An asteroid struck Mars 11 million years ago and sent pieces of the red planet hurtling through space. One in all these chunks of Mars eventually crashed into the Earth somewhere near Purdue and is one in every of the few meteorites that might be traced on to Mars. This meteorite was rediscovered in a drawer at Purdue University in 1931 and subsequently named the Lafayette Meteorite.
During early investigations of the Lafayette Meteorite, scientists discovered that it had interacted with liquid water while on Mars. Scientists have long wondered when that interaction with liquid water took place. A global collaboration of scientists including two from Purdue University’s College of Science have recently determined the age of the minerals within the Lafayette Meteorite that formed when there was liquid water. The team has published its findings in Geochemical Perspective Letters.
Marissa Tremblay, assistant professor with the Department of Earth, Atmospheric, and Planetary Sciences (EAPS) at Purdue University, is the lead creator of this publication. She uses noble gases like helium, neon and argon, to review the physical and chemical processes shaping the surfaces of Earth and other planets. She explains that some meteorites from Mars contain minerals that formed through interaction with liquid water while still on Mars.
“Dating these minerals can subsequently tell us when there was liquid water at or near the surface of Mars within the planet’s geologic past,” she says. “We dated these minerals within the Martian meteorite Lafayette and located that they formed 742 million years ago. We don’t think there was abundant liquid water on the surface of Mars presently. As an alternative, we predict the water got here from the melting of nearby subsurface ice called permafrost, and that the permafrost melting was brought on by magmatic activity that also occurs periodically on Mars to the current day.”
On this publication, her team demonstrated that the age obtained for the timing of water-rock interaction on Mars was robust and that the chronometer used was not affected by things that happened to Lafayette after it was altered within the presence of water.
“The age might have been affected by the impact that ejected the Lafayette Meteorite from Mars, the heating Lafayette experienced in the course of the 11 million years it was floating out in space, or the heating Lafayette experienced when it fell to Earth and burned up just a little bit in Earth’s atmosphere,” she says. “But we were in a position to display that none of this stuff affected the age of aqueous alteration in Lafayette.”
Ryan Ickert, senior research scientist with Purdue EAPS, is a co-author of the paper. He uses heavy radioactive and stable isotopes to review the timescales of geological processes. He demonstrated that other isotope data (previously used to estimate the timing of water-rock interaction on Mars) were problematic and had likely been affected by other processes.
“This meteorite uniquely has evidence that it has reacted with water. The precise date of this was controversial, and our publication dates when water was present,” he says.
Present in a drawer
Because of research, quite a bit is understood in regards to the Lafayette Meteorite’s origin story. It was ejected from the surface of Mars about 11 million years ago by an impact event.
“We all know this because once it was ejected from Mars, the meteorite experienced bombardment by cosmic ray particles in outer space, that caused certain isotopes to be produced in Lafayette,” Tremblay says. “Many meteoroids are produced by impacts on Mars and other planetary bodies, but only a handful will eventually fall to Earth.”
But once Lafayette hit Earth, the story gets just a little muddy. It is understood for certain that the meteorite was present in a drawer at Purdue University in 1931. But the way it got there remains to be a mystery. Tremblay and others made strides in explaining the history of the post-Earth timeline in a recent publication.
“We used organic contaminants from Earth found on Lafayette (specifically, crop diseases) that were particularly prevalent in certain years to narrow down when it may need fallen, and whether the meteorite fall could have been witnessed by someone,” Tremblay says.
Meteorites: time capsules of the universe
Meteorites are solid time capsules from planets and celestial bodies from our universe. They carry with them bits of knowledge that might be unlocked by geochronologists. They set themselves other than rocks that could be found on Earth by a crust that forms from its descent through our atmosphere and infrequently form a fiery entrance visible within the night’s sky.
“We will discover meteorites by studying what minerals are present in them and the relationships between these minerals contained in the meteorite,” says Tremblay. “Meteorites are sometimes denser than Earth rocks, contain metal, and are magnetic. We may also search for things like a fusion crust that forms during entry into Earth’s atmosphere. Finally, we are able to use the chemistry of meteorites (specifically their oxygen isotope composition) to fingerprint which planetary body they got here from or which variety of meteorite it belongs to.”
A global collab
The team involved with this publication included a world collaboration of scientists. The team also includes Darren F. Mark, Dan N. Barfod, Benjamin E. Cohen, Martin R. Lee, Tim Tomkinson and Caroline L. Smith representing the Scottish Universities Environmental Research Centre (SUERC), the Department of Earth and Environmental Science on the University of St Andrews, the School of Geographical and Earth Sciences on the University of Glasgow, the School of Earth Sciences on the University of Bristol, and the Science Group at The Natural History Museum in London.
“Before moving to Purdue, Ryan and I were each based on the Scottish Universities Environmental Research Centre, where the argon-argon isotopic analyses of the alteration minerals in Lafayette took place” Tremblay says. “Our collaborators at SUERC, the University of Glasgow, and the Natural History Museum have previously done lots of work studying the history of Lafayette.”
Dating the alteration minerals in Lafayette and, more generally, on this class of meteorites from Mars called nakhlites, has been a long-term objective in planetary science because scientists know that the alteration happened within the presence of liquid water on Mars. Nevertheless, these materials are especially difficult so far, and former attempts at dating them had either been very uncertain and/or likely affected by processes apart from aqueous alteration.
“We now have demonstrated a sturdy solution to date alteration minerals in meteorites that might be applied to other meteorites and planetary bodies to grasp when liquid water may need been present,” Tremblay says.
Due to Stahura Undergraduate Meteorite Fund, Tremblay and Ickert will give you the option to proceed studying the geochemistry and histories of meteorites and undergraduates at Purdue EAPS will give you the option to help on this research.
