During Sunday’s "supermoon," the moon will be 221,765 miles from Earth, measured center to center. It’s the closest the orbiting moon will get to our planet this year.

Katharine Robinson gets a lot closer than that, in a way. She studies moon rocks as a graduate assistant at the University of Hawaii at Manoa’s School of Ocean and Earth Science and Technology. UH has about 120 grams of moon rocks brought here in 1990 for study by a team of scientists.

"This is probably the biggest piece of the moon we have," she said, holding up a rock the size of a jelly bean. "This is Apollo 12 basalt. It’s roughly similar, looks similar to the basalts that we have here, the basalts that we have on the Big Island, from Kilauea. Compositionally it’s different."

In the lab the black rock seems to sparkle, but that’s not moonlight. It’s from a light-colored mineral called plagioclase feldspar, which cleaves along smooth surfaces when the rock is split and reflects light.

UH also has lunar dirt: a plagioclase-rich silvery soil collected by Apollo 16 from the light-colored lunar highlands, and dark-colored mare basalt pebbles from the shadowy parts of the moon’s surface collected by Apollo 17.

"About 17 to 18 percent of the moon is covered with the mare basalt," Robinson said. "The far side of the moon doesn’t have them. They’re all on the near side. It’s very, very odd."

Robinson looks for something called apatite in the moon rocks. Though it’s pronounced "appetite," it doesn’t refer to the hunger you get thinking about all the green cheese up there. It’s a mineral that has been found to contain water.

"It’s not water in a liquid sense; it’s water in a chemical sense," said Robinson. "It’s all bound up in minerals and trapped in (volcanic) glasses. So we’re trying to figure out how much water is in the lunar interior versus what comes to the moon on the surface from solar wind or in comets or other things."

Up until 2008 the moon was believed to have been dry at creation, Robinson said. Identification of the chemical equivalent of water embedded in moon rocks introduced what scientific journals called a "total game-changer" into the theories about the origins of the moon.

What is generally known is that the moon was produced by a massive collision of celestial objects that created a disk of molten rock and gases floating around Earth and eventually accreted into the moon.

"One of the things we’re trying to do is figure out how much water was there when it accreted or was it brought in later by impacts from big meteors and comets," Robinson said.

She gets to use some cool toys for her work. A high-powered microscope is used to visually examine "thin slices" of moon rock — particles that have been suspended in an epoxy and then sliced into a disk. If Robinson finds apatite, she’ll do further examination with an electron microscope or an ion microprobe, an instrument that looks like something out of a "Transformers" movie.

There are only 12 ion microprobes in the world, which are used to study everything from comet particles to Mars rocks and stardust. An ion microprobe works by hitting the moon rock with ions, which releases additional ions. By analyzing the effects of these collisions through a mass spectrometer, Robinson can determine whether the rocks contain hydrogen isotopes, a telltale sign of water. The process actually destroys part of the sample, so only scientists with clearance from NASA are allowed to experiment in this way.

"I blow very tiny holes in my rocks," Robinson said. "I make pits that are 25 microns in size, so about a quarter the width of a human hair. The machine can actually go much smaller than that."

A cheerful 28-year-old who grew up in Texas, Robinson "always liked rocks" as a child. She studied at the University of Chicago and at the Lunar and Planetary Institute in Houston before coming to UH. She initially got to study moon rocks during an internship, and now she is writing a paper on the recent changes in the study of moon rocks.

Sunday may be only a supermoon to the rest of us, but to Robinson it will be a reminder of just how lucky she is to be working with such a precious commodity. Weather permitting, she plans to join some friends who have telescopes to get a lunar look.

"You get used to working on these tiny little samples and your whole life is into looking at things that are 10, 20, 30 microns," she said. "And then you go outside and you look up and you go, ‘Wow, my rocks are from there. My samples are from there. I’m holding moon rocks!’ You kind of remember why you got into it in the first place."