[meteorite-list] Pluto May Have Comet-Like Tail

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri, 22 Apr 2011 22:51:42 -0500
Message-ID: <9E8060C0A17E492688123590BA8F3611_at_ATARIENGINE2>

Dear List,

Quoting from the PDF of the paper:
http://arxiv.org/PS_cache/arxiv/pdf/1104/1104.3014v1.pdf
    "The CO layer estimated to extend out
to ~4 R[adii of Pluto] is thus inside this flow
zone and can be expected to be stable.
Strobel (2008) models a slower hydrodynamic
outflow inside this region, but predicted
speeds only exceed our 0.04 km/s velocity
resolution above 4500 km, so effects on
the spectrum would be negligible. It is however
possible that the marginal CO line red-shift,
if real, could indicate a flow forming into
a comet-like tail directed away from the Sun."

So, the "comet-like" tail is one POSSIBLE
explanation of a SUGGESTED marginal red-shift
that MIGHT even be real. I suppose one highlights
that hypothesized but undemonstrated possibility
at the strongest point of the conclusion of the paper
because you know that's the one thing journalists
will run with and splash like ten-year-olds given
spray cans of red paint.

What does the paper (and the observation) actually
say? That the exosphere of Pluto expands in response
to solar conditions, changing on size and temperature
as it does so. The exosphere of the Earth's atmosphere
does too. And if there is a bit of an "anti-solar tail"
effect, perhaps one should remember that the same
is true of the boundaries of the Earth's exosphere as
well.

But that so boring in comparison to the opportunity
to tie the word "comet" to Pluto and appeal to assorted
prejudices of viewpoint. Forget that the paper says
the extended exosphere "can be expected to be stable,"
meaning it does NOT flow away like a comet's tail.
Obviously, if the atmosphere was lost in this manner
over the last four billion years, there wouldn't be ANY
atmosphere left to detect.

Congratulations, Greaves, Helling & Friberg, you have
accomplished the modern goal of Science -- you made
the tabloids!


Sterling K. Webb
--------------------------------------------------------------------------
----- Original Message -----
From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
Sent: Friday, April 22, 2011 3:24 PM
Subject: [meteorite-list] Pluto May Have Comet-Like Tail



http://www.technologyreview.com/blog/arxiv/26667/?ref=rss

Pluto May Have Comet-Like Tail
The Physics arXiv Blog
April 20, 2011

The latest measurements of Pluto's tenuous atmosphere indicate that it
may be shaped into a comet-like tail, say astronomers

Pluto's has a highly elliptical orbit that takes it inside the orbit of
Neptune and then out into the distant icy reaches of the Solar System.

Astronomers have long believed that this would have important effects on
the dwarf planet's atmosphere. Their models indicate that Pluto's
atmosphere is likely to swell as it moves closer to the Sun and the
poles sublimate. Later, the atmosphere should condense as it cools down.

That should make the surface of Pluto a barren windswept land that
constantly changes as it is battered by supersonic winds. Indeed, Hubble
images show that Pluto's surface has a number of interesting features
that seem to be changing.

In recent years, other evidence has emerged to back up suspicions that
Pluto is more complex than astronomers initially imagined.

Today, Jan Greaves at the University of St Andrews in Scotland and a
couple of buddies reveal the details of their own study of Pluto's
atmosphere using the 15 meter James Clerk Maxwell Telescope in Hawaii.

These guys find clear evidence of gaseous carbon dioxide at altitudes of
up to four times Pluto's radius. And they say there is significantly
more of the stuff than the last time CO was detected in 2000.

That's strange. Pluto is currently moving away from the Sun after its
closest approach in 1989 and ought to be cooling down. One explanation
is that the south pole has recently come out of shadow for the first
time in 120 years and for a short time may be evaporating more quickly
than the north pole is condensing.

But Greaves and co's most interesting discovery is a small red shift in
the CO spectrum indicating that Pluto's atmosphere must be moving away
from Earth in an unexpected way.

Their tentative explanation is exciting: "The marginal CO line
red-shift, if real, could indicate a ??,ow forming into a comet-like
tail
directed away from the Sun," they say.

The thinking is that the expanding atmosphere is interacting with the
solar wind and being shaped into a tail.

That could throw the cat among the pigeons next time Pluto's status as a
planet comes up for discussion. It gives ammunition to the naysayers who
can now claim that far from being a planet or even a dwarf planet, Pluto
is merely a giant comet.

Astronomers will find out more in the coming years. The world's
telescopes will be increasingly trained on Pluto as the arrival of the
New Horizons mission draws near. Its flyby is scheduled for 2105.

Ref: arxiv.org/abs/1104.3014 <http://arxiv.org/abs/1104.3014>: Discovery
Of Carbon Monoxide In The Upper Atmosphere Of Pluto
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Received on Fri 22 Apr 2011 11:51:42 PM PDT