I’ve been wanting to write this one for a bit, as I often stumble upon interesting articles that veer widely away from the core subject matter but still have a resonance with the hidden hydrology project (or at least my expansive view of it). While cosmic in nature, are there clues to be gleaned from other worlds and applied to our planet that can inform our relationship with water? Even if not, if you’re interested in water, it’s pretty fun to explore the most distant and hidden hydrological processes, even in brief, from the Moon, Mars, and some of the interstellar stories around our solar system.


Our Moon is unique is having been studied extensively, and due to proximity, having had humans visit and walk on the surface. There has been speculation on water on the Moon, and when viewed from afar, a long history of people seeing ‘rivers’ on the moon. These may be features like this depression, seen here via the Earth Science Picture of the Day, showing Rima Hadley, “…an ancient rille… [which] may be the remnant of a collapsed lava tube. Lava from an erupting fissure may assume drainage patterns similar to overland water flow.”

Rima Hadley – image via EPOD

More recent work is augmenting these hydrological stories with data about the actual presence of water. Some of this, via Express: “NASA’S scientists have found proof to suggest surface waters on the Moon have been hidden in plain sight for decades, according to a shocking lunar meteor impact study.” The water vapor released by the impacts explains a bit of the mystery of water on the Moon, which accumulates at the polar caps, which had been posited to have come from other sources like solar winds. The water vapor lasted a short time, which is indicative of the relatively small amounts of lunar water, around 200-500 parts per million. Or, by another measure, per the article: “It is so dry that one would need to process more than a metric ton of regolith in order to collect 16 ounces of water.


Similarly, the presence of subsurface water is also changing our perceptions of Mars. Most recently, a parade of articles discussed evidence of, water on the red planet, with some speculating on this a proof of alien life, others speculating about gushing rivers that were wider than the Mississippi. The consistent theme as mentioned in the Independent, is the presence of “…a vast and active system of water running underneath the surface of Mars.” While it is broadly a reference to our further our understanding of Mars as a planet, scientists say it could also yield some clues for Earth hydrology, as it is speculated that the water was coming from “a deep pressurized source from where water is pushed up.” This is a similar to desert systems here on our planet.

From the image above: “The bright top line represents the icy surface of Mars in this region. The south polar layered deposits – layers of ice and dust – are seen to a depth of about 1.5 km. Below is a base layer that in some areas is brighter than the surface reflections, highlighted in blue, while in other places is rather diffuse. The details of the reflected signals from the base layer yield properties that correspond to liquid water. “

Analysis of the specifics show the water ‘carving’ the landscape, and creating valleys, with additional topographic analysis revealing complex watershed on the surfaces.

” This colour-coded topographic view shows the relative heights of the terrain in and around the network of dried-up valleys on Mars. Lower parts of the surface are shown in blues and purples, while higher altitudes show up in whites, yellows, and reds, as indicated on the scale to the top right. ” via Independent

A similar story from Space.com explains the theories that “Mars Had Big Rivers for Billions of Years“, which discusses the persistence of flows after loss of atmosphere, up until a billion years ago. Scientists conducted: “a global survey of Mars’ ancient waterways, characterizing more than 200 such systems using imagery and other data captured from orbit. They derived age estimates for these rivers by counting craters in the surrounding terrain. The team’s work suggests that Martian rivers flowed intermittently but intensely over much of the planet’s 4.5-billion-year history, driven by precipitation-fed runoff. The rivers’ impressive width — in many cases, more than twice that of comparable Earth catchments — is a testament to that intensity.  It’s unclear how much water Martian rivers carried, because their depth is hard to estimate. Determining depth generally requires up-close analysis of riverbed rocks and pebbles, Kite said, and such work has only been done in a few locations on Mars, such as Gale Crater, which NASA’s Curiosity rover has been exploring since 2012.”

There are also lakes, which are indicated by reflectivity, adjacent to larger areas of frozen ice near the poles of Mars. The Guardian, from a 2018 article “Mars: huge underground lake raises prospects of life on planet, astronomers say.” which makes the connection not to Martians in the sci-fi sense, but rather to the conditions for simple life forms:

“It is the first time that researchers have identified a stable body of liquid water on the red planet. The finding raises the likelihood that any microbial life that arose on Mars may continue to eke out a rather bleak existence deep beneath the surface. “

A deeper dive worth reading is also this article from published in the Planetary Society in 2017, “Unraveling a Martian enigma: The hidden rivers of Arabia Terra” which provide more investigation of remnant traces of what may be “Mars’ largest flood plain”.

Topographic map of mars – via Planetary.org

Speculation on the climate of Mars as potentially hotter and wetter, which may . The author posits that frozen ice sheets in the northern segments regularly thawed from heating events, and this liquid water would flow and create river systems. Strangely enough, these former rivers express themselves in inverted channels, which are described below:

“A river preserved as a ridge seems like a bit of a paradox, but inverted channels are fairly common on Mars. They occur when the river sediment within the channel becomes resistant to erosion (this can happen chemically, due to interaction with water, or by the deposition of large pebbles and boulders within the channel). Once the channel ceases to flow, the material adjacent to the channel—perhaps flood plain deposits—gets eroded at a faster rate than the channel, leaving the channel upstanding in the landscape. Inverted channels are also found in desert environments on the Earth, such as in Oman or Utah, where low rates of erosion can aid with their preservation. “

Inverted channel on Mars (Aram Dorsum) – via Planetary.org
Inverted channel on Earth (Green River, Utah) – via Planetary.org


The beauty of these flows are represented similarly on Europa, a moon of Jupiter that has had an icy surface that shows a varying mosaic on its surface. From CNET: “New analysis of measurements taken by NASA’s Galileo spacecraft over 20 years ago provides more evidence that water from an ocean beneath Europa’s icy shell is shooting out into space via at least one large geyser.” The story goes on to add:

“Europa’s hidden waters have become a prime target in the search for extraterrestrial life…”

The layering of imagery from Galileo from 1997, combined with more detailed analysis. Below, the striations and flows are highlighted, and in the second shown with “The blue-white terrains indicate relatively pure water ice, whereas the reddish areas contain water ice mixed with hydrated salts, potentially magnesium sulfate or sulfuric acid.”

image via CNET

The space geysers are also reinforced with more recent views from the Hubble Telescope, which has necessitated a future mission to gather more info. A recent fly-by by Cassini of Saturn, which has moons of similar type with a large under-ice ocean, has also led to even alien life. This combination of heated water under ice, in a interstellar ocean of Europa, and a similar Saturn moon, Enceladus, could, as posited here, also be the building blocks for life on other planets.


Beyond Mars and the Moon, more distant planets also have also liquid stories. A 2017 article in Universe Today, pointed out that Titan, the largest moon of Saturn “…is the only other world in our Solar System that has stable liquid on its surface.” This liquid surface is not water, but made up of methane and ethane, along with nitrogen, and the Cassini mission provided interesting info on the constantly fluctuating surface, including a disappearing and reappearing island, along with speculation of wave action. It’s also pretty interesting to note that there is precipitation as well:

On Titan, it rains. But the rain is composed of extremely cold methane. As that methane falls to the surface, it absorbs significant amounts of nitrogen from the atmosphere. The rain hits Titan’s surface and collects in the lakes on the moon’s polar regions.

This is most evident in polar lakes, referred to as ‘mare‘, from the latin for sea, which, like the moon, reference their being seen as water bodies similar to earth.

Ligeia Mare, a large polar water body on Titan – image via Universe Today

To take this idea to the logical extreme, a map of the Ligeia Mare with the adjacent drainage shows that hydrology (In this case not hidden, just very distance), whether it be Earth-based on a distant moon of Saturn, and consisting of water or a brew of methane, still follows those similar characteristics of gravity, topography, and flow.

A Map of Ligeia Mare by an amateur cartographer (Peter Minton) – via Wikipedia

HEADER: Image of Mars taken by the European Space Agency’s Mars Express satellite show the marks that an ancient network of rivers have left on the planet’s surface – via Independent

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