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Monday 27 July 2015

I'm off on my honeymoon!

Above: A recently released high resolution map of Pluto's surface. courtesy of NASA
Hi everyone, I've just got married so I'm away on my honeymoon until mid august now, but don't worry I'll be back with a vengance before you know it.

In the meantime, here are a few predictions for the time period I'm away:

  • As  more data comes down from New Horizons our Picture Pluto will get more complex, including the presence of prebiotic molecules on the surface and near surface.
  • There will be at least one speculative article published on the possibility of life beneath the surface of Pluto - either earth like life near the core or life in cryogenic liquids (IE liquid nitrogen or methane) in the near sub surface.
  • Charon will be revealed to have had a tortured and geologically active early history.
  • Ceres will become a scientific arguing point, as evidence for activity and 'hazes' there is presented to the world.
  • The Philae lander will continue to make intermittent contact with its Rosetta mothership.
  • I will spend the next three weeks on a beach doing solar astronomy with my tan. :D
Be happy everyone,


Wednesday 22 July 2015

Water on Ceres?

Update: you can find the actual talk (mentioned below) by Chris Russel here, or if that's not working try going through the websit, here

I am getting married on Sunday, then jetting off on my honeymoon, so there's not a lot of time for me to write at the moment. But the universe has, it seems, given me the chance to leave you all with a real - and possibly game changing - mystery:

Is the dwarf planet Ceres hiding an interior warm enough to have an ocean?

Above: The still unexplained bright spots in Occator crater - they are so bright they are visible to Hubble, orbiting Earth
Right now Ceres is being studied by the Dawn mission, which had previously stopped at the giant asteroid Vesta. It's been guessed for a long time that Ceres could have a significant amount of water ice in its interior, and computer models have predicted that it could have retained enough heat for an ocean to persist near its core for billions of years. Spectral scans from Earth have found water related minerals onn the surface.On top of that the Herschel space telescope has caught a plume of water vapour over the Cerean surface.

So when Dawn arrived we weren't sure what we were going to find... and Ceres's still surprised us: the surface is spotted still unexplained, ultra reflective, bright spots. The brightest of these is located in Occator crater, and is basically just baffling. Although it sits at the bottom of the crater the bright area has seemingly been observed over the rim of the crater, as if it were elevated somehow.

Last night a couple of tweets from planetary science journalists surfaced:

"Andy Rivkin ‏@asrivkin:
Russell: Can see haze in crater with bright spots at some local times. Bright spots "indicate Ceres is active today." #nesf2015

Chris Russell at the NASA Exploration Science Forum"

...and then this one (link here):

"Whatever the cause of the bright spots, Ceres is active today".
Above: A 3D model of Occator crater, as seen at Chris Russels update.

These have both come out of Chris Russells Dawn update at the Exploration Science Forum at NASA Ames.
A few hours later this report (link here) from Emily Lakdewalla of the Planetary Society surfaced.The gist of the update is that the Dawn team have seen some sort of haze over the Occator crater, at various times. The haze is confined to the crater itself - and on a world with next to no atmosphere it's hard to come up with any other explanation than gas escaping from some sort of internal volcanic activity.

If Ceres is still active then, unless we've got something very wrong (always possible) there's probably still liquid water - and a possibility of life - lurking beneath the surface. And if stuff is escaping onto the surface we could examine that liquid water (perhaps) with a follow up mission to Dawn.

Sometimes these big announcements don't work out - this could be a camera fault, image processing artifact, or there might be some other explanation. But it's a good note to go away on, so I look forward to telling you all whether this discovery has been confirmed or not when I come back in three weeks....

Take care all,


Saturday 18 July 2015

What in the worlds made Pluto and Charon so complex?

Above: An artists impression of Charon, as seen from Pluto.
OK, at this point the New Horizons flyby of Pluto is well over. Data is trickling back to Earth at a steady rate, and this will be the norm now for several months at least. So I promise that this will be the last post where I geek out over the latest results to trek across deep space and arrive home (cough, cough)... but.....

Yesterday (Friday 17th July) NASA held a press conference on... all kinds of Pluto-y things: Firstly, the Pluto 'heart' where New Horizons has confirmed presence of carbon monoxide ice covering it, the only such high concentration on the planet. Carbon Monoxide is actually pretty rare across the rest of Pluto - and one part of the heart has so much the spectral signature is visible from Earth. Why it should have so  much really isn't clear, but it's possible there's a CO source in that region - which would indicate some kind of internal activity breaking out to the surface...

Above: The area of the 'Pluto heart' with the intense carbon monoxide ice signature. That's a lot of CO in one spot.... Courtesy of NASA
Another huge plain, Tombaugh Regio, is  broken into massive polygon shaped plates. Along the edges of the polygons are some sort of  cracks.... as well as weird mounds that almost seem to be growing out of them, and an unidentified dark material. Some of the cracks have ridges running along their centres:

Above: Some of the cacks with central ridges, indicating rowth, perhaps.

Above: Tombaugh Regio. The black things that look like they're growing out of the cracks are hills made of an unknown black material. Courtesy of NASA.
Origin, and precise shape of the strange hills is unknown. There're some sign that they rise above the surrounding plains, and the geophysics have two theories; They could be erupted from below, like volcanoes or could be harder material left behind as erosion from above lowers the height of the plain. They are - very unofficially - slightly leaning towards the eruption idea, but only very slightly:
“This terrain is not easy to explain,” said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team. “The discovery of vast, crater less, very young plains on Pluto exceeds all pre-flyby expectations.” One odd idea being bandied about by astrogeologists is that some of these features might be liquid carved, like the liquid methane rivers on Titan, This is defiantly an odds against idea, but there are some liquids that might exist on Pluto

Other news comes from the probe's analysis of Pluto's atmosphere, which is made of nitrogen, and is being stripped away by the solar wind at 500 tons per second. That rate of loss compares unfavourably even to Mars ( which looses its air at at 1 ton per second). Over the lifetime of Pluto that's equivalent to a loss of several thousand feet of nitrogen ice - assuming the atmosphere is being replenished by evaporating ice. The atmosphere s around 1000km deep - almost as deep as the dwarf planet is wide - and the winds in its lower levels strong enough to move particles and cause erosion, which means that Pluto's surface will be eroded and shaped by them. 
Some evidence of this has already been picked up as streaks on dark material, apparently blown by the wind, seen on surface. The origin of the dark stuff might be due to geyser like eruptions, or it might be entirely due to wind eroding deposits of dark material - there's no evidence of eruptions but the team will be looking.

Above: Mysterious streaks of windblown material across the frozen plains of Pluto...possibly a hint of subsurface activity?
On to the moons of Pluto: Nix as been imaged for first time - it's shown to be about 25km across, and about twice as long as it is wide:
Above: Our first view of Nix, Courtesy of NASA

....and Charon has a very strange looking mountain with a 'moat' all around it - the feature has everyone utterly baffled. But we'll know more soon:
Higher resolution images are coming, as well as data from other sensors like Charon atmosphere data (coming Sunday).

Above: Charon, showing off its weird mountain (upper left), courtesy of NASA.

Elsewhere on the Internet:
Jupiter twin
ISS crew man lifeboats
Continental crust on Mars
Zebra stripes in space

Wednesday 15 July 2015

The news from Pluto....

The first batch of the data New Horizons collected during its fly-through of the Pluto system has made it home. I think the best way to sum up the reaction of the science team at this evenings press conference is in the words of Kathy Olekin, New Horizon's deputy project manager : "This exceeds what we came for!"

First let's look at what the team were able to say -and show - about the largest moon, Charon:

Above: Charon, seen up close for the very first time in our solar systems 4.5 billion year history. Courtesy of NASA

Charon's dark northern region (known informally as 'Mordor'), seems to be covered in a thin layer of dark material - although why it's gathered around Charon's north pole isn't clear.  Massive cliffs stretch for hundreds of kilometres, and on the upper right a chasm perhaps nine kilometres deep can be seen. The surface has very few craters, just a few here and there. It all suggests a world whose crust has been cracked open by immense internal forces, and had its surface covered over by material welling up from deep inside -  and in the (geologically) recent past. On earth that would mean volcanoes of molten rock. On an ice world like Charon that means cryolava - a mixture of liquid water and other low temperature materials, like nitrogen and ammonia. It might imply the existence of an ocean buried deep beneath Charon's crust....

On to Pluto:
First a name for the dark plain on Pluto that tickled me, as it refers to a character from one of my favourite horror stories: Cthlhu Regio. Plutonian mountains, 3500 meters high and probably made of water ice (based on how strong they must be to get so tall), have been found. But they're covered in nitrogen and methane ice - and almost no craters are on them, so they are geologically young, 100 million years old or less.

Above: A video showing where the newly discovered mountains lie on Pluto. Courtesy of NASA.

Above: The mountains seen with a scale bar, and showing one of the huge pits in the surface. Courtesy of NASA.

Pluto also has huge, oddly puckered, dimples in the surface. We have no idea what they are, but here's one idea:Alan Stern and Keisi Singer have had a paper accepted today where they argue that the nitrogen on Pluto - both atmospheric and surface ice - might need an internal source to sustain them... so perhaps these are the sites of huge vents, or cryovolcanoes. Saturn's moon, Enceladus....

Above: Strength of the methane signal on Pluto. Green is more, red less. Courtesy of NASA.
There are also some really bizarre folded landscapes, that well, look like nothing I can really name. However it reminds me slightly of the active south pole of

Above: Enceladus' south polar region.Or possibly a monstrous brain... nah? Courtesy of NASA
It seems, right away, that both Pluto and Charon are hosts to internal activity, so what could be powering it? The ideas put forward at the press conference were:

1. Radioactive heat... (All bodies generally have radioactive materials in their deep interiors)
2. Body could probably store heat of formation for a really long period of time. Maybe there's an ocean (implied sub-surface) that's freezing and the heat released from it, is melting the crust..
There's a lot more data to come; New Horizons will be downloading for months yet. The other sensors may well have been able to detect organic molecules,  Methane, Ethane, Propane, polycylic hydrocarbons etc. It's not a given yet that either Pluto or Charon do have internal oceans, but there's clearly some source of geological energy!

There will be another conference to reveal more of the data that is streaming down on Friday - but until then you can watch the whole of today's conference here.

I think I'm justified in saying that with New Horizons at Pluto, Dawn at Ceres, Rosetta/ Philae at comet 67/P, Cassini at Saturn, Orbiters and Rovers at Mars, and other craft on their way to worlds like Jupiter... it's a really good time to be a space exploration geek!

Tuesday 14 July 2015

Some quick notes: New Horizons survives hazardous passage through the Pluto system, control team now eyes the next target....

Above: Images from new Horizons approach to Pluto.

There's so much going on with the New Horizons mission right now that it's hard to take it all in - there's a lot of data still to come home, and the ground control team are already thinking about the next world in the Kuiper belt they want to visit. But here're a few quick notes that I've been able to gather from the internet scuttlebutt:

  • Data from the flyby will begin coming down today, and will include huge images of both Pluto and its biggest moon, Charon.

  • There will be a media event at about 1900 GMT where NASA will release some more data.

Above: one of the first attempts at a colour image of Pluto, using data from various new horizons instruments. Courtesy of ZLD on

Monday 13 July 2015

Post 200: Here comes Pluto!

This will be my 200th post, and it couldn't have fallen at a more auspicious moment*: In a little under 12 hours the New Horizons space probe will tear past the dwarf planet Pluto at 15km/sec. The probe has been on a ten year voyage to the Kuiper belt -  a massive doughnut shaped ring of icy worlds with names like Sedna, Eris, Hauma, and Make-Make. New Horizons will fly through the middle of the Pluto system (Pluto and its moons Charon, Nix, Hydra and Kerberos) then move deeper into the Kuiper belt and visit more of the worlds there. As it rips through Plutonian space it'll be constantly manoeuvring, bringing it's sensors to bear on Pluto and its Moons. And you can track it as it does so, there's an app for it too!

Above: A simulation of New Horizons closest approach, courtesy of Fred Lochlear.

So what do we know so far?

Above: Five views of different segments of Pluto. The NH probe will zip by so fast that this will actually be the best view we get of some parts of Pluto. Start lobbying for a sequel mission folks! Courtesy of NASA.
Pluto has to be one of the oddest looking worlds we've encountered so far - there's pretty clearly a lot of things going on there: A very bright polar cap, areas covered in polygonal dark features, a huge ultra bright heart shaped plain, large dark plains near the edge of the disk, long belts of chaotic rumpled terrain.... what's going on? There are also features that look undeniably like titanic dunes, mountains.....

Above: The latest images of Pluto ad Charon, Courtesy of NASA.
New Horizons is already on the case, and NASA held press briefing (link here) this afternoon to reveal some early results: The bright areas are made of a mixture of methane and nitrogen ice, and the dark areas are depleted in methane ice. The dwarf planet is surrounded by a halo of ionised nitrogen, which was detectable from five days out, which might suggest some surprisingly violent activity gong on on the surface. The New Horizons team have also tweeted that there are signs of frost transport everywhere, meaning that the ice on the surface evaporates and re-condenses elsewhere.

Above: Some of the possible explanations for Pluto surface features.
Pluto's not the only mystery: Charon is already confounding everyone's expectations. Instead of a light polar cap of ice it has a dark one, and its surface seems to be torn up with massive chasms, suggesting immense internal activity - in the distant past gravitational stress might have driven cryovolcanism, the way the gravitational stress from Jupiter drives intense volcanic activity on Io....

One possibility for the dark material is something called tholin - an incredibly complex tangle of organic molecules, heavily implicated in the origins of life.

What can we expect tomorrow?
Well, although some of the 'wow' shots will be downloaded fairly fast, the vast majority of the data from the probe will take weeks, maybe more than a month, to download back to Earth. So, unless there's a stunningly obvious alien city o the surface don't expect any major discoveries right away. The reason for this is that New Horizons is deeper into space than almost all the human space craft that have ever flown - there ain't no Internet out there folks..
For a bit more of an informed opinion here's Emily Lakdewala's Pluto preview - listen here  - and here's the flyby schedule.

Wednesday 8 July 2015

What might live on Mars?

What could live on Mars? 
My last post I put up was asking 'why spend thirteen years on Mars'... and one answer, though by no means the only one one, was 'in the hope of finding evidence of alien life'. Maybe that's a vain hope. Maybe not. But, if anything does survive there today, what type of life might it be?

Well, one way to try and work out what our speculative Martian  might be like is to look at the Mars like environments on Earth, and see what eeks out a living there. And that is exactly what astrobiologists do: One of their favourite spots is the Atacama desert.

A weather station at Chott el Jerid, in the Atacama desert - but tell me you didn't wonder if that was Mars, just for a moment. Credit: Felipe Gómez/Europlanet
The weather station at Chott el Jerid. Credit: Felipe Gómez/Europlanet - See more at:
What lives in the Atacama, where it often doesn't rain for decades? Where the soil is loaded with poisonous perchlorate salts, like Mars, and the sunlight teems with sterilising UV, like Mars?

The truthful answer is 'not much' but something. In fact a few very tiny things have found ways to literally suck the water they need out of the air, while hid beneath the surface from the scorching UV . These micro-organisms, called 'halophiles', have come across a simple trick: In the terrifying Atacama wilderness they make their home inside layers of salt crystals. In the desert conditions actual liquid water is incredibly rare, but the salts a have special properties: Firstly They absorb water molecules directly out of the air. In a process called deliquescing the water molecules build up n the crystal structure until the salt actually dissolves into a blob of ultra salty water - and since the word 'halopjile'  means salt loving, guess what type of water these creatures can use? That's right microbe lovers*, water so salty it'd be poison to most creatures.
This salty water has other magic properties: The salts act as antifreeze, keeping it liquid and usable in the cold (down to minus fifty degrees Celsius in the case of some salts). And it stabilises the water against evaporation into the thin Martian atmosphere.
Above: Common NaCl table salt crystals deliquescing beneath a microscope, as the humidity crosses a threshold point. Courtesy of
Protected beneath the surface from the harsh conditions the halophiles eek out an existence in a place where - according to all the signs on the surface - life should be impossible.

A bit like Mars, in fact. "The conditions on Mars, where the relative humidity is high and the available water vapour is approximately 100 precipitable microns, is the equivalent of the drier parts of the Atacama Desert in Chile," John Rummel, of East Carolina University, told could something similar be happening there?

Above: Gale crater on mars, as seen by the Curiosity rover mission. there's strong evidence for flowing water there in the ancient past, and some evidence that tiny amounts still flow today. Courtesy of JPL/NASA
The idea of salts being the key to creating water on Mars does have some evidence: Evidence from the Curiosity rover suggests that the very perchlorate salts that poison the soil in the region deliquesce in exactly this way. Although they probably aren't producing enough water at Curiosity's location to support life, there are other regions of Mars where the potential amount of water that could form this way is much higher. There are even those who believe that the Phoenix mission to the Martian arctic saw water (or at least wet mud) formed in exactly this way.

Above: these blobs, caught on the leg of the Phoenix lander, were thought by many to be blobs of perchlorate laden mud. Courtesy of JPL/NASA.
But we also should be careful with the idea that this water could be supporting life: Mars is still much, much, harsher than the Atacama. The Martian sky bleeds radiation, the tiny amounts of water would be loaded with toxic substances, and the temperature can drop to extremes of cold no terrestrial environment could hope to match. Even the very toughest organisms might never be able to adapt.

Still, that won't stop us dreaming of the possibilities - and that's one reason why robots like Opportunity rover will keep on rolling...

Above: A video record of Opportunity rover's long journey across the Martian landscape. Courtesy of JPL/NASA

Latest Image of Pluto, from New Horizons:

One week to go, and Pluto is starting to resolve itself....

Japan responds to America's GIANT ROBOT CHALLENGE:

It's on....

Elsewhere on the internet:
Submarine for Titan under development
Solar sails forthe next step into deep space
NASA developing tech for exoploring lunar caves 
Exploring shadowed areas of the Moon

US vehicles to get laser weapons
Mercury data still being studied by MESSENGER team
Fast radio bursts could be local
New Zealand takes surprise lead in private space race

* That just mean folk who like microbes aesthetically. Nothing kinky. You weirdos.

Monday 6 July 2015

My unsubstantiated opinion: Thirteen years on Mars - why?

 Thirteen years on Mars
Thirteen years ago two robots named Spirit and Opportunity landed on the planet Mars. Today one of 'em's still going - and the other survived for years.  Not bad for machines hat only had 90 day warranties, but what's even more remarkable is this: Since that day back in 2002 humankind has had a nonstop presence at the red planet. A third rover, the car sized, laser toting, Curiosity rover joined the surviving Opportunity rover on the surface. Curiosity has found unequivocal evidence of ancient, habitable environments. In the space above Mars there's a fleet of five orbiters scanning the planet - with more orbiters, aircraft, chipsats, even swarms of mini robots either en route,under construction, or on the drawing board.
Above: After 13 years exploring Mars the Opportunity rover is forging it's way through Dingo pass (shown) to look for even more clues to Mars' 4.5 billion year history. Courtesy of NASA.
No other world can make such a claim. Why?

Are we all just obsessed with the colour red? Did we all just read War of the Worlds to much as kids? Maybe, but to my veteran-space-geek eye the reasons for the space exploration communities (some would say excessive) focus on Mars is actually a combination of a number of factors:

Above: Not those space aliens. I don't think we're looking for those space aliens, anyway. We could've just asked Buzz Light year about them, and saved some time.... Courtesy of Pixar
Lets get the green four eyed elephant in the room dealt with: Mars isn't the most hospitable environment today, but there's plenty of evidence that, whether it was 'cold and damp' or 'warm and wet' ancient Mars was at least hospitable to life some of the time. All the same chemicals that came to Earth and contributed to the making of life also went to Mars. So there is a real chance that Mars once had life - and we could find traces of it. Or, just maybe, in some secluded and more hospitable niche on modern Mars, its descendants.

Aliens we can actually find:

But, hang on, Mars' heyday was over four billion years ago. And even then it might not have been as promising or interesting an environment as some we know are actually present today!

There's Europa, a moon of Jupiter with a worldwide ocean that's warmed by volcanic heat.
Above: Jupiter's moon Europa. those cracks in the surface ice are the first clue that something special is going here.. courtesy of NASA.
There's Ganymede, another Jovian moon that also hosts a volcanically warmed worldwide ocean.
Above: Ganymede. Beneath that battered surface lurks a well hidden ocean. Courtesy of NASA.
Then there's Saturn's moon Enceladus, which has a sea around it's southern pole that's actually leaking out into space for us to measure. Because of this we know that that sea has organic chemistry, salinity, PH, and temperature suitable for life.

Above: The geysers of Enceladus, which conveniently shoot water from Enceladus' sea into space where we can study it. Courtesy of NASA.
Then we have unconfirmed but tantalisingly possible oasis' on other worlds like Charon, Ceres...... why does Mars, the victim of environment annihilating climate shift, hold a candle to these as a destination suitable for hunting life on?

Well, all thing being equal, it doesn't - but then all things are not equal: Europa and Ganymede are five years travel from Earth, and they hide their oceans beneath kilometre thick shells of ice. Enceladus is located in the Saturn system, which is seven years away, and has a thick shell of ice (albeit a leaky one, but leaks aren't the same as actually being able to get to the water).

Mars however has any evidence of life preserved in rocks that are conveniently near, or on, the surface for our robots to study, and is only months travel away. What's more, at this point. we know how to work on Mars fairly well, whereas we're still finding our way with those other worlds. The reasoning is that of being able to actually get the job done, in an environment we already understand well.

Is that good enough reasoning? Shouldn't we be pushing the boundaries and going for the big prizes a bit more aggressively? Ideally I believe we should, but in a risk adverse era where budgets can be made or broken on the back of good publicity... well it's easy to see how those folk with the actual job of running space programs think differently. We're on our way to exploring these worlds, but we won't be able to do it as fats and as effectively as we can Mars for a while yet.

....Life isn't the only game in space exploration:

Let me be clear: It's one of my biggest hopes in life to live to see alien life - even of the very humblest single-celled kind - discovered. But the following is still not remembered often enough by space exploration advocates: We go into space to do other kinds of exploration than just searching for evidence of alien life: Titan has one of the most bizarre yet fascinating environments we've ever discovered - a frozen reflection of primeval Earth. Jupiter's internal structure hold key clues to the early days of our solar system. Venus' geology, chemistry, and meteorology are worth a dozen probes. Doesn't that deserve a similar investment in time and money?
Above: Venus naked of its clouds...not sexy enough? Awww..Courtesy of ESA
Well, least in the minds of scientists as opposed to publicity hungry politicians (pardon my prejudices). But Mars exploration also covers many of the same fields tat, say, a dedicated program of Venus exploration would: Although Mars is associated with the hunt for alien life in most peoples minds, there's a lot about Mars that tells us about Earth, its history, it's environment, that has nothing to do with there being (or not being) life there: Mars began life as a similar type of planet,  in a similar part of the solar system, with a similarly habitable environment and geology. Then the two worlds evolved in different directions, one a hyper-arctic desert, the other a lush world. Understanding why the differences arose will teach us things about Earths geology, origin, environment, and how that environment might change.

Aboive: A 3D image of a mysterious mound on the Martian surface (you'll need red/green £D glasses to see it properly). Courtesy of charbob on
Still..... Mars is, in many ways emblematic of space exploration, and the things it seems it could do if it had the money, and the political will behind it. So much so that I wonder if the degree to which we're focused on Mars isn't partly because it's so much a part of our popular consciousness: After all, 'putting boots on Mars' has been a space dream that is just fifteen or twenty years away for as long as I've been alive, but there's no sign tat we're tiring of it. Which makes me wonder, in spite of all the good science that is being done at Mars, and all the even better science we'll do in the future: Are we really putting all our effort into Mars - and still putting hope into that eternally fifteen years distant dream of a manned landing - because that's the best route for science and exploration?

Or do some leaders believe we just need that dream....?

Well, at least it's keeping Matt Damon off the streets...

Elsewhere on the internet:

ESA gets a new director general

Massive ring of galaxies found

Gigantic black holes launch stars at extreme speeds

Reaction Engines begin testing new engine design:

Quantum communication satellite ready for lift off

Mini glider planned for Mars

Thursday 2 July 2015

What have Rosetta and Philae told us about comet 67P?

What we can learn from a comets acne:

The unfolding story of the Rossetta mission - and its comet lander robot Philae - is one of the big real-life 'to boldly go' dramas of recent times: The mission has swung from triumph to near disaster and back again, with the mothership taking amazing close up pictures before being force into deep space by the increasingly dangerous comets activity, the lander being the first human craft to land on a comet before being lost in the comets valleys for seven months and then dramatically returning.

Even the Starship Enterprise was actually supposed to explore the universe. Yep, pay attention and there's, like, fifteen whole seconds of that every episode before the space babes and Kirk vs lizard fistfights break out...
But ESA didn't actually send Rosetta and Philae to 67-P to get into hi-jinx. They sent them to learn about the comet - and that's what they've been doing. The most recent science release is about the pits that dot the surface of 67-P and other comets. The pits have been a tantalising mystery for as long as they've been known: On most worlds they'd be the result of impact with other objects, but comet surfaces are much to fast changing for that. They could be the result of pressure build up as gas build below the surface, but when the Rosetta team actually observed an explosive outgassing event it didn't remove anywhere near enough material.
Above: An ESA infographic on the pit Rosetta has been studying.
So what is behind the devastating acne of comets?
It looks like they're distant cousins to terrestrial sinkholes, and this tells us some unexpected things about how the inside of the comet is put together:
The pits range in size from around ten meters to over two hundred, and some are over two hundred meters deep. Their sides are lined with fractures, out of which the evaporating gasses from the interior gush. There are currently eighteen pits of interest on he comes surface, at various stages of growth, and they appear to tell the same story: The pits begin as vents, which are powered by evaporating ices n the subsurface. Over time the evaporation hollows out a cavern beneath the vent, and eventually the roof collapses, revealing a pit. Now the pit itself is exposed to the sunlight the erosion begins to move back from the pit walls, leaving a steep and jagged edge to the pit. Eventually the volatiles within reach of the surface are depleted, and the vent reaches a more gentle shape, and shuts down

So that's one mystery (tentatively solved) But what else has Rosetta told us so far? Here're just a few of the results released so far:

Meanwhile, at Ceres...

Everyone is still scratching their heads. The bright spots on the surface, the one's that are visible from Earth? Yeah, we still can't work those out. And, as well as bright spots which no one can work out....
Above: The Cerean bright spots, shown as a morph from the sun being high in their sky to the Sun being low in their sky. Courtesy of unmanned
...the dwarf planet Ceres has a pyramid shaped mountain, striped with white, that no-one understands either:
Above: The mysterious mountain/pyramid. It might be the cebntral peak of a masive impact crater.... but an impact that bg would be close to the size needed to shatter Ceres to rubble...