NASA Unveils Bennu Asteroid Sample Results

Today, Jan. 29, NASA released more details on the analysis of the samples of asteroid Bennu, returned in September 2023.  Bottom line up front: of the 20 amino acids known to create the proteins required for life on our planet, Bennu scientists have now found 14 of them. 

Bennu was the target of the mission called OSIRIS-REx that launched in 2016.  The ambitious mission was to get to the asteroid, get close enough to retrieve some samples of its surface by slapping into it and capturing the dust and pebbles that crash kicked up, then return that debris to Earth. 

In other words, OSIRIS-REx was meant to deliver untouched asteroid chunks home to be analyzed in a lab. This brilliant plan worked. The samples landed in the Utah desert in 2023, and scientists have been wringing those priceless pieces of Bennu for data ever since.

When the first results of looking at the 250 grams of returned pebbles and dust were released in October of '23, Mission Scientist Dante Lauretta, principal investigator from the University of Arizona, said scientists hit the jackpot with a sample that is nearly 5 percent carbon by mass and has abundant water in the form of hydrated clay minerals.

However, that was more or less expected (or at least actively hoped for as corroborative evidence of scientists' Bennu theories). The team's latest discoveries, which NASA unveiled on Wednesday (Jan. 29), come as a bit of a surprise, and pose many exciting questions. The most notable parts are probably that researchers found those aforementioned 14 amino acids, a high concentration of ammonia, and the five nucleobases life on Earth uses to transmit genetic instructions within DNA and RNA.

"Their findings do not show evidence of life itself, but they do suggest that the conditions necessary for the emergence of life were likely widespread across the early solar system," Nicky Fox, associate administrator, Science Mission Directorate, NASA Headquarters, Washington, told reporters during a Jan. 29 press conference. "This, of course, increases the odds that life could have formed on other planets."

Nicky Fox later added: "For me, the question is: Why didn't life form on Bennu?" A question that needs more work - probably more space missions to come close to answering.  Not that there's anything wrong with that. 

There's a lot interesting content in that Space.com article, including a great example of science as it should be done, but doesn't seem to be done anymore.  It's a little long to copy in its entirety, six paragraphs, but it concerns the chirality of the chemicals found on Bennu - a bit on the Chemistry geek side. Chirality is also known as optical isomers - most all of these compounds will rotate polarized light in a left or right handed direction: levo- or dextro- rotary in that order.  To drag in one quote:

A molecule is considered "chiral" if it can't be superimposed on a mirror image of itself no matter what you try to do. This means that there must be two versions of that molecule, a left-handed version and a right-handed version. (Think about your own left and right hands. If your palms are facing upward, they follow this principle, too).

One of the puzzles that biochemists face is that all life on Earth seems to be based on left handed molecules, and nobody has a good explanation for why that is. Furthermore, when pieces of meteors that have made it to the surface are examined, they're also left handed molecules.  One of the Bennu scientists has been working on the theory that the early solar system was biased to left handed isomers.  The results from Bennu completely invalidated his work.  

"I have to admit, I was a little disillusioned or disappointed," Glavin said. "I felt like this had invalidated 20 years of research in our lab and my career. But I mean, here's the thing: This is exactly why we explore. This is why we do these missions, right? If we knew everything in advance, we wouldn't need to do an OSIRIS REx to bring these samples back."

I'd like to think that's the way all science is, but I've seen enough to convince me he's more like an exception to the rule.   

OSIRIS-REx touching down on asteroid Bennu. (Image credit: NASA)