

Comet might hit Mars in 2014 - wsieroci
http://science.nbcnews.com/_news/2013/02/26/17107085-comet-just-might-hit-mars-in-2014

======
btilly
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.)

~~~
jessriedel
>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.

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

------
davidjohnstone
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>

~~~
tomjen3
Massive doesn't even come close. [http://www.truthistreason.net/ground-zero-
ii-interactive-nuc...](http://www.truthistreason.net/ground-zero-ii-
interactive-nuclear-blast-calculator-and-fallout-map) 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.

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

~~~
kamaal
>>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.

~~~
carleverett
"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.

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

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

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

~~~
eru
You can look it up in most countries.

------
tocomment
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.

<http://en.wikipedia.org/wiki/Hellas_Planitia>

~~~
tocomment
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?

~~~
Shivetya
There is an interesting bit from NASA here that covers your concerns,
[http://science.nasa.gov/science-news/science-at-
nasa/2004/25...](http://science.nasa.gov/science-news/science-at-
nasa/2004/25feb_greenhouses/)

------
uvdiv
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._

------
blaze33
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."

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

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

~~~
30thElement
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.

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

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

~~~
n3rdy
poor robot :(

------
mtgx
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.

~~~
Zuph
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.

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

~~~
Zuph
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.

------
Achshar
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?

~~~
maaku
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.

------
tocomment
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?)

~~~
jerf
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.

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

~~~
jerf
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.

~~~
scarmig
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.)

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

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

------
Thrymr
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...](http://www.slate.com/blogs/bad_astronomy/2013/02/28/mars_impact_the_red_planet_may_get_hit_by_a_comet_in_october_2014.html)

------
pixl97
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?

~~~
jerf
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.

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

~~~
ars
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.

------
meaty
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.

~~~
jerf
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.

~~~
meaty
Thanks for the detailed response :)

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

------
mtgx
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:

[http://www.colbertnation.com/full-episodes/tue-
february-26-2...](http://www.colbertnation.com/full-episodes/tue-
february-26-2013-dr--michio-kaku)

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

~~~
danielweber
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.")

