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Comet might hit Mars in 2014 (nbcnews.com)
115 points by wsieroci 1606 days ago | hide | past | web | 92 comments | favorite

Wow. What are the odds?

Just doing quick ratios and squaring them, if the comet follows the initial projections, there are only about 230 large objects coming this close for every one that actually lands on Mars. (And Earth gets hit with about 3.5 of these for every one that hits Mars. Our last is estimated to be 65,957,000 +- 11,000 years ago.) This is literally a once in a million years near miss!

Of course the odds now are much higher than they normally would be. The fact that it is on a hyperbolic orbit means that it comes from outside of the Solar System. The density of such objects is much higher near the galactic plane than elsewhere. However the Sun bobs up and down, spending most of its time away from the galactic plane and crossing it every 30 million years or so. We last crossed it something like 100,000 years ago and are now heading away, so are still in a period where interstellar objects are more likely to come barreling through. So the odds are higher than they normally are, but even if you generously account for the currently increased risk, this is still a once in a civilization near miss.

Of course the initial estimate may be wrong. From the article the uncertainty is much bigger than the distance to Mars. If the uncertainty is the stated 650,000 miles, then we've got roughly a 1/24,000 chance of a direct impact. (I am sure that more informed people will come up with much better estimates in the not too distant future.)

>Just doing quick ratios and squaring them, if the comet follows the initial projections, there are only about 230 large objects coming this close for every one that actually lands on Mars.

How did you come to this estimate? The Martian radius is 3,400 km while the current projected closest approach is 109,000 km. I think the uncertainty the maximizes the chance of impact is just the difference of those two, so my best guess for a chance of impact is (3.4/109)^2 = 0.1% (one in a thousand). And any other quoted uncertainty by the scientists should only decrease this probability.

EDIT: Ahh, I see, you must have used diameter. I think radius is more appropriate here, but I don't think either of us are accurate enough for a factor of 4 to matter much.

Whoops, I did use diameter. You're right, I should have used radius.

The comet has a hyperbolic orbit, but that doesn't mean it came from outside of the solar system. Most comets come from the Oort Cloud, where they orbit around the sun at great distance until their orbits are perturbed. It's postulated that the sun's path through the galactic plane is the source of these perturbations, but not the source of comets.

50km is massive.

Earth's largest crater[1] is 300km across, and that's thought to have been created by an asteroid 5-10km in diameter. The 180km Chicxulub crater[2] (this impact is generally believed to be largely responsible for the extinction of dinosaurs) was around 10km in diameter.

I'm kind of hoping this turns out to be something. I thought the Russian meteor the other week was a most amazing natural event, and something far bigger than that would be incredible (not to mention safe for humanity in this case).

EDIT: 50km is actually the upper estimated limit of the size of this comet. Wikipedia[3] says 8-50km. It's still huge.

1: http://en.wikipedia.org/wiki/Vredefort_crater 2: http://en.wikipedia.org/wiki/Chicxulub_Crater 3: http://en.wikipedia.org/wiki/C/2013_A1

Comets also are travelling waaaay faster than asteroids because they come from farther out in the solar system which gives them more potential/kinetic energy. Generally speaking a comet will be going about three times as fast and carry about nine times the kinetic energy as an asteroid of the same size.

Massive doesn't even come close. http://www.truthistreason.net/ground-zero-ii-interactive-nuc... allows you to nuke a given area and see the effects. Its biggest "bomb" is the Chicxulub crater - and compared to that, even the Tsabomba are a joke.

Witnessing such an event could help get humanity serious about existential risk, from comets or otherwise. I, for one, am hoping for an impact.

You would've thought the same thing about the meteor that exploded over Russia, knocked down a wall and shattered everybody's windows.

Russia is also a different planet.

The evidence of global warming is there to see, for all, at any time. And still people completely dismiss it out of hand. So, no. An event like this on Mars wont make any difference to public opinion what so ever.

If the impact happens - debris from this collision will come home to earth - and they may be bigger than dust.

What evidence do you have to suggest that a Martian impact will result in subsequent impacts on Earth?

We've found meteorites ejected from Martian impacts that have landed in Antarctica. Mars' gravity is such that a sufficiently large impact can create ejecta traveling at greater than escape velocity.

Beyond this wouldn't it provide good information on the effects of a comet impacting a planet. We have a bunch of stuff on or above Mars. Isn't there something to learn by seeing the impact with probes so close? Or do we know everything there is to know about such impacts?

The trouble with "getting serious" is there are far more threats on earth which are far more likely and thus more important to deal with. Why give big focus to a potential extinction threat when there are many flash points around the world. Korea for example.

You then have the rising threat of cyber attacks. I wonder how well the general population of a country would do if it lost power for a week or two. I woke up with no power and when it came to making breakfast I felt a bit lost..

A few weeks ago someone in UK had a new virus and was in an isolation ward. I would say as we become even more over-crowded and travel becomes even easier a pandemic would potentially be as devastating and more likely than earth being hit by a large object.

Korea can't destroy the planet, thankfully.

>>could help get humanity serious about existential risk

A comet hit Jupiter in the 90's (http://en.wikipedia.org/wiki/Comet_Shoemaker%E2%80%93Levy_9) we watched it and did nothing about it.

Yes I understand that we may get serious about our own house when the neighbors house is on fire. But frankly I don't think we will ever get serious.

Right now Mankind's main priorities are in inventing weapons and finding most ingenious ways to kill each other.

"Right now Mankind's main priorities are in inventing weapons and finding most ingenious ways to kill each other."

This comment is absurd. There are, what, maybe 100,000 people in the entire world right now actively working on creating new weapons. Certainly less than 1/1000 of the population. This has hardly been a priority of mankind since the atom bomb - far more people are directly involved with preventing climate change. Most people are pretty forward thinking.

As far as preparing for a meteor/comet collision with Earth, we would definitely need to see an imminent threat before we really started making progress. If we got a first-hand look at a significant collision with Mars and were able to document just how catastrophic it is to the planet, I definitely think more attention would be paid to preparing for a similar situation on Earth.

Exactly. I wouldn't go so far as to say "Most people are pretty forward thinking" but I'm pretty sure curing diseases and global warming are higher up on mankind's priorities list. And obsessing over the latest iPhone or clothing trend are even higher on the list.

Total percentage of manpower is only one way of measuring effort.

True, but can you show me any fair measurement of effort that would support weapons innovation being the world's main priority right now?

I don't have any data to point to, but I would be interested to see a breakdown of how many graduates of different fields go into defense.

Among my peers from college, a fairly broad spectrum of engineers, that number seems to be around 50%. I expect that is rather elevated due to particulars of that region, but I wonder what else can compare?

In other words, not "people working in weapons : the world" but rather "STEM workers in defense : STEM workers qualified to work in defense." Where are we allocating the brains of society?

Where do you think your tax dollars go, silly rabbit?

You can look it up in most countries.

Jupiter is too large for anyone to get their head around. It's too far away and just too alien for an impact to have any effect on the population.

On the other hand, Mars has been the subject of countless fantasies and observations, we have the surface well mapped and if we get a good look at the impact crater (or the impact itself) it will be a matter of hours before someone overlays a map of NYC or London on the imagery.

Mars being smaller than Earth also adds a lot of weight to the discussion. Something hitting Jupiter is just not unexpected, but if our smaller sibling gets struck then there is something to talk about.

More than just large, it's gaseous and thus unrelatable. People see grainy images of some dark object breaking up over Jupiter, but they can't wrap their head around what that is- what does an impact on a gaseous planet even look like? Mars, on the other hand, is much more visceral to people. We have pictures from the ground- and it looks like [places on] Earth.

Actually, we're not doing too bad in not killing each other (too much). See Pinker's "The Better Angels of Our Nature: Why Violence Has Declined" and related research. I do hope the trajectory continues though.

> A comet hit Jupiter in the 90's (http://en.wikipedia.org/wiki/Comet_Shoemaker%E2%80%93Levy_9) we watched it and did nothing about it.

and don't think for a second that the Jovians have forgotten about that. :(

Can't we help this happen somehow?

Not by 2014.

Almost certainly not by 2014, but there are still a lot of factors that are unknown. We certainly can't launch anything to go out there since the travel time alone forbids it. But if more accurate estimates come in a few months from now putting it very close, but missing, Mars, there might be some kind of crazy laser engineering to be done.

I realize how crazy this is, but there's always reason to dream and brainstorm.

> I, for one, am hoping for an impact.

I am, too, but not because of any higher principles or concern for humanity. I simply think it would be incredibly entertaining to watch something that big smash into a planet at Mach 164. The fact that we have quite a few cameras on and above Mars is a huge bonus. It would be the closest we could get to experiencing an impact of that magnitude without the unfortunate side effect of existential oblivion.

Well, collectively we certainly don't seem to be taking climate change seriously, the implications of which are known and more disastrous than a hypothetical comet striking our planet.

In a way this is why I'm a bit disappointed that meteor didn't pass across US. Since it passed across another country, I don't think they now see it as much of a "threat" as they would've if it passed across US' sky.

On the other hand, I'm glad at least it passed one of the big countries like Russia, which now want to form an international anti-asteroid defense system. If this would've passed across Iceland, nobody would've cared.

I got to thinking. Is there any chance we could nudge this to impact the Hellas Planitia on Mars. It's the lowest point of Mars and therefore already has a higher atmospheric density (.01 ATM). So if we could double the depth and potentially add more water, it would really get us closer to a great location for a colony.


Have you read the Mars Trilogy by Kim Stanley Robinson? I bet you have, but if you haven't, you should. It's the most amazing hard science fiction regarding terraforming and colonzing Mars. Planetary-scale engineering techniques to heat Mars up, add water, increase the atmospheric pressure, etc are discussed in detail.

"The Sky So Big and Black" by Johne Barnes is also a interesting read about Mars-forming. (And memes, too!)

I wonder what the minimum atmospheric pressure is to grow some kind of plants out in the open? (Or bio-engineer some plants to grow). Would this get us in that ballpark?

Also, what the minimum pressure a human could survive with just a breathing mask?

There is an interesting bit from NASA here that covers your concerns, http://science.nasa.gov/science-news/science-at-nasa/2004/25...

I think it would be a neat high-school-level science experiment to find some plant that reproduces quickly, and then put it in a bell jar with ever-decreasing levels of air pressure to try and force natural selection to make something that can survive at very low pressures. (Edit: You won't approach Mars-level pressures with these experiments.)

At the college level, I've read papers about inserting specific genes into plants to increase their hardiness with thin atmospheres.

No, it's far too big.

This is hyperbole. (no pun)

"Comet C/2013 A1 may fly past at a very safe distance of 0.008 AU (650,000 miles)," O'Neill wrote, "but to the other extreme, its orbital pass could put Mars directly in its path.

There is a more recent post from Leonid Elenin with updated data: http://spaceobs.org/en/tag/c2013-a1-siding-spring/

"the comet might pass just 41,000 km [...] from the planet’s centre [...] 100% certainty that the planet will pass through the gaseous envelope of the comet [...] will be subject to intensive bombardments by microparticles which, among other things, might cause malfunction of the space probes currently there."

Setting off a volcanic eruption, instantly oxygenating mars, saving Arnold Schwarzenegger

50 kilometers ... hmm ... how big must a stray celestial body bee to severely disturb the longterm stability of the solar system?

Assuming Mars and the comet are perfectly round and have the same density, this comet will change the speed of Mars by about 0.004 feet per year, or about a quadrillionth of it's current speed. A body large enough and fast enough to destabilize a planets orbit (in the short term) would have a pretty good chance of breaking the planet into pieces.

Of planeraty size and mass.

anything bigger than bumble.

Or how fast.

The obvious question: will Curiosity see it? If so, it should be able to get some AMAZING footage!

If Curiosity sees it, Curiosity's shortly to be in a whole world of hurt.

poor robot :(

Curiosity's dash cam? Better be playing house music.

Yes, if Curiosity can withstand the shockwave and other results of the impact, that is.

Wouldn't this be helping us terraform Mars faster? I think a lot of CO2 is trapped in ice on Mars, and we'd need that to make (presumably genetically enhanced) plants live there. A body that large hitting Mars could help raise its temperature.

It would also dig a deep crater. Depending on the depth of the hole, the atmosphere may be dense enough at the bottom that you wouldn't need anything more than an oxygen mask and a heavy coat to walk around outside. Some have proposed intentionally diverting comets into Mars to Terraform it, as they would add water and create craters which could be used as oases.

The atmosphere isn't dense enough for a crater to sustain that type of atmospheric density... yet...

It depends on the depth of a crater. A 15-20 mile deep crater would get you to Mt. Everest levels of density. Of course, that kind of a crater would require a direct impact from an object of this size, not a glancing impact.

It would probably throw up enough dust into orbit to prevent anything landing for the next 1000 years :(

The atmosphere is a little to thin to keep dust around for vary long.

I said orbit.

You can't throw a thing into orbit. Its trajectory will include the point where thrown.

I had to think about this, but much of the dust will not shoot straight up like a column (with no tangential component), but will be shot sideways, conceivably with enough initial momentum to attain orbital speeds (which are lower on Mars than Earth), with less drag to hinder.

Don't know if it would be 1000 years, but I'd guess it would coalesce into a ring like structure over time anyway.

Given one single impulse from the surface, you will either land back on the planet; or, with enough force, totally escape the planet (called a hyperbolic orbit, I think, which doesn't actually orbit).

Even amazing plans to build railguns on mountains to launch things to space requires some kind of secondary thrust to change into a new orbit that won't land back on the planet.

A small but finite amount of dust could fall in the range of initially traveling at escape velocity but then slowed to orbital velocity by the scant atmospheric drag. But definitely not 1000 years of opaque orbital debris.

Anyway, I would think atmospheric dust storms as the post-impact pressure wave cycles around the plant would make Mars more messy in the hypothetical aftermath than any orbital debris.

The Moon begs to differ.

The moon did not show up in earth after a collision, it destroyed the plant that was there, and then the earth and moon formed from the debris cloud.

Anyway, orbital mechanics are complex, Mars has 2 moons and the sun plus the solar wind all of which clean up it's orbit which is why it's so clear in the first place. However, it would be possible for Mars to collect this as another Moon which would be vary cool. Or worst case it collides with one of the existing moons and then you get a lot of junk in orbit.

Worst case it hit's one of the existing moons and you end up with a lot of crap in orbit. You would still be able to land easily, it would just make keeping satellites alive for long periods much harder, and significantly increase the amount of dangerous meteors that hit mars.

However, if it hits the planet your home free.

If it does infact hit, will there be enough time b/w impact and shock wave for curiosity to upload a high def video of the asteroid entreating the atmosphere to a satellite if it is in it's vicinity?

No. These things are pretty much store-and-forward. IF the timing is just right, Curiosity could transmit direct line-of-sight to Earth, but we're talking very low data rates.

Can anyone calculate how much this impact might heat up Mars? (I've heard even a little heating might set off a chain reaction and substantially increase the temperature?)

Over the long term, zero. The instantaneous hit is dominated by the still much larger amount of energy continuously entering Mars from the sun and leaving due to thermodynamics.

When we talk about impacts changing climate on Earth, it has nothing to do with the instantaneous heat increase itself. It has to do with how the impact can change the rate at which Earth receives and retains heat, by changing the atmosphere. And Mars hasn't got very much atmosphere to change, so even that isn't much of a factor.

But I'm thinking if it hits a pole it could release CO2 and permanently affect the temperature.

It's still unlikely. The universe tends to be stable, because if an impact could heat up Mars, it would have, over cosmological time. This is not Mars' first impact.

Our Earth intuitions are really wrong for dealing with the rest of the universe. The rest of the (known) universe doesn't have intelligent critters on it making active and wild changes in very short periods of cosmological time. The universe is generally full of stable systems, in the physics sense of the term "stable". To the extent that you think otherwise, it's because we humans are interested in the unstable bits and they get a lot of play in the press, but we know and talk about them because they are the exceptions.

Transients on this scale, however, could last hundreds of years. Even on Mars, CO2 takes a while to escape from the atmosphere; on human time scales we'd see a new metastable Martian temperature.

(Assuming a bunch of CO2 actually were dumped into the atmosphere, that is.)

Is there any info on how this would affect the rovers?

Depends where it hit, but it stands a good chance of destroying the rovers.

A direct hit doesn't seem to be all that probable, but Mars is still likely to pass within the comet's coma and be pelted by debris [1].

[1] http://www.slate.com/blogs/bad_astronomy/2013/02/28/mars_imp...

I would think that an impact of mars by this body would delay any further plans of visiting mars for a while. The level of atmospheric dust would be... tremendous. I wonder if 'backsplash' of rocks and other material would pose a threat to the mars orbiters?

Mars' atmosphere is very thin compared to ours. I seriously doubt we could get there before the effect has cleared from the atmosphere. Even if we left right now.

If we left right now, we'd be there before the comet hit.

No we wouldn't. A practical journey to mars takes about 2 years. If you had enough energy you could get there faster, but I don't think we have any rockets powerful enough.

Hm. Interesting to observe, but will this throw a lot more crap into space that we then have to worry about in a few decades?

I assume it'll knacker any landers we have there as well through either seismic activity or dust penetration.

Not much, if any. Even what we'd consider a very large impact still almost instantaneously accelerates the target matter, so it has a velocity that is radial away from the impact point. That's not an orbit velocity. Mass will either fall back to Mars or escape entirely, but little to none of it will enter any sort of permanent orbit. Same reason why you can't just shoot something into orbit from Earth's surface with one instantaneous acceleration, and that getting into orbit is not merely a matter of standing on a very tall tower.

Truly enormous impacts can change the rules if thing hitting Mars is large enough to shift the center of mass of the whole system. The Moon is thought to have been formed from something the size of Mars or so hitting Earth a very long time ago. But even in our rather violent universe, that's the exception, not the rule, obviously.

Thanks for the detailed response :)

Read the title as 'Comet might hit in March 2014' followed by '50 km' and almost choked to death on my morning Espresso.

Watch this recent episode of Colbert, and his interview with Michio Kaku, where they talk about the recent asteroids, and also about the much larger one "grazing" Earth's atmosphere in 2029, and that "may" hit Earth in 2036 (depending on how much it grazes Earth's atmosphere in 2029). It starts at 15:30 or so:


Fortunately, it won't hit us in 2036 either.

"Preliminary observations by Goldstone radar in January 2013 have effectively ruled out the possibility of an Earth impact by Apophis in 2036." http://en.wikipedia.org/wiki/99942_Apophis

On the bright side, it could take care of the 32-bit time_t problem.

But not soon enough for the 32-bit unsigned NTP wraparound.

(It's funny how 32 bits is about 70 years more than 31 bits, and the "31-bit epoch" started 70 years after the "32-bit epoch.")

If it's about the asteroid Apophis, then the last I heard was that it won't be hitting earth (I can't see the video on that link for some reason, but the dates rang a bell).


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