November 30, 2012

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


  1. Before anyone gets too excited, comets (and some meteorites) contain "organic" material just due to their very early solar system make-up and segregation of materials and later radiation processing. Such material would naturally accumulate and not vaporize at the poles similarly to water ice.

    1. So do you think that these are mere residues of comet impacts?

      Also how should we compare the "organic" description you give for comet material with the "complex organic" one said for the Mercurian case. It seems that it's not methane nor simple sugars but something more elaborate. Is that "complexity" in comets also?

  2. Complex organics can be formed - and have been observed - in the stellar disks of dust and gas around young stars and are naturally incorporated to comets. A recent study shows that simpler organics can go through prebiotic steps to complex organics even when being encased in ice.

  3. "So do you think that these are mere residues of comet impacts?"

    That would be my #1 explanation. Or, carbon-rich meteorites with a lot of solar wind (mostly protons) post-processing.


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