Cold As Ice

The surface of Mercury is typically thought to be too hot for ice to form, but studies over the years have suggested ice can be found on the planet closest to the Sun. Now, a new study carried out by a group of researchers from Brown University pushes the speculation further, claiming Mercury may be far icier than we originally thought.

The idea that Mercury may contain ice first began in 1990 when radar telescopes discovered highly reflective regions inside several craters near the planet's poles. Since Mercury has very little tilt, these craters receive little-to-no sunlight, resulting in dark, shadowy spots with low temperatures capable of forming ice.

Ariel Deutsch, the study’s lead author and Brown Ph.D candidate, worked with Gregory Neumann from NASA’s Goddard Space Flight Center to take a fresh look at data gathered by the NASA MESSENGER probe when it orbited Mercury from 2011 to 2015. The probe was equipped with tools enabling it to map elevation which the team realized it could also be used to detect reflective areas.

After calibrating the device, it detected new readings suggesting the existence of three large craters with sizable ice deposits. Combined, the craters are about 3,400 square kilometers (1,312 square miles) in size — slightly larger than the state of Rhode Island. Alongside the three large craters, four smaller ice deposits were also found, each with diameters of less than about 5 kilometers (3 miles).

“The assumption has been that surface ice on Mercury exists predominantly in large craters, but we show evidence for these smaller-scale deposits as well,” said Deutsch. “Adding these small-scale deposits to the large deposits within craters adds significantly to the surface ice inventory on Mercury.”

More to Find

The discovery of the smaller ice deposits could change the way we look for ice and water in the rest of our solar system. Jim Head, co-author of the research, explains the work "opens our eyes to new places to look for evidence of water, and suggests there’s a whole lot more of it on Mercury than we thought."

Similar deposits are believed to be on the Moon, which could be the next place we look. If true, it could double the amount of ice speculated to be on our lunar neighbor.

That said, it's still unclear how ice found its way to Mercury. Current theories speculate water was brought to the planet via comet and asteroid impacts, or perhaps that solar wind introduced hydrogen to the surface, which later mixed with oxygen to form water.

One thing is certain, however: we're not done with Mercury just yet. Between looking for more ice and plans to discover why it appears to be shrinking, the planet is in for a lot of new attention.

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