The OSIRIS-REx mission: To Bennu and back

OSIRIS-REx is expected to teach us more about our solar system and others beyond.

On Sept. 8, 2016, Dr. Vicky Hamilton watched as NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification Security, Regolith Explorer) lifted clear of Cape Canaveral’s Launch Complex 41 atop an Atlas V rocket, a roaring column of flame into the cloudless blue Florida sky. As deputy instrument scientist for the OSIRIS-REx Thermal Emission Spectrometer (OTES) and lead of the science team’s Spectral Analysis Working Group, she has spent five years preparing for this day. It is the first of many critical moments for the small spacecraft, built outside of Denver at the Lockheed Martin Space Sciences Company, as it becomes the first U.S. mission to orbit, sample and return a piece of the asteroid Bennu to Earth. If all goes as intended, it will parachute into the Utah desert in 2023, and it will be the largest piece of another world returned to Earth since the end of the Apollo moon program.

Hamilton has a long history in Colorado, growing up in Aurora and graduating from Smoky Hill High School before leaving to complete her college and graduate degrees. She then became a tenured professor at the Hawai’i Institute of Geophysics and Planetology at the University of Hawai’i at Manoa. Then she moved back to Colorado in 2008 and became a principal scientist at the Southwest Research Institute, located in downtown Boulder.

The near-Earth asteroid that was selected for investigation by OSIRIS-REx is 101955 Bennu. Hamilton explains that by studying and understanding this asteroid, scientists will have a better view of the early solar system.

“Asteroids are remnants of the period when our sun and solar system were forming,” she says. “They are essentially the only records of that earliest time in solar system history.”

This is because asteroids are leftovers of the original building blocks of our solar system. The most primitive asteroids, such as Bennu, are relatively carbon-rich and are believed to have not been significantly changed since they formed over 4.5 billon years ago.

“There is still much that we don’t understand about what happened in that early period of solar system history,” Hamilton says. “Yet, our solar system is our best template for understanding solar systems elsewhere in our galaxy and beyond. Now that we know there are thousands of planets orbiting other stars, it becomes even more interesting to understand the history of our own solar system.”

In addition, Hamilton explains Bennu may also hold clues to understanding how life may have taken hold.

“This particular asteroid is of a type that we believe is rich in organic material and water-bearing minerals,” she says. “This is important because organics and water are clearly crucial components of life as we know it, and we want to understand our origins.”

Hamilton gives the importance of the mission in this respect: “OSIRIS-REx is aimed at going and getting a piece of a truly pristine material. Unlike meteorites that land on Earth, Bennu hasn’t interacted with Earth’s atmosphere, surface or life, so it is free of contamination.”

OSIRIS-REx has a long journey ahead. The spacecraft will orbit the sun for a year before using a gravitational assist by Earth to propel it to Bennu. Once in orbit around Bennu (estimated for August 2018), the entire first year will be devoted to understanding the asteroid itself through detailed investigation and characterization of the mineralogy, geology and topology. After reviewing the data, the team will select a prime sampling location.

After the team is confident in the necessary spacecraft maneuvers, Hamilton indicates that the spacecraft will, as team members have described, “kiss the surface.” She explains that the spacecraft will never actually land but will only briefly touch the surface of Bennu with a sampling arm to retrieve pieces of the asteroid. “Kissing” the surface of Bennu, the sample arm will make contact for only roughly five seconds.

In March of 2021, OSIRIS-REx will begin its return journey to Earth, arriving two and a half years later in September 2023. As the spacecraft gets close to Earth the capsule containing the fragments of Bennu will be jettisoned.

The capsule will land and be collected at the Utah Test and Training Range. Once safely back on Earth, Hamilton and the OSIRIS-REx science team will analyze the first materials, which date back to the formation of our solar system, in laboratories throughout the United States, including here in Boulder. The majority of the material collected at Bennu will be preserved at the Johnson Space Flight Center in Houston, alongside the rocks brought back by the Apollo astronauts, for the use of future generations of scientists.

Boulder is home to several OSIRIS-REx team members. Alongside Dr. Hamilton are Dr. William Bottke and Dr. Kevin Walsh, both also at Southwest Research Institute, and Dr. Daniel Scheeres at the University of Colorado.

For more information, visit OSIRIS-REx online at:

Twitter: @OSIRISREx

Facebook: osiris_rex.

Mikki Osterloo, Ph.D. is a research scientist at the Laboratory for Atmospheric and Space Physics, University of Colorado-Boulder.


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