Mars holds watery secrets: Two ancient oceans beneath Jezero crater

April 17,长沙收U换人民币 2025  18:11

Mars continues to astonish: an international team of scientists has revealed that Jezero Crater, explored by NASA’s Perseverance rover, conceals evidence of not one but two distinct periods of water activity. This discovery, published in Science Advances, upends our understanding of the Red Planet’s past and widens the window for when life might have thrived. From surface minerals to deep sediments, Mars is telling the story of its ancient oceans.

Two Watery Chapters in Jezero

Jezero Crater, stretching 45 kilometers wide, has long been a prime target for studying Mars’ watery history. Once a lake fed by rivers, it left behind a delta rich in clays and carbonates. But this new study adds depth to the tale. Using Perseverance’s data, researchers uncovered:

• A surface layer in the Hogwallow Flats region, packed with minerals formed in a relatively recent era—likely the late Amazonian period (less than 3 billion years ago). These minerals suggest liquid water, perhaps in salty lakes or underground streams.
• Deeper deposits, over 80 meters down, detected by the RIMFAX radar. These point to an older water episode from the Noachian or early Hesperian period (roughly 4 to 3.5 billion years ago), when Mars was warmer and wetter.

These layers, separated by millions of years and distinct conditions, are “like pages in Mars’ history book,” according to scientists from Queensland University of Technology, who developed a method to analyze mineral crystal structures on-site.

How Was the Water Found?

Perseverance’s toolkit was key:

• RIMFAX(a subsurface radar) peered 20 meters deep, revealing horizontal sediment layers and erosion marks hinting at an ancient lake.
• PIXL and SHERLOCanalyzed chemistry and mineralogy, identifying sulfates and carbonates tied to water. Magnesium sulfates with 3–5 water molecules and anhydrous calcium sulfate in the Máaz and Séítah formations confirm water altered rocks at different times.
• A novel Australian technique “read” the crystal lattice of minerals, pinpointing their age and formation conditions.

In Hogwallow Flats, Perseverance found fine sediments that could preserve microfossils, similar to Earth’s lakebeds. Deeper in the delta, radar revealed signs of massive floods that hauled boulders, pointing to raging rivers.

What Does It Mean for Life?

This variety of water conditions boosts the odds that Mars was once habitable. Surface minerals suggest salty but stable lakes where microbes, akin to Earth’s extremophiles, might have survived. The older deposits evoke a time when rivers and lakes blanketed the planet, creating prime conditions for life.

“We haven’t found organics, but the minerals we see typically form in water. That means Jezero was livable—the question is for how long,” says Tanya Bosak from MIT. Samples collected by Perseverance, awaiting return to Earth via the Mars Sample Return mission (planned for 2031), could reveal whether microbes once thrived in these layers.

Mars: Not One Lake, but Many

The data confirms Jezero saw multiple phases:

1. Early Lake (4–3.5 billion years ago): Water surged through a breach, forming a lake up to 30 meters deep with a delta. Sediments, like those in Pinnacled Stand, might hold traces of life.
2. Later Water Episodes: Smaller lakes or groundwater left sulfates and clays, possibly salty ponds like those in Hogwallow Flats.

These phases were punctuated by erosion periods when the lake dried, and wind or floods reshaped the rocks. RIMFAX revealed two sedimentation and two erosion cycles, making Jezero a “geological archive” of Mars.

Why It Matters

This discovery reshapes our view of Mars:

• Hydrology: Water wasn’t a one-off but a recurring feature in the planet’s history. This aligns with findings from China’s Zhurong rover, which detected water traces in Utopia Planitia as recent as 1 million years ago.
• Search for Life: Layered sediments raise hopes of finding biosignatures, especially in carbonate-rich samples that preserve fossils on Earth.
• Future Missions: Understanding water phases will guide targets for probes like Europa Clipper, hunting for water on Jupiter’s moons.

What’s Next?

Perseverance has stockpiled 23 sample tubes, and if Mars Sample Return brings them to Earth, lab analysis could pinpoint the timing of water episodes and hunt for life’s traces. Scientists also want to compare Jezero to Gale Crater, where Curiosity found a longer-lasting lake, to unravel why Mars dried up.

Jezero Crater is no mere dusty basin—it’s a chronicle of Martian waters. From ancient floods to salty ponds, it paints a picture of a planet once alive with possibility. Perseverance is peeling back these layers, bringing us closer to answering: Was Mars ever home to life? Next time you gaze at the stars, consider: could another “Jezero” be out there?