Written by Phoebe Campbell, CAS communications intern

Dr. Meenakshi Wadhwa

On February 17, Dr. Meenakshi Wadhwa, director of the School of Earth and Space Exploration at Arizona State University, discussed the study of rocks from elsewhere in the solar system and how they provide insights into the origins and destruction of materials in our corner of the universe.

Wadhwa's lecture was part of the Annual Baldwin Frontiers in Geology Lecture, hosted by the Department of Geology and Environmental Earth Science and this year's co-sponsors, the Departments of Chemistry and Biochemistry, Microbiology, and the Institute for the Environment and Sustainability.

In an attempt to make her lecture accessible to all members of the audience, Dr. Wadhwa began by defining meteorites and their various types.

"[Meteorites] are rocky or metal-rich objects that come from elsewhere in our solar system," she said. "The vast majority come from asteroids," but she added that there are also a few that are thought to have come from the other sources, such as planet Mars.

Wadhwa divided meteorites into three categories: stony, iron, and stony-iron. She described the different information that each type of meteorite tells us about the formation and composition of materials in our solar system.

Five Key Points about Meteorites

"If you take nothing else from this talk, I'm going to give you 5 big things that we've learned from studying meteorites up to this point," Wadhwa said.

• "Meteorites tell us when and how our solar system formed," she explained for her first main point. This was precisely 4567.9 +/- 0.3 million years ago.
• Wadhwa's second point pertains to stardust, known as presolar grains. "There are dust grains in meteorites older than our solar system," she said. These miniscule grains, which include diamonds, "are thought to have condensed in stars prior to the formation of our solar system," providing insight into the formation of stars long before the birth of our planetary system.
• "Meteorites provide clues about the building blocks of the rocky planets," Wadhwa said. This is significant because they allow us to "sort of guess at the kinds of compositions that went into building our own planet."
• "Meteorites most likely brought the raw materials for life on our planet," she continued. "It's not just that they may have brought amino acids and other organics," but they also likely brought essential minerals that were necessary for the formation of life.
• Lastly, Wadhwa expressed her 5th point: "Meteorites have changed the course of life on Earth." She specifically pointed to the Cretaceous–Tertiary mass extinction, for which there is evidence that it was brought about by a large impact and wiped out an estimated 75% of Earth's species.

To conclude her lecture, Wadhwa highlighted some past and current projects that collect and study rock samples from elsewhere in our solar system, including the Apollo missions, the NEO [Near-Earth Object] Observations Program, and the Psyche mission.

"Meteorites really are nature's sample return missions," she said. "We have them here for free. They're a faster, cheaper, easier way to explore our solar system."

Audience Reception

Wadhwa's illuminating lecture was well-received by the Shriver Center audience, which was composed of students and professors with varying degrees of familiarity with her field of study.

"I'm in the process of studying meteorites with Dr. Claire McLeod as a research undergraduate program," said sophomore geology major Veronica Grilliot. "I felt the lecture was very informative, and I learned a lot that I wouldn't have otherwise gotten a chance to know from such an esteemed professor."

Keira Johnson — a freshman geology major — explained that while she was unfamiliar with topic, "I thought she did a really good job breaking it down to manageable level." She added, "I'll definitely look into the topic more because I thought it was really interesting."

The Baldwin family endowment, initiated at the time of emeritus faculty Dwight Baldwin's retirement, allows the Department of Geology and Environmental Earth Science to highlight prominent speakers like Dr. Wadhwa who are conducting cutting-edge research in the field of geosciences.