On Thu, 01 Nov 2007 17:57:24 GMT, "ThomA" wrote:

Being between the orbits of Mars and Jupiter and heading away, it's freaky
that Holmes is that volatile. The
solar flux at that distance is such that you have to wonder about this
unique comet.

It is interesting, but actually a body at 2 AU from the Sun (the
perihelion distance of this comet) can experience significant heating.
Depending on its emissivity (which is unknown), temperatures can easily
get much higher than the boiling point for many compounds known to exist
in comets (some of which show up in spectra for this one). Assuming a
dark crust- probably common in comets- and a porous makeup- probably
common as well- it would take months for the heat to soak meters down
into the nucleus and encounter older, more volatile material.

At its current distance from the Sun of 2.5 AU, it is still perfectly
capable of absorbing enough energy to vaporize many common compounds if
they were suddenly exposed at the surface by a shift of material (comet
quake) or a low energy collision with co-orbital material.

Nobody knows for sure what precipitated this release of material but any
of the above are reasonable possibilities. The precipitating event is
apparently unusual, but the large release of volatiles isn't that odd.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com