Friday, March 06, 2009

It Depends Where You're Standing

From its discovery in 1930 until 2006, Pluto was considered to be a planet; then the International Astronomical Union downgraded it to the status of minor or dwarf planet, causing an all-mighty ruckus. Now, politicians in the state of Illinois have decided enough is enough, and want to reinstate it as a planet - and have declared 13 March 'Pluto Day'. This isn't as crazy as declaring Pi to be exactly equal to 3; Pluto was discovered by Clyde Tombaugh, who was born in Illinois. Insult Pluto; you insult all of Illinois.

Thursday, March 05, 2009

Cradle Ceres

A few years ago I wrote a novel (The Secret of Life) that riffed on Paul Davis's hypothesis that the early Earth could have been seeded with life from Mars via rocks knocked off the red planet by big meteorite impacts while it was still warm and wet.

Now, Joop Houtkooper from the University of Giessen has suggested that the dwarf planet Ceres may have been the incubator of the Solar System's first life. Ceres may have retained a considerable amount of primordial water because it didn't suffer any large impacts immediately after it formed, would have cooled down more quickly than either Earth or Mars during the early history of the Solar System, so life could have started there first. And because it's a relatively small body, it doesn't take much of an impact to chip off life-bearing fragments that could have seeded Mars and Earth. (It occurs to me that it might have been some other dwarf planet that subsequently was shattered by some major impact, sending bacteria-ridden rocks in all directions.)

Not only that, but there might still be life on Ceres: like Europa, Ganymede, Triton, and a bunch of other icy moons, Ceres may have an internal ocean under its icy surface. Maybe those old pulp sf stories about tentacled beasties infesting asteroids weren't so far off the mark after all . . .

Mining For Gold

'Nowadays, keyboards and mice are the new ploughs and shears.'

I wrote about making a living by accumulating gold and other valuables in MMPORGs in my crime novel Players, published less than two years ago (I called it 'click farming' rather than 'gold farming'; same difference). It's an even bigger business now, and naturally enough most of the labour has mostly migrated to China, where it's cheapest. Wonder what these keyboard cowboys are going to do with all that processing power when gamers in the West can't afford to buy virtual wealth and prestige any more.

Wednesday, March 04, 2009

Lunar Koan

If a space probe crashes on the Moon and no one notices, did it really happen?

New Moon

The source of Saturn's tenuous G ring has just been discovered. The G ring is at the outer edge of the ring system, with only the E ring beyond. A couple of years ago, scientists discovered a partial arc of bright, icy dusty material at the ring's inner edge, and suspected that there must be a moon or moonlet embedded in it, as is the case with all other dusty rings and ring arcs. Now, they've confirmed that observations show a tiny moonlet is indeed embedded within the partial arc - the bright spot moving through the arc in the sequence of photos above, taken within ten minutes of each other.

It's too small for Cassini's cameras to resolve, but by comparing its brightness with a similar moonlet, Pallene, scientists reckon that it's just 500 metres across. Other measurements suggest that the moonlet is accompanied by debris between 1 and 100 metres across. Impacts of meteorites with this material and the moonlet would knock off dust to replenish the arc, which is about 250 kilometres across, and extends for about 150,000 kilometres, one sixth of the circumference of the rings.

The gravitational field of Mimas, which orbits just beyond the outer edge of the G ring, tugs the moonlet to and fro, and also keeps the ring arc together. Maybe tidal effects perturb that rubble too, causing collisions that create more dust. More complexity, but as always, it follows known physical laws. It isn't physics that limits our ideas of possible worlds; it's our imaginations.

UPDATE: Emily Lakdawalla's Planetary Society blog has a very good discussion of the new moon, and suggests that 'Cassini's beginning to venture into the murky terrain that separates "moons" from "ring particles."' And the Bad Astronomy blog has a great discussion that gets into the nitty-gritty details of how a moonlet can paint dust across the sky.

(Yes, I am a Saturn wonk.)

Tuesday, March 03, 2009

Summer On A Dwarf Planet

Everywhere we look, the Solar System is far more complex and exotic than we expected.

Take Pluto. Back when I started reading science fiction, and getting interested in astronomy, it was believed that Pluto was a lonely, deep-frozen ball of ice where nothing much happened. Now, we know that it orbits around a common centre shared with Charon, a body about half its size, while two small dark bodies, Hydra and Nix, orbit beyond the edge of a tenuous, dusty system of ring arcs - a compact toy of a system, as orderly and self-contained as an orrery. And we also know that Pluto has a thin atmosphere. It's been growing denser as the Pluto-Charon system swings through its closest approach to the Sun and surface ices warm and sublimate; and new results show that the atmosphere is warmer than expected because it contains about 0.5% methane, enough to cause a greenhouse effect (relatively warm, of course: it's still a chilly minus 180 degrees Centigrade). It's also warmer in the higher reaches of the atmosphere than near the surface, because sublimation of ices cools the surface while sunlight warms the resulting gases from the top down. When we get the same inversion effect here in London, smog is trapped under the warmer upper layer. Is there smog on Pluto, and if so, what is it made of? Still, pretty amazing that we can tell so much about a body so far away.

I was watching The Sky at Night yesterday, which had a nice bit on the Cassini orbiter's latest findings about Enceladus and Titan; there was also a piece on the various satellites currently orbiting the Moon, including the news ( to me) that the high-resolution camera aboard the Japanese SELENE (Kaguya) satellite had taken a picture of the Apollo 15 landing site. Turns out this happened last year, but I somehow missed it.

It's the pale blotch in the centre of the photo, visible because when the LEM return stage took off, its exhaust plume blew away dust on the surface, uncovering lighter material beneath. NASA is sending a new satellite, the Lunar Reconnaissance Orbiter, to the Moon later this year, with an even more powerful camera It's main mission os to study the poles, but it would very neat if it could take photographs of the Apollo 11 landing site, forty years on.
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