900 foot-wide asteroid to make close approach to Earth today | Hacker News Reader

900 foot-wide asteroid to make close approach to Earth today

independent.ie

40 pointsdrucken50 comments

Let's be clear, the probability of Apophis colliding with the Earth in the next 100 years is extremely small: 7.4e-06 [1]. And even then it wouldn't be an extinction event. To me this is a non-issue - the odds of a massive pandemic or nuclear war with greater destructive potential in the next 100 years are arguably higher.

There is some level of uncertainty with the estimates because the asteroid's orbit will change in 2029. But even if the estimates are off by a couple orders of magnitude in the worst case, we are still looking at a very small probability.

[1] http://neo.jpl.nasa.gov/risk/a99942.html

With asteroid close approaches I find it helpful to compare it to the earth to moon distance. In this case 9 million miles seems to be 37 times the earth to moon distance.

The 2029 event should be pretty cool to see (literally, magnitude 3.4 which is visible(sort-of) for a naked eye) if it really comes as close as 30 000 km. Geostationary satellites are 36 000 km...

News like this always reminds me how vulnerable our small planet is and despite all the technological development, we can be wiped out from the universe in a second and there is little we can do about it.

the terrifying thing is how hard they are to detect (basically spotting a black speck against the black of space).

But at least, if detected early enough, an asteroids path can be changed. If a star goes supernova within a few million light years of Earth, we'd all be fried.

Despite how mind boggling big space is, world extinction events are worryingly easy.

/me is pretty sure he'll have nightmares tonight...

"If a star goes supernova within a few million light years of Earth, we'd all be fried." Within a few light years, perhaps. The entire Milky Way galaxy is only a little over 100,000 light years across. A few million light years would be outside of the Local Group.

A few million light years could still be within our local group (depending on the exact value of "a few"), but you're right about my error. I'm not really sure where I pulled that epic brain-fart of a figure from...

We're getting fairly good at detecting asteroids though. Discovery from 1980 - 2010: http://www.youtube.com/watch?v=S_d-gs0WoUw

Apophis isn't getting closer than 9 million miles today. If you're interested in close passes, you may look forward to February 15th, when 2012 DA14 will pass only about 21,000 miles away, within the orbits of the moon and geosynchronous satellites. [1]

[1] http://earthsky.org/space/asteroid-2012-da14-will-pass-very-...

What are the chances of it wiping out our (artificial) satellites in 2029? It's pretty crowded up there, right?

If your definition for crowded is "mean distances between satellites is more than 1000km."

Space is big. The geostationary orbit has a diameter of 265000km, and there are something like 200 satellites up there.

The lower orbits have a lot of gunk on them, but this asteroid will only cross the geostationary orbit. It's pretty damn unlikely it will hit anything.

I think you mean the circumference of geostationary orbit is 265000km. Diameter is about 36000km.

just to help getting the scale in meters... 900 foot = 274.32 meters

Redirect it using electromagnetism?

The current preferred method is essentially firing painballs at one side of the asteroid.

http://web.mit.edu/newsoffice/2012/deflecting-an-asteroid-wi...

Hmm very interesting. So this would make it much more reflective, causing suns photons to bounce off and push it off orbit.

In order to further understand this, and forgive me here if it sounds strange, would a flat black car essentially be 'faster' than a gloss white car due to lack of reflection?

Photon radiation pressure is almost immeasurably tiny. It takes years to make a smallish deflection, and that's exposed to hard radiation.

A larger, related effect is visible with this desk toy: https://en.wikipedia.org/wiki/Crookes_radiometer

Since it takes 20 years to deflect it we'd better start soon

It's nice that the 2029 flyby provides an opportunity to launch a more aggressive mission (if it seems more necessary by then).

hmm, what if it doesn't hit earth, and hits venus, to which it is also on a collision course, and sets off a chain of events that unbalance our SS.

It would just bump Venus's orbit a bit - probably not even enough to notice. A single asteroid doesn't have the potential energy to destabilize a planetary orbit.

see: the pockmarked surface of the moon, which still has a stable orbit.

but what if it sets of some sort of chemical reaction, Venus does not have a atmosphere like earth, so he asteroid would hit its bare face, perhaps setting off some sort of volcanic reaction? Just saying, as I don't want us to be on the blind side of the fence.

Clearly, the whole system is our domain, and we should be know events like this are not to be ignored, as they are way bigger than your average metropolitan housing millions of you and me.

Venus does have an athmosphere, it's just not made of the same gasses as the Earth's athmosphere. There is no "bare face".

Venus' does have an atmosphere - and a denser one than Earth, at that.

This is a fairly small asteroid on the scale of planets. While it might have some negative consequences for the thin film of life clinging to the surface, the planet itself wouldn't even notice.

Impacts _much_ larger than this one have happened many times over the course of our planet's history, and have had no significant impact on our orbit.

thanks a lot, I got to know about slooh from this!

Foot? Doesn't make any sense.

http://en.wikipedia.org/wiki/99942_Apophis

It's Level 1 on the Torino impact hazard scale.

The close approach in 2029 will substantially alter the object's orbit, making predictions uncertain without more data.

If it hits Earth, then it's 500 megatons of TNT going off.

If it passes through a half mile "keyhole" which is unlikely, it will hit Earth in 2036.

Apophis broke the record for the highest level on the Torino Scale, being, for only a short time, a level 4, before it was lowered.

So worst case scenario: it hits the half mile keyhole and in 2036 the equivalent of a nuclear weapon (10 tsar bomba's at once) goes off on a certain city. But there is a plot twist. There will be weeks of warning, and the risk area where it will hit will be narrowed to the size of half the earth, or if we use the science, maybe a whole continent.

So it'll be like a hurricane evacuation, but instead of one state, it will be quarter of the earth's surface. Imagine the logistical nightmare if that happened near India/china. The prospect of relocating 5 billion people within 2 weeks notice with all of their junk and to do it sustainably? Plot for a cool sci fi movie there.

Not "the equivalent of a nuclear weapon", the equivalent of 10 times the Tsar Bomba, whose shockwave circled the earth three times.

I imagine it would be much cheaper to send three rockets to slightly nudge it off its course.

According to this model http://en.wikipedia.org/wiki/File:2036_Apophis_Path_of_Risk.... it seems to avoid highly populated regions (mostly). Tsar bomba was detonated in Novaya Zemlya which is arguably more remote, though.

It looks like we won't have to worry about the year 2038 problem anymore. Everyone can go back to 32 bit systems now.

There is a brilliant comedy about world-wide evacuation:

http://en.wikipedia.org/wiki/Nihon_Igai_Zenbu_Chinbotsu

It seems to be lowered to 0? http://neo.jpl.nasa.gov/risk/a99942.html

A three season HBO series I'd say. The actual evacuation, the event, and the reality a few years later. Directed by someone like Alfonso Cuarón (Children of Men). I know there are dozens of cheesy movies out their covering the subject, but this angle maeon3 is suggesting is really interesting!

There was a Scifi book series in my childhood, that really impacted my thinking: Commander Brandis. They needed to evacuate Europe, introduced prios for people, in the end the military just shot everyone trying to get evacuated and evacuated themselves.

I wonder what kind of weaponry and energy is required to push it away from Earth's orbit or just simply shatter it into much smaller piece so they'll burn up in the atmosphere.

If asteroid mining becomes a reality, I wonder if we could simply mine the thing down to nothing before impact.

Sure, but when you mine stuff, where does the stuff go?

Instead of deflecting the whole asteroid, you're suggesting chipping it into a bunch of pieces and deflecting those somewhere. Same problem.

We'd bring what we mined to earth or the moon, wherever the processing plants are. Mine != blow up and leave alone.

Changing the orbit of an asteroid is a function of its mass and orbit (net momentum).

De-aggregating the asteroid via mining does nothing to the net momentum of the asteroid. It would take just as much energy to re-orbit 1000 or 1,000,000 chunks of an asteroid as it would to re-orbit one. The energy transferred by multiple chunks of asteroid to the Earth is the same whether it arrives in one chunk or thousands.

The only thing that would possibly make sense would be to drive two parts of the asteroid in different orbits. The net momentum hasn't changed, but the two pieces would split the difference and pass to either side of earth, possibly missing crucial "keyhole" orbits which would dictate a subsequent impact, though you could likely accomplish the same thing by exerting a small thrust against the entire mass over a long time.

Mining doesn't change the fundamental orbital mechanics or energy costs.

Very valid point. However, wouldn't this be true for all asteroid mining? Meaning if mining becomes a reality, it's something that will have to be accounted for. I'm guessing though that even by 2036 we won't be mining asteroids this big .

If you blow it up and leave it alone, it still hits the earth with just as much energy.

That's not what mining is. Mining isn't deflecting. They would use and ideally process the material they mine. Not blow it up, not deflect it, possibly strip it down entirely and use as much of it as possible. Could be trillions of dollars of materials there.

Right. But unless you want the products to stay on the asteroid, you have to ship it somewhere. Shipping it somewhere would also move the asteroid.

So you are saying if they mine 10 tons of Iron, and bring it to earth, sans the rest of the asteroid, it'll blow up and cause destruction on earth? I think I missed that part in physics.

Otherwise I don't see your point.

Apophis has a mass of 27,000,000 tonnes.

10 tonnes is 1/2,700,000 the total mass of the asteroid.

This would be the equivalent of trying to reduce the impact of a 180 lb human by trying to reduce his mass by 0.001 oz (or 82 kg man by 0.03 grams for civilized humans).

Too small to matter.

Yeah, it was just an example number, earlier I mentioned mining it down to nothing and I still got "it's just as deadly" kind of comments. Unless I'm missing something from physics, stretching the potential energy of the out across ~10 years from mining it will not be the same as letting it hit the earth.

Shattering a big rock into smaller pieces doesn't actually change anything about how hard it hits. At these kinds of energy scales, it's really just all about the kinetic energy it delivers. Even if the entire asteroid was vaporized before it hit it would still hit more or less as hard.

It changes the aerodynamics properties, that are what protect us from most impacts.

You're still heating up the atmosphere and generating shock waves.

The difference is that you're distributing the initial shock over a larger area (and possibly longer time period). Any sufficiently large strike would create similar results by way of ejecta which would be thrown from the impact site and re-enter the atmosphere and strike the planet elsewhere.

You might be able to avoid certain order-of-magnitude effects, such as piercing the crust and exposing the mantle, but at that scale of impact, it's pretty much assured to be a bad day regardless.

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