Rocks

The image above is a composite compiled by the Planetary Society's Emily Lakdawalla, handily showing the relative sizes of all the asteroids and comets that have been visited by spacecraft to date. Check out the full-size version here. The largest by far is Lutetia, which the Dawn* spacecraft has just zipped past, on its way to even larger targets - Vesta in 2011-12 and Ceres, the largest body in the asteroid belt, in 2015. Vesta is about four times the size of Lutetia; Ceres, at an average 950 kilometres in diameter, is seven times larger. If it orbited Saturn it would be the gas giant's sixth largest moon (it's just a little bit smaller than Tethys), and is classified as a dwarf planet rather than an asteroid. Both Vesta and Ceres are massive enough to have been pulled into a spherical shape by their own gravity, and both are differentiated bodies with metallic cores and stony crusts. Vesta's surface is mostly rock, modified by flows of lava; Ceres is surfaced with water ice and clays and carbonates, and it's possible that there's an ocean of liquid water beneath its crust.

Asteroids are fantastically varied objects. Those imaged close-up all seem mostly similar, spattered with craters large and small, and with dusty intercrater plains. But while Eros, Ida and Itokawra are stony asteroids composed of iron and magnesium silicates, Mathilde is coated in primitive carbonaceous compounds, and tiny Braille is composed of olivine and pyroxene (Gaspara's composition appears to be midway between Braille and the stony asteroids). Lutetia is presently classified as a M-type asteroid; its dusty surface may cover a chunk of nickel-iron and other metals derived from the core of a larger body shattered during the early history of the Solar System. Itokawa, visited by the Hayabusa probe, which recently returned to Earth after a difficult five-year journey, is a rock pile, with a surface of dust and boulders mostly unmarked by impact craters.


Hard to think of making any kind of comfortable living on or in something as frankly ugly as that, but it's easy to think of tenting over a small crater of one of the other asteroids, or burrowing into their surfaces, or hanging sealed tenement buildings at the edges of cliffs. Smaller asteroids could be completely built over - mini-Trantors. (Many small asteroids are rock piles like Itokawa, putting paid to the cherished sf idea of manufacturing a habitat by hollowing out a small rock with a few nuclear bombs.) Although the total mass in the asteroid belt is just 4% of the mass of the Moon, the surface area is far greater. At an average diameter of around 130 kilometres, Lutetia has a surface area of some 31000 square kilometres, one and a half times the size of Wales. Plenty of room for settlements and cities. Tiny disputatious kingdoms and empires brought together and flung apart by orbital mechanics, trading with each other and with Earth and Mars, chasing after comets for water and organics . . . It's been done before, of course. Many times. But I can't help thinking that it may be time to do it again.

*EDIT My bad - it was the Rosetta spacecraft that zipped past Lutetia, on its way to rendezvous with comet 67P/Churyumov-Gerasimenko. Dawn is, however, on course for Vesta and Ceres. Hat-tip to Phil, for pointing out my confusion.

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Expecting Something Taller

So I finished the second draft of the new novel yesterday, and here it is, printed off. Hmm, 150,000 words plus doesn't look as big in the real world . . .

Now all I need is a break, and then a couple of red pens and a decent stretch of peace and quiet so that I can cut it into shape. Some people can compose and redraft and edit entire novels on screen. I need at least one go at an actual manuscript, with wide margins for notes and second- and third-thoughts. I started off writing on a manual typewriter, old habits die hard, and it's easier to spot goofs on the page than on the screen, for some reason. After that, there's at least one more on-screen draft before it's printed out again, and sent off to the publisher.

The title is a working title, by the way. Not yet officially approved. But I like it.

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A Dark River Across the Sky

The Astronomy Picture of the Day site regularly throws up amazing images, but this one is especially amazing. A lane of dust about 500 light years away and spanning some 100 light years runs across the sky towards an area rich in stellar beauty: a fabulous backdrop for a space opera about clashing interstellar empires.

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Helpless

So I finally got around to visiting Fiona Banner's installation at Tate Britain. And it's one of my most science-fictional experiences this year, and way more Ballardian than many of the pieces at Crash, the exhibition of art reflecting Ballardian themes and tropes staged by the Gagosian gallery.

Banner's installation is audaciously simple. A surreal magic trick. Two fighter planes are stranded in the atrium space of Tate Britain's Duveen gallery. A Jaguar is stranded upside down, paint stripped off its fuselage to leave a mirror finish. And a Sea Harrier is suspended nose-down from the ceiling from a single cable that pierces the skylight above, hanging like a trussed game-bird a handful of centimetres off the floor, its fuselage brushed with a faint pattern of feathers. Banner has form; she was commissioned to decorate the Tate's Christmas tree a few years ago, and hung it with scale models of every fighter plane currently in service. But this is a major step up. The two planes are bound, prone, helpless, yet they dominate the gallery space. Visitors tiptoe around them, marvelling at the gape of their afterburners, their lethal lines. There's a feeling of trespassing in the trophy room of a machine predator, or some futuristic armoury where decommissioned war robots crouch, waiting for their go codes, or a battlefield littered with machines beyond human comprehension. Children had a simpler, more innocent response, mind you: time and again they raced up to the suspended Sea Harrier and threw themselves under its nose, giggling and amazed at their own daring.

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Flying Over Ontario Lacus

When Cassini first arrived at the Saturn, in 2004, we knew almost nothing about the surface of its largest moon, Titan. We didn't know if it was covered in oceans of liquid methane, or in drifts of waxy organic snow; we didn't know if it was smooth or if it had hills and mountains. We know a lot more now. We know, like Earth, it not only has hills and mountains (although of water ice rather than rock), but it also has vast fields of dunes (of tarry organics rather than sand) and rivers and lakes (of liquid ethane, propane and methane, rather than water).

And now the Cassini science team have produced this terrific short video showing what it's like to fly around the shoreline of Ontario Lacus, the largest lake in Titan's southern hemisphere. It's amazing in its own right, but if you've read The Quiet War or Gardens of the Sun, you'll understand why I'm knocked out by it.



At about 15000 square kilometres, Ontario Lacus is a little smaller than its terrestrial namesake, Lake Ontario (or about three-quarters the size of Wales). Like Lake Ontario, it has a meandering shoreline fretted with bays, inlets, and beaches; there's a river that feeds into it via a delta that looks exactly like deltas formed by rivers on Earth. And like terrestrial lakes, Ontario Lacus is undergoing seasonal changes, too.

Titan's years, like Saturn's, are about 29 years long. When Cassini arrived, it was summer in Titan's southern hemisphere. Now, the days are dwindling down to autumn. Cassini first imaged Ontario Lacus in 2004; since then, its shoreline has receded by about 10 kilometres. And in four years of measuring the lake's depth by radar, its level has gone down by about a metre. For although the summer temperature in the southern hemisphere is minus 180 Centigrade, that's warm enough to allow evaporation of liquid methane. But now the temperature is dropping, that evaporation will cease. Soon, perhaps, the evaporated methane will condense into clouds and fall as winter rains, and run down the hills in rivers, and replenish the lakes...

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An Astronaut And His Mars-Adapted Dog

Explanation here. More great photos here.

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Asteroid and Saturn

Imaged by the Rosetta spacecraft July10 2010.

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Inception

Saw it last night but won't review it here as it's already being reviewed everywhere else. But will note just one thing: in dreams, where Inception is mostly set, no one uses mobile phones. Didn't realise this while watching the film, but afterwards, on the crowded and hot streets of the West End, where almost everyone was walking along talking into phones or gazing or pecking at little lighted screens in their hands, half in this world, half in cyberspace.

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Der Stille Krieg

I'm pleased to announce publication of the German edition of The Quiet War, translated by Sara Riffel, with a space-battle-tastic cover by Stephan Martiniere. Meanwhile, I'm closing in on the end of the second draft of the new novel, in which I fix most major inconsistencies and rough patches, and realise what still needs to be put in, and what needs to be taken out. Onwards.

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