When a NASA robot scooped a cup of gravel from an asteroid 200 million miles away, scientists were stunned.

Bennu, an ancient space island the size of the Empire State Building, didn't look or behave like they thought it would. Early temperature readings led them to believe it would be covered in tiny pebbles. Instead, closeup images showed boulders and a surface that acted like a plastic ball pit.

The OSIRIS-Rex mission team considered that the boulders could be full of holes, creating a very weak pile of rubble. Suddenly, understanding the space within the space rocks became an essential piece of the puzzle.

OSIRIS-Rex's spacecraft takes images of the boulders on Bennu. Credit: NASA's Goddard Space Flight Center / University of Arizona

That was three years ago. Now the spacecraft is zooming toward Earth, with the team preparing to command it to drop the sample 63,000 miles above our planet. If it works, a capsule containing bits of Bennu will fall from the heavens to Utah on Sept. 24.

In the meantime, you could say NASA has called upon the Vatican for a Hail Mary.

Brother Robert J. Macke, curator of the Vatican's meteorite collection, has designed a custom device that will fit inside the glovebox where scientists will handle the sample. Within days of OSIRIS-Rex's arrival, the Jesuit will leave Castel Gandolfo, where the pope sometimes summers, and head for Johnson Space Center in Houston. There he will don a protective coverall over his Roman collar and help scientists use his pycnometer, an instrument for measuring the density of tiny grains of gravel. Through these measurements, NASA hopes to get to the bottom of Bennu's mysterious boulders.

SEE ALSO: NASA's dropping off a space package from 63,000 miles high

Macke, as it turns out, is one of the foremost experts in holey space rocks.

With colleagues at the Vatican Observatory, he has refined techniques for measuring the density and porousness of meteorites — space rocks that have survived the inferno of falling through Earth's atmosphere to the ground. The Roman Catholic Church has about 1,200 specimens in its trove.

Little-known to the world, the Vatican has had an observatory staffed by Jesuit astronomers since the 1930s. Devout Catholic men who have taken vows of poverty, chastity, and obedience live together while studying the cosmos. The legacy extends even further back in history. In the mid-1800s, priest Angelo Secchi built an observatory on the roof of the Church of St. Ignatius of Loyola in Rome. The church conducted astronomical research to show the compatibility of Catholicism and science, the Jesuits say.

One might wonder how someone so committed to the Bible reckons with the theory that the universe is 13.8 billion years old.

"I see no conflict between faith and science," said Macke, known to many colleagues as simply Brother Bob. "There are people who interpret scripture literally, and that's not doing scripture justice. If you look, for instance, at the story of Genesis, that is not a recipe book for creation. It's not really a history. It was intended to be a story to express a fundamental truth."

Macke's path to the OSIRIS-Rex mission — short for Origins, Spectral Interpretation, Resource Identification, and Security Regolith Explorer — was long and windy. From a young age, he knew he loved space and building things from scratch. As one of six children, he learned to be thrifty and resourceful, using his dad's tools and making repairs. He crafted models out of paper and cardboard, like Star Trek's Starship Enterprise. Some of his early handiwork remains in his parents' basement.

Eventually, he went to MIT to study astrophysics, then Washington University, where he participated in a research group focused on "presolar grains," bits of stardust embedded in meteorites that survived the formation of the solar system.

But something wasn't clicking.

"I would be in the laboratory looking at the clock, thinking, 'Have I been in here long enough to justify the day?' and you can't do science that way," remembers Macke, now nearly 50.

When Macke attended a Catholic Student Center retreat, he felt called to a religious life. To some of his relatives' surprise, he dropped out of school to join the Society of Jesus, a Roman Catholic order of priests and brothers founded half a millennium ago.

Brother Robert J. Macke is a Jesuit astronomer at the Vatican Observatory. Credit: Robert J. Macke

It wasn't long before science reeled him back in, though. In 2004, while studying philosophy for his Jesuit formation, he met Brother Guy Consolmagno, who heads the Vatican Observatory today. He invited Macke to join him in the laboratory, where he was using a novel approach to measure the density of meteorites.

A brief explainer: There are two types of density. Bulk density is the volume of the entire outer surface of a rock, including any pore space; grain density, on the other hand, is the volume of the solid parts of the rock without the voids. If you have these two different densities, you can compare them to get porosity measurements.

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"I actually spent so much time working in the laboratory doing measurements of density and porosity of the meteorites here, that they kind of kicked me out of the lab towards the end and said, 'You're in Italy — go do Italy,'" Macke said.

He returned to the United States to finish his physics doctorate and wrote a dissertation in 2010 that included porosity data of over 1,000 meteorites from institutions around the world. The paper is cited often by other scientists.

Brother Robert Macke built NASA a pycnometer for the Bennu samples, even with the complicated restrictions. Credit: Robert J. Macke

Andrew Ryan, a co-investigator on the NASA mission, had never met Macke but knew he needed his help to solve a problem. Previous asteroid sample return missions by Japan's space agency weren't able to get these key measurements. And no off-the-shelf pycnometer would do the trick, Ryan said.

"I see no conflict between faith and science."

To prevent contamination of the sample, NASA's curation team had set stringent rules about what could go inside the glovebox. Only about 15 materials were approved, such as stainless steel, aluminum, and glass. Motors, computers, and circuitry were strictly prohibited. Companies that sell the ready-made devices, which cost about $20,000 apiece, weren't interested in telling Ryan how they could be retrofitted.

"In a few cases, they just sort of closed the conversation and were like, 'Well, that's all we can say here. Let us know if you want to buy one,'" he said.

In addition to being an expert in holey space rocks, Macke enjoys tinkering. On his Youtube channel, Macke Makerspace, his videos showcase models he makes from scratch with a 3D printer. One of his creations, a scale model of the Church of St. Ignatius of Loyola, will be on display for tourists during the Jubilee in 2025. Next he'll be working on what he calls a "zero-knowledge clock," which he'll try to build with no prior instructions.

Macke believed he could build NASA a pycnometer for the Bennu samples, even with the complicated restrictions. Over several months, and with University of Arizona students, Macke made an instrument of little steel chambers, metal tubes, and valves that open and close. All of the electronics are housed in a separate box kept off to the side of the clean room. Nitrogen gas will be pumped through the system. Then, before-and-after pressure calculations will indicate the volume displaced by the specimen.

It may seem like an obscure bit of data, but Ryan says it could be crucial for understanding Bennu, thought to be rubble leftover from a much older, larger asteroid that couldn't quite hack it as a planet.

"We're really hoping that we can use this porosity measurement to help us identify those two main boulder types that we saw on the surface, because otherwise it could be pretty hard," he said. "We're talking about boulders that were, in some cases, tens or hundreds of meters. And soon we're going to be looking at centimeter-sized particles."

NASA paid for the parts to make the pycnometer, amounting to about the same cost as an off-the-shelf instrument, Ryan said. It will remain in the Johnson clean room for decades. Macke received no compensation from the space agency for his contribution — a perk of hiring a Jesuit for the job.

"That's one of the nice things about (the vow of) poverty," Macke said, smiling. "I don't have to worry about that."

Scientists install Macke's pycnometer into the glovebox for OSIRIS-Rex's Bennu samples at NASA's Johnson Space Center. Credit: Andrew Ryan

Macke plans to say a few prayers before the sample touches down. But when he gets into the lab, he'll likely be chanting Shepard's Prayer, he said. That's not Psalm 23, "The lord is my shepherd. I shall not want," but the words uttered by Alan Shepard, the first American blasted into space in 1961.

As legend goes, the astronaut, waiting for ignition, said something along the lines of, "Dear lord, please don't let me fuck up."

Is Macke a Jesuit scientist or a scientist-Jesuit? The two halves of his life appear to be inextricably linked.

"I don't think that I would be complete as a person if I were just doing one or the other," he said. "I need the prayer to feel my work, and I need my work to give me something to pray about."