Fossilised water flow from the early Solar System found in an Antarctic meteorite

Posted on 25 November 2024 • Science, maths, computing and technology

I’ll let you in on a secret, some space rocks (meteorites in their common vernacular) preserve water held inside minerals. They are important because they likely played a significant role in the recipe for building habitable worlds, primarily by delivering water to the otherwise dry inner solar system planets (Mercury, Venus, Earth and Mars). But what if one of these hydrated meteorites could tell us even more – specifically showing how water flowed on early-formed rocky bodies? The Reckling Peak (RKP) 17085 meteorite found in Antarctica offers a rare and fascinating glimpse into how water once shaped asteroids billions of years ago.

The recent publication: “Early fluid migration and alteration fronts in the CM chondrite Reckling Peak 17085” by Musolino et al. investigates the properties of this unique meteorite, (termed RKP 17085). This research was a collaborative effort involving scientists from different institutions, including the University of Pisa (Italy), The Open University (OU), the Natural History Museum (UK), the National Astrophysics Laboratory of Arcetri (Italy), the University of New Mexico (USA), the LESIA-Observatoire de Paris and CEREGE (France).

This meteorite was discovered in the icy desert of Antarctica in 2017 by the Italian National Antarctic Program (PNRA), RKP 17085 was well-preserved from exposure to the terrestrial environment due to the dry and cold environment of Antarctica. It belongs to a meteorite group termed the CM chondrites. They are exceptional because they have high-water contents and abundant organic matter, suggesting they may have played an astrobiological, for example through the delivery of crucial ingredients for life to the Earth’s surface.

Today, more than 700 meteorites among our collection of >70,000 are classified as CM chondrites. Interestingly, they record evidence of geological activity that operated on their parent bodies 4.5 billion years ago. Most prominently they show evidence of significant water-rock interaction, forming hydrothermal environments that reprocessed their original mineralogy into a new mix of hydrated and oxidised minerals. Most CM chondrites are intensely affected by the aqueous alteration process, but RKP 17085 stands out for its limited interaction with water, and because it has been affected by a heating event (post-hydration thermal metamorphism, estimated at less than 700°C). Each of these features is interesting but what makes this meteorite truly special?

Anna Musolino, PhD student from the University of Aix-Marseille in France and lead author of the paper explains:

“RKP 17085 is unlike other CM chondrites it contains thin bands enriched in Fe, distributed homogeneously across the meteorite. These bands, called ‘alteration fronts’, are evidence of the water flow in the parent body of the meteorite. The water altered the asteroid, only to be abruptly halted by a sudden event that left behind precipitated iron-rich along the fronts – forming the bands we now see in the meteorite. Today, billions of years later, we can observe these structures and reconstruct fundamental constraints on how water flowed and where it started from within these important meteorites.”

The presence of the fossilized water flow in RKP 17085 is like an open window into the past, allowing researchers to directly observe a phenomenon that once shaped minor bodies in the Solar System. The alteration fronts in RKP 17085 suggest that water flowed from the melting of tiny (submilimetre) ice grains that accreted when the asteroid formed. Where did water come from? How was it incorporated into asteroids? How did it alter them? Meteorites like RKP 17085 can help answer these questions. However, it can be challenging, because meteorites can bring evidence of multiple alteration events. Finding clear evidence like alteration fronts in RKP 17085 is a rare breakthrough.

Martin D. Suttle, lecturer in Planetary Science at the OU and co-author of the paper, emphasized the broader significance of this research:

“The extraordinary content of hydrated minerals and organic molecules in meteorites like RKP 17085 may have contributed to the fertilization of primordial ‘arid’ regions of the inner Solar System, including the early Earth. Understanding the geological context in which primitive organic matter evolved during aqueous alteration on asteroids is therefore essential.”

As we continue to explore the mysteries of space, the Reckling Peak meteorite offers just a glimpse of the stories of these small bodies of the Solar System. Who knows what other secrets lie hidden, waiting to be uncovered?

Header image: The cover image of Meteoritics & Planetary Science (Volume 59, Issue 11) features a full thin section of RKP 17085 alongside a close-up of its alteration fronts. These brighter, irregular bands  surrounding a chondrule were captured using backscattered electron imaging (FEG-SEM), highlighting the intricate structures that provide evidence of ancient water flow within the meteorite. Credit: Anna Musolino