The entire universe in blog form

Nov. 27 2014 7:00 AM

Thankful for Saturn

I’m thankful for a lot of things in life — though appreciative might be a better word — but if I had to assess a list of astronomical gifts, then Saturn would be very high on that list.

This ridiculously gaudy bauble of the solar system never ceases to amaze me, filling my sciencey brain with wonder as it overwhelms my artsy brain with beauty.

Advertisement

So just to get you kickstarted for Thanksgiving, here are three portraits of Saturn for which we can all be grateful.

Up first: Rings and shadows.

Saturn
The knife-edge rings cast a wide shadow... actually, lots of them. Click to encronosenate.

Photo byNASA/JPL-Caltech/Space Science Institute

This image, taken by the Cassini spacecraft in Aug. 14, 2014, shows nearly the entire face of the planet. That’s no small feat, given Saturn’s 116,000 km girth.

Cassini was almost directly above Saturn’s equator when it took this, so the rings, similarly latituded, are seen as a narrow ribbon around the planet. But that’s an illusion of perspective; the rings are 270,000 km across, a huge span. That’s revealed by their shadow on Saturn’s southern hemisphere; a series of concentric arcs darkening the cloud tops.

I like how different rings cast darker or lighter shadows. The inner C ring is sparse, but the main B ring is thick and broad. The A ring, outside of B, is slightly less dense, so the shadow is lighter. The gap between them is called the Cassini Division, and since there’s less stuff there, it appears as a bright band on Saturn (it doesn’t cast a shadow, really). You can also see the Encke division, the very narrow strip near the bottom of A’s shadow. The shadows are like the rings in reverse, both in brightness and order.

By the way, did you spot the moons Tethys (off to the right) and Mimas (just above the rings, to the lower right of center)?

Cooool. The images making up the video, taken by Hubble, are from 1995, when Saturn’s tilt brought the Sun shining almost directly along the plane of the rings. That’s how the moons (Enceladus, Mimas, Dione, and Tethys) can cast long shadows on them. The video shows about 9.5 hours in the life of moons, and you can see just how far they move in that short time, tugged by Saturn’s immense gravity.

Saturn's storms
Blobs of atmosphere interact in Saturn's cloud tops.

Photo byNASA/JPL-Caltech/Space Science Institute

Finally: Intermix.

This spectacular shot threw me for a moment. I had never see the clouds on Saturn mixing like that before; usually they stay separate. But this is an image taken using a filter that only allows red light through, where methane absorbs light. That means you’re seeing the very top of the clouds, where mixing of winds is more common. That vortex appears to be drawing material from the bright band next to it. It’s a good reminder that air is a fluid — literally, something that can flow.

Perhaps it’s a bit odd of me to be thinking of Saturn on a day like today, but you know what? I’ll take odd, if it means being able to appreciate the intense and wondrous beauty of the natural world… or worlds.

Video Advertisement

Nov. 26 2014 7:00 AM

Does the Name Pavlof Ring a Bell?

In May 2013, the Aleutian island volcano Pavlof erupted mightily, blowing a stream of ash into the atmosphere and messing up airplane travel.

Last week, it was at it again. This eruption was even more violent than last year’s; the plume went 9 kilometers into the air, and was hundreds of kilometers long. It was seen by the Landsat 8 satellite on Nov. 15:

Pavlof volcano
Plume of ash blasted out from the Pavlof volcano on Nov. 15, 2014. Click to hephaestenate.

Photo by NASA Earth Observatory image by Jesse Allen, using Landsat data from theU.S. Geological Survey.

Advertisement

There’s a weird beauty to such things, as awful as they can be. I see them, I suppose, like a rabbit sees a snake: morbid fascination (mixed with a small to fair dose of terror). Even though, in terms of human settlements, Pavlof is remote, it still can muck up airplane travel. Ash is made of fine but very jagged particles of pulverized rock and glass, and if it gets into an airplane engine, it can jam it up but good.

That’s why, as I pointed out in last year’s article, we need the Alaska Volcano Observatory … which is generally under threat of a budget ax. That’s nuts, but then, that’s politics these days. When you have a group that denies the existence of everything around them, then dipping your toe into the presidential election campaign by mocking volcano observatories probably seems downright sane in comparison.

It isn’t.

Nov. 25 2014 7:00 AM

The Milky Way and the Tallest Mountain

Take one part Himalayan mountain, one part gigantic galaxy (seen from a distance), and one part photographer (premixed with talent + adventurousness), and mix them together to produce three minutes of magnificence:

That amazing video was shot by Alex Rivest (who previously has been featured on the blog for two stunning time-lapse videos using astronaut photography from the International Space Station). Just the view of the last rays of the setting Sun washing the peak of Mount Everest in yellow light is worth the watch, but then the Milky Way, our home galaxy, looming over it, dwarfing our sense of scale and distance? Gorgeous. 

Nov. 24 2014 7:00 AM

California (Nebula) Dreamin’

Rogelio Bernal Andreo is an astrophotographer … but saying that is like calling a world-class chef a “cook.” Andreo is a master, one of those people who can tease photons out of the sky and then turn them into works of art that nearly defy description.

For example, here is his mosaic of the sky showing two stunning objects: the California nebula, and the magnificent Pleiades star cluster:

Pleiades and California nebula
An intensely beautiful mosaic of the sky, featuring the California nebula (left) and the Pleiades (right). Click to ensubaruenate.

All photos by Rogelio Bernal Andreo, used by permission

Advertisement

Holy. Haleakala. Yes, you really really want to download the fully embiggened version of that, because it’ll freeze your brain with its beauty and scope.

It’s hard to know where to even start with this! So let’s take it one at a time. On the left is the ruddy glow of the California nebula, officially called NGC 1499. It’s a vast cloud of gas and dust stretching several dozen light-years in length, which is huge on anyone’s scale. It’s part of a large cloud of gas that long ago condensed to form baby stars. But don’t be fooled by the adjective; these are very, very ill-tempered babies indeed. Take a closer look:

California nebula
The Golden State looking a little red.

See that bright star just to the right of the gas, inside that arc of gas? That is Xi Persei, also called Menkib. It’s a beast, a monster 30 times the mass of the Sun, and blasting out light at a hair-raising 250,000 times the rate the Sun does. That’s so much radiation that we think that’s what’s setting the nebula aglow. Remember, that gas cloud is more than 400 trillion kilometers long, and it’s being lit up by a single star. The star and cloud are something like 1,000 light-years from Earth, yet the star is visible to the unaided eye. From that distance, you’d need a decent telescope to see the Sun at all.

The nebula is named because of how much it looks like its eponymous state, and I have to agree, it’s a good match (too bad it’s not nearer to the North America nebula). The ribbons and filaments you see inside the cloud are due to shock waves inside the gas, where waves of material slam into slower stuff, compressing it. The gas is expanding because long ago, several of the massive stars born from it lived out their lives and exploded as supernova, dumping huge amounts of energy in to the gas and causing it to rush away. The California nebula is only one segment, one arc of a far larger shell of gas that we cannot see because it has no nearby powerhouse stars illuminating it.

Pleides
The Seven Sisters, easily visible to the naked eye, take on a literally unearthly appearance in the deep photo. The size of the Moon on the sky is inset for comparison.

On the right of Bernal’s magnificent mosaic is the famed Pleiades cluster—the Seven Sisters—a collection of youngish stars all formed from a single cloud of gas and dust. The cluster is very roughly 400 light-years away (much closer to us than the California nebula), big enough and bright enough to be seen with the naked eye. In fact, a lot of people mistake them for the Little Dipper!

Deep, high-resolution pictures of the stars show them lighting up diaphanous sheets of material around them. Years ago, it was thought this was the material from which the stars formed, and that always bugged me. The cluster is about 100 million years old, which is way too old to still be surrounded by its birth cocoon. And, it turns out, that intuition is correct: that material belongs to an entirely different cloud of dust, and it just so happens the cluster is passing through it right now! Bernal’s photo makes this more clear; there are vast swaths of dust littering that whole part of the sky.

I have to point out the difference in color between the Pleiades and the California nebula. In the latter case, the gas in the nebula is being excited by ultraviolet light from Xi Persei. These photons hit the hydrogen atoms in the gas and are absorbed by the electrons in the atoms. The electrons dump that extra energy by emitting light, predominantly in the red part of the spectrum.

In the case of the Pleiades, the light is coming from dust near the stars that’s reflecting the starlight. The stars are blue, so the reflected light is blue, too. Because of this, we call the California nebula an emission nebula, while the Pleiades dust is a reflection nebula. The physics of this is actually pretty neat, and if you want to read more I have a detailed (and hopefully clear) description in an article about a gorgeous nebula that is both reflecting and emitting light. You really want to see (and read) that.

And do you want to know another amazing thing about this picture? Take a look at the Pleiades again in the big version of the full mosaic. See the diamond of four bright stars, just above the fifth star? On the sky, the full Moon is just about the same size as that diamond (this is shown in the zoomed picture above for clarity).

Now take a step back, and look at this full mosaic again. The whole thing is a staggering 18° across, 35 times the width of the full Moon! How much of the sky is that? Stand up, and hold your arm out in front you. Bend your wrist in, so you’re looking at the palm of your hand and your fingers: If you held your hand like that up to the sky, it would be cover about the same amount of real estate as Bernal’s photo. Wow.

Bernal’s work is simply phenomenal. You really need to peruse his site; everything there is a masterwork. (I’m a big fan of his portrait of the Big Dipper, for example.) Many are for sale, too.

And one final note: Years ago, I picked his “Orion from Head to Toe” as the best astrophoto for 2010. I cannot stress enough how much you want to click that link. To put this in perspective, I have seen thousands of astrophotographs over my life, and that Orion picture is one of my favorites of all time.

As usual, I have to smile wryly when I hear people try to distinguish art from science. The Universe is both, folks. You may try to tear them apart, but you cannot, for the artistry of the Universe is forever intertwined with how it works. They drive each other; the science is why the art is beautiful, and the art is one of the reasons we pursue the science.  

Nov. 23 2014 7:00 AM

Watch Today as Three More Humans Travel to Space

Update, Nov. 23, 2014, at 21:20 UTC: Eight and a half minutes after a textbook launch, and the Soyuz is in orbit and chasing down the space station. They'll rendezvous in about six hours. Apropos of the Twitter conversation I had with Samantha Cristoforetti (see below), here's a shot of her I grabbed from the NASA stream showing her using the Fing-Longer just after they achieved orbit. 

Finglonger
Good news, everyone!

Photo by NASA, from the live video stream

Today (Nov. 23, 2014) at 21:01 UTC (16:01 Eastern), a Soyuz rocket is scheduled to launch from Baikonur, Kazakhstan. On board will be three human beings: American Terry Virts, Russian Anton Shkaplerov, and Italian Samantha Cristoforetti.

Advertisement

You can watch the launch live on NASA TV, NASA’s Ustream feed (embedded below for your convenience), and the ESA live feed.


There are some cool things about this particular crew. For one, as AmericaSpace points out, all three are in the Air Force, though from three different countries. I’ll add that in our collective pasts, all three countries have been enemies at one point or another. Yet here we are, all three not just cooperating but sending members of their military into space together to work as a team.

That makes my heart soar.

All three are on Twitter: Virts, Shkaplerov, and Cristoforetti. Together, they make up the rest of the crew of Expedition 42, which began when the ISS hatch closed on the Soyuz capsule that brought three members of Expedition 41 back to Earth—at the time, three astronauts stayed on ISS, and now the team will be at full speed with six members.

This isn’t your ordinary space station crew. After all, would your everyday astronaut team pick this as their promotional poster?

Expedition 42
Don't tell Slartibartfast.

Photo by ESA

Heart? Still soaring.

I want to single out Cristoforetti for a moment. Not because she’s a female astronaut, though it’s perhaps worth noting that two women (the second being Elena Serova) will be on ISS together for only the second time since the orbiting facility was launched. And not because she’s the first astronaut named Samantha, either.

No, it’s because she’s cool. How do I know?

Back in August she tweeted a photo of the cabin of a Soyuz capsule. The seats are far enough back from the controls that they need to use extension wands to press some of the buttons, and Cristoforetti noted that the paperwork is done to get her pointer to fly.

I couldn’t help myself. I replied to her, and this conversation ensued.

(Note my typo; I meant “ad astra”, which means “to the stars,”, and is part of the phrase per aspera ad astra, or “through hardship to the stars.”)

All very nice and fun, and I got a good chuckle out of it. But then she became my favorite astronaut in the whole wide Universe when she picked the conversation back up a little while later:

And before you ask: I asked her, and she’s not bringing it into space with her. There goes the best promotional picture ever taken! Oh well.

Still: My heart is now well above the Kármán line.

So then, let me finally add: Per cordibus nostris, ad astra.

Nov. 22 2014 7:30 AM

The Art and Politics of an Icy Water World

Well, this is interesting: The folks at the Jet Propulsion Laboratory and SETI Institute have just released a remastered image of Jupiter’s moon Europa, and it’s breathtaking:

Europa
All these worlds are yours, including Europa. Attempt landings there.

Photo by NASA/JPL-Caltech/SETI Institute

That’s not even full-res; click it to see it in its splendor.

Advertisement

Europa is 3120 km (1930 miles) in diameter, a hair smaller than our own Moon. Unlike our Moon, which is rock through and through, Europa has a rocky core covered with water. And by water, I mean liquid water, an undersurface ocean covered with a kilometers-thick shell of ice. The water may be in a layer 100 km thick, and salty, making it a true ocean. In fact, it may have more liquid water than Earth does!

The cracks you see are where ice floes fit together; the brighter areas are nearly pure water ice, but the red/orange regions are cracks, possibly where briny water has been squeezed to the surface, and materials in it chemically affected by the intense radiation environment surrounding Jupiter (caused by its very strong magnetic field interacting with material blasted out by volcanoes on Jupiter’s moon Io).

All of this has made Europa a prime target for exploration for a long time. I was going to write a bit about that, but then saw that JPL made a very informative video explaining it all.

That video is very well-done, and as I watched it I couldn’t help but think it felt like a trailer or promotional video for a new mission in the works. I know a lot of planetary astronomers have wanted to send a dedicated mission to the moon to investigate it far more thoroughly…

… and then I found that, due to the mid-term elections, Rep. John Culberson (R-Tex) is now head of the House's Commerce, Justice, and Science (CJS) appropriations subcommittee. He’s long been an advocate for a Europa mission.

It cannot be coincidence that this new image and video were put out now. The feeling I got while watching it, I suspect, is based on reality. I will not be surprised in the least if, for the next fiscal year budget, NASA asks for a Europa mission, including something as dramatic and unprecedented and as some hardware that can penetrate the ice and take a peek into Europa’s dark, briny depths.

I can’t say I’m opposed to that. There’s a lot of reasons to look around Europa as the video makes clear. You could argue the same for Enceladus, the icy moon of Saturn that has water geysers erupting from its south pole. In many ways Enceladus is a juicier target… but on average Saturn is twice as far from Earth as Jupiter, making the mission longer and more difficult. I figure go close first, learn the lessons, then push the distance boundaries more. As much as I’d like to see what’s under the ice of Enceladus, the shorter trip to Europa makes it an easier goal.

I’ve had my issues with Culberson about NASA, but, depending on how it’s done — extra funding for NASA so that no current or other future missions will get bled of funding, for starters — then an orbiter, lander, and sub-lander to Europa could very well be something I could get behind.

This is something I think NASA should be doing: Pushing the frontier, doing what only a national space agency can do. This would be a huge undertaking, and one that would fire up the public imagination like nothing before it since Apollo. I'd very much like to see that happen.

Nov. 21 2014 7:30 AM

As the Earth Turns

Last week, I highlighted an amazing video of the Sun taken from space in super-hi-def resolution,  put together from NASA imagery by James Tyrwhitt-Drake.

Today, how about we turn that around, look down, and do the same thing for our fair planet?

Advertisement

Here’s the Earth, as seen by the Russian Roscosmos’s Elektro-L satellite from May 15–19, 2011, and put together into a video again by Tyrwhitt-Drake. Set it to maximum resolution and make it full screen, and soak up the incredible beauty of home.

Fantastic, isn’t it? But it also takes some explaining.

First, Elektro-L is an Earth-observing weather satellite. It’s in a geosynchronous orbit, meaning it goes around the Earth once every 24 hours, the time it takes the Earth to spin once. From our point of view that means the satellite is fixed in the sky, neither rising nor setting. From the satellite’s point of view the Earth always shows the same face; looking down it always sees the same part of Earth. That’s why a geosynch orbit is so useful for weather. The video makes that obvious, too.

The satellite has cameras sensitive to visible light—the kind we see—and near-infrared. Plants reflect that kind of light very strongly, so places where there’s vegetation show up strongly in the satellite images. Normally those are colored red in pictures, but for this video Tyrwhitt-Drake colored that channel a more natural-looking green. Plants aren't the only thing that reflect IR light, so some places look green that aren't; note Saudi Arabia, for example, and the Sahara, which have a yellow-green tint from sand.

If the motion looks odd to you, that’s because Tyrwhitt-Drake had to interpolate between frames taken every 30 minutes by Elektro-L. (I explain how this is done in a post about a video of the Curiosity Mars rover landing.) It creates an odd flowing effect but is far better than the jerky snap between images taken so long apart.

Also, the video only shows the Northern Hemisphere first, then the southern flipped over (note the shadow line between night and day, called the terminator, moves the other way), and then finally the whole Earth at lower but still spectacular resolution.

Incredibly, the images off the satellite are originally 11K x 11K (each 120 megapixels!), which Tyrwhitt-Drake resized down to 50 percent, presumably so it would take less than a century to render the video. He says his 5,568 x 5,568 pixel video is available upon request. That would be amazing … if I had a monitor with enough resolution to see it! Maybe I could stitch 25 TVs together …

Tip o' the chlorophyll to Fraser Cain.

Nov. 20 2014 7:00 AM

“Happy 10th Anniversary in Space,” He Said Swiftly

Ten years ago today—on Nov. 20, 2004, at 17:16 UTC—a Delta II rocket thundered into the sky. Sitting inside the payload cowling was NASA’s Swift observatory, awaiting its chance to revolutionize astronomy.

Swift was sent into orbit to look for gamma-ray bursts, the most violent bangs in the Universe since The Big One. These explosions are the birth cries of black holes and occur somewhere in the Universe every day.

Advertisement

They’re so luminous they can be seen clear across the Universe, but so short in duration that in some cases, literally, if you blink you’ll miss them. They made them incredibly hard to study; it was a lucky break when a burst in 1997 was caught by an X-ray satellite called BeppoSax, the first to have its distance accurately determined; it was a whopping 6 billion light-years away! The history of GRBs involves the cold war, nuclear bomb testing, and many, many years of astronomers scratching their heads. It was one of the most enduring mysteries in astronomy,* and Swift helped us understand them better than any observatory before it.

Swift was designed and built to detect GRBs in gamma rays, X-rays, ultraviolet, and optical light—a huge chunk of the electromagnetic spectrum—and rapidly slew over to point at them, sometimes in well under a minute. It was named after the acrobatic bird, which catches huge numbers of insects on the fly.

It turned out to be a good name.

hypernova
Artist's conception of a supermassive star exploding, forming a black hole and a gamma-ray burst.

Artwork by Dana Berry/NASA/SkyWorks Digital

Swift quickly became the go-to observatory for GRB detection. By the end of 2004 it found nine GRBs—averaging about one per week—even before its observational methods had been fine-tuned. As I write this, after 10 years, it’s detected 921 of these cosmic explosions! That’s stunning.

As soon as it detects a burst, it sends the coordinates out via the Gamma-Ray Coordinates Network. Telescopes hooked up to the network can automatically look for the burst within moments of its discovery that way, and hope to catch the rapidly fading afterglow, caused by the initial explosion sending out so much energy and high speed matter that in a few seconds it dwarfs the Sun’s entire energy output over its entire 11 billion year lifetime!

GRBs are awe-inspiring.

Along the way Swift’s also seen a magnetar explosion (one of the very few astronomical events that actually freak me out due to their mind-crushing violence and scale), watched a neutron star get torn apart by a black hole (!!!), observed hundreds of galaxies, exploding stars, asteroids, comets, and more ... including, get this, the single most luminous event ever witnessed by humans up to that time. And Swift is still up there, orbiting the Earth, scanning the skies diligently and patiently, waiting for the next burst. You can even see a map of the sky showing where the latest bursts have been seen.

Although I wasn’t involved with the science of the mission except tangentially, I worked for many years on the education and public outreach part of the mission. I wrote countless articles about Swift, including much of the EPO website. Our team at Sonoma State University designed a lot of activities for kids using Swift science, including brochures, a paper model of the satellite, classroom activities, a planetarium show, and a lot more. I’m still pretty proud of the work we did for Swift.

And I’m proud of the satellite. It was relatively inexpensive (the total mission cost was about $250 million), and it’s performed nearly flawlessly in the ravages of space for a decade. It’s a paragon of international cooperation to study the Universe, and a true achievement for NASA.

Congratulations to the entire Swift team, and happy anniversary. You deserve it.

* I wrote about this for my book Death From the Skies!, and/or you can read more about it here

Nov. 19 2014 7:30 AM

What Exploded Over Russia This Time?

Please see update below; it appears this was a ground blast and not a meteor.

On Nov. 14, 2014, something exploded over the skies of the Sverdlovsk region of Russia, about 1,500 kilometers east of Moscow. I’m not sure what it was, but the videos coming out are pretty dramatic:

Advertisement

As we learned from Chelyabinsk in 2013, Russian cars commonly have dashboard cameras, so I’m hoping more footage will surface soon. A couple of teenagers managed to catch it on a phone camera:

It’s very cloudy, but the light can be seen through them. The first obvious guess is that this was a bolide, a fireball caused by a chunk of debris entering our atmosphere from space at high speed. These happen pretty often.

The color is odd; the reddish glow, if accurately portrayed in these videos, isn’t something I generally see in bolide videos and photos (or from the few I have seen with my own eye). They tend to be green or blue, or just white. Not always, but just in general. Of course, the clouds may be affecting the color, too.

Also, it’s really hard to tell, but it doesn’t look like the light is moving, as you might expect from a meteor. The videos are both shaky, so it’s not easy to measure that. The movement looks minimal to me, though. That could be geometry: If the meteor is moving across your line of sight then there is a lot of motion, but if it’s headed more or less  toward or away from you as it moves through the air, sideways motion will be low. I’d expect that the two videos would show different geometries, but again they’re so shaky it’s hard to tell.

Update, Nov. 19, 2014, at 14:50 UTC: Another video has surfaced that shows what looks to be an intense burst of light on the ground. Pay attention about 20 seconds in:

It's brief, but it corresponds to the same flash in the sky. This also can apparently be seen in a video at LiveLeak. It looks like this was an explosion on the ground, reflected in the clouds (see the still frame from the video below). That would explain everything seen in the videos above, including lack of apparent motion and the red coloring. I don't know what the explosion or fire was, but I'm pretty satisfied this was some sort of ground blast, and NOT a meteoric event. My thanks to commenter beanfeast and Sasa Andonov for the tips.

sverdlovsk_fireball_groundflare
A flash on the ground can be seen at the same time as the one in the clouds, and a fireball of some kind becomes visible moments later on the ground as well.

Photo by Doble V Channel, from the video

There are some preliminary flashes in the teenagers’ video a few seconds before the big one, and that’s consistent with a meteoroid breaking up as it comes in. As a big rock rams through the air at many times the speed of sound, the pressure breaks the rock up into smaller pieces, creating flashes as the energy of motion is converted into light and heat. There can then be a much larger flash as the smaller rocks all disintegrate rapidly.

If this wasn’t a bolide, what was it? Beats me. It’s a bit odd to think that a biggish rock from interplanetary space is the most mundane and prosaic explanation, but in this case it is! However, I won’t make up my mind until more evidence is in.

Tip o’ the Whipple Shield to NASANeoCAM on Twitter.

Nov. 18 2014 7:30 AM

Distant Horizons

“Ah, but our reach should exceed our grasp, Or what are the heavens for?”
 —with apologies to Robert Browning

We humans have lived on Earth a long time. Hundreds of thousands of years, give or take, depending on what you define as human. And all that time we have yearned to reach the stars, to explore, to find out what exists elsewhere.

We’re just now starting to do just that. We’ve only been able to fly for a little over a century, and the elapsed time since we first left our atmosphere can be counted in decades, less than a human lifetime. We’re taking our first tentative steps.

And yet we have accomplished so much! We’ve sent our spacecraft to every major body in the solar system, and quite a few minor ones besides. We’ve continuously occupied space for years, and we’ve launched observatories into orbit that examine the Universe in every wavelength regime of the electromagnetic spectrum.

And we’ve done even more: We’ve set down on other worlds. Certainly, most have been through our robotic proxies, but given the inhospitable nature of so many of these worlds, that’s not surprising.

And now we can include an entirely new body to that list: a comet, thanks to the Philae lander sitting on the surface of 67P/Churyumov-Gerasimenko.

To celebrate that, Michiel Straathof has updated Mike Malaska’s classic “Distant Horizons” mosaic to show all the worlds that humans have touched.

READ MORE STORIES