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BAA electronic bulletin No. 00467 http://www.britastro.org/
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Mars Section: North polar cap
Mars comes to opposition tomorrow. It is to be hoped that the recent extreme
weather over the UK and Europe will not succeed in completely spoiling the
moment for everyone.
Just now, there is an especially interesting feature visible within the large
North polar cap, and observers should give it their attention. It is shown on
many images, but visual observers often miss it: an annular rift is observable
at all longitudes as a thin, dark line. When the seasonal carbon dioxide cap
has sublimed away, this feature (a permanent dune field) will mark the
boundary of the small cap remnant which persists throughout the summer. It is
also known as the polar collar, and its thickness varies with longitude. The
annular rift within the cap was well seen by Section members at the 1995
opposition, and it is also visible on amateur (and HST) images from other
oppositions during the 1990s decade. However, historical observations have
rarely shown it, suggesting that perhaps the thickness of the seasonal polar
deposit may vary slightly from year to year. Historical data are reviewed in
detail in our 1995 Section Report, which may be downloaded as a pdf file from
the Mars Section website (http://www.britastro.org/mars).
Observers are also reporting brighter parts of the cap near its southern
boundary: later on, irregularities and rifts will appear and portions of the
cap will become detached. The best-known and largest of the detached portions
is labelled Olympia on the telescopic maps. All of these details should be
carefully recorded, and the data sent to the undersigned.
Further notes about the current opposition will appear in the February number
of the BAA Journal.
Dr Richard McKim, Director, 2010 January 25
richardmckim@btinternet..com
======================================================================
BAA electronic bulletins service. E-mail: circadmin@britastro.org
Bulletin transmitted on Thu Jan 28 23:12:38 GMT 2010
(c) 2010 British Astronomical Association http://www.britastro.org/
======================================================================
BAA electronic bulletin No. 00467 http://www.britastro.org/
======================================================================
Mars Section: North polar cap
Mars comes to opposition tomorrow. It is to be hoped that the recent extreme
weather over the UK and Europe will not succeed in completely spoiling the
moment for everyone.
Just now, there is an especially interesting feature visible within the large
North polar cap, and observers should give it their attention. It is shown on
many images, but visual observers often miss it: an annular rift is observable
at all longitudes as a thin, dark line. When the seasonal carbon dioxide cap
has sublimed away, this feature (a permanent dune field) will mark the
boundary of the small cap remnant which persists throughout the summer. It is
also known as the polar collar, and its thickness varies with longitude. The
annular rift within the cap was well seen by Section members at the 1995
opposition, and it is also visible on amateur (and HST) images from other
oppositions during the 1990s decade. However, historical observations have
rarely shown it, suggesting that perhaps the thickness of the seasonal polar
deposit may vary slightly from year to year. Historical data are reviewed in
detail in our 1995 Section Report, which may be downloaded as a pdf file from
the Mars Section website (http://www.britastro.org/mars).
Observers are also reporting brighter parts of the cap near its southern
boundary: later on, irregularities and rifts will appear and portions of the
cap will become detached. The best-known and largest of the detached portions
is labelled Olympia on the telescopic maps. All of these details should be
carefully recorded, and the data sent to the undersigned.
Further notes about the current opposition will appear in the February number
of the BAA Journal.
Dr Richard McKim, Director, 2010 January 25
richardmckim@btinternet..com
======================================================================
BAA electronic bulletins service. E-mail: circadmin@britastro.org
Bulletin transmitted on Thu Jan 28 23:12:38 GMT 2010
(c) 2010 British Astronomical Association http://www.britastro.org/
======================================================================
--
Good Clear Skies
--
Astrocomet
--
Colin James Watling
--
Real Astronomer and head of the Comet section for LYRA (Lowestoft and Great Yarmouth Regional Astronomers) also head of K.A.G (Kessingland Astronomy Group) and Navigator (Astrogator) of the Stars (Fieldwork)
--
Web: http://lyra.freewebsites.com/
Good Clear Skies
--
Astrocomet
--
Colin James Watling
--
Real Astronomer and head of the Comet section for LYRA (Lowestoft and Great Yarmouth Regional Astronomers) also head of K.A.G (Kessingland Astronomy Group) and Navigator (Astrogator) of the Stars (Fieldwork)
--
Web: http://lyra.freewebsites.com/
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