Ice and "complex organic materials" on Mercury's poles

This is one of those perplexing astronomical news that make history and I can't but mention. US scientists have found, with the help of scout satellite MESSENGER,  that not just suspected Mercury's polar water ice (in shadowed craters) is indeed that but also that confusing dark regions around it are complex organic materials, possibly darkened by the intense solar radiation that bathes the small inner planet. 

The team found that the probe's reflectance measurements, taken via laser altimetry, matched up well with previously mapped radar-bright regions in Mercury's high northern latitudes. Two craters in particular were bright, both in radar and at laser wavelengths, indicating the possible presence of reflective ice. However, just south of these craters, others appeared dark with laser altimetry, but bright in radar.

This confused scientists for a while but eventually they realized that the puzzling regions actually hold water ice at a meter's depth into the soil, where the heat of the sun can't reach so easily. 

Radar-reflectant regions (ice) show in yellow

The most interesting part however is that the astronomers are almost certain now that the dark material must be complex organic matter, darkened by the extreme solar radiation.

Is there life in Mercury? 

Source: Science Daily.

Ref studies: 

1. David A. Paige, Matthew A. Siegler, John K. Harmon, Gregory A. Neumann, Erwan M. Mazarico, David E. Smith, Maria T. Zuber, Ellen Harju, Mona L. Delitsky, and Sean C. Solomon. Thermal Stability of Volatiles in the North Polar Region of Mercury. Science, 29 November 2012 DOI: 10.1126/science.1231106
2. Gregory A. Neumann, John F. Cavanaugh, Xiaoli Sun, Erwan M. Mazarico, David E. Smith, Maria T. Zuber, Dandan Mao, David A. Paige, Sean C. Solomon, Carolyn M. Ernst, and Olivier S. Barnouin. Bright and Dark Polar Deposits on Mercury: Evidence for Surface Volatiles. Science, 29 November 2012 DOI: 10.1126/science.1229764

Measure of Eris' diameter surprises discoverer

There's a particularly fascinating astronomy story today at Mike Brown's Planets blog: it is about how astronomers through the World have been trying to measure Eris' diameter with greater precision that was known so far.

This has been done by measuring the time of the occultation of a star as Eris passed in front of it.

Somewhat surprisingly Eris is in the low range of expected diameters, just about the size of Pluto. However it is known that it is quite more massive, what poses some intriguing questions about why, as Eris is not the only KBO more massive than Pluto.

Anyhow, Mike Brown explains it much better than I could, so go read the original story.