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It’s “J”!

This week will go down in history as a week of two very important decisions. On Thursday, the Scottish people will decide if they want to leave the United Kingdom and become an independent nation. But earlier today, many hundreds of miles away from Scotland, another decision was announced – the choice of the landing site on the nucleus of Comet 67P for the ESA “Rosetta” probe’s “Philae” lander.

Since arriving at 67P, the Rosetta probe has been mapping the comet in great detail, taking high resolution images for its mission scientists to scour in search of a suitable landing site for the little probe, which promises – if successful – to revolutionise our understanding of comets and maybe even of our species’ origins and place in the universe. As of last week, they had narrowed down the possible landing sites to these…


But which one? Well, while space enthusiasts obviously want Philae to set down somewhere amazing, in a spot straight out of “Armageddon” – you know, somewhere with jagged icy spires on all sides and great “OMG!!!” jets of dust and gas shooting up out of the ground – for Philae’s rather more practical and necessarily cautious scientists, “suitable” means somewhere on the comet that yes, offers useful views and great science, but is as safe as possible too, somewhere free of the lander-crippling boulders and cliffs, landslides and ledges which cover the comet. Not necessarily somewhere which looks appealingly smooth, because smooth areas might only be smooth because they’re the cometary equivalent of quicksand pools, and soon after setting down on one Philae might find itself sinking to a dusty doom, but definitely somewhere that doesn’t look like something out a Tim Burton film either.

Today there was a big press announcement at ESA HQ, and the choice of landing site (and a “Plan B” site) was revealed to the world. Which one was it? Was it (cue cheesy music)…


…this fascinating looking broad ledge, with steep cliffs dropping away on one side..? Or…


…the heart of the roughly circular crater (which STILL hasn’t got a name yet, or at least we haven’t been told its name, cos it must have one by now, surely? Come ON ESA! Give us the name!) on the front of the smaller of the comet’s two lobes, with its floor absolutely covered with lethal-looking boulders, rocks and stones? Or…


…this hummocky, hilly area with hole-in-one bunkers on all sides? Or…


…this intriguing area, with all the ledges, outcrops and ridges Bruce Willis and Ben Afleck could hope for? Or…


…which looks fairly flat, but has interesting stuff around it?

And the answer was…

(roll on the drums)


(cheers… applause….)

Come on, of course it was J. That seems to offer the right balance of safety vs scenery for the mission team, so that’s where they’re going to aim Philae on Nov 11th.

I say “aim” because this will not be a controlled landing, like an Apollo lunar module or a Mars rover. Basically, Philae is going to be pushed out of Rosetta and will then fall down to 67P’s surface like a baby bird falling out of a nest. The mission team will aim for the “J” landing site, and must be confident they can hit it, but boy, this is risky. Landing a space probe on a comet has never been attempted before, so this is genuinely, and in the truest sense of the word, a first in the story of space exploration. Probes have flown past comets before, but never landed ON one. So when Philae is sent on its way towards 67P it will be taking a leap into the unknown, and what happens shortly after will either have the Rosetta team leaping up into the air and whooping with relief or delight, or leave them sitting in silent despair with their heads in their hands. Philae will either set down safely on 67P, secure itself to the surface with its harpoon and start sending back breathtaking images and priceless data, or it will meet some horrible fate, and its mission will end as it is cruelly smashed to pieces against a house-sized boulder, sent tumbling down a steep, crumbling cliff, or bounces off the comet and goes spinning off into space, lost forever.

Dear god, imagine that… imagine if that happened, after all the triumphs and successes… No, surely not…

Well, such a disaster is a very real possibility. Nothing like Philae’s landing has ever been tried before. One can only imagine how the Rosetta team will feel on that day. I don’t envy them. How would you fancy trying to land a small, fragile, multi-million pound box of computers, cameras and state of the art scientific instruments from a great height onto a cracked, melting, unstable chunk of dirty ice covered in more spikes, rocks and ravines than it is possible to count?

But let’s not poke Fate in the eye with a sharp stick. On Landing Day whatever will happen, will happen. In the meantime, where is Site J, and what’s it like?

Site “J” is close to the aforementioned crater on the ‘front’ of the smaller of the comet’s two parts, or on the top of the rubber duck’s head if you would rather think of it that way. Here’s the official ESA image showing the location of Site “J”…


An image of 67P taken on Aug 17th shows the twin-lobe nature of the comet rather more clearly, and I’ve labelled Site J on it. Click on this image to enlarge it and look for the red circle…

17 aug J ringed

Let’s look at that area in a little more detail. ESA released some images of “J” after today’s big announcement, and I’ve done a bit of work on one of them to show Site J and its surroundings in more detail…

Philae_s_primary_landing_site_close-up sh1

A closer look at the surrounding area is very informative, and shows a variety of interesting features in the landscape…

enh 2 circled features

As you can see, it’s quite close to the edge of the big crater – and that is good because it makes it relatively easy to find on images of the comet taken in the past. All you have to do is find the big crater, and that “ramp” leading down to its floor from one side, and voila, you have the location of Site J!

Aug 17 image lines

So there you go, you should now never have any difficulty picking out Philae’s planned landing spot on images of 67P as they are released. Let’s look at Site J again…


It’s impossible to get a sense of scale from that picture isn’t it? Luckily, ESA provided a scale bar for us on a previous image release…

UuPtltP…which tells us that from top to bottom, and side to side, that image of Site J is about 1km across. 1km. Sounds tiny doesn’t it? Surely there can’t be too much risk of landing there? We’d be able to see anything dangerous, right? You think? Let’s take a look at a Google Earth image of central London – centered on Trafalgar Square actually – and see what that looks like…

trafalgar square 1kmSee that red line? That red line is 1km across. The same width as that image of Site J. Let’s put the two together…


That’s a bit scary, isn’t it??? Some of those boulders are bigger than buildings!

And that’s the SAFEST place they found to land…

And that is why this is going to be such a hard feat to pull off. When Philae drops down towards Site J it will be heading towards truly chaotic terrain – an unforgiving landscape of boulders, rocks, ridges and outcrops, each one a potential mission-killer. Really, all we’ll be able to do is squeeze our eyes tight shut, cross our fingers and, as we make a wish, keep whispering “I do believe in Philae… I DO believe in Philae…”

This will be ESA’s Apollo moment, for sure. When HUYGENS landed on Titan it was flying pretty much blind, it was pure pot luck what it landed on – if it landed at all. The true nature of the surface beneath HUYGENS as it descended on its parachute was unknown. But we have seen the surface beneath Philae, and it is proper scary. So, if ESA pulls this off, and Philae lands successfully, between boulders, between ledges, away from outcrops, it will be an incredible thing, an amazing thing, and if you’re a regular reader you’ll know how much I detest that word. If Philae lands safely the ESA control room will erupt, absolutely erupt in a volcano of relief and pride. Fists will pump the air, backs will be slapped, and tears will be shed. And the tens of thousands of us watching on our computers, tablets and phones, will celebrate too.

But no-one… no-one… should be under any illusions that this is going to be easy.

ROSETTA has already been a remarkable mission. It has imaged asteroids, planets, and now a comet. It has already revealed 67P to be a bewilderingly complicated and weird nightmare of a world, plucked from the most fevered dream of the most disturbed cosmic artist. For generations we have grown up believing that comets were really just fluffy, burpy snowballs, that melted if they foolishly wandered into the heat of the Sun. Now we know, thanks to ROSETTA, that they’re not. They’re really not. Peering through ROSETTA’s eyes we have watched 67P grow from a single, sequin pixel in the blackness of space, to a cluster of pixels, to a vague blur, to a strange, double blur, then to a weird rubber duck…

And now 67P is there before us, two spiky, spiny, twisted, tortured masses of ancient dusty ice joined together, tumbling through the darkness like a diseased, disfigured shark prowling the depths of the ocean. It’s an enemy to be defeated, a monster to be tamed.

But ESA is up to the challenge, of that I have no doubt. And right now, as you read this, ROSETTA scientists will be hunched over tables and desks, looking at blown up images of the landing site taken by the OSIRIS camera – images which I’m sure are far, far more detailed than we’ve been allowed to see – looking for anything and everything that could harm or kill little Philae on November 11th as she tries to make Mankind’s first landing on a comet. I wish them all the very best of luck.


2 Responses

  1. Super post Stu! I particularly liked the size comparison with central London. It’s often easy to forget the resolution of images from ROSETTA but you bring it to life with your usual aplomb!

  2. […] jetzt für eine große Tagung im Dezember angemeldet. Auch Interview-Clips zur Landestelle J (auch ein Artikel) und der zackigen Kern-Oberfläche – sowie ein überwundener Safe Mode auf Dawn und ein […]

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