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Big news about what was found in a few precious grams returned to Earth from a daring mission to an asteroid.
Back in 2023, NASA returned from space a tiny sample of the asteroid Bennu that was collected by their OSIRIS-REx mission (we even mentioned in a BINTEL article about there were problems removing the top of the container from the spacecraft that you can read about here.)
What was found in just 122 grams of material from this roughly 490m across asteroid is significant.
Mission scientist Jason Dworkin holds a vial containing part of the Bennu sample returned by OSIRIS-REx. Image via NASA
First of all, Bennu is an "time capsule" from the early part of the Solar System's history. It was likely formed by an impact with a much larger asteroid, around 100-200km across, in the Mars - Jupiter asteroid belt. This caused a large number of asteroid "chips" to fly off into space, with Bennu ending up being in a near Earth orbit.
We'd already suspected that Bennu likely contained water and this was confirmed by OSIRIS-REx on approach.
Illustration of the OSIRIS-REx spacecraft at Bennu - image via NASA
These grains of rock have shown that the building blocks of life and the conditions for making them existed on Bennu's parent body 4.5 billion years ago.
What was found on the asteroid?
NASA, along with other geoscientists from other institutes examined these tiny grains and published their results in Nature.
They found chemicals which are here on Earth form the basis for life including a wide variety of amino acids - 14 of the 20 that are present on Earth.
Without these aminos acids, life would not be here and that includes us!
These mean that Bennu's parent body - the larger asteroid is was knocked off - not only contained these important compounds but also had enough energy to keep water liquid. Many of these chemicals only form in the presence of salty water.
Salty water or brine has been detected elsewhere in the Solar System including on the moon of Saturn, Enceladus.
“NASA’s OSIRIS-REx mission already is rewriting the textbook on what we understand about the beginnings of our solar system,” said Nicky Fox, associate administrator, Science Mission Directorate at NASA Headquarters in Washington.
The samples from Bennu collected by the OSIRIS-REx space craft. Image via NASA
If these materials are on Bennu, what does this suggest about other parts of the Solar System?
Asteroids provide a time capsule into our home planet’s history, and Bennu’s samples are pivotal in our understanding of what ingredients in our solar system existed before life started on Earth.
It's not the first time these building blocks have been found in extraterrestrial rocks such as meteorites and they're also seen in interstellar gas and dust clouds further out in the Milky Way. The importance of the Bennu find is that we know it was a pristine sample collected in space.
“The clues we’re looking for are so minuscule and so easily destroyed or altered from exposure to Earth’s environment,” said Danny Glavin, a senior sample scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-lead author of the Nature Astronomy paper.
“That’s why some of these new discoveries would not be possible without a sample-return mission, meticulous contamination-control measures, and careful curation and storage of this precious material from Bennu.”
From these samples we know understand that the parent object formed some distance from the Sun now might contain life forming chemical compounds. After Bennu was knocked off its parent asteroid, further processes stopped. On larger bodies these processes might have continued.
Was there life on Bennu?
Not they we know of. These results do not suggest that life ever existed on Bennu. There's no signs of current life in the samples so fears about them contaminating Earth are also unfounded.
In fact, scientists take great care when sending missions to Mars and other bodies to sterilise spacecraft and landers to avoid Earth microbes and other tiny critters from here taking up residence on other worlds and making detection of local "wildlife" harder.
We already know that Earth life can survive the extreme environment of space for extended periods so the real risk is Earth life infecting the other bodies in the Solar System.
Have the samples from Bennu posed any questions about life here?
Yes. For example, some aminos acids are in mirror images of each other. There can exist in either left-handed or right-handed versions. Earth life almost always are formed from left-handed versions, however the Bennu samples contain an almost equal quantity of left and right handed version.
Why aminos acids in Earth life are left-handed is still unknown. (Bear in mind that this is do with chemical arrangements and has nothing to do with which hand you hold a pen with or the way you face when opening the batting for Australia.)
Are we going to find life in the Solar System?
Good question. We don't know but we are looking. There's currently multiple missions both planned and already underway that are examining the suitability of conditions for the presence of life. For example, NASA missions to Mars have tested for life going back to the Viking landers in 1976 and the Europa Clipper is traveling to Jupiter to investigate its moon as a possible host for life.
The main mission of the Perseverance Rover (or "Percy" to its mates) trundling slowly across the surface of Mars is to look for either signs of past life or areas where it could have survived. Percy recently deposited a number of samples on the surface of Mars and NASA is currently investigating how to return these carefully collected Martian samples.
I think many researchers feel that a definitive discovery about life elsewhere in the Solar System in highly likely, whereas others aren't so hopeful.
Needless to say, a second place in the Solar System where life once thrived, even it in ancient times, would have a profound effect on how we view the rest of the Universe further out into the Milky Way.
Does the Bennu results hint at life arriving on the Earth from meteorites or did it start locally?
Another good question! We're yet to positively work out where life started on Earth and that it arrived on a rock which crashed into a young Earth cannot be ruled out. This theory, called panspermia, does kick the can down the road about the original source of life.
Can I see Bennu with my telescope?
Sadly no. It's too faint and beyond the abilities of amateur telescopes. Many astronomy apps will show its location. What these samples do show is that when you look up at night, the asteroids and moons around gas giant planets and maybe even Mars contain the conditions where maybe life existed some day.
Cheers,
Earl White - BINTEL
30th January 2025
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