This solar system flips

This solar system flips

Geologist studies asteroids and moon dust to decode the history of the solar system

WEST LAFAYETTE, Ind. — Michelle Thompson is a geologist. But while “geo” means earth, it studies decidedly supernatural, or at least extraterrestrial things: the moon and asteroids.

“I study space weathering: how space environments affect tiny mineral particles on planetary surfaces,” said Thompson, assistant professor in the Department of Earth, Atmospheric and Planetary Sciences at the College. of Science from Purdue University. “We can learn so much from these tiny samples; we can learn about the evolution of planets and moons, including our own. More broadly, we study these tiny samples and can extrapolate the history of the solar system.

Moon shot

As humans prepare to return to the moon, scientists are acutely aware that the last human to leave a boot print on the lunar surface left 50 years ago when Apollo 17 began its journey from return on December 14, 1972.

Astronauts on the surface on that trip, Purdue alumni Eugene Cernan and Harrison “Jack” Schmitt, collected moon rocks and dust that scientists, including Thompson, are just beginning to analyze through the spacecraft program. analysis of Apollo Next Generation samples.

“It’s amazing, it’s surreal, to be standing in a Purdue lab analyzing moon dust collected by another Purdue alumnus – the last person to walk on the moon,” said Thompson.

The search is only possible because much of the more than 840 pounds of moon rock and dust has remained sacrosanct for nearly half a century. Today, scientists believe they have even better, more sensitive tools to study samples in depth and answer questions that were impossible to explore 50 years ago.

Thompson is an expert on how rocks interact and change due to their exposure to the vacuum of space – a phenomenon called space weathering. Analyzing the chemistry of moon rocks and moon dust can tell him about the moon’s environment, evolution, and history.

A lunar core sample, a small column of moon dust extracted from the lunar surface by Cernan and Schmitt, the first and only geologist to walk on the moon, gives Thompson and his lab this information. It comes from a part of the moon that may have suffered an avalanche, offering even deeper insight into the moon’s mineral and chemistry distribution and the processes that shape its surface. Thompson hopes his research team will be able to understand what the moon’s surface looked like before and after the avalanche, gaining a better understanding of how its soil, or regolith, developed over time. .

“When these samples were collected, when men walked on the moon, I wasn’t even born,” Thompson said. “This sample has been on Earth longer than I have. It’s been in storage, kept intact, waiting for scientists to analyze it since it was returned. Scientists now have tools and technologies that the original generation of astronauts could only dream of. So now it’s our turn to follow in their footsteps and study the moon rocks they brought back.

Future lunar missions — including Artemis — will bring back new samples, and new techniques will continue to shed light on the moon for geologists like Thompson.

Space time capsules

It’s counterintuitive, but one of the best ways to study how the Earth formed is to look at rocks that come from almost anywhere else.

“Asteroids are windows into the very first solar system; they are relics,” Thompson said. “These are time machines that show us what were the building blocks of the early solar system, what were the building blocks of life on Earth. The study of these asteroids gives us the recipe for the primitive solar system and the first organic molecules that were able to sow life on Earth.

Millions of meteorites and thousands of asteroids, including the Lafayette meteorite, a rocky body discovered at Purdue that is actually a broken piece of Mars, hit Earth. However, studying them, while interesting, cannot answer the same questions as space asteroids.

Even a short interaction with the Earth’s atmosphere, biosphere and minerals contaminates meteorites and asteroids and makes them more difficult to study. To obtain pristine materials and determine the history of these space rocks and the history of the solar system, scientists must intercept rocks – asteroids – in space. Scientists can study the asteroid and determine where it formed in the solar system, what other bodies it might have come into contact with (or where it might have come from), and how it evolved.

In his lab right now, Thompson has tiny fragments of one of the first asteroids ever sampled in space and transported to terrestrial labs: asteroid Ryugu, sampled by the Japanese spacecraft Hayabusa2 during the first spacecraft mission. rover operation on an asteroid. The Japan Aerospace Exploration Agency launched the mission in 2014. The spacecraft reached Ryugu in 2018 and deployed its rovers. In 2019, it fired what was essentially an anti-tank missile at the surface of the asteroid to collect samples underground. These samples landed on Earth in 2020 and were made available to NASA scientists, including Thompson. Studying asteroids, comparing and contrasting them with the surface of the moon, allows scientists to better understand the origins and diversity of bodies in the solar system.

tiger team

Next year, the adventure takes on even more momentum. Thompson is part of the “tiger team” – an elite team of experts – in meteorite studies for NASA’s OSIRIS-REx mission to asteroid Bennu. NASA deployed a team of tigers to bring the Apollo 13 crew home. OSIRIS-REx (or Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) will bring rock samples, not besieged astronauts, to Earth. Samples will land in Utah and then be flown to clean, secure labs in Texas. Thompson will be among the first humans – and the first woman – to study the Bennu pieces. She and the other four members of the Tiger team will have 72 hours to study the asteroid sample and prepare a preliminary report for NASA.

OSIRIS-REx used two different techniques to collect samples from the asteroid. Some sort of robot vacuum sucked up much of the material from the surface – probably well over 60 grams, which was the minimum the scientists had hoped for.

The second method was to gently and passively take samples from the surface.

“When the spacecraft touched down on the surface of the asteroid, it landed on these little circular pads, kind of like Velcro, which trapped the material right on the surface of the asteroid,” Thompson said. “We call them contact pads. Small specks of dust, dust particles, get stuck in the Velcro. We study these tiny dust particles. All I care about are the surface processes, what happens to the most premium material.

Writer/media contact: Brittany Steff,

Source: Michael Thompson

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