Facts worth sharing
- Asteroids are leftover planet-building materials from the birth of our solar system. We think some brought water and the building blocks of life to Earth.
- NASA’s OSIRIS-REx spacecraft will collect a sample of asteroid Bennu and return it to Earth, where we can study the sample in ways that we can't in space.
- OSIRIS-REx is a backronym that stands for Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer.
Why do we need OSIRIS-REx?
Our solar system is filled with countless asteroids, comets, and other small worlds left over from the disk of dust and gas that formed the planets 4.5 billion years ago. We think some of these worlds slammed into early Earth, bringing water and carbon-containing materials called organics here that formed the basis of life as we know it.
On Earth, weather and geological processes constantly alter the surface, but that's not the case on asteroids, which have remained largely unchanged. By studying them, we see what our infant solar system was like. Bennu is a near-Earth asteroid containing carbon and water. Although modern spacecraft instruments can tell us a lot about other worlds, there are certain kinds of experiments that can only be done on Earth. What we really need is a sample, so OSIRIS-REx will bring us one in 2023.
OSIRIS-REx will also help us learn more about defending our planet from dangerous asteroids. Small worlds like Bennu, which is just 500 meters (a third of a mile) across, can have their orbits altered by small forces like heat emission in ways we don’t fully understand. These forces can add up over time and mean the difference between an asteroid missing Earth or slamming into it. OSIRIS-REx will study one of these forces, called the Yarkovsky effect.
In 2013, The Planetary Society, University of Arizona, and MIT held a naming contest for asteroid Bennu, which until then had been called 1999 RQ36. We also collected names to travel aboard OSIRIS-REx through our Messages from Earth program. If you sent your name, you can look up your certificate here!
How OSIRIS-REx works
OSIRIS-REx is a van-sized spacecraft weighing more than 2 metric tons, with half of that weight in fuel. It has a 3-meter-long sample arm and solar panels that fold back, giving it extra room to maneuver near Bennu’s surface and protect it from debris kicked up during sample collection. The spacecraft's small instrument deck is packed with science gear to study Bennu’s composition, map the surface, and more.
OSIRIS-REx launched in 2016 and arrived at Bennu in 2018. It set a record for orbiting the smallest-ever world, which was no small feat considering Bennu hardly has any gravity. The asteroid is actually a loose collection of barely stuck-together rocks and boulders. If you were to sit Bennu on Earth, it would likely fall apart!
Upon arrival, OSIRIS-REx found that Bennu was much rockier than expected, with no areas that met engineers' original safety criteria for collecting a sample. Fortunately the spacecraft navigates with high precision, comparing the view from its cameras to stored images of Bennu’s landscape. This allowed scientists to settle on a sample location no larger than a few parking spaces.
To collect a sample, OSIRIS-REx will gently high-five Bennu with a cylindrical device called TAGSAM at the end of its sample arm. It will fire a blast of nitrogen gas into the surface, stirring rocks and soil into a collection chamber inside TAGSAM. The spacecraft will eventually stow TAGSAM in a small capsule, depart for Earth, and release the capsule into our planet’s atmosphere. The capsule will land via parachute in the Utah desert, where scientists will collect the precious samples for analysis.
How you can support OSIRIS-REx
Planetary Society co-founder Carl Sagan once said that "when you’re in love, you want to tell the world." Space missions like OSIRIS-REx are dependent upon sustained public enthusiasm from people like you. You know your audience best; we've got tools to help.
- Find out why missions to asteroids, comets, and other small worlds are so important
- Stay up to date on OSIRIS-REx and other missions by signing up for The Downlink, our weekly newsletter
- Find out how The Planetary Society is working to reduce the cost of sample collection with PlanetVac
- Learn how NASA picks missions based on the decadal survey (OSIRIS-REx is a New Frontiers-class mission)
Tell the world:
- Spread the Facts Worth Sharing at the top of this article on social media
- Send this page to others using the short URL planetary.org/osiris-rex
- Share pretty pictures of asteroid Bennu
Ready to take your next steps as a space advocate? Become a member and find out how you can take action in your community and government.
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