2025-08-31T22:27:00Z

Imagine this: a spacecraft returns not just with rocks but with the answers to cosmic questions that have puzzled scientists for eons. That’s exactly what NASA’s OSIRIS-REx mission achieved when it returned from asteroid Bennu in 2023, delivering more than just ancient space rocks—it delivered revelations about the origins of our solar system and even the building blocks of life!

Among the most compelling mysteries was the enigma of two seemingly identical asteroids, Bennu and Ryugu. Both visited by sample return missions, these ancient celestial bodies, formed around 4.5 billion years ago, are made of similar dark, carbon-rich materials. So, you’d think they would reflect light in much the same way, right? But surprise! While Ryugu presents a faintly red hue, Bennu shines with a distinct blue. Why the difference?

Enter Michelle Thompson, a Purdue University planetary scientist whose curiosity has led her to excavate the secrets buried within these asteroids' surfaces. Her groundbreaking research, part of three newly published papers analyzing samples from Bennu, sheds light on how despite their similarities, these asteroids are undergoing different stages of the same weathering processes influenced by the cosmos.

What’s space weathering, you ask? It’s the relentless bombardment of rocky bodies by solar radiation, cosmic rays, and micrometeorite impacts. This constant onslaught gradually alters the surface of asteroids, almost like giving them a ‘tan’. The way they reflect light changes over time—affecting their color when viewed from Earth.

The breakthrough came when Thompson and her team compared the exposure ages of surface particles from both asteroids. They uncovered that the grains from Ryugu were fresh, having been exposed to space for only a few thousand years, while those from Bennu had been weathered for tens of thousands of years. This age discrepancy explains the color difference: Bennu’s blue signifies advanced weathering, while Ryugu’s red hint at an earlier stage in the cosmic dance of weathering.

With approximately 1.45 million known asteroids in our solar system, visiting even a small fraction is far from practical. However, this research highlights how crucial it is to link what telescopes observe with real sample analysis. By understanding how surface weathering impacts an asteroid's appearance, scientists can make better-informed decisions about future missions—whether for exploration or potential mining operations.

But that’s not all; the samples from Bennu reveal yet more astonishing secrets about the origins of life itself. Previous studies indicated the presence of salts, including phosphates vital for life on Earth, suggesting an environment conducive to the chemistry that could lead to life.

As Michelle Thompson puts it, “Looking at the organic molecules from Bennu, we are gaining insights into the potential building blocks that could have eventually evolved into life on early Earth.” This research underscores how asteroids act as time capsules—preserving the raw materials from which planets formed, unlike Earth, where billions of years of geological processes have transformed the original ingredients.

The resolution of the color mystery proves that sample-return missions are revolutionizing our understanding of space. By bringing pieces of these distant worlds to Earth’s advanced labs, scientists can uncover secrets that remain hidden when relying solely on observation from afar. This paves the way for new discoveries about our solar system’s history and the potential origins of life itself.