Comic by Hannah Blumenreich. Happy Caturday!

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An item on my wish list: See a sunrise from orbit.

Sunrise from Orbit

Earth’s atmosphere scatters out the blue from sunlight. The scattered light makes the atmosphere look blue, but the sunlight has all of its blue photons scattered out from it, giving it that distinctive sunset orange colour. It’s somehow even more apparent when seen from space like this. Billions of molecules scattering trillions of photons lighting up Earth’s atmosphere like a jewel in the night as you pass out from behind the planet’s shadow.


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Winter Wonderland

A few days ago, the Cassini spacecraft, 1.61 billion kilometres away in orbit around Saturn, made its closest ever pass of Saturn’s tiny moon Enceladus. It flew by around 49 km above Enceladus’ south pole – perilously close by astronomical standards. For comparison, Felix Baumgartner‘s record breaking skydive was from 39 km above Earth’s surface.

The objective of Cassini’s daredevil stunt was to take a close look at the watery plumes being ejected by the tiny moon to try and work out what drives them. And to gain some insight on the extent of Enceladus’ expected subsurface ocean.

While it was passing by though, Cassini also snapped this closeup image of the little planet’s surface…

Actually, the surface gravity on Enceladus is only 0.113 m/s² (compared with Earth's 9.807 m/s²). So you could probably jump over those bumps and ridges a bit like Super Mario...

What you’re seeing here (after image correction to fix the blurring – that craft was going extremely fast) is the wrinkled surface of the icy little world. The white scale bar is 1 km on this scale. Which means that all of those ridges are about the same size as streets and roads we may be more familiar with. To be honest, this part of Enceladus looks like a terrible place to go hiking.

While this may be the closest image of the surface we’ve ever seen, it’s by no means the only one. In case you’re curious about what it might be like to visit this tiny iceworld, here are a few others…

Give it a couple of hundred years, and I’d be very surprised if no one’s opened a skiing resort on Enceladus…

All images: NASA/JPL-Caltech/Space Science Institute.

I have to agree with @TychoGirl – The Khumbu icefall looks comparatively inviting!

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Painted leaves

Sunset on Mars

Ladies and gentlemen and variations thereupon, I’d like to introduce you to Chrissy Sparks, – who creates some really quite marvellous space art, which she sells in her store on Etsy. You can also get a slightly more behind-the-scenes look via her instagram feed. Her necklaces are gorgeous, but I’m really a huge fan of the painted leaves she makes. When I eventually get an office of my own, this is the kind of thing which I’ll probably use to decorate my walls…


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This is a completely gratutous Saturn system appreciation post. Because Saturn.

Images found courtesy of wanderingspace.net

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Postcards from Pluto

New Horizons passed Pluto some time ago, but it’s still slowly dripping data back to us. The tiny craft wasn’t optimised for data transfer, so its hard drives are still packed to the gills with exciting discoveries which we’ll all be hearing more about as the months go by. Also, it gives it something to do now that the excitement is over.

One of the most exciting things I’ve seen lately is this huge juicy mosaic made by the LORRI instrument. It’s false colour to emphasise certain surface features and it’s just big enough to get slightly lost in. Emily Lakdawalla can tell you more details about it, but I just want to feast my eyes on how gorgeous this little world is…

False colour portrait

Pluto is watching you!

I sort of feel like Pluto might be a nice place to go hiking...

From the craters, the surface looks older here...

Marbled swirls on the shores of Pluto's heart...

It's not just me, right? It really does looks snowy, doesn't it...

Pluto has such odd landforms. Odd and really pretty!

Oh you beautiful little frostball. I can still barely believe we’ve finally visited you!

The original NASA release is here.

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Words matter

This gifset has been going around Tumblr awhile now (1,408,824 notes while I’m writing this!), and I think it’s a very important message.









Gender is irrelevant really. Kids all like science. I know I did, and I think the same is true of everyone I know who ended up in science, no matter what their gender may be. The unfortunate thing is that we tell kids that science is for boys, while discouraging girls. Science toys are marketed at boys because it’s ok for boys to play with chemistry sets or catch bugs or break rocks in two to look for fossils. The idea that girls shouldn’t do these things is ridiculously old fashioned.

Conversely, I wish people would stop having “brilliant” ideas of making science appeal to girls by making it girly. What’s so bad about just, you know, encouraging girls to like something as it is? After a conversation I had with @girlandkat a few weeks ago, I find myself thinking along the same lines more and more. Gender is only an issue because we make it an issue. We should stop making things for children which are so needlessly gender defined, and stop pushing children down such narrow gender-based avenues. I’m quite certain the increased diversity will benefit everyone.

In the meantime, for anyone reading this with children or younger family members, I’d ask you to please keep one thing in mind. Push interests not gender roles. If a kid is interested in something, you should encourage them. Not tell them to stop it because outdated values claim that it’s not appropriate for someone with their anatomy.

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Twilight on Pluto

It turns out, Pluto has blue skies. And water ice on its surface. Which, at a cursory glance might make it seem a little bit like home. But only a little bit.

Some notable experts were a little puzzled to find that at first, Pluto appeared to have no haze. One of the most knowledgeable people to listen to about hazes on small worlds is Sarah Hörst, an expert on Titan, who seemed rather puzzled at the idea that Pluto may be haze-free. From its night side though, Pluto reveals its hazy goodness.

Die himmel ist blau...

This image is about as close to true colour as you can get. The glow comes from a deep layer of haze which swathes all of Pluto, and yes, it’s a lovely indigo blue colour. It looks strikingly like the haze in the upper atmosphere of Titan, and is quite probably made the same way. Hazes form when nitrogen molecules and small hydrocarbons are bombarded by ultraviolet in a planet’s upper atmosphere. They form into carbonaceous particles made of tarry material called tholin which then proceeds to fall back down to the planet’s surface. Here on Earth, the same thing happens over cities to form smog.

Look closely at the images of Pluto’s atmosphere and you’ll even see striations in the haze, showing different atmospheric layers. It’s really rather fascinating!

The air's full of smoggy haze and there's no liquid water. Sounds a little bit like Southern California...

Haze on Pluto means that the tiny world has a rich, active chemistry going on, which is something I’d very much like to know more about. Hopefully we’ll learn more as New Horizons continues sending back data.

For the record though, the blue colour is due to the fact that tholins tend to be an orangey red colour (which is why Titan’s clouds are that beautiful orange colour). As a result the tholin particles in the atmosphere scatter red/orange light away. It’s the reason for the reddish colour of the little planet’s surface. While Pluto’s atmosphere is too thin to see this normally, when seen in silhouette, the sunlight passing though the atmosphere has very few red photons left in it so you see blue haze. The fact that martian dust does something similar is why sunsets are blue on Mars.

In other words, Pluto may seem to have blue skies, but it doesn’t. And the blue you see in that picture up there shows skies which are not actually blue like Earth. Actually, they’re blue like Mars!

Actually, given how little sunlight makes it out that far, Pluto is permanently a twilight world...

This twilight Pluto image has been colourised by myself. The original was gorgeous but grayscale. There’s another version out there, but I think mine’s slightly more accurate…

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Snowball Moon

Enceladus is, without question, one of the most interesting locations in our solar system, and for a lot of reasons. Quite simply, this tiny Cronian moon is a mystery. We know what we see, but we have utterly no idea what makes it tick!

Oh, and that yellow glow in this picture? That's saturnshine. Sunlight reflected off the yellowy cloudtops of saturn.

What we see, as it happens, is geysers of pure water spraying out of four fissures in Enceladus’ surface. They spray so high and with such force that much of the water escapes the moon’s feeble gravitational pull and actually create one of Saturn’s rings! (The rest eventually falls back down as snow, giving Enceladus a ratheryouthful appearance). The thing is, a diminutive object like Enceladus shouldn’t, by rights, be active at all. It’s so small that it’s likely only just large enough to even be spherical. Smaller objects cool faster, so while a reasonably sized planet like Earth still has a molten core, our planet’s own moon is mostly solid by now.

Small but mighty

Enceladus, however, contains a lot of internal heat and it’s still not entirely clear where it all comes from. Because when I say it’s tiny, I’m really not exaggerating. The image above shows a handful of tiny worlds recently visited by humanity, compared with Earth’s moon. As you can see, Enceladus is so small that it could easily become a moon for an object the size of our moon (which would make it a moon moon, I suppose).

There are hotspots near it’s south side, resulting in a series of fissures nicknamed “tiger stripes”, and it certainly receives tidal heating due to Saturn’s considerable gravity pulling and squeezing it as it orbits. But it’s still difficult to explain why this little moon is so warm. Or why it seems to contain liquid water. Or why it sprays that water so high into Saturn’s orbit the way it does. Studies have suggested that tidal heating alone can account for about 1.1 gigawatts of power being supplied to Enceladus. But the Cassini probe’s observations suggest that there are about 4.7 gigawatts powering Enceladus’ hotspot. There’s a lot of heat which is still going unaccounted for…

While it’s been accepted for some time that there must be a subsurface ocean under Enceladus’ south pole, the latest suggestions are that this ocean may actually be global (just like Europa!). Actually, the evidence is fairly compelling. Essentially, as it orbits, Enceladus shows a slight wobble. It’s not very pronounced, but it appears to be more apparent than it would be if Enceladus was mostly rigid. This suggests that its surface is actually detached from its core, as it would be if its icy crust was floating on a global ocean of liquid. Given that an ocean of water would be a good place to look for signs of extraterrestrial life, many consider Enceladus to be a priority target in space exploration.

So excitingly enough, NASA planetary scientists have schemed something quite fun. Cassini’s taken a few close passes of Enceladus lately, giving us some more detailed views. Following up on this, on October 28th (that’s this Wednesday), they’re going to plough Cassini straight through the plume of icy water being sprayed out of Enceladus. Cassini is, to date, one of the most successful robotic probes ever launched. It’s been orbiting Saturn for over a decade now. As a result, I guess its pilots aren’t afraid to take a few risks (it’s always fun when spacecraft pilots aren’t afraid to be a little gung-ho). After all, there surely can’t be that much more data it can usefully collect. I’m quite excited to see what they might find out…

What secrets are you hiding, little moon...?

And as we all know, 1.1 gigawatts isn’t even enough power to travel into the future

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Meteor Chemistry

Have you ever noticed that not all meteors you see falling are the same colour? Growing up in the dark countryside away from city lights, I saw them sometimes, and their colour occasionally seemed to be an unusual and striking shade. Other times entire meteor showers tend to be a certain colour (the Quadrantids, for instance, tend to be blue). The reason for this is all down to what chemical elements are found in the meteors.

I stumbled across this image from AccuWeather.com somewhere on the internet and thought it seemed pretty cool. It’s a handy little chart for determining what’s in a meteor based on its colour.

The purple ones are pretty rare.

These look accurate to me. Incidentally, a flame test for Calcium shows a rich red colour, but in this case I’d assume that you don’t find Calcium without Magnesium, so you’d get purple. As for the oxygen/nitrogen meteors, I’d guess the colour is due to chemical compounds in the meteor breaking down. Atomic oxygen emits red light when it’s excited. Which is actually why aurorae are red after heavy solar storms, when charged particles from the sun are energetic enough to reach Earth’s inner atmosphere. There, they fragment oxygen atoms and make a red glow.

So now you can know a little bit more about what you’re seeing if ever you watch a meteor shower. Adds an extra dimension, I think…

I always love seeing a bright blue one. This one looks like it has a tinge or purple too...

Image is “Fireball over Banff Rundle Mountain” © Brett Abernethy. His photos are spectacular and make me wish I had a better camera!

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