List, Greg, Richard,
The study Fox News is citing may be a new
one or it may be this one from a year ago,
(one author of which is Sansaturio), which
is downloadable at:
http://arxiv.org/abs/0901.3631
101955 1999 RQ36 has a poorly determined
composition and shape. It has been frequently
considered for an asteroidal mission (including
Osiris) as it is very easy to reach (low delta-v).
We could go kick its tires...
As of observations through 2006, the odds of
a 2182 impact are rated at 3570-to-1:
http://neo.jpl.nasa.gov/risk/a101955.html
While I am no defender of Fox News, please note
that somebody, presumably Sansaturio, got
FOX NEWS of all people, to not only mention
but correctly define the Yarkovski Effect!
The end of the world may indeed be near...
Usually a change in odds means only that the
ellipse of uncertainty has necessarily become
larger. Paradoxically, while the odds of an impact
go up, so does the uncertainty of any particular
outcome.
It's not a party we'd want to miss the invitation
to, as the impact energy is 2700 Megatons. As for
waiting until the probability is 100%, Richard, you
have to realize that to many people that means
waiting until it's a week away. That's not the
message we want to send, is it? (Keep that
funding coming.)
NASA put 1999 RQ36 on the Sentry Risk page
at #2, trailing long time favorite 1950DA: "The
second object, (101955) 1999 RQ36, currently
has non-zero impact probabilities on numerous
occasions during the years after 2165. This is
analyzed in a paper published by Milani et al.
(Icarus, Vol. 203, pp. 460-471, 2009), which is
available as here..." But that link is broken.
Maybe it's at No. 2 with a bullet...
As for cumulative probabilities, nothing in
this kind of orbit persists for more than a few
million years, maybe ten million years, so the
probability that it hits either the planet whose
orbit it crosses or, less likely, an object in a
similar orbit is, in the long term, always 100%.
We, however, are just going to hope that the
folks up in 2150 have a better handle on it
than we do, aren't we? (I include an exception
to this last crack for Rob Matson and you,
of course.)
As for me, much as I'd like to, I do not think
it's time to dig out that old DVD of "Armageddon"
or order enough beer for the Impact Party.
Sterling K. Webb
-----------------------------------------------------------------
----- Original Message -----
From: "Richard Kowalski" <[email protected]>
To: "Meteorite List" <[email protected]>
Sent: Wednesday, July 28, 2010 5:51 PM
Subject: Re: [meteorite-list] Scientist Warns Massive Asteroid Could Hit
Earth in 2182
Wow what a sham(e).
A friend asked me about this earlier today but he cited a British rag.
I told him that the British tabloids still report this
sensationalistic crap every so often but the media in the US has
figured out to ignore it. Well at least most of them have.
A quick explanation:
When we observe an asteroid, there is some uncertainty in our
observations so while we get a good handle on the orbit, the orbit
isn't exactly known to a precise amount. As such, there are often a
number of similar orbits that satisfy the set of observations of the
object we have on hand.
There are scientists at JPL and elsewhere who's job it is to determine
which NEOs will come close to the Earth. During their calculations
they run all the possible orbits that satisfy the observations and
determine which objects have possible orbits that intersect the Earth,
when the Earth is at that intersection. These objects that have such a
possible orbit are then referred to as "Virtual Impactors" or VI for
short. The way we reduce this uncertainty of the orbits for a given
object is to re-observe it over time. As we continue to obtain
additional observations the number of possible orbits that satisfy all
of the observations gets smaller until we come to an orbital solution
that is most likely the one that the object actually is in.
When an object has been determined to be a VI that alerts
observatories around the world to obtain additional observations of
this object.
NASA & JPL have a page on the NEO Program website (
http://neo.jpl.nasa.gov/ ) that is updated daily as new observations
come in and get folded into the dataset. It is the Impact Risk page
at: http://neo.jpl.nasa.gov/risk/
If you visit the page you'll see information on the object in
question, but you'll also note that there are other objects that are
also of interest, Watch it every day and you'll see "impact
probabilities" for any given object rise and fall, with new ones
appearing as they are discovered and others dropping off the list
entirely as more observations come in and the orbits become more
refined.
My advice is unless you hear of a 100% chance of impact, ignore the
story. The media is just wasting your time by making a story out of
something that is not news... But then again that does seem to be the
business they are actually in now, isn't it?
--
Richard Kowalski
Catalina Sky Survey
Lunar and Planetary Laboratory
University of Arizona
http://www.lpl.arizona.edu/css/
--- On Wed, 7/28/10, Thunder Stone <[email protected]> wrote:
> From: Thunder Stone <[email protected]>
> Subject: [meteorite-list] Scientist Warns Massive Asteroid Could Hit
> Earth in
2182
> To: [email protected]
> Date: Wednesday, July 28, 2010, 3:23 PM
>
> Wow - that's only 72 years from now... Don't think I'll be
> around
>
> Greg S.
>
>
>
http://www.foxnews.com/scitech/2010/07/28/massive-asteroid-hit-earth-warn-scientists/?test=faces
>
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