That's exactly what's happening this month, though, as NASA's OSIRIS-REx project brings home pieces of the asteroid Bennu.
The culmination of more than a decade of work by a team of thousands, samples of the asteroid will land Sept. 24 in the Utah desert and be whisked off to a clean lab at NASA's Johnson Space Center in Houston. There, Michelle Thompson, associate professor of earth, atmospheric, and planetary sciences in Purdue's College of Science, will be one of the first six lead investigators from the science team - and the first woman - to study the samples.
"This is a truly once-in-a-lifetime - maybe a once-in-several-lifetimes - experience," Thompson said. "OSIRIS-REx was selected in 2011, the year I started my PhD, and launched in 2016, the year I got my PhD. It reached Bennu in 2018, the year I came to Purdue. And now I am going to be one of the first humans to get to study it. Bennu is a treasure trove of information; this is literally the project of my career."
Two other missions, Hayabusa and Hayabusa2, both launched by the Japan Aerospace Exploration Agency, have brought asteroid samples back to Earth. However, each of those missions returned much smaller amounts of sample material. Hayabusa brought back less than a milligram - approximately the weight of a single grain of granulated sugar - from the asteroid Itokawa. Hayabusa2 brought back 5.4 grams of material - about the weight of a nickel - from the asteroid Ryugu.
Scientists aren't yet sure exactly how much material OSIRIS-REx is bringing back, but its collection cannister appears to be packed. The mission's goal was to return 60 grams of sample. However, from camera observations, there may be more than 100 grams of material: about the weight of a stick of butter or a baby panda.
That is enough to keep hundreds of scientists busy for the length of their careers. But, along with five other colleagues, NASA selected Thompson to be one of the scientists who will get the first look: They will have 72 hours to analyze the samples to inform the science team and the public of their initial characterization.
How's the weather, whether or not we're together
Thompson is an expert in how asteroids, moons and other planetary bodies react with space - a process called space weathering. Understanding the surface, the very top few millimeters of rock and dust, called regolith, will shed light on the composition of asteroids and how their properties change and reflect their makeup. She has previously studied samples of moondust brought to Earth by the Apollo missions and has spent months at Johnson Space Center preparing for the asteroid samples' arrival.
OSIRIS-REx's name, which stands for Origins, Spectral Interpretation, Resource Identification and Security - Regolith Explorer, encapsulates the program's goal. Results will help give scientists insight into the origin of the planets and the earliest history of our solar system.
Understanding an asteroid's surface chemistry and how it compares to measurements and observations astronomers can make from Earth or orbital spacecraft will help scientists better understand how to interpret what they see.
"Observing asteroids from spacecraft and telescopes is incredibly important, but nothing can replace analyzing samples in the laboratory," Thompson said. "Sample return missions are a cornerstone of planetary science, and this close-up look at Bennu material will give us details we couldn't see from orbit and help us understand how to interpret what we're seeing on other faraway asteroids. It makes our understanding more comprehensive, more three-dimensional."
Other motivations include understanding what asteroids are made of to help future humans and explorers find whatever they might need to mine for future vehicles, missions and habitats. Scientists also hope to gain more understanding of asteroids' physical chemistry and how its orbit is changing with time, particularly of asteroids like Bennu that come close to Earth - and even have a chance, however minuscule, of impacting Earth.
"Asteroids are relics of the early solar system," Thompson said. "They're like time capsules. We can use them to examine the origin of our solar system and to open a window to the origin of life on Earth."
Bennu is a carbonaceous asteroid, which means that the element carbon - a fundamental building block of life - makes up a part of its composition. Like charcoal, a common carbonaceous material, many of these asteroids are dark and difficult to spot and see well in their entirety. Almost three-quarters of all asteroids are carbonaceous, so information gleaned from Bennu is likely to be applicable to many other asteroids in the solar system.
Asteroid Prime Delivery
Of course, pieces of asteroids can fall to Earth on their own. It's just that when they do, they don't get here unscathed. Screaming through the friction of Earth's atmosphere is a violent process, and not many rocks make it to the surface intact. If they do land in one piece, they can be altered and contaminated by the atmosphere and their surroundings on Earth.
Escorting the rock down, gently and insulated in still-pristine condition, using human innovation, means that scientists will get to look at the asteroid as it was in its original environment, lending understanding to a wide range of planetary science.
"These samples have been on their way back to us for a couple of years," Thompson said. "We have had years to prepare for what we might find and how we might study the sample."
According to NASA, after the samples land, they will be collected and flown back to the Johnson Space Center in Houston. There, Thompson and the team will be waiting, clad in clean clothes and prepped in a lab, to get the first peek at Bennu. Within the first few weeks, they will be able to present their initial findings to NASA and the world.
Thompson's expertise in the equipment and protocols of studying the chemistry of very small particles and rock samples gives her an edge in figuring out what elements and compounds make up Bennu's surface and how that structure might have changed over the history of the solar system.
Earth and other large planets have volcanoes or plate tectonics that have shaped and reshaped their surfaces over the history of our solar system. Asteroids like Bennu have experienced minimal alteration since their formation over 4.5 billion years ago. Analyzing their composition gives scientists hints to what materials might have been present as the solar system and all the planets formed and as life began to move on the surface of Earth itself.
"Looking at the organic molecules from Bennu, we're going to get an understanding of what kinds of molecules could have seeded life on early Earth," Thompson said. "Information about what compounds, what elements are there, and in what proportions. We won't find life itself, but we're definitely looking at the building blocks that could have eventually evolved into life."
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