Passing the baton: OSIRIS-REx makes history and continues as OSIRIS-APEX
The OSIRIS-REx mission's aim was more than just returning 60 grams of rocks and dust from Bennu. It also had the explicit goal of training the next generation of scientists.
If all goes well on Sunday, Sept. 24 – when the spacecraft jettisons the sample return capsule in the Utah desert – then the mission will be hugely successful in both endeavors.
In the first, scientists estimate that the spacecraft will return roughly 250 grams of asteroid material, which is made up of the remnants from the earliest days of the solar system. The sample could shed light on the origins of our cosmic neighborhood and even life itself.
In the second, NASA has extended the mission and renamed it OSIRIS-APEX, short for OSIRIS-APophis EXplorer. After dropping the sample return capsule, the spacecraft will fire its thrusters to begin its journey to Apophis, which it will reach in 2029. There, it will study and map the asteroid's surface for 18 months. It is on this extended mission that present-day early-career scientists, many of whom served in junior roles on OSIRIS-REx, will take the helm.
Dani DellaGiustina – assistant professor in the Department of Planetary Sciences and the Lunar and Planetary Laboratory and OSIRIS-REx deputy principal investigator – will serve as principal investigator for OSIRIS-APEX. She started working on the OSIRIS-REx mission in 2006 as an undergraduate student. She left to pursue a master's degree before returning and being hired on as the lead imaging scientist on the mission while simultaneously obtaining a doctorate from the Department of Geosciences. In 2021, she became OSIRIS-REx's deputy principal investigator.
Dante Lauretta, Regents Professor of planetary sciences at LPL, will remain principal investigator of OSIRIS-REx through the remaining two-year sample analysis phase of the mission. OSIRIS-REx veterans, like Lauretta, will also work closely with these early-career scientists as mentors in the initial mission phases of OSIRIS-APEX. By the time the spacecraft arrives at Apophis, members of the next generation will fully step into their leadership roles on the extended mission.
Apophis is an "infamous" asteroid, DellaGiustina said, and the perfect target for this mission. When Apophis was discovered in 2004, it was thought that it would impact the Earth in 2029. Subsequent observation ruled that out. Then, it was thought that it would hit in 2036. That was also ruled out. Now scientists agree that Earth is safe from Apophis for at least 100 years.
While it won't hit Earth anytime soon, it will come very close – less than 20,000 miles from our planet, or one-tenth the distance between the Earth and moon, DellaGiustina said.
This is exactly what makes it such an interesting target of study.
Planetary scientists are interested in studying how Earth's gravitational influence during this close approach by the spacecraft – which will disturb the asteroid's rotation rate and surface, potentially revealing what lies just beneath – changes the asteroid. Instruments onboard the spacecraft will snap pictures and collect data as it travels to the asteroid and will continue to monitor any changes after the close approach.
Scientists are also interested in learning more about the composition of this asteroid. OSIRIS-REx's target asteroid, Bennu, is a carbonaceous asteroid, which means it is relatively rich in carbon-bearing material such as organic molecules. Apophis, on the other hand, is a stony asteroid and is slightly smaller than Bennu.
The knowledge gained through OSIRIS-APEX will inform our understanding of potentially hazardous asteroids and how we might secure the Earth against future collisions with these solar system wanderers.