Spot Discovered on Haumea Rich With Organics and Minerals
Written by Nancy Atkinson
A dark red area discovered on dwarf planet Haumea appears to be richer in minerals and organic compounds than the surrounding icy surface. Since Haumea is so small and far away, it shows up in telescopes as just a point of light, but the spot was discovered by measuring changes in brightness as it rotates. Small but persistent differences indicate that the dark spot is slightly redder in visible light and slightly bluer at infrared wavelengths.
The spot could be from a recent impact, so scientists aren't sure if the materials come from Haumea or the impactor. The dwarf planet is thought to be a rocky body covered in ice.
“Our very first measurements of Haumea told us there was a spot on the surface" said Dr. Pedro Lacerda, from Queen?s University in Belfast. "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.”
Possible interpretations of the changes in the light curve are that the spot is richer in minerals and organic compounds, or that it contains a higher fraction of crystalline ice.
Light curve of Haumea in two wavelenths.
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, 2,000 km by 1,600 km by 1,000 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 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.
Artist concept of Haumea. Credit: NASA
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” said Lacerda.
Source: Europlanet
Filed under: Planet News
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September 15th, 2009 at 7:13 pm
Bet it's an impact crater. Hence the fast spin.
September 16th, 2009 at 1:10 am
I agree with bsercombe. An impact with a smaller Kuiper belt object could explain the organic-rich spot. It would also explain the crystalline water ice, which requires relatively warm temperatures to form and turns back into amorphous water ice pretty quickly.
September 16th, 2009 at 4:01 am
That's putting spin on things.
If that simulation is correct, I don't see how but the putative impact counteracted some of the previous spin. What am I missing?
If it indeed counteracted the earlier spin, imagine how fast Haumea was spinning before. Or perhaps the spot is simply indicative of deeper layers, if Haumea fragmented on the original impact. (On the side facing away from the impact and remodeled after.)
September 16th, 2009 at 5:10 am
Torbjorn Larsson OM,
Couldn't Haumea have just had a "normal" rotation rate, and the asteroid impact caused the anomalous shape that is observed today?
September 16th, 2009 at 6:44 am
The light curve shows the rotational period. The curve shows when the different colored area moves past the side facing the earth.
September 17th, 2009 at 10:47 am
Interesting article but is the headline misleading? The main text says that organics are a proposed interpretation, not that there is direct evidence for them.