Old Mars

“…Yet across the gulf of space, intellects vast and cool and unsympathetic, regarded our planet with envious eyes, and slowly and surely drew their plans against us….”

Yes, I’m listening to Jeff Wayne’s version on ‘War of the Worlds’.

Wells’s opening narration has to be one of the most wonderfully chilling things I think I’ve ever read. On the face of it, it breaks every narrative rule in the book (third person, passive voice, no dialogue, pure exposition) and yet, I find it impossible to read without shivering.

Interestingly, for its day, ‘The War of the Worlds’ was also scientifically-plausible. The Victorian Mars was believed to be a living world, if likely rather a dry and desolate one. Indeed there was even some evidence of supposed activity on the surface – the infamous ‘cannali’. (Actually ‘channels’ – the word was mistranslated into English as ‘canals’, which are a rather different entity from that which Schiapperelli meant to imply!)

Of course, Science Has Marched On (as it’s rather prone to). Our Mars is a nearly-airless, lifeless world. If anything does live on it – and there can’t be very much, else we would long since have known of it – then it couldn’t be more than a few microbes, perhaps huddling in some warm, wet reservoir beneath the surface. Our Mars almost certainly did have liquid water, warmth and air, but that phase was billions of years ago.

Our Mars is just too small.

Its core cooled and froze out aeons ago, stilling the planet’s internal dynamo. With no global magnetic field, there was nothing to shield it from the solar wind, and the storms of the Sun slowly stripped away its air. In addition, without plate tectonics, the atmospheric cycle slowly ground to a holt. Mar’s air was gradually lost to sediments deposited at the beds of the Noachian oceans. Then those oceans themselves gradually evaporated, their vapour rising into the stratosphere, where solar ultraviolet broke apart the heavy water molecules. The light hydrogen atoms would simply have escaped into space, Mars’s low gravity being too weak to hold them. The oxygen would have been lost into compounds by reaction with other materials in the Marian crust and air – oxygen is a notably reactive gas! (And as well it is – if it were any less reactive, our entire human metabolic system would be quite impossible.)

Over the millennia, these processes ran their course. Mars was left dry, desolate and lifeless. If there ever was anything living there, it does not seem to have been able to survive the transition from Blue Mars to Red Mars. Today, Mars averages something like -60 Celsius and it has a surface air pressure of a mere 7.6 millibars, or less than 1% that of the Earth. The only remaining water are some suspected permafrosts and the two small, bright caps of ice at either pole. There is also a breath or so of water vapour in the thin atmosphere, but not enough to form more than a single pond. Our Mars is a cold, cratered orb, staring blindly into the heavens.

Still, one has to wonder.

“…The chances of anything coming from Mars, he said, were a million to one…”

Image credit: NASA, via Wikimedia Commons

Everything Else Is Speculation…

…I did promise I’d break my silence if anything interesting comes up, and I guess Kepler-22b counts. It’s just a pity that the news has already been enveloped in a fog of the worst sort of pseudo-scientific disinformation.

I think Kepler-22b is an exciting and significant result, and I’m enjoying watching the Kepler candidates followed up. However, I’m depressed to see that the press coverage here has been even more woeful than usual.

Here’s the TL;DR version; the relevant paper is right here. It’s a planet, it exists, it’s ‘Earthlike’ in the sense that it’s probably-but-not-certainly a terrestrial, and it orbits inside a star’s habitable zone. Other than that, we don’t know that much about it.

Longer version … there’s a lot of crap floating around about this object. Allow me to cut through the haze by listing the details that aren’t speculative:

• The star (Kepler 22) is a type G5, so somewhat solar-like, but also somewhat cooler and fainter (K-22 has an effective temperature of 5518 K, against 5578 K for the Sun).
• The planet has a radius of 2.38 times that of the Earth, with an error range of 0.13. Or to put it another way, it’s somewhere between 28,700 Km and 32,000 Km in diameter. (I’m rounding to the nearest ~100 Km there, incidentally.)
• Based on the (lack of) Doppler shifting in the star’s light, the planet must weigh less than 124 Earth masses. By contrast, Jupiter weighs 317.7 Earth masses, so K-22b is definitely a planet and not a star or brown dwarf.
• The orbital period is 290 days.
• The blackbody temperature for 22b – assuming a terrestrial reflectivity! – is 262 K, or -11 degrees Celsius.

And, umm, that’s it.

The temperature figures that are getting a lot of attention are somewhat inferential. First off, the orbital period has been used to infer an orbital radius; this isn’t a problem, incidentally. (Although note that it tells us little about the temperature on K-22b today, as the number you’ll get out from this won’t tell you anything about eccentricity, inclination and so on, and these could all impact on surface temperature.)

The real issue is that this number doesn’t include any atmospheric effects – the number of 22 degrees was arrived at by assuming an exactly Earthlike reflectivity and an exactly Earthlike atmosphere. (The blackbody temperature for Earth is -19 degrees Celsius; the atmosphere adds another 30 or so degrees in greenhouse heating.) Neither of these is likely at all for K-22b. The combination is particularly unlikely.

The paper-writers, I want to note, make no bones about the limitations of this calculation:

• …Using Equation 2, and assuming a planet with a surface and an atmosphere with thermal properties similar to that of the Earth (which is unlikely) and a Bond albedo of 0.29, the surface temperature of Kepler-22b would be approximately 295 K. [295 K = 22 Celsius. Emboldening added by me]

Needless to say, the press are conveniently ignoring that bit. If they even noticed that it was there in the first place, that is.

Depressingly, the press coverage about this object seems to be telling us a lot more about the media than it is about exoplanets. It’s almost a classic case of ‘churnalism‘, where lazy and/or time-pressed journalists simply regurgitate press releases, with neither fact-checking nor criticism. It’s also one of the reasons why more and more people are abandoning the mainstream media – if all you get is a mix of rented-mouth political propaganda and stale churnalism, one has to wonder what the point of the media actually is?

Ahem. Yes, as it happens, I do feel strongly about factual accuracy in science-related articles (note that I’m not linking to any of the offending articles – if you must find them, Google is your friend). Anyway, ranting about press releases and dodgy newspapers aside, I think the point I’m trying to make is that Kepler-22b and their ilk are interesting and exciting objects, and as such they deserve to be considered on their own, factual merits, not on the basis of vague, ill-informed, emotive guff.

Also, there is a further problem with this. Declaring each new planet ‘habitable’ could have the effect of raising the public’s expectations – only to dash them down again. First off, it’s not a fair way to treat people, secondly it’s bad for public understanding of science and thirdly, it could backfire on the world of astronomy. Do we want the taxpaying public to be conditioned into a cynical expectation of disappointment? I think not!

Anyway, I would write more, but I don’t wish to add any more idle speculation to an already ill-informed debate.

A degree of digital success

I thought this might quickly be worth breaking my silence for:

And the much bigger dA version…

Although it’s a long way from perfect, I’ve had more success with this piece than I usually seem to with digital art.

There are various things that could be tweaked, but I decided it would probably do here! I’m not 100% sure about the texturing attempt on the rifle, for instance, but I think it’ll do as it is. I’ve also fixed the eyes – they were well off before – and I’ve tweaked a few bits of the shadows here and there. (That said, the shadowing/lighting could be a lot better than it is.

The painting itself is essentially a bit of playing with ideas for a current writing project of mine. I say ‘current’ but I actually haven’t got anything done since August on it (gah! need to be less busy! gah!)…

Not Dead…

…and now, the inevitable and obligatory “not dead” post!

I am, of course, very quiet at the moment. That’s because I’m well into the thesis-writing season. If that wasn’t enough, I’m also drafting a second paper – and unlike the last one, this one is on a pretty tight deadline. I need to get it submitted by Christmas; given that the last one took 18 months, this could prove interesting, shall we say.

Anyway, when writing for this thing I try to aim for interesting and high-quality articles. Unfortunately, that comes with a price, in the form of research time, drafting-time and proof-reading time. And time is rather in short supply at the moment! I could tap out lots of poorly-researched, badly-written, typo-filled pieces of article-padding, but I’m not going to do that. I have no desire to patronise the collective intelligence of the readership!

So I guess this is an extended way of saying that it’s likely to be a bit quiet around here for the next few months. If anything truly exceptional/unexpected happens, I may break my silence, but that’s a possibility rather than a promise.

Anyway, in the meantime, there’s a presentation I need to go and work on…

Hardly my greatest painting success…

…but, here it is anyway:

(A much larger version is available on my dA page, as always.)

Today’s Token Achievement

I’ve been meaning to do this for a while, but I’ve finally got round to writing myself a set of webpages about my research. It’s here:

UKIDSS T dwarfs and the Galactic halo.

It’s a boringly low-tech HTML site, and I need to sit down and properly proof-read it … but it exists now, at least.

Bad Times

Just a small PSA regarding the current events around the UK; I’m horrified by all of it. In fact I suppose I should admit that watching the news the other day had me close to tears. This is a dreadful business, and I hope it stops soon. This violence and looting isn’t helping anybody. It’s just harming the economy, and thus people’s jobs, and it’s also destroyed the homes and property of many innocent people. It’s not making any kind of point now, and in fact may well end up backfiring badly on the people doing it. (I dread to think how this is going to combine with the immigrant-phobia meme that seems so prevalent around the country now.)

It’s time this stuff ended. Please. Before any of this gets any worse.

I hope that everyone reading this is safe, and I hope that things remain that way.

(Regarding my own situation, I’m very fortunate that where I am seems to be calm at the moment, and there’s no sign of that changing. Thank goodness.)

Moon of the Day (3)

Today’s pick comes from the Jovian system:

Image via: Wikipedia and the Galileo orbiter.

Ganymede is hard to miss. It’s sufficiently prominent that it was originally discovered by Galileo on the 7th of January, 1610 – in fact, it may well have been the first object ever discovered via a telescope. (We just don’t know precisely which of the Galilean Moons Galileo saw first; we do know that he saw all four of them on the same night!) Ganymede is actually fairly bright, for an outer-system object. At magnitude 4.5ish, it would actually be a naked-eye object, except for the glare from Jupiter.

Dione

Saturn, I have to admit, is a bit of an easy target for this sort of thing, given that it has something like 60 or so moons. With that many satellites, it’s pretty much inevitable that you’ll find some interesting oddballs. Dione is another such moon of Saturn.

Credit: Cassini/NASA, via Wikipedia

Dione was first observed in 1684 by Giovanni Cassini, who also discovered three others of Saturn’s satellites[0]. Dione wasn’t actually formally named until 1847; Cassini called his discoveries the ‘Sidera Lodoicea’ (‘Stars of Louis’) after his patron, the French king Louis XIV. (This sort of fawning was entirely normal at that point in history … luckily, it’s one practise we seem to have left behind!)

Hyperion

I was having a browse of some of the Cassini pictures the other day. The orbiter has returned some absolutely amazing images of the Saturnian moon system. My eye was particularly caught by Hyperion … but not because it’s pretty. In fact, it may possibly be the most ugly-looking thing in the Solar System (bar a few politicians).

(Image via Wikipedia, from Cassini’s September ’05 flyby.)

Hyperion is weird.

No, really, it’s weird.

First of all it has a massively eccentric orbit around Saturn. Secondly, despite being fairly large, the moon itself is appreciably egg-shaped (as you can clearly see in the above photo!). Its longest axis is 360 Km, its shortest is 205. Egg-shaped orbit, egg-shaped moon, apparently!

But there’s more. In terms of composition, Hyperion also appears to be a freak. Its mass is tiny. Despite being around 2/3rds the size of Mimas, it has only 15% of that other Saturnian moon’s mass. Probably this is partly why it’s so un-spherical; there’s just not enough surface gravity to flatten things out. Hyperion’s density is also rather low. In fact, some estimates claim that its insides are as much as 40% empty space.

Yup, that’s right, it appears to be partly-hollow. Presumably its interior must contain some absolutely massive caves.

Of the bits of it that actually are solid, current thinking holds that they’re mainly composed of water ice. This at least is fairly normal for Saturn’s moons. At Saturn’s distance from the Sun, things are cold enough for water to remain frozen pretty much indefinitely; it’s only once you get inside the asteroid belt that solar radiation would have been intense enough to evaporate off the early store of water. (That’s one of the reasons why there’s such a sharp compositional change between the rocky inner planets and the big, icy moons of the gas giants; basically we live inside the so-called ‘snow line’.)

However, in addition to its icy surface, Hyperion also appears to be covered in some sort of dark material. Its reflectivity is too low for pure ice; Hyperion reflects about 20-30% of incoming light. By comparison, snow reflects about 70-80%. What exactly this material is isn’t known, although there is a suggestion that its source might be another moon called Phoebe.

Another bit of compositional weirdness is the dark material that fills the bottom of Hyperion’s craters. This dark reddish substance appears to be some sort of hydrocarbon, perhaps similar to the stuff that gives Iapetus its dark hemisphere. But again, this material has never been directly-sampled, so its exact nature is uncertain.

There is one final point of high weirdness. Hyperion’s rotation is unstable. Its rotational axis flops around pretty much at random, almost as if the moon were severely drunk. This appears to be down to the conflicting tides it experiences from Saturn and Titan, and also due to the dramatic eccentricity of its orbit. (The tidal force falls off with the cube of the distance, not the square, and so is very sensitive even to small changes in orbital distance.)

Although possibly the ugliest moon in the solar system, Hyperion is an interesting object, and one which poses some interesting questions for models of planetary formation and structure. It also seems to be one of these things where we know just enough for it to be really tantalising, but not quite enough yet for any really concrete answers.