On Topic Wednesday: The Snows of 2003 UB 313

From astronomer Mike Brown's webpage:

http://www.gps.caltech.edu/~mbrown/planetlila/

"When we initially guessed how big [2003 UB 313] was, we thought
it was likely a bit larger, because we guessed that it probably reflected
the same amount of sunlight as Pluto (about 60%). But this new size
measurement tells us that the planet reflects considerably more sunlight
than Pluto (86 +/- 7%)!. For more on this see below on what the planet
is made out of."

2003 UB 313 (which I will refer to by its unofficial placeholder
name, Xena) is the large Kuiper Belt Object that may or may not be the
10th planet, depending on the definition of "planet".

An albedo (the amount of light reflected by the planet) of
between 93 and 79 percent is remarkably high: Pluto's is about 60
percent and the Moon's is about 12 percent (about the same as
coal, as I recall). In fact, the only other known body with a similar
colour and albedo is Enceladus, which is covered in freshly fallen
snow.

Brown mentions the peculiar activity of Enceladus but rejects
the idea of Xena being an active body because there seems to be no
source of energy for that on Xena. Instead, he proposes that the
solution can be found in Xena's orbit, which takes that world from
about 38 AU out to about 100 AU. Accordingly, the amount of light it
gets from the Sun varies by a factor of around ten and the temperature
varies by the fourth root of ten, ignoring other factors. This may
be enough that an atmosphere composed of methane (which has been
detected on the surface) could cycle between its solid and gaseous
forms, depending on where the world is in its orbit.

Which gets us to this post's topic: Extreme Climates

Earth enjoys a relatively stable climate: only a small
fraction of the atmosphere (mainly water and sometimes CO2)
cycles between solid and gas state and the giant repositories of
materials like water and methane don't often give up their
stores in a tremendous burst. Rather oddly, we seem to be
well adapted to a world that usually changes only slowly,
as though a process of natural selection had winnowed us
with local conditions.

It does not have to be that way. It is possible Mars'
obliquity changes on a fairly short time scale, producing
huge changes in the conditions on the surface and as we see
from Xena, an eccentric orbit will do as well.

Another way to produce extremes of climate is to
give the world an axial tilt like Uranus, so that twice
a year the poles point at the sun. This would give the
world seasons like our on steroids. Larry Niven's Known
Space is known for its unfortunately selected worlds and
one of them, We Made It, is of this sort.

Dave Duncan's WEST OF JANUARY features a world
whose day is about one part in a hundred different from
its year, with the result that sunup to sunup takes about
a hundred years. This has had an effect on the local weather
and on the poor bastards who settled the world.

I'd mention one of Geoffrey Landis' short stories here
but the fact that the solution involves climate is an extreme
spoiler. Suffice it to say that when you settle a new world,
you should be aware of all the material cycles present and not
assume just because _Earth_ doesn't pull crap like having the
entire ocean boil or all air fall to the ground in pretty pretty
snow, other worlds cannot cycle more of their volatiles than
we are used to.


--
http://www.cic.gc.ca/english/immigrate/
http://www.livejournal.com/users/james_nicoll
.