Science Interviews

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Wed, 25th Jan 2012

Astronomical Imaging, NEOShield and the Aurora

Dr Robert Massey, Royal Astronomical Society

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Robert Massey returns with a roundup of news from the Royal Astronomical Society.  This month; The history of astronomical imaging, Near Earth Objects and Auroras above northern Britain...

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I am a little confused about a subject that often comes regarding the different techniques that might be applied.

It has been stated that we are given a certain amount of protection from impact objects from our atmosphere.  Objects of a certain mass hit our atmosphere and are destroyed before they reach the ground, Tunguska for example.  I do not understand when scientists in this field say it is not a good idea to blow a larger object into lots of smaller ones.  Surely lots of smaller ones, the more the merrier, would be the ideal solution thus bringing them down to a size our atmosphere can give us some protection from?

I think what these scientists should advise is, please do not use Nukes on these things as we will end up irradiating the whole planet, find a way of creating a massive explosion using some of the antimatter from CERN. Of course they are going to have to learn how to store it for longer hey?

Also one big hit from an object is going to be like a knock out punch from a boxer instead of lots of happy slaps!

In my opinion the best solution is to spot it a long way off, then slow it down into an Earth orbit and use it as a high orbit space station.  Or maybe even a lunar orbit!  ?
Aaron_Thomas, Fri, 27th Jan 2012

Earth gets hit once or twice a century with an object, maybe 1 to 10 meters in diameter.  Then the effect really depends on where it hits.  Oceans (tidal waves?) Rural, or the very few highly concentrated urban areas.

An impact from a meteorite in excess of 1km in diameter would be a whole different story. 

The problem is that it might cost us a $1 trillion to keep a 10m asteroid from impacting in the middle of the Sahara desert. 

If we started building a defense missile  system capable of knocking out a 1km "Planet Killer", it would certainly become obsolete before it was ever needed.  But, if we had to build it from scratch in 12 months, we might not get it finished.

It also depends on the trajectory.  A comet could literally come out of nowhere, and impact Earth on its first pass.  Such an event might be extremely hard to prevent.

For known NEO's, perhaps one could calculate their course a couple of orbits ahead, but maybe only down to a 50% chance of hitting...    somewhere.  That might give us adequate response time to snag the meteorite on a near pass before the final pass.  But, how much would we choose to invest in preventing a small meteorite from impacting somewhere?

I agree.
If one pulverizes the meteorite, it should have less impact, although one would still be left with much of the heavy metals that might survive the atmosphere.  But, say if one had a 100m meteorite, and blew it up into 100, ten meter meteorites...  rather than having one big impact crater, one would get quite a few smaller ones, but still big enough to cause a lot of damage and thus less concentrated damage, but a higher risk of hitting a major city.

A fission triggered H-Bomb would likely cause some fallout.  However, hopefully it would be spread out far enough that it would be less than what we all received from the earlier above ground nuclear testing in the 60's. CliffordK, Sat, 28th Jan 2012

Imagine the politics of one big hit and some possible diversion but not avoidance! 

The further away you obliterate it the more pieces will miss the Earth, more pieces will be destroyed in the atmosphere, and yes more chance of a populated area being hit.  I have heard the analogy of a rifle bullet compared to a shotgun blast.  However what this analogy fails to address is the distance at which this shot takes place.  I would rather be shot with a shot gun at 500mt then a rifle bullet! Aaron_Thomas, Sat, 28th Jan 2012

I do not think one trillion dollars would buy enough anti matter to zap an asteroid considering the rate at which it is produced at present. syhprum, Sat, 28th Jan 2012


I suppose that even if one could trap all the antimatter that is produced...  it would still be a problem.

Making it 1 atom at a time.
It takes 6x1023 hydrogen atoms to make a gram.  So, making a few dozen atoms doesn't amount to much.

I have wondered if it would be easier to make an antimatter trap in space than making it on Earth.

I suppose if one is making a bomb...  Rather than making a fission/fusion bomb, it would be possible to make an antimatter/fusion bomb that would be much "cleaner", and really wouldn't need much antimatter to trigger it.

However if the future of the Earth is at stake, I don't think I'd be too concerned about exploding a single plutonium/fusion bomb in space.  Depending on velocity vectors from the explosion, much of the plutonium and products would never reach Earth, and the radioactive material that would reach earth would be spread out to nearly background levels.

The biggest issue would be if there was a critical failure before the bomb exploded, leaving an unexploded nuclear ordinance on an impact course with Earth, or otherwise having it destroyed in a limited area in the atmosphere. CliffordK, Sat, 28th Jan 2012

If the Earth was at stake I suppose I would expect there to be a few more missiles heading towards the offending target then ONE!  Talk about putting all your eggs in one basket.......  Then the question might be, what levels of radiation can we treat as acceptable in such a scenario. 

I still think we should go out and bring one of the objects into an Earth or Lunar orbit.  I heard this mentioned on the Podcast recently and it has got my imagination spinning....  Somewhere out there is an object that is just right.  We are good at putting satellites into orbits around other objects. 

One way of getting over the problem of fuel required would be to launch a rocket from space.  Is that possible? Aaron_Thomas, Sat, 28th Jan 2012

Capturing an object would require both altering the course, and slowing it down significantly.  Perhaps using  lunar slingshot to dump velocity into the moon.  Could you use atmospheric braking without breaking up the object, or loosing it?

Anyway, the energy requirement would be much greater to capture it than just making it avoid the planet.  And, there may be greater risk.  For example, an atmospheric braking maneuver could go wrong in many ways.

Ideally, one would use the object itself to produce some of the fuel for maneuvers.  An ion engine dumping ions from the object, or perhaps hydrolysis of ice.

How big of an asteroid are you wishing to capture? 
Something 10m in diameter might be possible to capture.
Something 10km in diameter would be great for building a space station, but would push our engineering capabilities to their limits.

As far as refueling in space, or even assembling a rocket in space, I don't see any problem with that.  It wouldn't take too much "extra" energy to stop in an orbit, before escaping Earth's gravity.  Hydrogen and Oxygen are usually stored at a low pressure, but one could build a mirror/heat sink like the JWST to keep the fuel at very low temperatures, then just build a recovery system to recapture any leaking fuel. CliffordK, Sat, 28th Jan 2012

A 10 Km diameter size asteroid would be perfect for building an orbital space station on.  Even better if it had some ice present and other useful resources. 

One solution could be to try and use Jupiter as a target planet to capture it.  Once you then have it under control in a stable orbit around Jupiter the next step could be Mars and finally Earth. 

Another use of this Asteroid would be as a space anchor for a space elevator as well as a large space station.  If you had one around the Moon and Mars you also have the perfect platform for planetary missions.

Ceres is about 900km across.  It orbits the sun in 4.6yrs.  And looks like it is a prime candidate for a new Moon for Mars.  You might even be able to stir the geological activity up a bit on Mars with Ceres as a Moon.

We could also use Asteroids as impactors for objects heading for Earth.

I like the idea of using one for a space station.  The possibilities with an object like that as an artificial satellite are endless.

Aaron_Thomas, Sun, 29th Jan 2012

Moving an object that is 1021 kilos would not be easy.

The ice is likely a resource that one would choose to preserve.  But, one would have to stabilize the ice before attempting to move the dwarf planet.  Otherwise one would undoubtedly loose the ice when it was moved closer to the sun.  Perhaps mining the core and building a shell around the icy planetoid, or stabilizing the rotation, then building a big heat shield (+ solar panels) between the sun and the rest of the dwarf planet.

Then, add a plasma engine... 

And, with a little luck, 100 years later it could be nudged into place.

One might practice aerobraking (somewhere other than at Earth) with an iron core asteroid/dwarf planet, but it would be a very tricky maneuver.  However, ice is likely a resource that one would choose to preserve, and thus, no aerobraking.  More likely, one would choose to slowly reduce orbital energy with something like a robotic controlled solar powered plasma engine over a period of a century or more. 

If one wanted to try to dump something into orbit around Mars, one might try 5261 Eureka.

However, since it is in a good, stable location, with a small gravity well, one might choose to just leave it alone, and pick another one of the many Mars Grazing asteroids that would have less potential for future in-situ utilization.

At this point, however, I think the next big frontier is to build a permanent lunar colony/base/station. CliffordK, Sun, 29th Jan 2012

How big does an asteroid need to be so that when you blow it up, its own gravity pulls it back together? Chemistry4me, Sun, 29th Jan 2012


Well I am thinking that would depend on several factors.  The force used, and the time allowed for reconstitution.  Other factors would include the gravitational effects of other large objects, Jupiter for example.  You might include some kind of escape velocity of any objects leaving the original mass to establish what force is required over a given time to prevent the object re-coalescing.

And of course the larger the object the more energy required to blow it up!  Aaron_Thomas, Sun, 29th Jan 2012

Yes I suppose it would be rather hard to calculate even as a purely theoretical exercise. Chemistry4me, Sun, 29th Jan 2012

Energy of moving is more useful than energy of blast for a changing of  asteroid direction.Only attack should be early.Electromagnetic lunar accelerator can do it. simplified, Sun, 29th Jan 2012

I guess what they did in the movie Armageddon wouldn't have worked in real life Chemistry4me, Sun, 29th Jan 2012

A few things.

What is the extent of our detection ability?  Do we have some kind of planetary sonar?  It just seems that the chances of someone seeing an incoming object with a telescope would have worse odds than the lottery.  Also, if we somehow did detect it, how fast are these objects usually moving?  Would we have time to do anything?  If we did have time to prepare a NEO killing package would our current propulsion systems be able to intercept it far enough away to not cause more damage to us than if left alone?  Going with the shotgun / rifle analogy, a shotgun does far more damage at close range than a rifle.

For me it seems that the best plan, assuming we could get to the object in time, would be to steer it away.  Maybe smash a bomb into the side of it.  Not to destroy it but to change its course.  Of course I doubt we currently have the tech for that either.

Lastly, I really like the astroid space station idea.  No telling what kind of new elements we could find on that beside all the other uses.  My only question, what effect would having a 10km object orbiting the Earth have on the Earth?  Does a 10km object have enough gravity to damage or change our planet?
Michalec, Sun, 29th Jan 2012

Astronomers have been pretty good at predicting what will not hit the planet, and are now tracking thousands of NEOs.

There are already predictions of when Halley's Comet will pass by Earth in 2134.

In 2008, the first meteor impact was successfully predicted.
http://en.wikipedia.org/wiki/2008_TC3
http://en.wikipedia.org/wiki/Near-Earth_object#Historic_impacts

With a whopping 20 hours between detection, and the actual impact.

Note, in the last decade, there have been 2 other slightly larger meteorites about 10m in diameter that were NOT detected before impact.

Had we chosen to try to destroy the meteorite, perhaps one could use our current anti-missile technology which would have worked to fragment it.  (the shotgun approach).  But, each fragment would have been exposed to more air, so perhaps the actual effect at the surface of the earth would have been lessened. 

One possibility, rather than using nukes would be kinetic impact, especially for small asteroids of a few meters in diameter.  Larger ones in excess of 1km in diameter may not be significantly damaged by the kinetic impact from a rocket, although it could still knock the asteroid a fraction of a degree off course. CliffordK, Sun, 29th Jan 2012

Should we bother to defend against them? There are numerous supervolcanos waiting to blow which will have the same effect, so it might be best to focus our efforts into working out how to get the world's population through events of that scale instead of worrying about much lesser threats from space.

Even the big one that "wiped out the dinosaurs" disn't completely wipe them out - there were birds back then (ducks and parrots, for example - presumably many of the bird types found towards the start of a well-structured bird book) and there are still birds today, so somehow they managed to keep warm and find food through however many years of darkness it was. Rocks rained down out of the sky, but it was local - round the other side of the planet it was just a thin layer of dust.

I actually do think it's worthwhile trying to stop asteroid and comet's hitting us, but that should be as an addition to the main task which is to create underground zoos and livestock collections for restocking the planet as rapidly as possible after a major event, plus a bunker under every house with sufficient tinned/dried food to last for a decade. A lead-lining would also be a good idea to guard against being killed by a gamma ray burst - if you've got a good bunker, you might as well be in it when you're asleep or if you're just sitting around watching TV or surfing the Web. New houses should be built primarily underground, with only a relatively modest expendable part above the surface which will be blown away by a Tunguska style event. David Cooper, Sun, 29th Jan 2012

Maybe instead of all the money in the world going into the production of things made to kill each other we could use that money to become that adventurous traveler who decided to abandon war over dwindling resources and leave Africa for a better life.

It's really a shame because we should have been on the Moon by now!  A serious threat globally might be what is needed to bring us all back together again as humanity and put things into perspective and begin to explore again.



Aaron_Thomas, Sun, 29th Jan 2012

I suppose one should find it disturbing that in lay-terms, impact events are often described in "Hiroshima Bomb", or Tsar Bomba Equivalents 

I don't think we need to be building big underground bunkers for a possible asteroid impact sometime in the next 10 million years.

The Nemesis Hypothesis suggests asteroid impact extinction events every 26 million years, with the next one due in about 15 million years.  Whether or not Nemesis exists...  there may be some periodicity to the "Big Ones".

However, I think the idea of seed banks in naturally cold areas is good. 

Perhaps we should also build an seed&egg&tissue bank in Antarctica. 

Or, on the moon.  Access would be a pain, but one could put a seed&egg&tissue bank in a polar crater on the moon.  Temperature could be held very low.  It would be reasonably protected, except for cosmic rays, which could be protected from with a good vault design. 

If the Earth got pummeled by a meteor shower, the moon might also get hit, although having both a North and a South polar vault would give some amount of protection.

A permanent off-planet colony (moon, Mars, Venus, or elsewhere) would, of course, also give an amount of redundant protection. CliffordK, Tue, 31st Jan 2012

Maybe there something similar exists already. ::) simplified, Tue, 31st Jan 2012

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