[meteorite-list] Dwarf Planet 'Becoming A Comet' (2003 EL61)

From: E.P. Grondine <epgrondine_at_meteoritecentral.com>
Date: Mon, 19 Feb 2007 12:37:19 -0800 (PST)
Message-ID: <20070219203719.21421.qmail_at_web36914.mail.mud.yahoo.com>

Hi Sterling -

For a history of the effects in North, Central, and
South America of Earth's recent encounter with Comet
Encke, see my book "Man and Impact in the Americas".

The current thinking is that SW3 will sublimate into
dust, but I am not very sure about that. In the worst
 case, it appears to be no big hazard, with say only
5kt-15kt blasts in 2022, and Earth is a big planet.

good hunting,
Ed


--- "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
wrote:

> Hi,
>
> This speculation that 2003 EL61 could become an
> inner system Giant Comet is a very, very strange
> one.
> I find it extremely puzzling. But, if 2003 EL61 did,
> it
> would just be the capper on this strangest of all
> strange
> worlds in the solar system! I posted some
> information
> about EL61 last year if you're looking for more:
>
<http://www.mail-archive.com/meteorite-list at meteoritecentral.com/msg48060.html>
>
> Its dimensions are 1960 km one way, 1518 km the
> other,
> and 996 km through the axis of rotation. Hmm, can
> you
> picture that? Neither can I. So, here's a picture of
> the
> shape of 2003 EL61:
>
http://hepwww.physics.yale.edu/quest/sedna/2003_el61.html
>
> Now, if you spin something fast enough (and EL61
> spins
> in under 4 hours per dizzy) and it's stretchy, you
> end up with
> a shape like a squashed ball, or an oblate spheroid
> (or ellipsoid).
> But 2003 EL61 is not a squashed ball, round and
> flattened.
> No, it's much longer one way across than the other
> way across.
>
> Whatever 2003 EL61 is made of, it has to be
> stiff enough
> to hold this shape as it whirls around every 3.9154
> hours. That
> creates a huge amount of force. It has to be VERY
> stiff stuff.
> We can calculate just how stiff it has to be to hold
> on its
> elliptical midriff bulge while spinning, figure out
> its modulus of
> rigidity and then look to see what materials are
> that stiff. The
> answer is ROCK, rock of a high density. The
> estimates run from
> a density of 2.6 to 3.4 gm/cm^3. For comparison, our
> Moon
> has a density of about 3.3 gm/cm^3.
>
> The currently favored explanation for the rapid
> rotation is
> a giant impact. Likewise, the existence of two moons
> circling
> 2003 EL61 is attributed to a giant impact, like our
> Moon, like
> Pluto and Charon; it's the moon-maker of choice
> these days...
>
> 2003 EL61 is a very bright body, reflecting 70%
> of the
> light that falls on it, and it is indeed, as you
> would suspect
> from this brightness, covered with water ice. BUT,
> it's not
> old water ice, but new, freshly fallen crystalline
> ice,
> otherwise known on our planet as snow. Apparently,
> EL61
> is like Enceledus, the moon of Saturn, with water
> geysers
> which must be driven by internal heat.
>
> Now, we come to the Giant Comet Notion.
> Obviously,
> 2003 EL61's ice is a surface feature, a thin layer
> of volatiles
> over what is essentially a rocky body. So, how much
> material
> is there to be warmed by the Sun if EL61 got
> shuttled into the
> inner solar system?
>
> Let's compare it to Comet Hale/Bopp, which more
> people
> saw as a naked eye object than any recent comet
> (McNaught has
> been sneaky). Hale/Bopp was 40 kilometers across and
> we don't
> know how much of it was volatiles or how much of its
> surface
> was volatilized by the Sun, but certainly not more
> than a small
> percentage of the comet's bulk. If ALL of Hale/Bopp
> had been
> volatilized, it would have been a hundred times (or
> more) brighter
> and a thousand times more spectacular!
>
> If the water ice on the surface of 2003 EL61
> were a mile deep,
> it would have the volume of 136,460 Hale/Bopps! In
> fact, the
> top one foot of 2003 EL61's icy surface contains 2.6
> times the
> volume of Comet Hale/Bopp!
>
> Since it seems likely that the freshness of the
> surface ice on
> EL61 is because it is supplied by deep water
> geysers, there
> would seem to be some depth of ice on EL61. If it
> were 5 miles
> deep, the ice volume would be equivalent to the
> total volume of
> 682,300 Hale/Bopps. And if the layer were 20 miles
> deep, the
> ice volume would be the equivalent to the total
> volume of
> 2,729,200 Hale/Bopps!
>
> Incidentally, my Ice Unit, 1.0 Hale/Bopp Unit,
> is exactly
> 268,082.57 cubic kilometers, or 2.6808257 x 10^14
> cubic
> meters of ice, weighing 2.6808257 x 10^17
> kilograms!
> This amount of ice, One Hale/Bopp Unit, is 7.5 times
> the mass of ALL the interplanetary dust presently in
> the
> solar system, that which causes the visible
> reflection
> which we can see with our naked eye, the Zodiacal
> Light.
>
> The crucial question would be how deeply into
> the solar
> system a perturbed 2003 EL61 would travel in its
> new,
> perturbed orbit? If its perihelion were in Saturn
> Country,
> it would simply become the Big Cheese of the Centaur
> Group (of which there a 100 or so) and the Super
> Comet
> might show traces of coma in a telescope. If its
> perihelion
> were near to Jupiter (what an unstable orbit that
> would be!),
> it would be both bright and visually comet-like.
>
> If its perihelion were any closer, there is
> another factor
> to consider: Danger. Brown treats this (at least as
> quoted
> in this press story) as an almost "touristy" event:
> "When it
> becomes a comet, it will be the brightest we will
> ever see."
>
> But if its perihelion were INSIDE Jupiter's
> orbit, it would
> pass through (and thus perturb) the Asteroid Belt!
> Hey now!
> Wait a minute! Perturb the Asteroids? That doesn't
> sound
> so great. No, definitely not a Great Idea. Lively,
> but not prudent.
>
> Anybody have a lot of enthusiasm for a Rain of
> Ice and
> Iron like we haven't seem in Eons? No? I don't have
> much...
> That's not "a good thing" (to quote Martha Stewart).
> Having
> a planet-sized body traversing the Asteroid Belt can
> only
> spell Big Trouble.
>
> Well, what if it didn't pass through the
> Asteroid Belt?
> No way of knowing what the inclination of a
> perturbed
> 2003 EL61 would be, after all. What if its
> perihelion was
> closer in than the Asteroids?
>
> It certainly would have a vaster and more
> extensive coma
> then, wouldn't it? If it came in as far as Mars or
> even the Earth,
> it would be incredibly bright, visible both day and
> night, with
> a tail many millions of kilometers long, and a coma
> 10 or 20
> thousand kilometers across, perhaps 100,000
> kilometers
> across if it got warm enough. That certainly
> qualifies as a
> celestial "tourist event"!
>
> And if the perihelion were even closer to the
> Sun , the
> volume of material pouring off the new "comet" would
> be
> many millions of tons per second. The solar wind
> pushes
> against dispersed material, dust, gas, ice; that's
> what forms
> a comet's tail. But if the volume were great enough,
> the inner
> solar system would fill up with, and become clouded
> with,
> a fog of highly reflective particles, despite the
> best efforts of
> the solar wind.
>
> The Sun's light would be scattered, diffused and
> dispersed.
> The skies would be brighter at night and dimmer in
> the daytime.
> Eventually, they would look the same both night and
> day as
> the volume of cometary "fog" increased. There would
> be no
> more night. The amount of solar energy reaching the
> inner
> planets would be drastically reduced.
>
> The situation would be exactly like passing
> through a GMC
> (Giant Molecular Complex) or interstellar cloud,
> only much worse.
> This amount of volatiles released in the inner solar
> system would
> "cocoon" the Sun in a gas and dust envelope.
>
> If the Earth's solar input dropped by 1%, the
> planet's mean
> temperature would drop by less than 1 degree C. No
> problemo!
> We'd get rid of that pesky Global Warming, you know.
>
> A mere 10% decrease would lower the planetary
> temperature
> by 7 degrees C. That's not so pleasant. That's less
> than what
> the global temperature was during the last Ice Age
> (6 degrees
> cooler). We don't want the Ice Age back, do we? No,
> I don't
> think so...
>
> A 20% decrease would lower the planetary
> temperature by 15
> degrees C! You might be saying that a 15 degree drop
> doesn't
> sound all that bad, but we're talking about the
> planetary mean
> temperature. It hasn't been that low in the entire
> geological history
> of the Earth, including the era when there was sea
> ice at the equator!
> At this temperature, the entire planet would be
> covered by ice
> from Pole to Pole, frozen solid!
>
> That's from a 20% decrease, but the gas
> production of a truly
> planet-sized "comet" could easily produce a 30% to
> 50% reduction
> in solar incidence, which would drop mean
> temperatures by up
> to 50 degrees C. The equatorial temperature of the
> Earth would be
> about what the temperature of Antarctica is now.
> Mars would fall
> to the temperature range of Saturn (or Pluto). Even
> Venus, the solar
> system's Hellball, could become too cool for
> comfort. Everything
> from the Asteroids on out would be at the
> temperature the Kuiper
> Belt is now.
>
> So, you see, it's not exactly a tourist bonanza
> nor a celestial
> event to be anticipated with bouncy enthusiasm. No,
> this is not
> good at all. This is worse than being bombarded with
> big asteroidal
> impactors and other assorted cosmic disasters. It
> would not only
> make our own planet uninhabitable, but also all the
> other worlds
> where we might conceivably, with herculean effort,
> attempt to take
> refuge, mucking up the entire solar system. (You got
> any relatives
> at Alpha Centauri?) Actually, there's a name for
> this sort of event...
>
> I believe it's called The End of The World.
>
> So, I have to ask myself: how likely is this? Is
> this going to
> happen? Ever?
>
> > Brown has calculated that the object could be due
> [for] a close
> > encounter with the planet Neptune. If so,
> Neptune's gravity could
> > catapult it into the inner Solar System as a
> short-period comet.
>
> The likelihood of any "close encounter"
> repeating itself
> is easy to calculate. Suppose two bodies with
> orbital periods
> of 2 and 3 years respectively have a "close
> encounter." Two
> years later, when the first body has returned, the
> slower body
> is still a year away from the potential encounter
> point. Wait
> another two years (four years total); the slower
> body is now
> a year past the encounter point. Only after six
> years will the
> encounter repeat. That is the product of the two
> orbital
> periods ( 2 times 3 = 6 ) and is the time between
> encounters,
> or indeed any specific configuration of the two
> orbits.
>
> 2003 EL61's period of 284.5 years times
> Neptune's period
> of 164.88 years is 46,900.36 years. That means that
> the two
> had an encounter like what is proposed 46,900 years
> before, and
> another such close encounter 46,900 years before
> that, and...
> Well, 21+ such encounters every million years. Since
> the very
> beginning of the solar system, they've had almost
> 96,000 such
> encounters, and in exactly NONE of them has 2003
> EL61 gone
> off to visit the inner solar system, not even once.
>
> How likely is it that next close encounter will
> have that
> result? Or even the next 100 close encounters? How
> has EL61
> managed to hang onto its moons through all these
> "close"
> encounters? Why, after the solar system has held
> together
> for more than four billion years, should it decide
> to unravel
> right now? Is the solar system just coming apart?
>
> On the other hand, there's this: we explain 2003
> EL61's
> extraordinary shape and fantastic spin to a Major
> Collision
> with Something. We also assume it happened in the
> far distant
> past, early in the history of the solar system
> (mostly because
> it was more crowded then and also because we don't
> want
> to think it could happen now). What if the body that
> "collided"
> with 2003 EL61 was a moon of Neptune? What if the
> collision
> was "recent," meaning "only" half a billion years
> ago (or less)
> and that the collision altered EL61's orbit to make
> a too-close
> encounter and a voyage to the inner solar system
> possible?
>
> Now, there's a nasty thought...
>
> Which is why, instead of a news snippet with
> three sentences
> of potential information, there ought to be an
> actual publication,
> however informal, with, you know, real numbers and
> real
> calculations and real information. To modify a great
> movie line:
> Show me the numbers!
>
> Since EL61 has only been observed for 2-3 years
> of its 285
> year orbit (1%) and the earliest prediscovery photo
> is 1955 (18%
> of an orbit ago), just how accurate are those
> orbital determinations
> and the resultant calculations? Inquiring minds want
> to know...
>
> My considered scientific opinion?
>
> 'Tain't happenin', dude!
>
>
> Sterling K. Webb
>
-------------------------------------------------------------------------------------------
> ----- Original Message -----
> From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
> To: "Meteorite Mailing List"
> <meteorite-list at meteoritecentral.com>
> Sent: Wednesday, January 17, 2007 11:32 AM
> Subject: [meteorite-list] Dwarf Planet 'Becoming A
> Comet' (2003 EL61)
>
>
http://news.bbc.co.uk/2/hi/science/nature/6268799.stm
>
> Dwarf planet 'becoming a comet'
> By Paul Rincon
> BBC News
> January 17, 2007
>
> An unusual dwarf planet discovered in the outer
> Solar System could be en
> route to becoming the brightest comet ever known.
>
> 2003 EL61 is a large, dense, rugby-ball-shaped hunk
> of rock with a fast
> rotation rate.
>
> Professor Mike Brown has calculated that the object
> could be due a close
> encounter with the planet Neptune.
>
> If so, Neptune's gravity could catapult it into the
> inner Solar System
> as a short-period comet.
>
> "If you came back in two million years, EL61 could
> well be a comet,"
> said Professor Brown, from the California Institute
> of Technology
> (Caltech) in Pasadena.
>
> "When it becomes a comet, it will be the brightest
> we will ever see."
>
> Cosmic oddball
>
> 2003 EL61 is a large object; it is as big as Pluto
> along its longest
> dimension. It is one of the largest of a swarm of
> icy objects that
> inhabit a region of the outer Solar System known as
> the Kuiper Belt.
>
> But it is extremely unusual: spinning on its axis
> every four hours, it
> has developed an elongated shape.
>
> 2003 EL61 is apparently composed of rock with just a
> thin veneer of
> water-ice covering its surface. Other Kuiper Belt
> Objects (KBOs) contain
> much more water-ice.
>
> Professor Brown's computer simulations show that the
> object is on a very
> unstable orbit and set for a close encounter with
> Neptune.
>
> The eighth planet's gravitational force could either
> sling the icy rock
> ball into the inner Solar System as a comet, out
> into the distant Oort
> Cloud region, or even into interstellar space.
>
> Orbits of Kuiper Belt Objects tend to be very
> stable, but the region is
> thought to be a reservoir for short-period comets.
>
> Occasionally, some of these objects must get tossed
> inward to become the
> fizzing lumps of ice and dust that criss-cross our
> cosmic neighbourhood.
>
> Shedding surface
>
> Mike Brown and his colleagues have come up with a
> scenario to explain
> 2003 EL61's physical characteristics and behaviour.
>
> About 4.5 billion years ago, the object that became
> 2003 EL61 was a
> ball, half composed of ice and half of rock - like
> Pluto - and about the
> same size as Pluto.
>
> Some time early in its history, it was smacked, edge
> on, by another
> large KBO. This broke off much of 2003 EL61's icy
> mantle, which
> coalesced to form several satellites.
>
> As expected, the satellites seem to be composed of
> very pure water-ice.
>
> Professor Brown suggested that some of 2003 EL61's
> mantle may already
> have made it into the inner Solar System as cometary
> material.
>
> The oblique impact also caused 2003 EL61 to spin
> rapidly. This rapid
> rotation elongated 2003 EL61 into the rugby ball
> shape we see today.
>
> "It's a bit like the story of Mercury," Professor
> Brown explained.
>
> "Mercury got hit by a large object early in the
> Solar System. It left
> mostly a big iron core, with a little bit of rock on
> the outside. This
> is mostly a rock core with a little bit of ice on
> the outside."
>
> Mike Brown outlined details of his work during a
> plenary lecture at the
> recent American Astronomical Society meeting in
> Seattle.
>
>
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Received on Mon 19 Feb 2007 03:37:19 PM PST