A catastrophic flood from Valles Marineris, the largest canyon system in the Solar System, released an estimated 1,245 trillion cubic metres of water onto the surface of ancient Mars, potentially raising the global mean level of a hypothesised Martian ocean by approximately 34 metres, according to new research published in the peer-reviewed journal Icarus.
The study offers a quantitative estimate of the volume of water that may have discharged from the canyon system during episodic flooding events on early Mars. The figure, 1,245 trillion cubic metres, would represent one of the largest single water releases theorised in the planet’s geological history. If the released water reached a standing body of water — what planetary scientists often refer to as a hypothesised northern ocean — the flood could have raised the ocean’s mean surface level by about 34 metres.
Valles Marineris stretches roughly 4,000 kilometres across the Martian surface and reaches depths of up to 7 kilometres in places. The canyon system is widely studied as evidence of past fluid activity on Mars, with researchers having previously identified features consistent with large-scale outflow events. The new estimate places a specific number on a process that, until recently, had been inferred primarily from geological morphology rather than hydrological modelling.
What Happened
The research team constructed a hydrological model of Valles Marineris to estimate the volume of water that could have been released during the canyon’s formation and subsequent flooding episodes. The model’s central output — 1,245 trillion cubic metres — is derived from the canyon’s geometric dimensions, the depth of excavation implied by its walls, and assumptions about the degree to which the surrounding terrain contributed sediment and water to the discharge.
When translated into oceanographic terms, that volume corresponds to a roughly 34-metre rise in the mean surface elevation of a hypothesised northern plains ocean. The northern lowlands of Mars, which sit several kilometres below the planetary mean elevation, have long been considered the most plausible location for a sustained standing body of water during the Noachian and Hesperian periods, roughly 3.7 to 3 billion years ago.
The study does not claim to prove that such an ocean existed. It does, however, supply a volumetric figure that any future shoreline reconstruction must be able to accommodate. If the northern lowlands did host an ocean, the Valles Marineris discharge alone would have produced a measurable and potentially identifiable change in its shoreline position.
Why It Matters
The estimate matters for two reasons. First, it provides one of the first concrete volumetric anchors for early Martian hydrology. Previous models have relied on indirect proxies: the width and depth of valley networks, the morphology of outflow channels, the distribution of phyllosilicates and other water-altered minerals, and the inferred extent of putative shorelines in the northern lowlands. Each of those proxies carries its own uncertainty. A modelled discharge figure, even one with wide confidence bounds, allows those separate lines of evidence to be cross-checked against a single quantitative claim.
Second, the figure has direct implications for the duration and episodicity of Martian water activity. A single flood event of this magnitude suggests that episodic catastrophic discharges, rather than long-lived steady-state flow, may have dominated the planet’s late-stage hydrological cycle. That pattern is analogous to, but far larger than, the outburst floods that shaped the Channeled Scablands of Washington State on Earth, where the breaching of glacial Lake Missoula released volumes on the order of cubic kilometres over hours to days.
If Martian water was concentrated in episodic mega-floods rather than distributed across sustained precipitation and runoff, the window during which the surface was habitable may have been shorter and more punctuated than earlier models assumed. That distinction is significant for astrobiological arguments about where and when microbial life could have persisted on Mars.
Background and Context
The question of whether Mars once hosted an ocean has been contested for decades. Early spacecraft imaging of the northern lowlands revealed what appeared to be smooth, flat terrain at a roughly uniform elevation, consistent with a former sea floor. Subsequent mapping identified candidate shorelines with elevations that, within measurement uncertainty, could correspond to a single past sea level. Critics have pointed out that some of the proposed shoreline features may be volcanic in origin, and that the apparent uniformity of elevation could reflect other geological processes.
Valles Marineris has been central to that debate because it sits near the dichotomy boundary between the southern highlands and the northern lowlands. The canyon is widely interpreted as having formed through a combination of tectonic rifting and fluid-driven erosion, with later outflow events enlarging and modifying its structure. The mineralogical evidence along the canyon’s walls, including sulphate deposits and hydrated minerals, supports the presence of liquid water at multiple points in its history.
The new study extends that body of work by attempting to quantify the total water budget associated with one of the canyon’s principal formation mechanisms. Its authors draw on topographic data from orbiting missions and on laboratory-derived estimates of sediment transport efficiency to bound the upper and lower limits of plausible discharge.
Analysis:
The study’s reliance on modelled discharge estimates, rather than direct measurement, means the figures should be treated as a credible upper-bound estimate pending further geological confirmation. Independent corroboration through shoreline mapping, sediment analysis, or crater-count dating of associated features would strengthen the case.
The 34-metre ocean-rise figure also depends on assumptions about the surface area and mean depth of the hypothesised northern ocean. Different published estimates of that ocean’s extent span a wide range, and the resulting rise figure is sensitive to which value is adopted. A smaller ocean would rise further under the same input volume, and a larger one would rise less. The study’s authors report their figure as an indicative central estimate rather than a fixed value.
The episodicity framing also carries implications for how the Mars science community interprets the planet’s climate history. A hydrological cycle dominated by catastrophic discharge is more consistent with a cold, icy early Mars in which subsurface reservoirs episodically destabilised than with a warm, wet Mars in which sustained precipitation maintained river networks over long intervals. Recent climate models have increasingly favoured the cold-and-icy scenario, partly on the grounds that sustained warmth under Mars’s early faint young Sun is difficult to reproduce. The new Valles Marineris estimate is consistent with that trend.
What to Watch Next
Several lines of evidence could confirm, refine, or overturn the new estimate in coming years. The most direct test would be independent shoreline mapping in the northern lowlands, using high-resolution imaging and topographic data from current and planned Mars orbiters to identify features consistent with the predicted 34-metre elevation shift. The Mars Reconnaissance Orbiter, the Mars Express mission, and the Trace Gas Orbiter continue to return data relevant to that effort.
A second line of evidence is sediment analysis. If the Valles Marineris flood deposited a recognisable sedimentary signature downstream — for example, in the Chryse Planitia lowlands, which sit at the terminus of several outflow channels — future landed missions could in principle sample and date that signature. The ExoMars Rosalind Franklin rover, currently slated for a later launch window, and the Mars Sample Return architecture under development by NASA and ESA, would both be relevant to that work.
A third, more speculative line is the detection of groundwater or ice deposits that retain a chemical fingerprint of past catastrophic discharge. Some researchers have argued that the deuterium-to-hydrogen ratio of present-day Martian water reservoirs could record the loss of large volumes of hydrogen to space; catastrophic floods would, in principle, accelerate that loss.
Conclusion
The new Icarus study does not settle the question of whether Mars once hosted an ocean. It does, however, put a specific number on one of the most consequential hydrological events in the planet’s history and shows that a single flood from Valles Marineris could have produced a geophysical signal — a 34-metre ocean rise — that should be detectable in the geological record if the ocean existed at all.
For a field that has long operated on indirect proxies and competing models, a quantitative anchor of this kind is unusually consequential. It will allow future shoreline, sediment, and climate studies to be tested against a specific volumetric claim rather than against each other. Whether that claim survives that testing is the next chapter of the story.
The Hindu – National: https://www.thehindu.com/news/national/kerala/valles-marineris-flood-may-have-raised-ancient-martian-sea-level-by-34-metres/article71427793.ece
Source: The Hindu – National
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Story synopsis gathered from: The Hindu – National — source
