Scientists Propose New Classification System for Martian Soil

Planetary researchers at the University of Sydney have proposed a new way to classify Martian soil, along with a new term to describe it: Ares, the Greek name for Mars.

A new framework for classifying Martian soil

Mars has no formal, workable soil classification system. Earth’s soil classification methods rely heavily on vertical layers, or horizons, but researchers do not yet have detailed, depth-by-depth data for Martian soil.

The new system, called the Provisional Polythetic Ares Classification System (PPACS), instead relies primarily on surface and near-surface properties inferred from orbital data.

“This is the first time a classification system of this scale has been developed for Martian soil,” said doctoral student Daniel Irving, corresponding author of the study.

“Scientists have previously mapped Mars’ geology, mineralogy, and chemistry, but our system brings together multiple properties into a single framework that will help us understand how different Martian soils relate to each other and where they are found.”

Why Martian soil matters for future greenhouses

Professor Alex McBratney, lead author of the study, said future greenhouses on Mars will need more than air, water, and light. They will also need information about the material beneath them to identify a better starting point for growing plants.

“Future greenhouses on Mars will need more than air, water and light,” McBratney said. “That builder also needs to know what’s underneath to understand a better starting point for growing plants.”

PPACS classifies 2,000 Martian soil types

The PPACS system has three tiers. Its 10 realms are divided into 10 collections, with each collection divided into 20 forms. Together, these categories correspond to 2,000 terminal soil classes.

The classification is accompanied by a detailed map covering 92% of Mars’ surface, allowing researchers to visualize the distribution of different Martian soil types.

As a proof of concept, the researchers evaluated all 2,000 soil types for properties important to plant production, including water-holding capacity, pH, profile thickness, clay content, and gravel content.

Nohibareth identified as a promising soil class

One soil class, known as Nohibareth, emerged as the most likely candidate for plant production, scoring 0.93 on the study’s rating scale of 0 to 1.

“People often think that soils need a lot of organic matter to function, but there are soil types around the world, especially in arid regions, that have very little organic matter,” Professor McBratney said.

“These results from Mars actually make us think more deeply about this type of soil on Earth and what we can do with it.”

A framework that can evolve with new Mars data

“Every rover mission collects valuable information about Mars, but scientists need a consistent way to organize and compare that knowledge,” Irving said.

“This gives us a framework that can grow and evolve as new data becomes available.”

The study was published in the journal Catena on October 7, 2026.

Read the study.

_____

Alex McBratney et al. 2026. Ares and the Provisional Polythetic Ares Classification System (PPACS): A hierarchical and nomenclature framework for soil classification on Mars. Catena 275: 110649. doi: 10.1016/j.catena.2026.110649