Why I think Mars One is a really stupid notion

I posted last week about the silliness of trying to colonise Mars on a one-way basis, unless you’re sending Justin Bieber.

Sure, most colonists here on Earth made the trip one-way. But Earth’s way more hospitable. Even Roanoke. You can breathe the air, for a start.

Artists' impression of the Orion EFT-1 mission. NASA, public domain.

Artists’ impression of the Orion EFT-1 mission. NASA, public domain. Eventually, Orion may be part of the system that takes us to Mars – and brings us back.

Mars – that’s another planet. It has red skies and blue sunsets, temperatures that make Antarctica look summery, and surface air pressure about 0.6% that of Earth, though that’s academic because it’s mostly carbon dioxide anyway. Mars also has no magnetic field, which means the surface is irradiated from space. Then there’s the dirt, which the Phoenix lander found was saturated with naturally-formed perchlorates. Know what perchlorate is? Rocket fuel. It’s nasty stuff, it’s toxic, and the chances of keeping the habitat clear of it after a few EVA’s seems low.

The biggest problem is that nobody’s been there yet. There’s bound to be a curve ball we don’t know about. It’ll be discovered the hard way.

That was the Apollo experience forty years ago. It turned out lunar dust is abrasive and insidious. As early as Apollo 12, astronauts found dust in the seals when they re-donned their suits for a second EVA – moon-walker Pete Conrad reported that ‘there’s no doubt in my mind that with a couple more EVA’s something could have ground to a halt’. All the later Apollo astronauts hit it; leak rates soared in the suits as dust worked its way into the sealing rings.

I think it’s safe to say something of equal practical difficulty will be discovered about Mars, one way or another. Not good if you’ve just arrived – permanently. Besides, what happens if someone gets needs a hospital now? Or is injured? Well, that’s a no-brainer. You can imagine the colony consisting of a cluster of grounded Dragons with a row of graves next to it.

Cut-away of the modified Apollo/SIVB 'wet lab' configuration for the 1973-74 Venus flyby. NASA, public domain, via Wikipedia.

Cut-away of the modified Apollo/SIVB ‘wet lab’ configuration for the 1973-74 Venus flyby. NASA, public domain, via Wikipedia.

Mars One plan to send more missions every two years, each with four colonists to join the happy bunch. If they’re alive. My money says they won’t be. This is Scott of the Antarctic territory – high-tech for the day (Scott even had motorised tractors) but still gimcrack.

The main reason we’ve not gone there yet, despite space agencies making serious plans since the 1960s, is cost. Manned interplanetary fly-bys were (just) within reach of the hardware built for the Moon landings – and until the Apollo Applications Programme was slashed to just Skylab, NASA was looking at a manned Venus flyby for 1973-74, using Apollo hardware.

Composite panorama of Mars. Not going to be seen by the 2018 expedition, as they'll fly past the night side. NASA, public domain.

Composite panorama of Mars. NASA, public domain.

Unfortunately, stopping at the destination, landing on it, and all the rest was another matter. It was easy to accelerate an Apollo CSM and habitat module into a free-return Venus or Mars trajectory; no further fuel was needed, it’d whip past the target at interplanetary velocities, and the CM could aerobrake to a safe landing on Earth. But stopping at the destination, landing and then returning home? In rocketry – whether chemical or nuclear-thermal (NERVA), the two technologies available until recently, mass-ratios are critical.

Mass ratio is the difference in mass between an empty and fuelled rocket at all times, and fuel takes fuel to accelerate it. It’s a calculation of sharply diminishing returns, and the upshot for NASA and other Mars mission planners in the twentieth century was that a practical manned landing mission was going to (a) require a colossal amount of fuel, and (b) would still transit by low-energy Hohmann orbit requiring a 256 day flight each way, meaning more life support, which meant more fuel (see what I mean?).

Some plans looked to refuel the system from Martian resources, but that had challenges of its own. Either way, the biggest challenge in all Mars mission schemes was the first step, lifting the Mars ship off Earth into a parking orbit. No single rocket could do that in one go, meaning multiple launches and assembly in orbit, raising cost and complexity still further. With figures in tens and hundreds of billions of dollars being bandied about, and no real public enthusiasm for space after Apollo, it’s small wonder governments were daunted.

ROMBUS in Mars orbit: Mars Excursion Module backs away ready for landing. Public domain, NASA.

Conceptual art of Philip Bono’s colossal ROMBUS booster in Mars orbit: Mars Excursion Module backs away ready for landing. Public domain, NASA.

My take – which is far from original to me – is don’t try going to Mars now. Focus on building a space-to-space propulsion system that offers better impulse than chemical or nuclear-thermal motors. Do that and the 256-day trans-Mars cruise – which is what drives the scale and risk of the mission, including problems with radiation doses in deep space – goes away. One promising option is the Variable Specific Impulse Magnetoplasma Rocket (VASIMIR), a high-powered ion drive that might do the trick if it works as envisaged. Another is the FDR (Fusion Driven Rocket). Current projections suggest Earth-Mars transit times as low as 30 days.

Of course, if your drive won’t light when you need it to slow down, you’re on a one-way trip out of the solar system. But hey…

Maybe we should send Justin Bieber on that first VASIMIR mission, just in case…

Copyright © Matthew Wright 2015

Yes – a Kiwi might go to Mars, but I still wish it was Justin Bieber

A New Zealander’s reached the short-list of 100 possible candidates for the one-way Mars One mission proposed for 2025-26 by Dutch entrepreneur Bas Lansdorp, co-founder of the project.

Personally I’d have preferred they despatched Justin Bieber and left it at that. But the presence of a Kiwi isn’t bad given that the original long-list ran to 202,586 individuals.

Conceptual artwork by Pat Rawlings of a Mars mission rendezvous from 1995. NASA, public domain, via Wikipedia.

Conceptual artwork by Pat Rawlings of a Mars mission rendezvous from 1995. NASA, public domain, via Wikipedia.

Still, I can’t quite believe the plan. Settlers will be lobbed to Mars in batches of four, inside modified Space-X Dragon capsules. They’ll land, build a habitat based on inflatable modules and several Dragons, and remain there for the rest of their lives. Kind of like Robinson Crusoe, but with all of it beamed back to us for our – well, I hesitate to use the word under these circumstance. Entertainment.

I doubt that the show will run for many seasons. The development timing for the mission seems optimistic – a point I am not alone in observing. There have been a wide range of practical objections raised by engineers at MIT. But apart from that, nobody’s been to Mars before. Sure, we’ve despatched over 50 robots, 7 of which are still operational. But that doesn’t reduce the challenges involved in keeping humans alive in a hostile environment for their natural lives, and I figure from the Apollo experience that there’ll be curve balls along the way.

Those challenges will begin as soon as the colonists are cruising to Mars, a 256 day journey jammed into a 10-cubic metre metal can along – eventually – with 256 days worth of their wastes. Think about it. Popeye lived in a garbage can. The first Mars colonists? Well, they’re going to live in a commode. Hazards (apart from launch-day waste bags bursting on Day 255) include staying fit in micro-gravity and radiation flux. That last is the killer. The trans-Mars radiation environment was measured by the Curiosity rover, en route, and turned out to be – on that trip anyway – 300 millisieverts, the equivalent of 15 years’ worth of the exposure allowed to nuclear power plant workers. A typical airport X-ray scan, for comparison, delivers 0.25 millisieverts.

I suppose the heightened risk of cancer isn’t really an issue, given their life expectancy on Mars (68 days, according to MIT). Though if the sun flares – well, that’ll be too bad. (‘My goodness, what a lovely blue glow. Nice tan.’)

A large solar flare observed on 8 September 2010 by NASA's Solar Dynamics Observatory. Public Domain, NASA.

A large solar flare observed on 8 September 2010 by NASA’s Solar Dynamics Observatory. Public Domain, NASA.

Unfortunately the radiation problem continues on the surface of Mars. The planet lacks a magnetic field like Earth’s and its atmosphere is thin, meaning radiation is a threat even after you’ve landed. The answer is to bury yourself under Martian dirt, but Space One’s plans don’t seem to include that. There also a possible problem – which we’ll look at next time – with the nature of that dirt.

Whether the intrepid colonists will get away is entirely another matter. Apart from the hilariously optimistic timetable, the project relies on a modified version of Space-X’s Dragon, which has yet to be human-rated. And then there’s funding, which I understand will come from media coverage. But I suspect the likely barrier will be regulatory. These people will be flying inexorably and certainly to their deaths, and odds are on it will be before the natural end of their lives. Will the nation that hosts the launch permit that?

Still, let’s suppose there are no legislative barriers. And let’s say the colonists get to Mars without their hair falling out or the waste bags bursting and filling the cabin with – well, let’s not go there. Let’s say they land safely. Suddenly they’re on Mars. Forever. What now? And what about those curve-balls?

More next week.

Copyright © Matthew Wright 2015

Making ancient mysteries like Gobekli Tepe go away – with science!

I am always intrigued by the way ‘ancient mysteries’ go away with new science discoveries. All without recourse to secret ancient civilisations or helpful aliens.

Gobelkili Tepe by Teomancimit. Creative Commons license via Wikipedia.

Gobelkli Tepe by Teomancimit. Creative Commons license via Wikipedia.

Take Gobekli Tepe. This construction in southeastern Turkey is made of 7-10 ton upright stones, elaborately carved, and was recognised for what it was in the early 1990s by archaeologist Klaus Schmidt. Current theory suggests it was a gathering place for worship from a wide area.

There’s no mystery about how it was built; it’s within the capability of classic late paleolithic tech, providing they had an organised labour force and surplus food. That’s the point. Archaeologists have given the technology available to ice-age humans many names and classifications, often based on where variants were found – all of which is rather academic because in the broadest sense the people who invented this technology were as smart as we are, and it was smart tech, making best use of available materials; not just stone but also fire, wood, animal products, plant products, minerals and resins.

The only problem with Gobekli Tepe is when it went up – around 11,000 years before present, before villages and agriculture. That’s the mystery. Hunter-gatherer bands were typically a close-related kin group of around 150. We know this because that lifestyle is still followed in places today, such as the Kalahari. This, it seems, is the maximum scale of community that hunter-gathering can reasonably feed (humans today are apparently hard-wired to personally know groups of about 150 - something anthropologist Robin Dunbar puts down to that hunter-gatherer ancestry).

The thing is that hunter-gatherers, theoretically, didn’t have surplus production (food) for luxuries like temple building. The conventional view is this. Between about 11,000 and 8000 years before the present, einkorn wheat opened up agriculture in the northern reaches of the Middle East. Animal domestication followed. All this opened the gates to larger communities, notably Jericho and Catal Huyuk. The latter was a curious ‘one building’ city that flourished from around 9000 years before the present in what is now central Turkey, supporting a population estimated at anywhere from 6000 to 10,000. These agricultural centres could support specialists and feed a labour force that didn’t contribute, itself, to food growing – making larger-scale constructions possible.

Smithsonian Institution, Public Domain, via Wikipedia.

Smithsonian Institution, Public Domain, via Wikipedia.

So what about Gobekli Tepe? Humans at the end of the ice age were still hunter-gatherers. No agriculture. But – clearly – there was surplus food and organised labour. What gives? Explanations have included assertions about alien originated civilisations, unknown to conventional archaeology but obvious in ‘clues’ that only enthusiasts are able to detect. Or it has been called the Garden of Eden.

How can I put this? Folks – it’s bullshit. Even in conventional terms there’s no mystery to Gobleki Tepe once we understand how agriculture rose after the ice ages. It turns out that neither flour, nor domestication of animals, nor villages were new. All had been invented before, largely by the Gravettian culture that flourished from Bulgaria to the Crimea, around 30,000 years ago.

The Oruanui eruption, Taupo, 26,500 BP. From http://en.wikipedia.org/wiki/File:Taupo_2.png

The Oruanui eruption, Taupo, 26,500 BP. Public domain, http://en.wikipedia.org/wiki/File:Taupo_2.png

These people were well on the way to an agricultural revolution nearly twenty millennia before ‘our’ one. They had semi-permanent habitations and had learned to make bread from wild wheat. They had grain stores. They had horticulture. They fished – indeed, analysis of nitrogen isotope ratios has shown that a lot of their protein came from fish. There is evidence of semi-domesticated animals, certainly domesticated dogs. But that came to an abrupt end when the world plunged into new glaciation some 26,500 years ago, culminating in the Last Glacial Maximum around 20,000 years ago. The cause, possibly, was the Taupo super-volcano in New Zealand, which erupted with world-shattering effect and may have triggered a catastrophic climatic downturn.

World climates oscillated for a while, but began decisively warming with the end of the Younger Dryas glaciation some 11,500 years ago. Humans began moving into what is now eastern Europe. And it seems their version of hunter-gathering was supplemented with wild wheat. Grinding stones have been found as an accompaniment to their camps across a wide region, implying that flour was being ground from wheat before it was domesticated.

Mix that potential with determination and intellect – remembering these people were just as smart as we are and just as capable of doing stuff – and that, I think, is all we need to explain Gobekli Tepe. No secret ancient super-civilisation or alien woo required. Sure, later discoveries make other things possible – but that doesn’t reduce the intellect or humanity of those who achieved things with the technologies on which later developments rest.

Lest there be any doubt, New Zealand Maori, up until the point of contact with Britain, had a similar mix of technology to those who built Gobleki Tepe, and in many ways fewer opportunities. The Maori economy was a composite of hunter-gathering, with significant fishing, supplemented with horticulture north of the ‘kumara line’, but they had no wheat, corn, or metals, and no domestic animals other than the Polynesian dog (a type that went extinct in colonial times). Clay was available, but pottery – though known in the ancestral Polynesian islands from which Maori came – was not used.

Otatara pa with reconstructed elements of palisade, Taradale, Napier. Click to enlarge.

Otatara pa with reconstructed elements of palisade, Taradale, Napier. Click to enlarge.

What happened? Maori developed a complex, sophisticated, vibrant and organised society able to build over six thousand pa (fortified places) across New Zealand between about 1500 and 1800 CE, all demanding surplus production and a social scale of organisation that often ran way beyond the 150-ish figure of the main Maori social structure, the hapu. Some of these, such as the horticulture on Mount Eden or the pa at Otatara, far outstrip Gobleki Tepe in scale. When the British arrived, mainly after 1800 CE, they had to invent a whole new classification (the ‘noble savage’, in settler period terms) to explain a people who, to British thinking of the nineteenth century, ran outside what was ‘supposed’ to happen by what the British knew at the time. But Maori had done it anyway, by their own capabilities. The problem, of course, was with how nineteenth century British thinkers saw the world.

Now go figure about those late ice-age folks and Gobleki Tepe.

Copyright © Matthew Wright 2015

Where woo woo comes from and why it’s so seductive

If we are to explore some of the woo woo that’s been peddled about perfectly ordinary – and hugely spectacular – things on the planet, like ancient pyramids or apparently mysterious rock formations, I guess the first port of call is to understand why these things get turned into mysteries in the first place.

Some 20 km east of Lake Taupo in New Zealand’s North Island is a curious natural structure known as the ‘Kaimanawa Wall’. It’s made of ignimbrite and was formed by a pyroclastic flow that rolled across this part of New Zealand some 330,000 years ago. As the flow cooled, it split in a way that left the exposed side of the flow looking remarkably like a stone wall.

Needless to say, the fact that it looks like a stone wall has meant, to various ‘independent thinkers’, that it therefore is one, thus ‘proving’ that an ancient civilisation existed in New Zealand. The total lack of any actual evidence of such an entity hasn’t stopped them. Nor does the hard scientific data, which shows its natural origins. That’s rejected because, after all, the wall is obviously a wall.

It’s a style of thinking I have a hard job fathoming.

Modern scientific thinking runs something like this. There are hidden truths behind the superficial appearance of most things, the issue is finding out what they are. So we look at the ‘Kaimanawa Wall’, hypothesise that it might be an artificial structure, and the first question is whether that is literally true. We test the hypothesis, carefully investigating the material it’s made of and its context, to discover what lies beneath the superficial appearance – its composition, age and so forth. From that emerges the actual story of its origins – origins which, I might add, are consistent with the known geology of the era.

The ‘woo brigade’, on the other hand, also assume that there are hidden truths behind what they see up front, but have a very different idea about how these truths are hidden. They  look at the ‘Kaimanawa Wall’, note the similarity to an artificial structure on the face of it, and take that to be a literal and immutable truth. No testing is needed, because it seems self-evident, and from that assumption flows questions about how such a structure might have been built.

1195430130203966891liftarn_Writing_My_Master_s_Words_svg_medIt’s a kind of logic that was used by Medieval monks and other thinkers of a millennium or more ago – the world we see is literally what it seems, and points to hidden truths that can be discovered not by experimentation, but by deductive logic.  The approach was superseded by the very different thinking of the Early Modern period and the Age of Reason.

The consequence is that the woo brigade assume that the literal appearance of many of the apparently ‘mysterious’ artefacts and structures around the world reveals the actuality of what they see, and do not question the conclusions that follow. But if that initial premise is in fact not true, then the whole chain of logic they build after that breaks down – because it’s built on a faulty assumption.

This is me doing my 'writing getaway' impression on Rarotonga.

This is me doing my ‘writing getaway’ impression on Rarotonga, the key island from which Polynesians migrated to New Zealand around 1280 AD. The departure place is marked on the island. (Yes, it’s that well known).

That, of course, is why modern scientific method demands that we have to test that first assumption, as the very first port of call.

The other point is that woo offers simple certainties; anybody can ‘get’ the obvious literal answers it provides. And that’s attractive.

I’ve gone into this in some detail because it explains a good deal about how ‘woo’ gets traction in terms of various apparent archaeological mysteries and phenomena, around the world. More on this soon.

As for the ‘Kaimanawa Wall’ – well, the main problem with the woo brigade here isn’t that they think it’s artificial. It’s the rest of what follows – a fantasy construction about ancient ‘pre-Maori’ civilisations in New Zealand that inevitably ends up being tangled up with the assumption that these imaginary ‘pre-Maori’ settlers were ‘Celtic’. Dog-whistle code, in short, for some extremely unpalatable present-day bigotry.

The take-home facts? The ‘Kaimanawa Wall’, a natural formation, was already ancient around 1280 AD when New Zealand became the last large land mass in the world to be settled by humans. These settlers probably landed on the Wairau Bar, were probably preceded by exploratory voyages, and were Polynesians who came from the Cook and Marquesas islands. This has been established beyond doubt from a wide range of disparate evidence – genetic, linguistic, archaeological and so forth. No humans existed in New Zealand before then – evidenced, among other things, by the fact that the original flora and fauna were untouched when the Polynesians arrived, but succumbed quickly soon afterwards in the last of the great Pleistocene collisions. A distinctly ‘Maori’ culture emerged indigenously from the Polynesian settlements during the fifteenth century, a turbulent time of significant culture change.

All this is well established – as, indeed, is the origin of the ‘Kaimanawa Wall’. No woo required.

Copyright © Matthew Wright 2015

The science of being smart – and why we didn’t need alien help

Human stupidity never seems to stop giving. News surfaced this week that some guy in the Egyptian Museum broke King Tutankhamen’s mask while cleaning it, and stuck the part back on with epoxy. Bad move. Not only is it a conservation nightmare, but everybody knows you should use alien fantasy woo-woo tech like the Pharoahs had. Or something.

Neanderthal family group approximately 60,000 years ago. Artwork by Randii Oliver, public domain, courtesy NASA/JPL-Caltech.

Neanderthal family group approximately 60,000 years ago. Artwork by Randii Oliver, public domain, courtesy NASA/JPL-Caltech.

My bet’s with the ‘or something’. In the last few decades there’s been a popular trend towards dissing a lot of older human achievements – imagining that ancient civilisations couldn’t raise pyramids, build Gobleki Tepi or whatever, and must have had ‘alien’ help. Total rubbish, of course; the notion speaks more about our own credulousness and prejudices than it does of past realities.

Take epoxy. Did aliens give it to us? Hardly. And was it a modern invention? Noooo. According to archaeologists, the first artificial epoxy was invented at least 80,000 years ago – and you know who invented it? Neanderthals. Who, it turns out, had bigger brains than ours and were easily as smart. And they invented a method for making an artificial viscoelastic polymer out of birch bark, using a dry distillation process requiring an oxygen-free environment and temperatures of 650 degrees F – all with stone age tech. Woah!

Neanderthal engineers used the stuff to glue stone spear heads to shafts. The bond – reinforced with fibre whipping – had to be solid, because Neanderthals were physically twice as strong as we are, and their hunting techniques involved sticking a large beast with one of those spears and then hanging on while the thing bucked (they got the same injuries out of it that rodeo riders do today).

Jump forward a bit and we come to the pyramids – always a favourite for the alien astronaut woo brigade. The reality? The ancient Egyptians actually lagged a bit, tech-wise, by comparison with their neighbours; they lacked bronze for a long time, for instance. But they had enough know-how – and, more crucially, economic scale – to build the pyramids. Despite efforts during the twentieth century by ‘independent thinkers’ to assert the whole thing was a product of space aliens, there’s nothing magical there, and the way it was done is well documented. The only argument is over precisely which technique the Egyptians deployed.

The aqua-blue water is really that colour, it's a by-product of ground glacial rock flour suspended in the water.

Tekapo canal, a small part of a monolithic 1970s-1980s construction project that created whole rivers, lakes and diverted watershed flows in New Zealand for power generation. The aqua-blue water is really that colour, it’s a by-product of ground glacial rock flour.

The same applies to the assertion that we couldn’t build pyramids today, which inevitably goes with the ‘aliens did it’ claim. What this usually means is that the ‘independent thinker’ doesn’t themselves know how it was done back then, mistakes the debate over specific technique by the archaeological community for ‘nobody knows’, and assumes that it therefore couldn’t be repeated today.

Actually, given the money, we could build pyramids just like the Egyptians did. Though our modern tech would make the job faster, easier and cheaper. We’ve already done the harder job of un-building some of the more complex Egyptian stone-works – don’t forget the way the Abu Simbel temples and other monumental works were disassembled, moved and then reassembled with modern tools and heavy lifting equipment when the Aswan High Dam went in during the mid-late 1960s.

The Aswan High Dam also underscores the astonishing scale of the engineering works that go on today, worldwide. Even here in New Zealand, for instance, the Upper Waitaki power system  – which involved redirecting whole rivers – represents a raw scale of construction that dwarfs the pyramids.

All of which underscores one point. We’re conditioned to suppose that technology is a relentless ‘advance’; and of late it certainly has been. But that also seems to come with the notion that ‘old’ is ‘less sophisticated’, even ‘stupid’. It sets us up to underestimate what people of earlier ages knew and could do. Remember – they were just as smart as we are. There’s a difference between being ‘uninformed’ and being ‘stupid’. And ‘uninformed’ also doesn’t equate to ‘incapable’.

Unlike the guy that thought they could repair King Tut’s mask with superglue. Urrrgh!

More soon, as I get on to looking into ‘ancient mysteries’ in detail. Lots more detail.

Copyright © Matthew Wright 2015

How long is the ‘now’ moment we live in?

How long is ‘now’ – you know, the evanescent moment we live in and usually let past without properly experiencing it.

Wright_AuthorPhoto2014_LoNow, like time itself, is largely seen as a philosophical issue; a personal perception that stretches or shrinks depending on what we are doing. For a kid, an hour spent in a classroom listening to the teacher drone on about stuff the kid neither knows nor care about is an eternity; yet an hour hurtling about with friends at play disappears in a flash. Adults have a different perception of time again; that same elasticity flowing from interest and enthusiasm, but metered often by a sense of purpose. Yes the job’s boring, but it has to be done.

Beyond that is the concept of the ‘moment’ itself. What is ‘now’? In Buddhist philosophy it means being mindful – fully and properly aware of one’s immediate self, immediate place, and immediate environment. It means having awareness of the fullness of the moment, even in its transience, even as we think about past or future.

But what ‘is’ a ‘moment’, scientifically? The reported research indicated that a ‘moment’, to most people, is two or three seconds. Then that perception of ‘now’ vanishes and is replaced by a new one.

If we match that to attention spans we find that the typical time spent on any one item on the internet is literally only a couple of ‘moments’. And then when we realise how shallow the internet must be.

It also underscores just how important and valuable mindfulness actually is. Because a couple of blinks, literally, and the ‘now’ moment is gone.

Copyright © Matthew Wright 2015

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Searching for that elusive exo-Earth

In the nearly 20 years since Michel Mayer and Didier Queloz confirmed the first known exoplanet around 51 Pegasi, the number of known exoplanets has risen to over 1860 – and there are more to come. The Kepler space telescope, before being hobbled by mechanical failure, created a massive database of planet candidates orbiting the 150,000 stars it looked at – some 4,175 in fact – which are still being checked. Eight new planets were confirmed just last week.

We can be sure there are a lot more out there. Kepler scanned just 0.28 percent of the sky in the direction of Draco, out to 3000 light years. In that patch, it could only detect planets whose orbits cross the disk of their star from our viewpoint. Other planetary systems, tilted at different angles, aren’t detectable by the transit method. But they will be there. And now the hot question – how many planets are like Earth?

Simulated Exo-Earth. A picture I made. Apart from the fractal artefacts, does anybody notice what's wrong with it?

Exo-Earth. A picture I made. Apart from fractal artefacts, does anybody notice what’s wrong?

Astronomers have found a few planets Earth-sized and below – including two of last week’s confirmations. Some are in the ‘Goldilocks’ orbit where the star’s warmth would allow liquid water to flow on a planetary surface. Though bear in mind that an observer using Kepler to scan our solar system would classify Venus as “Earth-sized” in the habitable zone. The problem is that transit-detection gives us diameter and orbital period, hence mass and density of the planet (and of its parent star). But it doesn’t give visual data – we can’t do spectroscopy on the atmosphere, for instance, though that’s possible with other techniques, and some data has been fielded about planetary atmospheres.

However, it’s only a matter of time (and money) before instruments are able to pick up more data from subtle fluctuations of stellar light. A photon here, a photon there – literally. From that, we’ll learn about planetary colour, atmospheric composition (via changes to starlight passing through it). Maybe we’ll learn whether any have large moons, if the orbit of that moon is in line with the star. Though I wonder. We’re looking for another Earth – but who says our world has been replicated?

Neptune. A picture I made with my trusty Celestia installation (cool, free science software).

Neptune. A picture I made with my trusty Celestia installation (cool, free science software).

One of the types we’ve found is the ‘hot Neptune’ – a world maybe twice the diameter of Earth with eight or more times the mass. About 19.3 percent of exoplanets found so far fall into this category, as opposed to 5.3 percent of Earth-sized worlds. They also orbit relatively closely to their stars. This is largely a function of technical limits – we can detect the bigger worlds more easily, and picking up the orbits of worlds that are distant from their stars requires years-long observations. So these proportions will likely change. But for the moment that’s where the data points.

Close to its primary, such worlds could be water planets, rather than the ice giants we have in our solar system. Maybe these ‘exo-Neptunes’ define ‘normal’. Or maybe every world is unique – product of many variables, obeying the same laws of physics but emerging in variations defined by subtle differences in composition, size, ambient temperature, and so on. Check out Jupiter’s biggest moons – all different, all formed in the same place at the same time.

The realities of physics mean we won’t travel to these exo-worlds any time soon. Or later (and yes, I know about the ‘Alcubierre drive’). But it’s fun to speculate…and I have a question. Suppose we found another Earth and arrived, en masse. Do you think we’d ruin it, the way we’re making a good job of ruining the Earth we’ve got? Just wondering…

Copyright © Matthew Wright 2015

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