldacchini: “Colorazione similsindonica di tessuti di lino tramite radiazione nel lontano ultravioletto: riassunto dei risultati ottenuti presso il Centro ENEA di Frascati negli anni 2005 -2010” RT/2011/14/ENEA (2011).

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Pierre Ducharme / Reuters

The space shuttle Atlantis lands at NASA's Kennedy Space Center in Florida on July 21, ending 30 years' worth of shuttle missions. Click on the image to see msnbc.com's "Year in Space" slideshow.

During 2011, NASA said goodbye to the Spirit Mars rover and the space shuttle program — but there's hope that during 2012, new players will strut their stuff on the space effort's huge stage, stretching from Cape Canaveral to the Red Planet.

This is my 15th annual "Year in Space" roundup, and in all those years I can't think of a starker time of transition between the year that's past and the year to come. The space shuttles are being readied for museums, and work hasn't yet started on the big rocket that NASA says it will need for the next era of human space exploration. The space agency's plans for commercializing operations in low Earth orbit could well be tied up in budgetary knots, and there are questions about how much farther its robotic Mars exploration program can go.

Farewells and failures, including Russia's Soyuz glitch and Phobos-Grunt gremlins, dominated the news from space over the past year.

But it's not all gloom and doom: One of NASA's Mars rovers may have given up the ghost, but the other one — Opportunity — has begin its most ambitious adventure yet, exploring the 14-mile-wide Endeavour Crater on Mars. Juno, GRAIL and Mars Science Laboratory were launched toward Jupiter, the moon and Mars, respectively. Other planetary probes are purring along, all the way from Mercury to the solar system's edge.

One of the most promising frontiers for 2012 is being explored by NASA's planet-hunting Kepler spacecraft: The past month has seen the unveiling of Earth-sized planets as well as a Neptune-sized planet sitting in the habitable zone around its parent star. Those alien Earths are still too hot for life, but lots of folks are speculating that we could hear about the first Earth-sized planets in an Earth-type orbit within a year or two.

Which outer-space tales has intrigued you the most over the past year, and what sounds most intriguing for the year ahead? That's what this lineup is all about. I'll list five top stories for 2011, and five top trends for 2012. You can pick your favorite using the Live Vote ballots. Who knows? Your preferences may influence my to-do list for the coming year. Take a run through our "Year in Space Pictures" slideshow to refresh your memory, then cast your vote. We'll crown the winners in an update next week.

Top stories of 2011
It's always tough to limit the list to five, so I'm including an "other" category in this bunch. Please tell me in your comments why you think I'm underplaying or missing your favorite outer-space story.

• NASA ends space shuttle program: Policymakers decided years ago that the shuttle program would have to end once the International Space Station was complete, due to safety and cost concerns. The end finally came in July. Grounding the shuttles theoretically frees up money for exploration programs that go beyond Earth orbit, but in the short term, thousands of jobs are lost. For the time being, NASA has to depend on Russia and other countries for space transport.
• Spirit rover gives up the ghost: After months of trying to re-establish contact with the six-wheeled little trouper, NASA declared that Spirit was really most sincerely dead — felled by stuck wheels and a winter freeze-up. It had a good run: Six years of operation on Mars as part of a mission that was expected to last only 90 days. The Opportunity rover soldiers on, reaching Endeavour Crater after three years of trekking. And it recently made a significant find: gypsum deposits that appear to confirm water once flowed on Mars.
• 'Hubble's successor' dodges a bullet: NASA's James Webb Space Telescope had been in danger of cancellation, but the White House and Congress worked out a deal to keep the project alive on an $8 billion budget. However, the budget negotiations dealt a heavy blow to the White House's request for commercial crew vehicle development, and there are continuing worries about other space science programs, such as the ExoMars missions that NASA is supposed to be working on with the Europeans.
• Earth-sized planets and super-Earths: As I mentioned above, the Kepler science team has been finding a bonanza of planets, including super-hot super-Earths. A parallel effort led by European astronomers is also yielding scores of promising planets. All these discoveries are providing new target lists for colleagues who have been searching for signals from intelligent aliens.
• Downers in Earth orbit: Sometimes the sky seemed to be falling in 2011. In August, an unmanned Soyuz rocket blew up after launch, sparking an investigation that might have led to the evacuation of the International Space Station. NASA's Upper Atmospheric Research Satellite fell to Earth in September, and the German-built ROSAT satellite followed in October. There was lots of hand-wringing over the potential risk from falling debris, but nobody got hurt. The glitch that affected Russia's Phobos-Grunt probe in November will eventually lead to another fall in the new year (see below).
• Other top stories: China tests orbital docking. High-profile love story focuses on congresswoman and astronaut. Alien bacterial claim causes a stir. Asteroid threat downgraded. NASA probes reach Mercury and Vesta. Other spacecraft head for Jupiter and the moon. Auroras put on spectacular shows.

Top trends of 2012
As Yogi Berra supposedly said, "It's tough to make predictions, especially about the future." I'm signaling the speculative nature of the prediction business by sprinkling a few question marks here and there:

• Commercial flights to space station? SpaceX's Dragon cargo craft is currently scheduled to link up with the International Space Station for the first time in February, potentially marking the beginning of a new age in NASA's orbital operations. Orbital Sciences is due to follow later in the year. Meanwhile, commercial ventures will be working on designs for spacecraft capable of putting astronauts in orbit by 2017 or so. How far will NASA's funding get them?
• Monster rover reaches Mars: NASA's November launch of the $2.5 billion Mars Science Laboratory could justifiably rank as one of 2011's top stories, but the real payoff comes in August, when a rocket-powered sky crane is due to drop the 1-ton, car-sized Curiosity rover onto Gale Crater's scientifically intriguing terrain. The big question is: Will that thing really work? But if the rover sets down safely on the surface, we could be in for years of stunning imagery and scientific discovery.   
• Earth's twin detected at last? As the Kepler probe takes more observations, Earth-size candidates that lie in Earth-type orbits may well be added to the list of potential planets. Further confirmation would be required to make sure the candidates are truly alien Earths, but even hints that such worlds are on the list could cause a sensation of "Avatar" proportions.
• NASA works on future course: NASA wants to go to an asteroid in the mid-2020s, and send astronauts as far as Mars in the 2030s. But there are lots of blank spaces that still need to be filled in. For example, who'll help NASA build the multibillion-dollar heavy-lift rocket that Congress mandated? What will happen to space science priorities such as Mars sample return and  proposed missions to the moons of Jupiter and Saturn? In an era of tightening budgets, how much exploration can NASA afford? Will the presidential election lead to yet another change of vision?
• SpaceShipTwo actually in space? Virgin Galactic's founder, British billionaire Richard Branson, has said powered tests of the company's SpaceShipTwo rocket plane will begin in 2012, and he may well take a ride with his family as a Christmas present next year. If he sticks to that schedule, humans will ride into outer space on a privately developed rocket ship for the first time since SpaceShipOne's trips in 2004. But the tests to date have not been glitch-free, and a question mark is definitely in order.
• Other top stories: Phobos-Grunt plunges in January. Transit of Venus in June. Total solar eclipse in November. Doomsday hype in December. Solar activity rises toward maximum.

There you have it: Click on the links to get more background, weigh the field, and cast your vote. This could be more fun than the Iowa caucus, and I'm saying that as a former Hawkeye. For even more end-of-the-year musings, check out these links:

• Space.com's most memorable spaceflight stories
• Space.com's most amazing astronomy stories
• Space.com: Biggest space flops of the year
• Next steps in the new space race
• 2011: The Year in Space Pictures
• NASA: Year in Review 2011

For something completely different, check out my review of the year's top ancient mysteries.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

(C) 2011 EUMETSAT

This picture of Earth was taken at 06:00 GMT on Dec. 21 by Eumetsat's Meteosat-9, a meteorological satellite that is stationed in geosynchronous orbit above a point close to Africa's west coast. The picture illustrates how Earth's tilt with respect to the sun creates the darkest night of the year for the Northern Hemisphere, and the longest stretch of daylight for the Southern Hemisphere.

Tonight is the longest night of the year for the Northern Hemisphere, due to the winter solstice. The season officially changes from autumn to winter at 12:30 a.m. ET Thursday ... unless you're south of the equator. In that case, spring is turning to summer.

You probably learned in school why the seasons (and the temperatures) change during the course of the year, but in case you need a refresher on how the 23.5-degree tilt of Earth's axis affects the weather, we have the full story for you. This picture, snapped by Eumetsat's Meteosat-9 weather satellite today, shows the situation graphically.

Meteosat-9 is camped out in a geosynchronous orbit that puts it precisely above an equatorial point on the west coast of Africa. Every day at around 6 a.m. local time, it has a great view of the terminator line between day and night, cutting straight across Earth's disk. The slant of that line changes from day to day, due to the changing orientation of Earth's tilted axis with respect to the sun.

On the day of the December solstice, the slant is at its most extreme angle, leaving the north pole in the dark while exposing the south pole to 24 hours of daylight. That's what you're seeing in the photo above. National borders and crosshairs have been added to help you get oriented properly.

This video, put together by NASA's Goddard Space Flight Center, shows you how the slant changes from one September equinox to the next:

If you check out Eumetsat's near-real-time imagery from Meteosat-9 for 1 a.m. ET (06:00 GMT) Thursday, you can see the solstice effect pretty much at its peak. These pictures of the shifting seasons serve as tonight's offering from the Cosmic Log Space Advent Calendar, which has been featuring daily images of Earth from space during the run-up to Christmas. Feel free to click through these previous images in the series, and check back on Thursday for another satellite image that will take the edge off winter.

• The full Cosmic Log Space Advent Calendar
• Dec. 1: An ornament in outer space
• Dec. 2: The masses in Mecca
• Dec. 3: Santa's shrinking domain
• Dec. 4: The monster of Madagascar
• Dec. 5: Antarctica stripped naked
• Dec. 6: Streaking for home
• Dec. 7: Pearl Harbor from above, 1941-2011
• Dec. 8: The rise and fall of the Dead Sea
• Dec. 9: How an eclipse dims Earth
• Dec. 10: Psychedelic storm
• Dec. 11: Beauty of the Inland Sea
• Dec. 12: Drone-spotting stirs up debate
• Dec. 13: Light up your St. Lucy's Day
• Dec. 14: Satellite spots Chinese aircraft carrier
• Dec. 15: Hooray for Hollywood
• Dec. 16: Olympics under construction
• Dec. 17: Mystery in the Gobi Desert
• Dec. 18: Glow over Miami
• Dec. 19: North Korea's dark ages
• Dec. 20: Happy Hanukkah from space
• Hubble calendar, from The Atlantic's In Focus
• 2011 Zooniverse Advent calendar

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Lockheed Martin

The robotic K-Max helicopter shown here in a file photo is flying re-supply missions in Afghanistan, opening up the era of unmanned logistics.

Robotic helicopters capable of ferrying 3.5 tons of cargo in a single load are at work supplying NATO troops in Afghanistan, according to a defense technology blog.

The helicopter is a Lockheed Martin / Kaman Aerospace K-Max designed for battlefield cargo resupply. Confirmation of its use in Afghanistan means "we're now in the age of unmanned logistics," Paul Mcleary writes for Aviation Week's Ares blog. 

The technology will put fewer soldiers at risk flying over enemy lines on re-supply missions. That doesn't mean, however, that the military will put the helicopters directly in harm's way. 

"Most of the missions will be conducted at night and at higher altitudes," Marine Capt. Caleb Joiner, mission commander, said in a news release. "This will allow us to keep out of small arms range."

While the helicopter should save lives on the battlefield, how might robotic choppers and other supply vehicles translate to civilian life? Feel free to share your wishes in the comments section below.

More on military robots:

• Military faces overload from robot swarms
• Dog vs. robot: Which is the better soldier?
• Military developing robot-insect cyborg
• Scientists debate a robot war
• Future of war: Private robot armies fight it out