They wanted to visit it because previous surveys showed it is covered in moraines pushed into their present location from the ancient movements of the East Antarctica Ice Sheet.
“We use those mountains as a yardstick basically because as the ice sheet grows or shrinks, it goes up and down the sides of these mountains, and it leaves moraines as it does so,” Bromley said.
It’s particularly well suited for the helium-3 analysis that is the focus of their work.
“A lot of time is taken to separate the different minerals from one another,” Bromley said.
There, they’ve started processing them and grinding them up to their constituent parts.
“We measure [cosmogenic nuclides] in certain minerals,” Balco said.
Over the past two years, researchers ventured to remote areas along the mountain range to decipher how high ancient glaciers reached, by studying the rocks they left behind.
“We go to places that are not now covered by ice, and look for some kind of evidence that they were covered by ice at some point in the past, and try to date it,” said Greg Balco, a glacial geologist at the Berkley Geochronology Center.
“If you know the rate at which those nuclides are produced in the rock and you can measure how much you have inside the rock, then you can calculate how long that rock has been exposed on the hillside, exposed to the atmosphere,” Bromley said.
“If the rock is part of a moraine, it tells you when that ice was last at that limit.” Walking along the edges of the moraines, the team searched for rocks that look like they haven’t been disturbed since they were spit out of the ice.
When they found ones that looks promising, they pulled out their chisels and hammers and chipped off a hunk of rock from the top.
“You can see a whole series of horizontal and sloping lines going up into the sky showing where the ice sheet surface used to be.” After carefully mapping the moraines, the team set about collecting rock samples from the top of them in order to date when the glaciers last spit out debris.
To do so, they have to measure exactly how much radiation from outer space these rocks have been exposed to.