September 2, 2014 | By John Perney
Researching the age of craters on the far side of the Moon one year into a college experience is one thing. Focusing on a specific crater named decades ago for a 19th-century alumnus of the same college is something else.
Marina Baker, ’17, had that unique opportunity this summer, and made initial inroads with associate professor of physics Nicolle Zellner toward a goal of determining the age of the Moulton Crater, named for 1894 Albion graduate Forest Ray Moulton, a leading American astronomer during the first half of the 20th century.
“It’s near the south pole, but it’s just over the limb, where the near side becomes the far side, so we can’t see it,” Baker said. Along with the Albion connection, she added, “There’s almost nothing known about this region of the moon, that’s kind of why we picked it.”
Baker's project is being coordinated through the College's Foundation for Undergraduate Research, Scholarship, and Creative Activity (FURSCA). Along with Zellner, she worked with researchers at the Lunar and Planetary Institute in Houston and the Florida Institute of Technology in Melbourne, downloading and using special software to begin learning about the crater's geology and counting the many smaller, individual unnamed craters contained within the larger Moulton Crater. So far, the group has identified more than 450 craters on the floor of Moulton.
After that comes the even tougher work of determining the age of the crater. That’s where the importance of crater-counting comes into play.
One of the software programs includes crater-counting capability, “so you can count the craters inside of the crater we’re looking at,” Baker said. “From the crater density, you could calculate the approximate age of the [main] crater.” She described this can be done by comparing the density with already catalogued crater densities of big lunar basins, whose approximate age is already known—in part from samples collected during the Apollo missions.
It’s tricky photo work even for the specialists, given Moulton’s location on the Moon’s far side, which never faces Earth due to the tidal-locking phenomenon. High-resolution orbital data, from the Lunar Reconnaissance Orbiter and Clementine, for example, have made these far-side explorations possible.
“This is a region of the Moon that nobody has looked at,” Zellner said. “So being able to just get at the data or know what kind of data exist was a huge first step.”
The end goal, according to Baker and Zellner, will be to determine whether Moulton and the adjacent Chamberlin Crater were formed between 3.85 billion and 4.5 billion years ago, which would fall in line with a hypothesis that almost all of the Moon’s large craters were formed early on in the Moon's history. But there are gaps within that time frame.
“The big piece is going to be the age,” Zellner explains. “If we can get the crater counts, and if we can find ages for [Moulton and Chamberlin] and put them in the context of the rest of the Moon, I think that’s going to be a good contribution. We’ll know when the Moon got hit. We can start to fill in that timeline.”