When NASA’s OSIRIS-REx spacecraft returned from its mission to asteroid Bennu in 2023, it introduced again extra than simply historical area rocks, it delivered solutions to puzzles which have baffled astronomers for years. Among the many most intriguing questions was why asteroids that ought to look an identical by way of telescopes seem strikingly completely different colors from Earth.
The thriller cantered on two remarkably related asteroids – Bennu and Ryugu which have been each visited by pattern return missions. These historical rocks are fabricated from the identical darkish, carbon wealthy supplies and shaped across the identical time in the course of the beginning of our Photo voltaic System 4.5 billion years in the past. Logic suggests they need to mirror gentle identically, but when studied by spacecraft, Ryugu seems faintly crimson whereas Bennu seems to be distinctly blue.
OSIRIS-REx in Launch Configuration (Credit score : NASA Kennedy from United StatesNASA/Glenn Benson)
Michelle Thompson, a Purdue College planetary scientist and skilled on area weathering, has been learning samples from each asteroids to crack this thriller. Her analysis, a part of three newly revealed papers based mostly on evaluation of Bennu samples by worldwide consultants, exhibits that these asteroids are present process the identical weathering processes however at completely different levels of a repeating cycle.
House weathering is the fixed bombardment that rocky our bodies endure from photo voltaic radiation, cosmic rays, and micrometeorite impacts. This fixed assault step by step adjustments how asteroid surfaces mirror gentle, basically giving them what we would name a ‘tan’ that alters their obvious color when seen from Earth.
The breakthrough got here when Thompson and her colleagues in contrast the publicity ages of floor particles from each asteroids. They found that grains collected from Ryugu’s floor have been uncovered to area for just a few thousand years, whereas floor grains from Bennu have been uncovered for tens of hundreds of years.
It is a colored view of the C-type asteroid 162173 Ryugu, seen by the ONC-T digicam on board of Hayabusa2 (Credit score : ISAS/JAXA)
This age distinction explains the whole lot. Somewhat than representing two completely different weathering processes, the asteroids present two snapshots of the identical cycle. Rubble pile asteroids commonly refresh their surfaces by way of impacts and gravitational shifts, exposing contemporary materials that then begins weathering once more. Bennu’s bluer look signifies extra superior weathering, whereas Ryugu’s reddish tint represents an earlier stage.
With 1.45 million identified asteroids in our Photo voltaic System, it is neither economically nor bodily possible to go to even a fraction of them. With the ability to extrapolate and perceive the character of assorted asteroids by analysing them from Earth is essential to understanding these historical remnants.
This analysis permits scientists to correlate what telescopes see with precise pattern evaluation. Such calibration is essential for future asteroid exploration, whether or not for scientific examine or potential mining operations. Figuring out how floor weathering impacts an asteroid’s look helps mission planners choose targets with higher confidence.
However the Bennu samples reveal much more exceptional secrets and techniques about our Photo voltaic System’s origins. Earlier analysis found salts within the samples, together with phosphates essential to life on Earth and important for metabolism and DNA. Scientists discovered proof of an atmosphere properly suited to kick begin precursor compounds for the chemistry of life.
“Trying on the natural molecules from Bennu, we’re getting an understanding of what sorts of molecules may have seeded life on early Earth. We cannot discover life itself, however we’re trying on the constructing blocks that would have finally developed into life.” – Michelle Thompson from Purdue College
These supplies stay pristine as a result of asteroids are basically time capsules, unchanged because the Photo voltaic System’s formation. Not like Earth, the place billions of years of geological and organic processes have blended and remodeled the unique elements, asteroids protect the uncooked supplies from which planets shaped.
The color thriller’s resolution demonstrates how pattern return missions revolutionise our understanding of area. By bringing items of distant worlds again to Earth’s subtle laboratories, scientists can decode secrets and techniques that stay hidden when observing from afar, opening new home windows into each our Photo voltaic System’s historical past and the potential origins of life itself.
