Mercury has ice — lots of it.
NASA announced Wednesday that its MESSENGER orbiter has discovered ice on Mercury, a discovery that raises the prospects of finding the building blocks of life on other planets and moons in the solar system.
In a statement released by the U.S. space agency on Thursday, NASA officials explained the finding saying an estimated one-hundred billion tons of ice may like litter the bottoms of craters scattered across the planet nearest to the sun. The ice, which NASA scientists say is likely made up of water, is located deep within a series of Mercury craters located near the north pole. It is believed the south pole harbors ice as well, though there are no hard data to support it. The MESSENGER team estimates that the planet could hold upwards of one trillion tons of ice.
“If you add it all up, you have on the order of 100 billion to 1 trillion metric tons of ice,” said David Lawrence of the Applied Physics Laboratory at Johns Hopkins University. “The uncertainty on that number is just how deep it goes.”
The announcement comes nearly ten months to the day after the MESSENGER probe began its mission. The orbiting probe uses neutron spectroscopy to measure average hydrogen concentrations within Mercury’s radar-bright regions. Ice concentrations are derived, in turn, from the hydrogen measurements, which NASA explains allows them to differentiate between certain compounds on the surface.
“The neutron data indicate that Mercury’s radar-bright polar deposits contain, on average, a hydrogen-rich layer more than tens of centimeters thick beneath a surficial layer 10 to 20 centimeters thick that is less rich in hydrogen,” says Lawrence. “The buried layer has a hydrogen content consistent with nearly pure water ice.”
“These reflectance anomalies are concentrated on poleward-facing slopes and are spatially collocated with areas of high radar backscatter postulated to be the result of near-surface water ice,” said Gregory Neumann of the NASA Goddard Space Flight Center. “Correlation of observed reflectance with modeled temperatures indicates that the optically bright regions are consistent with surface water ice.”
Additional details of the finding were published in three papers published online today in Science Express, according to NASA. The series of papers detail data collected by MESSENGER, which utilized neutron spectroscopy to measure average hydrogen concentrations within Mercury’s radar-bright regions. The data, collected over the course of the past ten months, likely provides the first compelling support for the long-held hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed polar craters.
According to NASA, the latest data from MESSENGER “strongly indicates that water ice is the major constituent of Mercury’s north polar deposits, that ice is exposed at the surface in the coldest of those deposits, but that the ice is buried beneath an unusually dark material across most of the deposits, areas where temperatures are a bit too warm for ice to be stable at the surface itself.”
The announcement is likely to raise the prospect of discovering similar icy compounds on other planets within the solar system. NASA scientists refused to speculate on whether the finding could lead to changes in how its Mars Curiosity rover would approach future missions searching for signs of past water, saying only that the Mercury data provides additional evidence that water is an abundant compound throughout our solar system.
“The more we examine the solar system, the more we realize it’s a soggy place,” Jim Green, the director of NASA’s Planetary Science Division, said during a separate press conference.
“And that’s really quite exciting, because that means the amount of water that we have here on Earth — that was not only inherent when it was originally formed but probably brought here — that water and other volatiles were brought to many other places in the solar system,” Green added. “So it really bodes well for us to continue on the exploration, following the water and its signs throughout the solar system.”
The announcement also captured the attention to space enthusiasts around the U.S. Sean Solomon of the Columbia University’s Lamont-Doherty Earth Observatory, principal investigator of the MESSENGER mission, noted that dark insulating material discovered near trace amounts of ice added a new wrinkle to the story: the possibility of discovering organic compounds throughout the solar system.
“For more than 20 years the jury has been deliberating on whether the planet closest to the Sun hosts abundant water ice in its permanently shadowed polar regions. MESSENGER has now supplied a unanimous affirmative verdict,” said Soloman. “But the new observations have also raised new questions. Do the dark materials in the polar deposits consist mostly of organic compounds? What kind of chemical reactions has that material experienced? Are there any regions on or within Mercury that might have both liquid water and organic compounds? Only with the continued exploration of Mercury can we hope to make progress on these new questions.”