Gretchen Benedix – Curtin University

The Accidental Astro-geologist

Gretchen’s journey into the stars wasn’t a straight line. Growing up in rural Idaho, she was captivated by the “brilliant stuff at night”, but she originally enrolled in university to study psychology.

However, a single elective – called Astronomy 101 – changed the trajectory of her life.

 

One Elective To Change It All

A field trip to an observatory in Santa Cruz provided a “perspective shift” when she saw Saturn through the historical telescope. “It looks exactly like the pictures,” she recalled, realising the planet wasn’t just an image in a textbook. This spark led her to pivot to physics and, eventually, the tangible world of geology.

For Gretchen, geology offered a satisfaction she couldn’t find while studying physics: the ability to pick up a rock and understand its history through touch and composition.

 

From Logbooks to Algorithms

The scale of modern discovery is best understood by looking back. In 1989, Gretchen worked on an internship identifying asteroids. At the time, researchers painstakingly compared physical logbooks and photos by eye to find objects that moved. They had identified only 132 asteroids. Today, thanks to space telescopes and automation, that number has grown to over a million.

When Gretchen began focusing on Martian craters, the existing gold standard was a database of 385,000 craters larger than one kilometre, which had been manually catalogued by a PhD student.

An impressive feat, yet this manual method was limited by resolution and human endurance. To see the “finer” details of Martian history – like when rivers began to flow or how the northern hemisphere evolved – Gretchen knew they needed to count the small craters.

 

The YOLO Moment: 94 Million Craters

In collaboration with the Pawsey Supercomputing Research Centre and the Curtin Institute of Computation (CIC), Gretchen’s team moved away from traditional algorithms. They turned to YOLO (You Only Look Once), an open-source algorithm originally designed for facial recognition.

The challenge wasn’t just the algorithm; it was the training data. The team had to manually identify craters across various resolutions so the computer could learn that a “circle” on the Martian surface was, in fact, an impact site. Once the training was complete, they ran a global 5-meter-per-pixel dataset through the supercomputer.

The result was staggering: the system identified 94 million craters in a single 24-hour period. This leap in data allows researchers to look at “discreet points in time,” shifting the scale of analysis from billions of years to mere millions.

 

A Planetary Detective Story

This massive database isn’t just for counting; it’s a tool for a larger “detective story”. By using radioactive isotopes to date meteorites found on Earth, researchers can determine three things: when a rock solidified, when it was launched off Mars by an impact, and when it landed on Earth.

By matching these ages with the crater density of specific regions on Mars, Gretchen’s team was able to narrow down 70,000 potential impact sites to just 19 most likely source craters for Martian meteorites. “We have identified two areas… that look like those are the areas they’d come from,” she noted, providing a vital geological context for rocks that were once “gifted” to us from space without a return address.

 

Why This All Matters

For Gretchen, studying these “space rocks” is about understanding the solar system as a whole. The Earth does not exist in a bubble; its unique environment is a product of the solar system’s chaotic history, including theories that Jupiter once wandered near Earth’s orbit.

As missions like the Europa Clipper head to Jupiter’s moons and Dragonfly prepares to explore the nitrogen-rich atmosphere of Titan, the work being done at Curtin University provides the foundational “puzzle pieces” needed to understand our place in the galaxy.

“Science…has found ways to explain things that previously were unknown and kind of scary,” Gretchen concluded.

By turning the “unknown” into data, her team isn’t just counting holes in the ground – they are reading the history of the universe, one crater at a time.