How broken crystal surfaces help shape clouds, life and climate

29/10/2026

The edges of crystals are like broken Lego constructions. Where pieces have broken off, new building blocks can attach, allowing new things to take shape. At the edges of crystals, atoms and molecules find places to attach, interact and react. These tiny reaction surfaces can act as 'seeds' for some of the most fundamental processes that have shaped our planet as we know it. They contribute to how Earth looks from space, how life formed, and how we may interact with climate.

By Kathelijne Bonne. Support GondwanaTalks through a one-time or recurring donation through this easy way.

One intriguing snippet of knowledge is that raindrops do not simply appear out of nowhere. Every individual drop needs a 'seed', a tiny particle around which water vapour can condense to form a droplet or ice crystal. This little fact has vast consequences, because from droplets, clouds are born.

Marbled blue planet is born from crystals

The bright white cloud masses that give our planet its marbled blue appearance reflect sunlight. The more radiation is reflected back into space, the less the planet warms. In this way, clouds form part of the natural system that has kept the climate relatively stable, which has helped life persist on Earth for billions of years, both protecting and insulating the planet's surface.

Next to clouds, water vapour, oxygen and nitrogen, the atmosphere is loaded with tiny dust particles that enter our lungs with every breath. These particles swirl around the planet in aerosols, permeating our environment and our cells.

In the air, many of these solid particles act as 'condensation nuclei': when moist air cools, water molecules can cluster and accumulate upon the particles, coalescing into droplets and eventually forming clouds and rain.

Clouds have contributed to a stable climate over eons (NASA, 2017, Lunar Recnonaissance Explorer)

Dust in the wind

There is an abundance of natural particles capable of seeding clouds, but humans too stir up dust in many ways—most notably through pollution, such as smoke and soot, and by intensifying soil erosion, as happened during the Dust Bowl. Yet producing particles in a controlled way—in the form of aerosols to mitigate climate impacts—has long been a topic of scientific research.

Global warming could theoretically be slowed by introducing certain aerosols into the atmosphere. On more local scales, cloud-seeding experiments have already produced measurable effects in some circumstances, although the technique is far from a silver bullet.

Without natural aerosols, there wouldn't be life as we know it. But how is dust produced and how is it lifted into the atmosphere?

What are aerosols made of, and how do they form? Much of the mineral dust in natural aerosols comes from sediment loosened from the Earth's crust through weathering and soil formation. Soil is the interface between solid rock, life, atmosphere and water. Weathering breaks down rock into particles of different sizes, such as sand, silt and clay, made up of many different minerals. The finer the particles, the more easily they are picked up by the wind.

Volcanoes also contribute substantially to atmospheric particles, sometimes enough for a single eruption to affect the climate. Pollen, spores, viruses, organic matter and sea salt can also be carried in aerosols. Winds and atmospheric currents transport these particles over great distances, sometimes around the globe.

But the most obvious sources of dust are deserts. The Sahara, for example, produces immense quantities of mineral dust that blow across the Atlantic. Remarkably, the seemingly lifeless Sahara fertilises both the ocean and the Amazon rainforest (or what is left of it) with natural nutrients such as iron.

Foam from waves whipped up by wind and storms gives rise to sea spray rich in salt and organic matter from marine life. In low-lying Belgium and the Netherlands, and along coastlines elsewhere, clouds often form around these sea-salt particles.

Condensation nuclei have the size of a butterfly's wing scale

Among airborne particles, fine dust—including particles smaller than two microns, roughly the thickness of a butterfly's wing scale—can act effectively as condensation nuclei.

Cloud seeding, and how geo-engineers (wish to) use aerosols

Cloud-seeding particles provide the tiny starting points around which water droplets gather and clouds begin to form. Cloud seeding has already been used in geoengineering, climate-intervention and weather-modification experiments, whatever name we wish to give these planetary tweaks. Different types of particles work in different ways, each influencing the atmosphere in its own way.

For very high, extremely cold clouds, silver iodide and dry ice (solid CO₂) have been used, whereas for lower, warmer clouds, salt particles can be more suitable. The dry southwestern United States may already have benefited from such experiments. Since the 1960s, researchers have tried to stimulate snowfall and rainfall in the Sierra Nevada to increase meltwater for farming—with modest success. The technique is far from miraculous: moisture and the right type of cloud must already be present.

Microcline feldspar as a cloud seeder

A compelling discovery in cloud formation concerns feldspar, a group of minerals found almost everywhere on Earth. Feldspar is abundant in igneous and metamorphic rocks and, through erosion, also occurs in sedimentary rocks. But unlike quartz, which is fairly resistant to weathering, feldspar readily breaks down into clay minerals, especially in warm, humid climates.

The chemical transformations that take place during weathering—exchanging atoms and molecules and forming new minerals, dissolved substances and other products—make feldspar an important component in the cycles and feedbacks that help regulate the climate.

One type of feldspar, microcline, is an exceptionally effective ice-nucleating particle. Why this particular mineral works so well has puzzled researchers for a long time. A 2023 study in Vienna revealed that the answer lies in the structure and behaviour of its crystal surfaces.

Using an atomic-force microscope, researcher Giada Franceschi and her team discovered that when feldspar surfaces break, hydroxyl groups can form at the exposed sites. These groups act like tiny hooks or anchor points, each consisting of one oxygen and one hydrogen atom (chemically written as –OH). They are polar and can attract water molecules. 'Like attracts like', and since water molecules are themselves polar, they readily interact with suitable polar surfaces. These special sites on microcline help water molecules arrange themselves into ice, making the mineral a highly effective ice nucleus.

Microcline is already present in atmospheric mineral dust. Understanding how different aerosol particles behave adds one more small building block to the grand edifice of knowledge—a metaphor palaeontologist Richard Fortey loved to evoke—from which we hope to find ways to tackle climate challenges.

Crystals and life

Studying mineral surfaces is far from futile. It has already led to remarkable scientific insights, including a deeper understanding of how life may have emerged when Earth was young, after the collision with the protoplanet Theia that gave rise to the Moon.

Not only microcline but many minerals have reactive, broken crystal surfaces. Imagine breaking a Lego house in two: protruding pieces will remain. Similarly, exposed sites on mineral surfaces can interact with their surroundings, attracting certain molecules and repelling others. Mineral surfaces are also special because their atoms are arranged in geometric, repeating patterns.

Some of the earliest building blocks of life, floating in water, may have accumulated on mineral surfaces. There, they could have lined up, guided by the structure of the rock or mineral grains. Crystal surfaces may have acted as catalysts, making it easier for molecules to cluster, bind and form longer chains (polymers). Without these surfaces, the early formation of complex biomolecules might have been much slower or more difficult. Such processes may have contributed to the chemistry from which the earliest organisms eventually emerged.

The handedness of life: no mirror image

Crystals may also have played a role in a phenomenon that has fascinated me ever since I first immersed myself in organic chemistry at university: the 'handedness', or chirality, of life. Chirality refers to the fact that two objects can be mirror images of each other without being identical in three dimensions. Objects are chiral when they cannot be superimposed on their mirror images, like our two hands.

Some of the building blocks of life—amino acids and sugars—show a striking preference for one handedness. Their mirror-image forms exist, but living systems overwhelmingly use one orientation rather than the other.

What is extraordinary is that proteins in life are built almost exclusively from 'left-handed' amino acids, while the sugars in DNA and RNA are 'right-handed'. Their mirror images have different biological properties and are not generally interchangeable in living systems. Why this asymmetry emerged remains a mystery, but there are hypotheses.

Crystal surfaces may have helped give life its handedness.

We've seen that crystals also play a role in what happens in clouds and climate. However, cloud-seeding techniques will never be a complete solution; they are just one small part of a much larger range of approaches. Just as we cannot yet create life from non-life, we cannot produce rain where there is no moisture.

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Explore our articles on supereruptions and how we might survive them, how the Great Plains recovered after the Dust Bowl, or dive into the supercontinent Gondwana, Snowball Earth, and how trilobites once viewed the world.

Kathelijne, editor of GondwanaTalks: I am intrigued by how earth, life, air, ocean and societies interact on geological and human timescales.

Why on earth I started GondwanaTalks.

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