[meteorite-list] range on the Haumea

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Thu, 17 Sep 2009 13:55:10 -0500
Message-ID: <9d15b5dkepd3rmdff4rgedmkp35do5msc4_at_4ax.com>

http://www.sciencedaily.com/releases/2009/09/090916092538.htm

Spot Discovered On Dwarf Planet Haumea Shows Up Red And Rich With Organics

ScienceDaily (Sep. 16, 2009) ? A dark red area discovered on the dwarf planet
Haumea appears to be richer in minerals and organic compounds than the
surrounding icy surface.

The discovery will be presented at the European Planetary Science Congress in
Potsdam by Dr Pedro Lacerda on Wednesday 16 September.

The spot was discovered by measuring changes in its brightness as it rotates.
The origin of the spot is unknown, however its ?light curve?, which describes
variations in its brightness over time, is not exactly the same shape in all
wavelengths. Small but persistent differences indicate that the dark spot is
slightly redder in visible light and slightly bluer at infrared wavelengths.

?Our very first measurements of Haumea told us there was a spot on the surface.
The two brightness maxima and the two minima of the light curve are not exactly
equal, as would be expected from a uniform surface. This indicates the presence
of a dark spot on the otherwise bright surface. But Haumea?s light curve has
told us more and it was only when we got the infrared data that were we able to
begin to understand what the spot might be,? said Dr. Pedro Lacerda, Newton
Fellow at Queen?s University Belfast.

Possible interpretations of these measurements are that the spot is richer in
minerals and organic compounds, or that it contains a higher fraction of
crystalline ice. If the spot is a scar of a recent impact onto Haumea then the
spot material might resemble the composition of the impactor, perhaps mixed with
material from the inner layers of Haumea.

Haumea orbits the Sun beyond Neptune, in a region known as the Kuiper belt. It
is the fourth largest known Kuiper belt object (KBO) after Eris, Pluto and
Makemake. These large KBOs, together with main-belt asteroid Ceres, are known as
dwarf planets. One of the most surprising characteristics of Haumea is its very
fast rotation, with one day lasting only 3.9 Earth hours. No other large object
in the solar system spins as fast as Haumea. The rapid spin deforms Haumea into
an elongated ellipsoid, 2000 km by 1600 km by 1000 km, whose shape balances
gravitational and rotational accelerations. It is believed that Haumea was spun
up by a massive impact more than a billion years ago.

Because of its large distance from the Earth, Haumea is visible only as a rather
uninformative point of light. Most of what we know about this object was derived
from its brightness variations, or ?light curve?. Because of its rotation and
elongated shape, Haumea brightens and dims periodically as it reflects more and
less sunlight. The extent of this variation tells us how elongated Haumea is,
and the time between each brightening and dimming is a measure of the rotation
period. The precise Haumea shape and spin period imply that it has a density 2.5
times that of water. Since we know from spectroscopic observations that Haumea
is covered in water ice, this high density implies Haumea must have a rocky
interior, in contrast with its bright icy surface.

New observations of this spot are planned for early 2010 using the ESO Very
Large Telescope. ?Now we will get detailed spectroscopy of the spot to hopefully
identify its chemical composition and solve the puzzle of its origin? Lacerda
concluded.
Received on Thu 17 Sep 2009 02:55:10 PM PDT