Around 11 million years ago, an asteroid collided with Mars, scattering fragments of the red planet into space. One of these Martian chunks ultimately made its way to Earth near Purdue University and is among the rare meteorites that can be directly linked to Mars. This meteorite was found in a drawer at Purdue University in 1931, leading to its designation as the Lafayette Meteorite.
Initial studies of the Lafayette Meteorite revealed that it had come into contact with liquid water while on Mars. Scientists have long been curious about the timing of this interaction. Recently, a collaborative team of scientists, which includes two from Purdue University’s College of Science, has successfully dated the minerals in the Lafayette Meteorite that were formed during this watery period. Their research has been published in Geochemical Perspective Letters.
Marissa Tremblay, an assistant professor in the Department of Earth, Atmospheric, and Planetary Sciences (EAPS) at Purdue, is the lead author of the publication. She employs noble gases such as helium, neon, and argon to investigate the geological processes affecting the surfaces of Earth and other celestial bodies. Tremblay notes that some Martian meteorites contain minerals that resulted from their interaction with liquid water while still on Mars.
“By dating these minerals, we can determine when liquid water existed at or near the surface of Mars in its geological history,” she explains. “For the Martian meteorite Lafayette, we found that these minerals formed approximately 742 million years ago. We believe that there wasn’t a significant amount of liquid water present on the surface at that time. Instead, the water likely originated from melting subsurface ice known as permafrost, which was probably triggered by ongoing magmatic activity that persists on Mars today.”
The research team validated that the age derived for the water-rock interaction on Mars is reliable and that the dating method was unaffected by subsequent events in Lafayette’s history after its exposure to water.
“The age might have been influenced by the impact that launched the Lafayette Meteorite from Mars, heating from its 11 million years drift in space, or the heating it experienced upon entering Earth’s atmosphere,” she adds. “However, our findings demonstrate that none of these factors altered the age of the water-related changes in Lafayette.”
Ryan Ickert, a senior research scientist with Purdue EAPS and a co-author of the study, investigates geological timelines using radioactive and stable isotopes. He pointed out that earlier isotope data, which attempted to estimate the timing of water-rock interactions on Mars, were problematic and likely influenced by various other factors.
“This meteorite distinctly shows evidence of reacting with water. The timing of this event was uncertain, but our research pinpoints when water was present,” he states.
Found in a drawer
Through ongoing research, we now have considerable knowledge about the Lafayette Meteorite’s origins. It was blasted from Mars approximately 11 million years ago as a result of an impact event.
“We determined this because, after being ejected from Mars, the meteorite was bombarded by cosmic rays in space, which resulted in specific isotopes forming in Lafayette,” Tremblay explains. “While many meteoroids come from impacts on Mars and other planetary bodies, only a limited number will eventually arrive on Earth.”
Once it landed on Earth, however, the details become less clear. We know with certainty that the meteorite was discovered in a drawer at Purdue University in 1931, but the circumstances surrounding its arrival remain mysterious. Tremblay and her team made progress in clarifying the timeline after its landing in a recent study.
“We analyzed organic contaminants from Earth found on Lafayette (notably crop diseases) that were prominent during specific years, helping us narrow down when it might have fallen and whether someone might have witnessed its arrival,” Tremblay says.
Meteorites: time capsules of the universe
Meteorites serve as solid time capsules, containing fragments of planets and celestial bodies across the universe. They hold data that can be analyzed by geochronologists. They are distinguished from Earth rocks by a crust formed during their descent through the atmosphere, often creating a fiery spectacle in the night sky.
“We can identify meteorites by examining the minerals they contain and their interrelationships,” Tremblay notes. “Typically, meteorites have a higher density than Earth rocks, feature metallic components, and exhibit magnetic properties. We also look for a fusion crust that occurs during atmospheric entry. Furthermore, we can utilize the chemistry of meteorites, specifically their oxygen isotopes, to identify their planetary origins or categorize them.”
An international collaboration
The research team involved in this publication comprises an international group of scientists, including Darren F. Mark, Dan N. Barfod, Benjamin E. Cohen, Martin R. Lee, Tim Tomkinson, and Caroline L. Smith, who represent various institutions such as the Scottish Universities Environmental Research Centre (SUERC), the Department of Earth and Environmental Science at the University of St Andrews, the School of Geographical and Earth Sciences at the University of Glasgow, the School of Earth Sciences at the University of Bristol, and The Natural History Museum in London.
“Before our time at Purdue, Ryan and I were both affiliated with the Scottish Universities Environmental Research Centre, where we conducted the argon-argon isotopic analyses of the alteration minerals in Lafayette,” Tremblay adds. “Our colleagues at SUERC, the University of Glasgow, and The Natural History Museum have previously contributed significantly to studying Lafayette’s history.”
Dating the alteration minerals in Lafayette, alongside those in Martian meteorites known as nakhlites, has been a key objective in planetary science because scientists recognize that alteration occurred in the presence of liquid water on Mars. However, dating these materials proves to be particularly challenging, with previous attempts yielding uncertain results that likely stemmed from factors beyond the aqueous alteration process.
“We have shown a reliable method of dating alteration minerals in meteorites that can be applied to other meteorites and celestial bodies to discern when liquid water may have been present,” Tremblay concludes.
Thanks to the Stahura Undergraduate Meteorite Fund, Tremblay and Ickert will continue exploring the geochemistry and histories of meteorites, offering opportunities for undergraduates at Purdue EAPS to participate in this research.
