The yellow spots represent icy areas.
Ice? On the planet closest to the Sun? You heard right: Mercury’s northern pole may have craters containing frozen water.
The evidence, presented in three papers published last week in Science, comes from several sources. The Mercury Laser Altimeter, an instrument on the Mercury space probe, MESSENGER, helps scientists map the topography of the planet by firing lasers at its surface and recording the time it takes for the light to return. The instrument also records the intensity of the return beams, and the bright spots reflecting off Mercury’s surface suggest the presence of ice.
These bright spots corresponded to regions that, according to astronomers’ maps of Mercury, would be permanently in shadow, supporting the idea that they could be frozen despite Mercury’s scorching temperatures elsewhere. MESSENGER’s neutron spectrometer has also detected the presence of large amounts of hydrogen, a large component of water, at the north pole.
This is not a brand-new idea. Ice has been found in craters on the Moon, and several planets have ice in some form. In 1992 researchers reported evidence of ice on Mercury when they saw bright spots on radar images that could be caused by ice. And in March, at the 2012 Lunar and Planetary Science Conference, scientists had presented some of these newly published results. The new Science papers report altimeter data that reach farther north, though, than they had in the past, as Emily Lakdawalla of the Planetary Society reported. The altimeter data from March were consistent with a layer of ice buried under what could be carbon-containing compounds, the new data provide evidence for patches of exposed ice.
The detection of water near what might be organic matter is exciting because those are the two main ingredients for life. So far, though, even at the north pole, no evidence of a Mercurial Santa Claus has been found.
Image courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory