Ancient Mars may have been warmer, wetter, and weirder than expected, according to an accidental discovery made by NASA‘s Mars Perseverance rover, offering clues about the Red Planet‘s past habitability.
In recent research, Purdue University’s Roger Wiens had NASA’s Perseverance rover direct its laser at a pile of unusual white rocks. The rover detected high levels of aluminum associated with the mineral kaolinite, which only forms in warm and wet conditions, offering new insights that have planetary scientists rethinking the Martian past.
A Martian Expert in Command
“On Earth, these minerals form where there is intense rainfall and a warm climate or in hydrothermal systems such as hot springs. Both environments are ideal conditions for life as we know it,” Wiens said. “These minerals are what’s left behind when rock has been in flowing water for eons.
“Over time, the warm water leaches away all the elements except those that are really insoluble, leaving behind what we found on Mars. It’s fascinating. It’s unexpected on a cold, dry planet like Mars,” he explained.
Wiens, a professor in Earth, Atmospheric, and Planetary Sciences at Purdue University, specializes in studies on Mars, which has given him an extensive history with Perseverance. He led the researchers and engineers that developed the SuperCam, the blocky, “head”-like appendage on top of the rover that contains instruments used to observe the Martian surface. After producing the SuperCam in a collaborative effort between Los Alamos National Laboratory and the French Institut de Recherche en Astrophysique et Planétologie, Wiens now leads the research team operating the device on Mars.
Ignored at First Glance
Initially, researchers judged the pale rocks to be of little concern. Despite observing small white pebbles on the day the rover landed, the team on Earth was too preoccupied with other tasks to investigate them at that time. Over time, scientists continually found more rocks with the same pale color strewn across the surface, not part of the bedrock. Scientists refer to such stones as float rocks because they “float” above the bedrock, away from where they formed.
“These rocks are very different from anything we’ve seen on Mars before,” Wiens said. “They’re enigmas.”
MARS
Above: Diagram detailing SuperCam RMI color images of rock formations of interest to the Purdue team during their recent investigations (Credit: Communications Earth & Environment).
A Purdue University team developed a detailed plan to study the rocks in depth, identifying their composition and structure. The researchers located 4,000 of the unusual stones across the Martian surface.
A Warm, Wet Mars
The most intriguing element of their kaolinite composition is how the mineral forms in warm, wet environments conducive to microbial life. Intense hydrothermal environments, ancient soils, and coastlines deposit kaolinite in sediment on Earth, where the mineral is typically much softer than the Martian samples. The exact reason why the Martian kaolinite is harder than on Earth is not yet understood.
The rocks also contain spinel, a magnesium-aluminum oxide mineral. Like kaolinite, spinel usually forms in igneous or metamorphic environments and is often found in sediment. Wiens’s team remains uncertain whether the spinel formed from the kaolinite or whether the kaolinite developed around the spinel.
Questions of Water and Habitability
One of the perplexing mysteries about the discovery is that only float rocks have been located so far. Without discovering samples in the bedrock where they formed, it isn’t easy to test any hypotheses regarding how the kaolinite came to be.
nitrogen-9
However, answers may be on the horizon as the Perseverance rover is currently exploring the Jezero crater’s rim. Satellite observations have confirmed that this location contains large amounts of kaolinite-rich rocks. Investigating the location may answer questions about the Red Planet’s past habitability.
“The big questions about Mars are about water,” Wiens said. “How much water was there? How long was there water? Given how cold and dry Mars is now, where did all that water go?
“As a mineral, kaolinite has a lot of water bound up in its structure,” he adds. “It’s possible that a lot of the water is still there on Mars, bound up in the minerals.”
The paper “Intense Alteration on Early Mars Revealed by High-aluminum Rocks at Jezero Crater” appeared on November 7, 2024, in Communications Earth & Environment.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted atryan@thedebrief.org, and follow him on Twitter@mdntwvlf.