Curiosity Rover Uncovers Evidence of Late-Stage Groundwater on Mars

NASA's Curiosity Mars rover has spent approximately six months exploring a region of Mount Sharp characterized by "boxwork" geological formations. Findings from this exploration suggest that ancient groundwater was present in this part of Mars later than previously understood, leading to further investigation into the potential duration of water-sustaining conditions on the planet billions of years ago.

Exploring Mount Sharp's Unique Boxwork Terrain

The Curiosity rover has been navigating boxwork terrain on Mount Sharp, a 3-mile (5-kilometer) tall mountain. These formations consist of interconnected low ridges, approximately 3 to 6 feet (1 to 2 meters) tall, with sandy hollows between them. The features span miles across the surface. Navigating these ridges, which are often not much wider than the rover, required careful path planning by engineers.

Mount Sharp's layers reflect different eras of Mars' ancient climate. Higher elevations show increasing signs of water drying out, interspersed with periods when rivers and lakes were present. Prior to Curiosity's arrival, the detailed appearance and formation process of these structures were not fully understood from orbital observations.

New Clues to Mars' Ancient Groundwater

The extensive presence of boxwork high on Mount Sharp indicates that the ancient groundwater table was considerably elevated.

This suggests that water, a component considered essential for sustaining microbial life, might have persisted for a longer duration than previous orbital observations indicated.

Scientists hypothesize that groundwater once permeated large fractures within the bedrock, depositing minerals. These minerals strengthened the areas that subsequently became ridges, while unreinforced sections were eroded by wind, forming hollows. Curiosity's close-up investigation confirmed that dark lines observed in previous orbital imagery within the boxwork are central fractures, consistent with the hypothesis that these were pathways for groundwater where minerals concentrated.

Nodules Point to Multiple Groundwater Episodes

During its exploration, the rover also identified bumpy textures known as nodules, which are indicators of past groundwater. These nodules were observed along the ridge walls and in the hollows between them, rather than exclusively near the central fractures. Researchers are currently investigating the positioning of these nodules. One hypothesis suggests that ridges may have been cemented by minerals first, followed by subsequent groundwater episodes that formed the nodules.

Unlocking Chemical Secrets from Martian Rocks

Curiosity collected and analyzed three rock samples from the boxwork region. X-ray analyses of these samples revealed clay minerals in a ridgetop sample and carbonate minerals in a hollow sample, providing further insights into the formation processes of these features.

A fourth sample recently underwent a specialized wet chemistry analysis. This technique involves reacting pulverized rock with chemical reagents in the rover's high-temperature oven, a process designed to enhance the detection of organic compounds, which are carbon-based molecules.

What's Next for Curiosity: The Sulfate Layer

Curiosity is scheduled to conclude its exploration of the boxwork formations in March. The rover will then proceed to explore a sulfate-enriched layer on Mount Sharp for the upcoming year. This layer formed as water dried out on Mars, and its study is expected to further understanding of the planet's ancient climate changes.

The Curiosity mission is developed and managed by NASA’s Jet Propulsion Laboratory as part of NASA’s Mars Exploration Program.