NASA’s Curiosity Rover Reveals Concealed Insights About Mars’ Pristine Atmosphere

NASA’s Curiosity rover has achieved a remarkable breakthrough on Mars by detecting a mineral that had previously eluded orbiting spacecraft. During its journey across the Red Planet’s surface, the rover discovered siderite — an iron carbonate — within rock samples retrieved from Mount Sharp, a prominent peak in Gale Crater.

This finding may serve as crucial evidence bolstering the hypothesis that Mars once possessed a robust atmosphere rich in carbon dioxide. Such an atmosphere would have fostered a warmer climate conducive to maintaining bodies of liquid water such as oceans, lakes, and rivers.

Curiosity, a mobile laboratory comparable in size to a car, drilled through four distinct rock layers at various heights on Mount Sharp. Three of these samples revealed substantial amounts of siderite, whereas the fourth, which did not contain siderite, displayed indications of other iron-rich minerals that might arise from the degradation of siderite.

On Earth, siderite occurs under specific circumstances involving water, iron, and carbon dioxide. The existence of this mineral on Mars implies that comparable environmental conditions may have existed in the past. Findings published in the journal Science suggest that Mars’ crust may harbor more carbon than previously thought. If additional sulfate-rich locations also contain carbonates similar to siderite, they could represent an undiscovered store of Mars’ ancient atmosphere.

“The identification of plentiful siderite in Gale Crater marks both an unexpected and significant advancement in our comprehension of Mars’ geological and atmospheric development,” stated Benjamin Tutolo, the lead author of the research.

This new evidence contributes to the expanding array of studies proposing that ancient Mars possessed the ideal conditions to support liquid water and an active carbon cycle — both vital elements for a potentially habitable setting.

Researchers have long speculated that Mars once harbored surface water. For this to occur, the planet would have required a considerably thicker atmosphere to retain heat and sustain elevated air pressure. Although present-day Martian atmosphere is remarkably thin, scientists contend it was once dense and laden with carbon dioxide, possibly attributed to volcanic activity. Over the years, much of that gas likely dissipated into space, although enough may have persisted to enable flowing water.

Despite decades of investigation indicating ancient water on Mars, one significant query has lingered: Where are the carbonate minerals that should have resulted from the interaction of carbon dioxide, water, and rock? The discovery of siderite might finally provide an answer to that puzzle.

At a location referred to as Ubajara, Curiosity drilled just under two inches into the surface and employed its CheMin instrument to conduct X-ray diffraction analysis on the rock and soil. The findings imply that the rocks formed in tranquil, aquatic settings akin to lakebeds — not through volcanic processes. On Earth, siderite typically develops in shallow lakes and wetlands.

Curiosity also uncovered sulfates, which crystallize as water evaporates. The order in which these minerals manifest offers insights into Mars’ environmental history. The fact that siderite emerged prior to the sulfates indicates a slow drying of ancient Martian lakes. The sample that lacked siderite but included its decomposition products bolsters the notion that Mars once possessed an active carbon cycle that ultimately became disrupted.

“Drilling through the stratified Martian surface is akin to traversing a history book,” remarked Thomas Bristow, a NASA research scientist and co-author of the study. “Just a few centimeters down provides us with a clear understanding of the minerals that developed at or near the surface approximately 3.5 billion years ago.”

If analogues of these carbonates are identified in other sulfate-dominant regions on Mars, they might encompass substantial amounts of carbon — potentially as much or exceeding what lingers in the planet’s current atmosphere. Future missions and observations may validate these findings and enhance our understanding of how Mars transitioned from a potentially hospitable world to the desolate terrain observable today.