Doesn't Pluto have an atmosphere?

"JackPeters" wrote in message
...
I was under the impression that Pluto has a tenuous atmosphere. At
least, I remember back in the 90s when it was inside the orbit of
Neptune, there were Hubble photos of apparent cloud patterns. I
believe the explanation was it was an atmosphere primarily of
sublimation and not in equilibrium as Pluto does not have enough
gravity to sustain it.

It just seems logical to me that a "planet" should have an atmosphere.

1) Round by self-gravity
2) In orbit around the sun
3) Maintains an atmosphere

That would give us nine planets. Perhaps a few more KBOs would
qualify eventually?

But that would probably exclude Mercury
http://sci.esa.int/science-e/www/obj...objectid=31275 as none of
its atmospheric components are 'trapped' as such by its gravity.

Mercury does have a slight Atmosphere composed of helium.

"Ed" wrote in message
ups.com...

Mercury does have a slight Atmosphere composed of helium.


The 'atmosphere' of Mercury is almost entirely a short term effect from
outgassing from surface rocks. I had a quick browse online and read
somewhere that it is so tenuous that the constituents of the atmosphere are
more likely to collide with the surface than other atoms, i.e. most
atomic/molecular paths are ballistic rather than 'random walk'.

A general description of atmospheres would include a requirement that one be
significantly held by the parent planet - but this is not the case for
Mercury. Were it not for outgassing there would not be an atmosphere.

Owen

On Fri, 25 Aug 2006 19:50:15 +0100, "OG"
wrote:


"JackPeters" wrote in message
.. .

It just seems logical to me that a "planet" should have an atmosphere.

1) Round by self-gravity
2) In orbit around the sun
3) Maintains an atmosphere

That would give us nine planets. Perhaps a few more KBOs would
qualify eventually?

Since the demands of #3 are greater than #1, #1 could be dropped.

a few more KBOs? That is the problem they have already discovered
over 1000 KBOs and 783 of those have known orbits in the Kuiper Belt.
If every Pluto sized object was included as a planet WE WOULD HAVE 53
PLANETS AND CLIMBING. Do we want to include those 44 Plutos + 1
asteroid (Ceres) in the same league as the 8 Major Planets?

But that would probably exclude Mercury
http://sci.esa.int/science-e/www/obj...objectid=31275 as none of
its atmospheric components are 'trapped' as such by its gravity.

Mercury is big enough to have an atmosphere but impacting high-energy
photons and ions from the Sun stripped it away.

I guess is some ways the solar system is kind of like house values:
location, location, location. And I don't want 44+ Plutos to de-value
the other 8 (Major Planets). Dwarf Planets is a good title for them.

Pluto isn't even the largest Dwarf: Xena is.

-- Kevin Heider

West Coast Swing Photos at:
http://www.pbase.com/kheider

Kevin Heider wrote:
On Fri, 25 Aug 2006 19:50:15 +0100, "OG"
wrote:
snip

Do we want to include those 44 Plutos + 1
asteroid (Ceres) in the same league as the 8 Major Planets?

snip

Frankly, I don't care. I don't really care what they call them. They
are there regardless of what we think of them or name them. The whole
idea of "planet" is a cultural concept. What there are are thousands
of bodies of various sizes and compositions in orbit around the sun,
and they are all worthy of study.

This whole fiasco is a tempest in a teapot.

wrote:

Frankly, I don't care. I don't really care what they call them. They
are there regardless of what we think of them or name them. The whole
idea of "planet" is a cultural concept. What there are are thousands
of bodies of various sizes and compositions in orbit around the sun,
and they are all worthy of study.

This whole fiasco is a tempest in a teapot.

Yes, but that's the primary activity of "pure" science: to discern
differences and then categorize and name things.

Ed T

ED T wrote:
Yes, but that's the primary activity of "pure" science: to discern
differences and then categorize and name things.

No--that is not the primary activity of science. (I don't know what
the term "pure" means in this context--do you mean exclusive of, say,
engineering?) The purpose of science is to find patterns in natural
phenomena, and to relate them to other natural phenomena.

We often call this latter activity "explaining," but in this context it
means something just a little different from what it means in casual
use. In particular, it excludes explanations of the "Just So" variety.
Such a "Just So" statement might be made, but it is not a categorical
statement of truth, rather an admission that we really don't understand
why things seem to act the way they do.

This whole business of categorizing and naming things is only an
ancillary purpose of science, being useful only to the extent that it
facilitates talking about the objects of study.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html

Brian Tung wrote:
ED T wrote:
Yes, but that's the primary activity of "pure" science: to discern
differences and then categorize and name things.

No--that is not the primary activity of science. (I don't know what
the term "pure" means in this context--do you mean exclusive of, say,
engineering?) The purpose of science is to find patterns in natural
phenomena, and to relate them to other natural phenomena.

We often call this latter activity "explaining," but in this context it
means something just a little different from what it means in casual
use. In particular, it excludes explanations of the "Just So" variety.
Such a "Just So" statement might be made, but it is not a categorical
statement of truth, rather an admission that we really don't understand
why things seem to act the way they do.

This whole business of categorizing and naming things is only an
ancillary purpose of science, being useful only to the extent that it
facilitates talking about the objects of study.



No--that is not the primary activity of science. (I don't know what
the term "pure" means in this context--do you mean exclusive of, say,
engineering?)

Yes, I was trying to exclude "applied" science, "technology", etc.

This whole business of categorizing and naming things is only an
ancillary purpose of science, being useful only to the extent that it
facilitates talking about the objects of study.

I wouldn't reduce science to "cataloging" but in practice there is a
great deal of it required to move to the next step. While it is not the
primary purpose of science, I'm not sure it isn't the primary activity.

Ed T.

ED T wrote:
I wouldn't reduce science to "cataloging" but in practice there is a
great deal of it required to move to the next step. While it is not the
primary purpose of science, I'm not sure it isn't the primary activity.

For a wide variety of fields, I am sure it isn't.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html

In article , Brian Tung wrote:

ED T wrote:
Yes, but that's the primary activity of "pure" science: to discern
differences and then categorize and name things.

No--that is not the primary activity of science. (I don't know what
the term "pure" means in this context--do you mean exclusive of, say,
engineering?)

No - science (pure as well as applied science) is finding out patterns
in natural phenomena - engineering is using these known patterns for
some useful purpose.

The purpose of science is to find patterns in natural phenomena, and
to relate them to other natural phenomena.

Yep!

Pure science: finding these patterns just for getting to know them - no
matter if knowledge of these patterns serves any useful purpose or not.

Applied science: Explicitly focusing on finding patterns which are
useful for some purpose.

Applied science is typically funded by private companies which hope
to be able to commercially exploit the findings in some product.
Pure science is typically funded publicly.


We often call this latter activity "explaining," but in this context it
means something just a little different from what it means in casual
use. In particular, it excludes explanations of the "Just So" variety.
Such a "Just So" statement might be made, but it is not a categorical
statement of truth, rather an admission that we really don't understand
why things seem to act the way they do.

This whole business of categorizing and naming things is only an
ancillary purpose of science, being useful only to the extent that it
facilitates talking about the objects of study.

In some sciences the categorizing and naming is quite fundamental. What
would e.g. botany and zoology be, if we hadn't categorized and named
the plants and the animals?

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
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