Search This Blog

Wednesday, 30 March 2016

How an interstellar dust wisp could devastate our planet

Space looks empty, but it isn't - not completely. There's a 'soup' of dust and gas that fills the space between the stars. Called the Interstellar medium (ISM), it's thin - ranging from only a handful of atoms per cubic meter at it's thinnest, to millions of atoms per cubic centimetre and higher in places.

The ISM doesn't reach the space near Earth though: The Sun puts out a magnetic bubble which both pushes back the ISM and deflects the highest energy cosmic radiation away from us.

Above: A graphic showing the structure of the Sun's protective magnetic bubble, courtesy of NASA.
So far, so 'thank-you-very-much-mother-nature'. But there's a bit of a catch: Right now our solar system's moving through a fairly thin bit of the ISM called 'the local bubble'. That allows  the Suns' magnetic field to expand out to its fullest. But in a few thousand years we'll hit a denser patch of the ISM, called 'the G-cloud' - the local bubble is already getting turbulent, as we leave it's edge. When we reach it the magnetic bubble will be forced inwards, shrinking towards the Sun. It could be pushed as far in as the orbit of Jupiter, which would cause a serious increase in the amount of radiation hitting Earth.

Above: A map of the local ISM, showing the local cloud/bubble and the G-clouds the Sun is heading towards.

It's also possible that there are even denser regions nearby, unseen. In the worst case scenario, the magnetic bubble could be pushed inwards even further: Molecular hydrogen from the ISM would flood into the inner solar system, getting ionised and turned into a barrage of cosmic rays by the Sun. These cosmic rays would strip off Earth's ozone layer (more reading in the to this NASA report), devastating plant life and the animals that feed on plants. 

Luckily for us the distances in space are huge, so we're looking at millennia at least for such scenarios to happen. The main thing that's interesting about all this is that interstellar clouds might be responsible for some of Earth's sudden climate shifts and extinctions. Most of all it shows Earth is not a special and isolated place in the universe, but a part of it - a fact we need to consider when thinking about the future of our civilisation.


Elsewhere in the Universe:

Experimental inflatable section to be added to ISS.

Jupiter may have just been hit by a comet.

Tim Peak's Principa mission:



Monday, 28 March 2016

How dark are dark nebula?


Recently I was asked* 'how opaque is a dark nebula?' I went with it as a topic since, as a dark nebula is just a nebula with no stars to illuminate it, it gives me a perfect excuse to look at lots of stunning space images.

However.... we get those images from huge telescopes,  which are designed to collect as much light and detail as possible. That means they aren't a very good indicator of what a human eye would see. So I went and did some reading.

And it turns out that 'nebula' are a bit more complicated than I realised**....

She's complicated, true. But someone should try to understand her. Ahem, sorry, Marvel movies geek here.
Before we start, we need a reference point: The air you're breathing (I assume you breathe air on planet Earth, no offence if you've logged on from... elsewhere) has roughly 10,000,000,000,000,000,000 molecules per cubic centimetre.

So let's start at the beginning: Go out on a clear night, somewhere far from any city lights. You'll be able to see countless objects that are immense distances away, including nebula - they don't look like they do in the pictures, but if you know what to look for they're visible. So, pretty obviously, space is empty and transparent, and the nebula are clouds of glowing (or dark) dust and gas, over there somewhere....

....and then, just before the Sun comes up, you see this: 

Above: Zodiacal light, appearing above the European Southern Observatory
That glow (called zodiacal light) is sunlight being reflected by the cloud of dust and gas that fills our solar system - yep, we are actually inside a disk shaped nebula right now, and it's barely visible to us - and that's a big hint. But our nebula is thin  only 100 atoms per centimetre (and varying amounts of space dust) at most, so it's surprising we can see it at all.

Above: A particle of space dust, as seen under an electron microscope.
In fact we're in a nebula inside another nebula - it's called the interstellar medium (ISM), a thin soup of dust and gas that varies in thickness from place to place, and it surrounds our solar system.

Beyond our solar system's boundaries the ISM makes a fantastically complicated (and mostly invisible) 'ecosystem', busily becoming stars and planets and then turning back into dust and gas when they die. And, while it's tenuous, it's huge - it makes up roughly 5% of the mass of our Milky Way galaxy. ESA has mapped it, and their results should give you get an idea of how complex it is:

Above: A map of the cool portion of the interstellar medium, from ESA.
That's the ISM, the 'soup' between the solid things in our galaxy, made bright enough to see.
There's no real distinction between this soup and a nebula: There's no edge you can cross and say 'now I'm inside a nebula' - the soup just gets steadily denser, up to maybe 10,000 atoms per cubic centimetre. But, ok, you can just head towards something like the Carinae nebula.....

Above: The Carinae nebula, as seen byt the European Southern observatory. Awww... pretty! Invisible to human eyes, but pretty.
.... and stop when your spaceship's sensors tell you you're in the densest bit. What do you see?

Weirdly... not much, just like with the cloud surrounding our solar system. Maybe a faint glow, or slight dimming of the background stars, but from inside it would be almost completely invisible to a human eye.  
True, the damn thing looks almost solid in the picture. But so do ordinary terrestrial mists at a distance, and once you get inside those you can usually see fine:

The view from inside a mist bank, courtesy of StevesDigicam.com. That mist bank is far thicker than any nebula, but it's not visible at all until you look at something in the far distance.
Factor in that most nebula are many, many, times thinner than the thinnest terrestrial mists... and the lack of a show inside one starts to make sense.  

The reason why there appear so vivid in our telescopes is because a telescope concentrates the light from a big collecting mirror into one small image. A telescope will also spend hours staring at one spot, slowly collecting enough light to bring out normally invisible details. But get up close and the light (or shadows) from the nebula would spread out all around you, too thin to trigger your eye.

So... is that the answer: There's only one nebula, and it's actually see through? Not quite. Let's go back to our picture of the Carinae nebula:

Here it is again.
Do you see those little clumpy bits? Those are called Bok globules: Regions where gravity has made the ISM 'soup' collapse in on itself. The globules still don't have a defined edge, and through most of their structure they only have maybe 1000,000 atoms per cubic centimetre - denser than the usual soup, but still far thinner than air, mist, or smoke. But they are big, light years thick, which means they can still block out the stars behind them, and appear dark. 

Above: Bok globules blocking out light. For reference, the big one in the top right is about five light years long. Courtesy of NASA/JPL
In the centre of these globules solar systems are congealing out of the gas and dust: Gravity is crushing the soup into things as dense and solid as rock and ice****. The density in the middle eventually gets up to something like a planetary atmosphere, and then even higher than that as the central protostar forms. 

Here, in the heart of the densest part of a nebula within a nebula (within a nebula), we've found a spot where the human eye would see something - or, more accurately, nothing: Surrounded by light years of globule, and with the star growing in the middle still to young to shine, it would be totally, utterly, black

Which is a pity, because it's also full of newly minted comet cores, and you might want to spot those coming...

Above: A comet nucleus, one of the first objects to form from the Bok Globule that gave birth to our solar system. Courtesy of NASA.
To answer the original question: There's only one nebula really, and how opaque it is varies a lot. But generally it's much more transparent than terrestrial air - you have to really go looking to find a very opaque spot.

But that's not the most... interesting... thing I discovered researching this.

Next post: Why the ISM space soup could destroy civilisation (no joke).

* Yes, you can just ask me stuff and (if I feel like it) I'll research an answer for you. The contact form should be in the border of the post.

**In fact they are really, really complicated, so I apologise to all nebula boffins*** for all the oversimplifications I've committed.

***Yes that is an actual job - I even applied to be one once. 

**** It's a lot more complicated than that. But you start with the ISM, apply gravity, and end up with rocks - that's the gist of it, and it's almost my lunch time******.

****** Plus the number of *'s I'm needing is getting ridiculous and I've never figured out how to make Blogger do superscript.

Friday, 25 March 2016

Just six months of NASA's budget would pay for a lunar base?


There seems to be a lot of deep thought going on about the Moon recently, and the latest is that the New Space journal has published a special edition (edited by Christopher P. McKay and Alexandra Hall of NASA) looking at how much it would cost, and how long it would take, to set up a International Space Station style base on the Moon.

Above: An astronaut working on the exterior of the ISS. Courtesy of NASA.



Their conclusions are..... fairly surprising: Rather than the many tens (often hundreds) of billions often quoted for a Moonbase, the workshop has concluded it might be possible for a total cost in region of $10 billion - that's just over half of NASA's annual budget. What's more, it could be done for that cost as soon as 2022
If this analysis pans out it could have a serious impact on the (seemingly never ending) arguments over NASA's exploration priority's*. As professor Chris McKay put it  ‘‘Wouldn’t there be much less argument over Moon versus Mars if the lunar exploration piece was much cheaper?’’
 
The papers are free to read, and go into the costs, the site and construction methods, and aims of such a base. One noteworthy conclusion they come to is that the aim of the $10 billion lunar outpost shouldn't just to be a symbol, or a science base: It should aim to start a lunar economy.
 
Above: A graphic showing an ambitious Japanese idea for a lunar solar power farm. Courtesy of JAXA.
 
That's not as out there as it sounds: There's already an ongoing economic expansion in space, where satellites of various kinds make use of space as resource in many ways and contribute hundreds of billions every year to the global economy. A lunar economy would be an extension of our existing space economy, embracing what economic opportunities the Moon has to offer. The reports suggest these might include:
These actually match up quite well with existing concepts for expanding our economy in near Earth space, such as the space based solar power ideas that I wrote about earlier this week.

Do I expect to see a lunar base by 2022? No. Although ESA is looking at the idea of a lunar base, it's not on any agency or private groups list of construction projects at present. But these reports demonstrate that some out of the box thinking could make a Lunar base a realistic goal within my lifetime - and that's a good thought.
 
 
Above: ESA's plans for a 3D printed 'Lunar Village'.


Elsewhere in the Universe:

The Moon's axis has wandered

To add to the moon's scientific appeal: Results released this week by the Southern Methodist University suggest that the Moon's poles have wandered by up to five degrees since the little world formed. The findings centre around the shape of the ice deposits at the lunar poles, which are oddly elongated.

Above: An SMU video demonstrating the Moon's polar wander.
 

The Sun may be a baaaad neighbour:

A lot of people know that the Sun can give out storms and solar flares, which can sometimes interfere with radio equipment and cause damage to power grids. But new research  suggests that our Sun could produce superflares: Storms powerful enough to devastate electronics worldwide, and even damage our atmosphere. It may already have produced a small superflare in 775 AD, which left a measurable imprint of radioactive carbon in tree rings.

Above: The Sun spits outs a tounge of plasma.
* By which I mean it will probably make them worse, and lot's of militant Lunatics and Martians will have flame wars all across the internet. But I'm cynical....

Wednesday, 23 March 2016

Solar power stations in space - a revolutionary idea, or a pipe dream?

Above: An artists impression of a space based solar power station. Courtesy of NASA
'Solar panel power stations in space'..... if you're anything like me (or even if you're nothing like me but can spot the obvious a mile away) your first thought* on hearing that idea is 'why send them into space - surely it'd cost less to build more on the ground?

Well... yes. But looking at this idea gives us a chance to look at some other cool space technologies that are in development too. And, when you examine it closely, there are some advantages to putting solar panels in space: 
  • The sunlight is simply stronger up there - Earth's atmosphere cuts out a quarter to a half of the Sun's intensity. In space all of it could be collected. Not a huge advantage admittedly (the extra energy doesn't offset the cost of getting the satellite up there) but it's worth mentioning
  • There's no nighttime in space, so the power can be generated non-stop.. that overcomes one of the huge inherent problems with solar power on the ground - sunset! Ground based systems can store power in batteries overnight, but that comes with a bunch of its own problems. 
  • Being in space gets you away from the elements, and the wildlife.weather, wildlife, plant life... all contribute to the wear and tear that means components need constant service and maintenance. By comparison there are solar powered satellites still drawing power after decades without a service.
  • A satellite (or a small constellation of them) can beam power anywhere on Earth. This is, in my opinion, one of the areas where space based solar power shows real potential: To pick up power beamed from a satellite all you need is a lightweight mesh antenna. Consider how useful that could be for military forward  bases, disaster relief... anything where you need to get power to somewhere inaccessible, fast.
For certain applications - even if not mass power generation -  it's a technology worth looking into. But lets look at some of the problems:

  • It's expensive, and risky, sending things into space, never mind a huge solar power satellite.
  • You have to beam the power back to Earth as microwaves or laser light, which is not such an easy task itself.
  • The power transmitting technology is not yet up to snuff . 
  • But the biggest problem is, and always has been, launching enough solar power stations into space be useful: Conventional rockets are just too expensive it make it cost-effective.
So.... nice try but no energy revolution?

Not quite..... There have been commercial start ups that have tried to develop the technology - Solaren and SpaceEnergy come to mind - and though they've begun in a blaze of glory and faded into nothing they prove there's some commercial interest in the idea. More interestingly the U.S. military have begun researching the idea.
Then there are the technologies being developed that could change things in space solar power's favour: One is re-usable rocket technology, like that being developed by SpaceX, which many hope will bring down the cost of space launches. Another is 3D printing in space - this is a revolution in the making, where launching delicate components into space becomes unneeded - we can just launch the raw materials and have a 3D printer turn out the needed parts! In space satellite re-fuelling and repair is another needed technology that is on the rise. Even the beaming technology is getting better...

 
Above: A NASA test of wireless power beaming technology.

....but the holy grail for space solar power would be the ability to mine the materials in space, and need no launch at all. At least one company - Planetary Resources - is actively working toward this, but it's still a long way off.

All these things are very much in their infancy, and will have to reach maturity before solar power stations in space can really happen . So watch this promising idea carefully - but don't hold your breath too much...



* First printable, relevant, non lunch related thought that is.

Tuesday, 22 March 2016

My deepest sympathies....

..to the victims of this morning's bombings in Brussels. I know no words can take away the pain of those who have lost loved ones, or the suffering of the injured and their famillies. 

All decent people stand with you.

Monday, 21 March 2016

A noisy Universe!

Above: The Parkes Radio Telescope at dusk...

The vast majority of the Universe is vacuum, so it should be utterly, utterly, silent.  Yet, paradoxically, it has turned out to be an incredibly noisy place. And I'm not talking about the unbelievable volume a hungry 6 month old can produce at 3am. The  universe is filled with electromagnetic signals - and, we now know, gravitational signals.
Some of it is a bit more structured than just white noise - sometimes with an eerie beauty. My favourite is Neptune, which makes  noise that somehow reminds me of a choppy ocean... 

 
Other objects in the universe make stranger 'sounds': The comet 67-P that the Rosetta spacecraft explored gives of magnetic oscillations that translate into a sound like this:



Pulsars - rapidly spinning neutron stars that give out beams of intense radiation - give out a radio noise like someone knocking on a wooden table....


And, with the advent of gravitational wave detection, we can listen in on the gravitational wave 'noise' of gigantic black holes colliding.....
 
 
Some signals are simply unknowns - one such are the 'fast radio bursts', which are still baffling radio astronomers, and don't seem related to any astrophysical phenomena:
 
 

So, it's less a 'silent night' out there, more 'sky shouting at us'. If you'd like a truly unique musical experiance, run your audio through a decent pair of speakeres, then loop all the above soundtracks, and play them together in a dim room.
And, just in case you don't believe me that the sky is singing to you, here's how to pick them up yourself....

Friday, 18 March 2016

Water on Ceres, the Moon, and Mars:

Above: The LPSC 2016 banner. Courtesy of LPSC 2016
Next week is 2016's Lunar and Planetary Science conference - one of the big events on the space geek calender. It's a meeting for the top researchers, or at least those whose institution will cough up the price of a ticket. Talks and presentations cover everything from space dust to solar storms and planetary geology. But two worlds that always receive a lot of attention are Mars and the Moon - and this year there seems to be a lot of focus on the presence (or absence) of water and water ice.

There're a lot of other topics too (it's definitely worth looking through the papers in
Titan session, and the Pluto session), and I've had a day off ill - so a chance to rad the papers! Ahem. Here's the program, with links to the abstracts. To keep this post manageable I've focused on the Moon, Ceres, and Mars - here are a few that caught my eye:

About the Moon: 


 

 
There's been a fair bit of talk over the last decade or so about the possibility of water ice at the Moon's poles, and the presence of a thin layer of water molecules spread across the lunar surface. But this paper looks volcanic material, brought up from the Moon's deep interior, and finds it that some of it contains a surprisingly large amount of chemically bound water, which helps us understand the Moon's geologic history.
 
"MINI-RF/AO BISTATIC OBSERVATIONS OF THE FLOOR OF CABEUS CRATER AND THEIR IMPLICATIONS FOR THE PRESENCE OF WATER ICE"

The Lunar Reconnaissance Orbiter has been probing the Moon's permanently shadowed craters with radar, and has detected signals that suggest the presence of ice in clumps roughly 26 cm in size, or bigger. However there's a question mark over the result, and the team cautions that more investigation is needed.


"TOP HYDRATION LAYER NEAR POLES FROM LRO/CRATER: SEARCH FOR TIME-OF DAY DEPENDENCE."

More results from LRO, this time about the top layer of lunar soil near the lunar poles. It's been known for a while that this layer contains a certain amount of H2O and HO, but now it's been seen that the amount of hydration varies with the time of lunar day. 


About Mars:


"CEMENTATION AND AQUEOUS ALTERATION OF A SANDSTONE UNIT UNDER ACIDIC CONDITIONS IN GALE CRATER, MARS"
The history of water at Gale crater lake is a complex one, but it seems to have included both episodes of 'friendly' PH neutral water, and episodes of much more acidic water.
 

"CADENCE AND CAUSE OF LAKE-FORMING CLIMATES ON MARS"

The 'when' of lake formation on Mars poses a few puzzlers - it certainly doesn't look like they all formed at the same time, during the same period of clement climate. This paper looks at one possible explanation: That Mars has had repeated periods where the climate was suitable to form lakes.


"THE NATURE AND EXTENT OF AQUEOUS DEPOSITS RELATED TO THE HALE IMPACT CRATER ON MARS"

A long time ago I read about the most likely way to get liquid water (in substantial amounts) under Mars' present day climate regime: Crash a big-ish asteroid into an ice rich area, and the resulting pulse of heat would melt the subsurface ice, leading to an underground hydrothermal system. And that seems to have been exactly what happened with Hale crater.


"
PERCHLORATE REDUCING BACTERIA: EVALUATING THE POTENTIAL FOR GROWTH UTILIZING NUTRIENT SOURCES IDENTIFIED ON MARS"

Definitely a speculative paper, but one backed by lab tests that suggesting that microbes which can make use of perchlorate salts - an abundant chemical on Mars - could subsist off the available nutrients on the red planet.


RECURRING SLOPE LINEA (RSL)

A whole section on the discoloured sections of some slopes which, last year, were fingered as solid evidence of present day liquid on Mars. 


About Ceres:



"ELEMENTAL COMPOSITION OF CERES BY DAWN’S GAMMA RAY AND NEUTRON DETECTOR"

The Dawn spacecraft has found lots of hydrogen on Ceres, which very likely indicates lots of water ice just beneath the surface


"GEOCHEMISTRY, THERMAL EVOLUTION, AND CRYOVOLCANISM ON CERES WITH
A MUDDY ICE MANTLE"

Ceres may well have an ocean of mud deep beneath its surface.

 

"IMPACT INDUCED HEATING OF OCCATOR CRATER ON ASTEROID 1 CERES"

Occator crater has been the site of the biggest of the mysterious bright spots, and also of some strange 'hazes' at certain times of the Cerean day. This paper looks at the possibility that heat from the impact that caused the crater created an undergraound hydrothermal water resevoir, and how that might relate to these phenomena.

There's a hell of a lot more than that going on, the above ajust a taster. Expect some good bits of science and exploration to come to light in the next week
!

Wednesday, 16 March 2016

What colors are other worlds?

On the face of it 'what colors are the other worlds?' seems like a no brainer that can be solved by fifteen seconds on Google images: Mercury is grey, Venus is white, the Moon is grey, Mars is red.... true, things get a bit more complicated when we get to Jupiter (stripey), and its moons (we have to say things like 'imagine a reeaaly angry pizza' to describe Io)....

Io, the volcanic hate-pizza world. I mean, look at it: It makes Deadpools fave look nice. Every swirl is a lava flow, every black spot an active volcano. It hates everyone. £30 says that someone tries to land there before 2100AD

...but Saturn is yellow, Uranus and Neptune are blue, and that's it, right?

Well of course not, or that'd be the end of this article.

The thing about other worlds is that they are, well, worlds. There's a lot of room on each for lots of different colours. Lets take a look at the Moon, our nearest neighbour: Since it's so conveniently close you may actually be able to stick your head out the window and do this, and it probably looks a silvery white colour

But, if you land on it, you see a landscape like this:
The Moon: A smorgasboard of grey
The word you're looking for is 'grey'. Except... look closer still, and it's not. Let's take a close look at the lunar soil samples returned to Earth. There are white, grey, and black particles in there. But amongst them are particles like this...

Turquoise particles of lunar soil, courtesy fo JPL.
...and this....

Green and yellow  lunar soil, courtesy of JP..
...and this....

Red and plum coloured soil particles, courtesy of JPL.
Above: Orange lunar soil, near 'Shorty'  crater. Courtesy of JPL/ NASA.
These are all coloured beads of volcanic glass, spat out by lunar volcanoes. The different colours are caused by differing chemical impurities

Patches of oddly coloured soil can be found all across the Moon, where one impurity or another has come to dominate for some reason.  
So, the colour of the Moon depends on how closely, and where, you look at it. 

How about  Mars? It's red, right?

Uh-uh. To keep this manageable, let's just focus on the Martian sky:
No human has ever been to Mars, so what we know of the colours there comes from cameras. And a lot depends on how your calibrate your camera: Even a fairly small change can turn an alien sky....


 ....into an Earth like one:



That's caused a lot of 'NASA is hiding the truth about Mars!*' stories over the years. But, even when you get the colour balance right, the Martian sky really does change colour from hour to hour. During the day the sky is technically a faint blue**, but endless dust in the atmosphere changes it to a light pink or butterscotch:


Above: The view from Opportunity rover. Courtesy of JPL/ Cumbrian sky.


 When it's cloudy the sky can appear white, or grey:

Above:  A winters day at the landing site of the Viking spacecraft. Courtesy of NASA
During a Martian sunset the sky is often a vivid blue, due to ice particles in the upper atmosphere:
 
A Martian sunset, captured by the Curiosity rover.  Courtesy of JPL.


Mars actually gives pretty good value for money when it comes to spectacular skies.....

I don't remember where on Mars this is, possibly the arctic plain where the Phoenix lander explored? But look at that sky....

Above: Mercury with the colour vaiations exaggerated enough to see.
So the Moon isn't white and the sky on Mars is blue, (or tan, or white, and it could all be wrong anyway if the camera's haven't been set up right). 

We could keep going all day with examples of how colour is a complicated question on other worlds: There's 'enhanced colour' where a computer program brings out colour differences too subtle for the human eye to detect. Then there're colours beyond the range of a human eye, like infrared and ultraviolet, which are very important on worlds like Titan: There the sky is opaque orange in visible light, but clear in the infrared - so when you see maps like these, taken from space, of Titan's methane/ethane lakes you're actually looking at infra red colours no normal eye can see.

Above: Titan's lakes, easily visible in these infra-red colours, but obscured by orage smog in visible light. Courtesy of JPL/ NASA.
So go forth and Google, feast your eyes on the many colours of the solar system out probes are sending home - and remember that every world can throw us surprising new shades of beautiful...


Elsewhere in the Universe:

China plans a dockable space telescope
Blue Orgin opens its doors to reporters
ESA probe find vast 'magnetic void' around comet

* I'm not saying they aren't hiding the truth about Mars, just that if they got the colour wrong it's more likely they just ballsed up the color balance. 

** The process that makes Earth's sk blue, Rayleigh scattering, also works on Mars. But the yellow/pink colur of alll the dust in the air overpowers it on all bu the calmest days.