Bennu and some of the biggest science questions of our generation

Bennu and some of the biggest science questions of our generation
by Lonnie Shekhtman
Washington DC (SPX) May 24, 2023

This week, NASA's OSIRIS-REx science team is meeting as a whole for the last time before the sample of asteroid Bennu arrives on Earth. This occasion marks the last chance for the group to convene to make sure team members, lab facilities, and sample-analysis techniques are working as expected and ready for the delivery of Bennu's rocks this September.

In the post below, Jason Dworkin, OSIRIS-REx project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, reflects on the big science questions that inspired this daring mission.

There are only a few months left until NASA's OSIRIS-REx delivers a sample of asteroid Bennu on Sept. 24, 2023. It's feeling more and more real every day. I feel as though I have so much left to do, even though I've already spent 19 years preparing for this moment.

When the sample returns, 233 scientists globally, including me, will get to explore the asteroid in our labs. In doing so, we will address dozens of questions about asteroids, the early solar system, and the origins of life. You can see these questions reflected in the full name of the mission and spacecraft: Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer. (I'll get deeper into the name later.)

I am an astrobiologist at NASA Goddard. I'm also the project scientist for OSIRIS-REx, which means I help manage mission science. My specialization is in the chemistry related to the origins of life, and so I work a lot with space rocks. My team in the Astrobiology Analytical Laboratory studies meteorites, Apollo Moon samples, comet samples from NASA's Stardust mission, and asteroid samples (we've analyzed pieces of Itokawa and Ryugu, asteroids sampled by our partner, JAXA, or the Japanese Aerospace Agency). JAXA is among the many institutions that will get pieces of Bennu.

When our Goddard lab receives the first pieces of Bennu in October 2023, we will analyze them like a forensics lab, including grinding them into dust and subjecting them to boiling water, acid, and more. All this to gain insight into the chemistry of the compounds in the rocks.

Besides my own work and that of my global colleagues, one of the most exciting things for me about the OSIRIS-REx mission is that 0.75 of the Bennu sample will be put aside for the global scientific community and for the future. This practice is a legacy from the Apollo missions - we're still opening and analyzing new caches of Moon rocks brought here by astronauts about 50 years ago! Saving extraterrestrial samples for the future ensures that they can be analyzed by scientists not yet born, using techniques not yet invented, to address questions that were unanswerable when the samples were collected.

We don't know what questions future scientists will have about asteroids, but here are some of the biggest ones driving the science of this generation:

Does the sample contain organic compounds that could have influenced the origins of life?
This question relates to the Origins, "O," part of the OSIRIS-REx acronym as it applies to NASA's search for the origins of life on Earth and possibly elsewhere in the solar system and beyond. All Earth life has specific chemicals, such as amino acids and sugars. We know that asteroids contain the molecular precursors to these chemicals, and we suspect that asteroids may have delivered these precursors to Earth. With Bennu samples, we will analyze the properties of these precursor chemical compounds and try to map out if, and how, these chemicals could have evolved into life.

How does the Bennu sample compare with our interpretation of data collected at the asteroid?
This question is related to the Spectral Interpretation, "SI," and Resource Identification, "RI," parts of OSIRIS-REx. We will analyze the mineral and chemical makeup of the samples to see if it aligns with what we expected based on spectral, thermal, and physical data gathered by the spacecraft at the asteroid. Being able to test our interpretation of spacecraft data in this unprecedented way - by comparing data from space to pieces of the physical object - will help us improve future missions and interpretations of telescopic and spacecraft data.

What does the sample tell us about the history of the solar system?
This question relates to the rest of the Origins, "O," and some of the Security, "S," parts of OSIRIS-REx. Besides the origins of life, we are also interested in the origin of our solar system. Because we suspect that Bennu could be older than our solar system, we hope the sample will open a window into the earliest time of solar system formation.

We are interested in learning more about the condensation of gas and dust that formed the Sun; the formation and destruction of Bennu's parent asteroid (we think Bennu broke off a larger asteroid during a collision billions of years ago); the formation of Bennu and its migration to the inner solar system, where its orbit will continue inching closer to Earth's over hundreds of years; and to the formation of the crater on Bennu's surface where we collected our sample.

How has the sample changed since the spacecraft collected it?
The act of sample collection, the Regolith Explorer, "REx," part of the mission name, was violent and may have influenced the chemistry of the pieces that are coming home, not to mention their three-year journey between Bennu and our laboratories. Thus, we will study the sample to understand what kinds of physical and chemical changes it experienced to ensure that we can draw accurate conclusions from our laboratory experiments.