For decades, Mars has held a quiet contradiction: a world once shaped by flowing water and a thick carbon-rich atmosphere, yet nearly stripped of the carbonate minerals that such conditions should have left behind. A JAXA-led team of geochemists may have resolved this planetary riddle not by looking outward, but downward — their simulations suggest that ancient groundwater systematically carried Mars' carbonates beneath the surface, burying the evidence of a wetter world deep within the crust. The finding reframes not only how we read Mars' past, but where future explorers must look to find it
Underground Carbonates May Solve Mars' Missing Water Rock Mystery
The carbonates didn't vanish—they sank.
Mark
So the basic problem is that Mars should have way more carbonate rocks on the surface than it actually does, right?
Mimi
Exactly. We have strong evidence Mars was wet for a long time—rivers, lakes, maybe an ocean. With all that water and a CO2-rich atmosphere, you'd expect carbonates everywhere. But rovers and orbiters find very little.
Luke
And this study is saying the carbonates are just buried underground instead of gone?
Mimi
That's the hypothesis. The simulations show that groundwater moving through certain rock types—especially feldspar-rich rocks—would dissolve carbonates near the surface and carry them deeper down where they'd precipitate again.
Mark
Why does the type of rock matter so much?
Mimi
Because different rocks react differently with water. Feldspar-rich rocks readily form calcium and iron-rich carbonates. Mafic rocks, which are more common, tend to form magnesium-rich carbonates instead. The team found that feldspar rocks match what we actually observe in the two carbonate groups scientists have found.
Luke
But wait—how confident are we that these simulations actually represent what happened on Mars? They're models based on assumptions about early Martian conditions.
Mimi
That's fair. The models are constrained by what we know about Mars' past climate and geology, but you're right that we can't directly observe what happened billions of years ago. The strength is that the simulations explain both the scarcity of surface carbonates and the two distinct carbonate types we've actually found.
Mark
What does this mean for future missions?
Mimi
It suggests that drilling into feldspar-rich terrain could find buried carbonates and potentially access subsurface water. Since any long-term Mars exploration will need underground water sources, this points to where to look.
Luke
So the next step is actually drilling and testing whether the carbonates are really down there?
Mimi
Yes. The models make a prediction, but ground truth requires drilling. That's how you move from "this could explain the mystery" to "this is what actually happened."
El Pulso
- Mars' surface tells an incomplete story — the carbonate minerals that should mark billions of years of water-atmosphere interaction are conspicuously, almost impossibly, absent.
- A JAXA-led research team ran geochemical simulations revealing that feldspar-rich rocks — increasingly detected across Mars — readily produce calcium and iron-rich carbonates when water moves through them, unlike the mafic rocks scientists had long assumed dominated the planet's chemistry.
- The critical twist: percolating groundwater doesn't just create carbonates near the surface — it dissolves and transports them downward, redepositing them deep underground where no orbiter or rover has yet reached.
- The missing carbonates may not be missing at all, but buried — a vast geological archive of Mars' wet era locked beneath the planet's crust, waiting for a drill to find it.
- Future missions targeting feldspar terrain with subsurface drilling could simultaneously recover the planet's hidden geological history and locate the underground water reserves any sustained human presence on Mars would require.
For decades, Mars has held a quiet contradiction: a world once shaped by flowing water and a thick carbon-rich atmosphere, yet nearly stripped of the carbonate minerals that such conditions should have left behind. A JAXA-led team of geochemists may have resolved this planetary riddle not by looking outward, but downward — their simulations suggest that ancient groundwater systematically carried Mars' carbonates beneath the surface, burying the evidence of a wetter world deep within the crust. The finding reframes not only how we read Mars' past, but where future explorers must look to find it.
Mars presents a paradox that has unsettled planetary scientists for generations. The planet bears unmistakable signs of a watery past — river channels, ancient lake beds, and the possible remnants of a northern ocean — yet its surface holds far fewer carbonate rocks than that history demands. A world wet enough and atmospheric enough to carve such features should be rich in carbonates, the mineral record of water and carbon dioxide reacting with rock. Instead, the surface is nearly bare of them.
A research team led by doctoral student Chang-Chin Wang, working under Professor Tomohiro Usui at JAXA and Associate Professor Mohit Melwani Daswani at the Earth-Life Science Institute, set out to trace where those carbonates went. Using the PHREEQC geochemical modeling code, they simulated water moving through different Martian rock types across timescales stretching from years to 100,000 years, testing both standing water and flowing groundwater conditions.
The results reframed the question. Feldspar-rich rocks — which contain elevated calcium, sodium, and aluminum, and have been increasingly detected on the Martian surface — proved far more productive at generating calcium and iron-rich carbonates than the mafic rocks previously assumed to dominate Mars' crust. Mafic rock produced those carbonates only briefly before magnesium shifted the chemistry elsewhere.
More consequentially, the simulations showed that groundwater didn't merely create carbonates — it buried them. Percolating water dissolved near-surface carbonates and carried them downward, where they reprecipitated deep underground. This mechanism offers a coherent answer to the decades-old mystery: the carbonates were never truly lost, only relocated beneath the planet's crust by ancient hydrological cycles.
The findings, published in JGR Planets, carry forward-looking weight. Subsurface drilling missions targeting feldspar-rich terrain could recover both the geological record of Mars' warmer, wetter era and the underground water reserves that any long-term human presence on the planet would depend upon — two searches that may, it turns out, lead to the same place.
Mars presents a puzzle that has nagged at planetary scientists for decades. We know the planet once flowed with water—rivers carved its surface, lakes pooled in its basins, and a vast ocean may have covered much of the northern hemisphere. We know too that Mars once had a thick atmosphere rich in carbon dioxide. And yet when orbiters and rovers scan the Martian surface today, they find carbonate rocks in surprisingly small quantities. The math doesn't add up. A planet that was wet for so long should be littered with carbonates, the mineral signature of water and atmosphere interacting with rock. Instead, the surface is nearly bare of them.
A team of researchers from Japan's space agency and Tokyo's universities may have found where those missing carbonates went. Led by doctoral student Chang-Chin Wang under the guidance of Professor Tomohiro Usui at JAXA's Institute of Space and Astronautical Science and Associate Professor Mohit Melwani Daswani from the Earth-Life Science Institute, the group ran geochemical simulations to track what happens when water moves through different types of Martian rock. Their findings, published in the journal JGR Planets, suggest that the carbonates didn't vanish—they sank.
The mystery has another layer. The carbonate rocks scientists have found on Mars fall into two distinct chemical families: one rich in calcium and iron, the other rich in magnesium. Previous research assumed that water had interacted with mafic rocks, the iron- and magnesium-heavy minerals that dominate the Martian crust. But in recent years, orbiters and rovers have detected increasing amounts of feldspar-rich rocks on the surface. These minerals, which make up 60 percent of Earth's crust, contain higher concentrations of calcium, sodium, and aluminum. Evidence suggests they may once have been widespread across Mars.
Wang's team built one-dimensional thermochemical models to simulate what happens when water percolates through these different rock types under conditions that existed on early Mars. Using the PHREEQC geochemical code, they tracked mineral dissolution and precipitation over timescales ranging from a few years to 100,000 years. They tested two modes of water movement: diffusion through standing water and downward flow through groundwater. The results were striking. Feldspar-rich rock readily produced calcium and iron-rich carbonates under most conditions tested. Mafic rock, by contrast, only produced those carbonates briefly, before dissolved magnesium shifted the chemistry toward magnesium-rich carbonates instead.
But the most consequential finding concerned what happened to the carbonates once they formed. The simulations showed that percolating groundwater was far more efficient at creating carbonates than standing water. More importantly, groundwater dissolved these carbonates near the surface and carried them downward, where they reprecipitated deeper underground. This mechanism could explain where Mars' missing carbonates have gone. Rather than vanishing, they may have been systematically buried as groundwater cycled through the planet's crust billions of years ago.
The implications ripple outward. If substantial carbonate deposits lie beneath the Martian surface, future drilling missions could tap into them as evidence of the planet's warmer, wetter past. The same subsurface drilling could locate water that retreated underground as Mars cooled and dried. Since any sustained human presence on Mars will depend on accessing underground aquifers, these findings point toward where future explorers should look. Targeting feldspar-rich terrain for drilling operations could unlock both the planet's geological history and the water resources necessary for continued exploration.
Citas Notables
Feldspar-rich rock readily produces calcium/iron-rich carbonates under most conditions, while mafic rock only does so during brief periods of alteration.— Study findings via Wang et al., JGR Planets
Quieres la nota completa?
Lee el original en Universe Today ↗