NASA’s Messenger (Mercury Surface, Space Environment, Geochemistry and Ranging) space probe has found new evidence of water ice in the polar regions of the planet Mercury, particularly on the floors of craters. The ice is covered by darker materials that may be organic compounds.
Of the existence of the ice there are three proofs: an excess of hydrogen measured by the Messenger space probe’s Neutron Spectrometer, the measurement of Mercury’s polar deposits’ reflectance at near infrared light with the Messenger’s Mercury Laser Altimeter (MLA) and the first detailed of the surface and near surface temperature models of the polar regions of Mercury that use the actual topography of the planet’s surface again measured with the MLA instrument.
The suspect that on Mercury’s polar regions there may be ice originated a long time ago but the observations of the planet are really hard. The big problem is its proximity to the Sun, which consequence is that observing Mercury with a telescope there’s a serious risk of ruining its optical exposing it to the direct light of the Sun. It’s therefore necessary to observe it after sunset but even in those conditions the planet is so small and far away that telescopes have trouble resolving its features.
The real studies of Mercury started only in the ’70s with space missions such as the Mariner 10 spacecraft. Today, the Messenger space probe has much more sophisticated instruments, allowing much better analyzes of the characteristics of the planet closest to the Sun.
Mercury looks like the Moon in many ways but because of its proximity to the Sun its surface temperatures can exceed 400 degrees Celsius (more than 750 degrees Fahrenheit). Therefore, that looks like a place where finding ice is really impossible but another peculiarity of this planet is that it has an axis with almost no inclination. This means that at the poles there are permanently shadowed areas, therefore, given the lack of atmosphere, the estimated temperatures can drop to -223 degrees Celsius (about -370 degrees Fahrenheit).
The new data collected by the Messenger spacecraft provide a strong indication that water ice is the major constituent of the deposits at the north pole of Mercury, that the ice is exposed to the surface in the coldest of those deposits but it’s buried under dark materials in most of the deposits. These materials act as insulators in warmer areas where the ice would melt.
Probably, these materials are of organic kind arrived on Mercury with the water in comets that collided with the planet. It’s possible that their color has become darker due to exposure to radiation on the surface, very strong even in the perennial shadowed areas.
Further investigations on these materials will be needed to prove that they are indeed organic and what types of chemical reactions take place in that environment. It would be very interesting to see if there may be areas where the water is in its liquid state and mixed with organic materials.
The organic compounds arrived on Earth are among the building blocks of life: it’s highly unlikely that on Mercury there are areas where any life forms can be born but some areas of the planet may give us an idea of what elements are present in the phase preceding the emergence of life.