There’s ice and organic material on Mercury, says NASA. Data from the MESSENGER spacecraft orbiting the planet confirms that impact craters in its polar regions (pictured above) are home to not just vast amounts of frozen water, but black patches of dark organic material. Initial evidence for water ice on the planet dates back twenty years, and was reinforced with initial findings from MESSENGER last year. But skepticism was laid to rest this week thanks to data from the probe's laser altimeter and neutron spectrometer, which measure the reflectance and hydrogen-richness of targets on the planet’s surface. The findings were published online in three papers for Science Express.
Compared to rock, ice is shiny and high in hydrogen, allowing the probe's instruments to spot it. In contrast, observed regions that are "dark" to the altimeter, but contain high amounts of hydrogen, are consistent with water ice lying below a layer of organic material like coal or soot. For comparison, the Curiosity Rover has yet to find organics on Mars. And while the initial 1991 evidence for ice on Mercury was gathered from Earth, to which less than 50 percent of the planet is visible, the MESSENGER probe is giving scientists a much more detailed picture of its entire surface.
"It could be that it's not just a question of having planets in a habitable zone."
Mercury is just a stone’s throw from the Sun, about a third as far as the Earth, with a surface temperature that gets as high as 800 degrees Farenheit. But its low axial tilt keeps the poles in perpetual darkness, allowing ice to form and stopping it from melting. According to NASA, the ice appears to be from a recent (in geological time) or ongoing process, and could have been delivered by comets from the far reaches of the solar system. Similarly, the organic material could have also hitched a ride, which means the find isn’t the same as proving life existed on Mercury. But the discovery could affect the hunt for alien life elsewhere. University of California planetary Scientist David Paige said to Discovery News, “It could be that it’s not just a question of having planets in a habitable zone. Maybe you need all these other ices and organics out there in the outer solar system to seed the planet, to provide the raw the material.”